United States Department of Agriculture / Forest Service

Rocky Mountain Research Station

General Technical Report RMRS-GTR-261WWW

December 2011

Multicentury Fire and Forest Histories at 19 Sites in 

Utah and Eastern Nevada

Emily K. Heyerdahl, Peter M. Brown, 

Stanley G. Kitchen, and Marc H. Weber

0 75 150 miles

"

" " 

"

"

" " "

"

37°N

gridded site

non-gridded site

Nevada Utah

111°W

42°N 

H

BOM

HNR

ABM

EPH

BCL

WUN BRO

MUR

N

OWP

RAY

TVP

UFR

N
Available only online at http://www.fs.fed.us/rm/pubs/rmrs_gtr261.html.

Heyerdahl, Emily K.; Brown, Peter M.; Kitchen, Stanley G.; Weber, Marc H. 

2011. Multicentury fire and forest histories at 19 sites in Utah and eastern 

Nevada. Gen. Tech. Rep. RMRS-GTR-261WWW. Fort Collins, CO: U.S. 

Department of Agriculture, Forest Service, Rocky Mountain Research Station. 

192 p.

Abstract

Our objective is to provide site-specific fire and forest histories from Utah and 

eastern Nevada that can be used for land management or additional research. We 

systematically sampled fire scars and tree-recruitment dates across broad gradients in 

elevation and forest type at 13 sites in Utah and 1 in eastern Nevada to characterize

spatial and temporal variation in historical fire regimes as well as forest structure and 

composition. We collected similar data non-systematically at five additional sites 

in Utah. These 19 sites include a broad range of forest types (from pinyon-juniper 

woodlands to spruce-fir forests) and fire regime types. In this report, we summarize 

local-scale spatial and temporal variation with site-specific details of historical fire 

regimes and forests that will be useful for local natural resource and fire management 

of the individual sites. For each site, we report topography, chronologies of fire and 

tree recruitment, and properties derived from those chronologies such as timeaveraged fire regime parameters (mean fire interval and fire severity) and changes in 

forest composition and structure that have occurred since the late 1800s.

Keywords: fire scars, dendrochronology, crossdate, fire history, fire regimes, forest 

structure

Authors

Emily K. Heyerdahl is a Research Forester with the U.S. Department of Agriculture 

(USDA) Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory 

in Missoula, Montana.

Peter M. Brown is the founder and Director of Rocky Mountain Tree-Ring Research, 

Fort Collins, Colorado—a nonprofit research organization involved in tree-ring 

studies around the world.

Stanley G. Kitchen is a Research Botanist with the USDA Forest Service, Rocky 

Mountain Research Station, Shrub Sciences Laboratory in Provo, Utah.

Marc H. Weber was a Biologist with the USDA Forest Service, Rocky Mountain 

Research Station, Fire Sciences Laboratory in Missoula, Montana. He is a Geographer 

with the U.S. Environmental Protection Agency, Western Ecology Division in 

Corvallis, Oregon.
Acknowledgments

For help with field collection and sample processing, we thank Dan Bentley, Jim 

Bentley, Stephanie Carlson, Brandon Collins, Katie L. Collins, Gerad Dean, Chris 

Gentry, David Hanley, Joslin Heyn, Myron Holland, Andy Kitchen, Kevin Lee Hayes, 

Covy D. Jones, Gary Jorgensen, Brian Latta, Rachel Laurie, Kristy Miller, Heidi Neeley, 

Brad Newton, Eric O’Neil, Matt Proett, Becca Pyne, Matt Pyne, James P. Riser II, 

Gretchen Baker, Tyson Swetnam, Jeff Taylor, Tonya Thygerson, Heather Vice, Clay 

Waley, Brad Weaver, Nancy Williams, and Rosalind Wu. For help with logistics, we 

thank Evan Boshell, Robert Campbell, Linda Chappell, Rob Cruz, Kevin Greenhalgh, 

Gary Hall, Susie Hatch, Donna Owens, Jolie Pollet, Clark Tucker, and L.J. Western. 

We thank Aaron Wilson and Ann Wolf for help with data and GIS analysis and/or 

for assistance with figures, and Denny Simmerman for help with photographs and 

figures. For reviews of the manuscript, we thank Matthew Bekker, Robert Campbell, 

Linda Chappell, Beth Corbin, Peter Fulé, Sherel Goodrich, George Gruell, Bob 

Keane, Don Long, Doug Page, James P. Riser II, William Romme, and Elaine Kennedy 

Sutherland. We acknowledge primary funding from the Joint Fire Science Program 

under Project JFSP 01C-3-3-22 with additional funding from the USDA Forest Service 

(Fishlake National Forest and Rocky Mountain Research Station); USDI Bureau of 

Land Management, Utah State Office; and Rocky Mountain Tree-Ring Research, Inc. 

(partly through Research Joint Venture Agreement 03-JV-11222048-043 between the 

UDSA Forest Service, Rocky Mountain Research Station, and Rocky Mountain TreeRing Research, Inc.).

Contents

Introduction........................................................................................................................................ 1

Methods.............................................................................................................................................. 1

Results and Discussion...................................................................................................................... 12

Management Implications................................................................................................................. 14

For More Information ....................................................................................................................... 15

References ........................................................................................................................................ 15

Appendix A. Henry Mountains, Bureau of Land Management (HNR) ............................................... 19

Topography.............................................................................................................................. 19

Tree Demography .................................................................................................................... 19

Historical and Current Forest Structure and Composition ......................................................... 19

Fire Scars................................................................................................................................. 19

Post-Fire Cohorts...................................................................................................................... 20

Spatial Variation in Fire Regimes.............................................................................................. 20

Appendix B. Wah Wah Mountains, Bureau of Land Management (WAH) ......................................... 28

Topography.............................................................................................................................. 28

Tree Demography .................................................................................................................... 28

Historical and Current Forest Structure and Composition ......................................................... 28

Fire Scars................................................................................................................................. 28

Post-Fire Cohorts...................................................................................................................... 29

Spatial Variation in Fire Regimes.............................................................................................. 29

Appendix C. Book Cliffs, Bureau of Land Management (BCL)........................................................... 44

Topography.............................................................................................................................. 44

Tree Demography .................................................................................................................... 44

Historical and Current Forest Structure and Composition ......................................................... 44

Fire Scars................................................................................................................................. 44

Post-Fire Cohorts...................................................................................................................... 45

Spatial Variation in Fire Regimes.............................................................................................. 45

i
Appendix D. East Tavaputs Plateau, Bureau of Land Management (TVP)........................................... 53

Appendix E. Ray Mesa, Bureau of Land Management (RAY).............................................................. 54

Topography.............................................................................................................................. 54

Tree Demography .................................................................................................................... 54

Historical and Current Forest Structure and Composition ......................................................... 54

Fire Scars................................................................................................................................. 54

Post-Fire Cohorts...................................................................................................................... 54

Spatial Variation in Fire Regimes.............................................................................................. 55

Appendix F. Snake Range, Great Basin National Park (BMC)............................................................. 61

Topography.............................................................................................................................. 61

Tree Demography .................................................................................................................... 61

Historical and Current Forest Structure and Composition ......................................................... 61

Fire Scars................................................................................................................................. 61

Post-Fire Cohorts...................................................................................................................... 62

Spatial Variation in Fire Regimes.............................................................................................. 62

Appendix G. Paunsaugunt Plateau, Dixie National Forest (PSG)....................................................... 74

Topography.............................................................................................................................. 74

Tree Demography .................................................................................................................... 74

Historical and Current Forest Structure and Composition ......................................................... 74

Fire Scars................................................................................................................................. 74

Post-Fire Cohorts...................................................................................................................... 75

Spatial Variation in Fire Regimes.............................................................................................. 75

Appendix H. Boulder Mountain, Dixie National Forest (BOM)......................................................... 87

Topography.............................................................................................................................. 87

Tree Demography .................................................................................................................... 87

Historical and Current Forest Structure and Composition ......................................................... 87

Fire Scars................................................................................................................................. 87

Post-Fire Cohorts...................................................................................................................... 88

Spatial Variation in Fire Regimes.............................................................................................. 88

Appendix I. Beaver River, Tushar Mountains, Fishlake National Forest (RBC).................................... 99

Topography.............................................................................................................................. 99

Tree Demography .................................................................................................................... 99

Historical and Current Forest Structure and Composition ......................................................... 99

Fire Scars................................................................................................................................. 99

Post-Fire Cohorts.................................................................................................................... 100

Spatial Variation in Fire Regimes............................................................................................ 100

Appendix J. Indian Creek, Tushar Mountains, Fishlake National Forest (INC) ................................. 115

Topography............................................................................................................................ 115

Tree Demography .................................................................................................................. 115

Historical and Current Forest Structure and Composition ....................................................... 115

Fire Scars............................................................................................................................... 115

Post-Fire Cohorts.................................................................................................................... 116

Spatial Variation in Fire Regimes............................................................................................ 116

Appendix K. Upper Fremont River, Mytoge Mountains, Fishlake National Forest (UFR) ................. 124

Topography............................................................................................................................ 124

Tree Demography .................................................................................................................. 124

Historical and Current Forest Structure and Composition ....................................................... 124

Fire Scars............................................................................................................................... 124

Post-Fire Cohorts.................................................................................................................... 125

Spatial Variation in Fire Regimes............................................................................................ 125

ii
Appendix L. Wasatch Plateau, Fishlake National Forest (OWP) ...................................................... 131

Appendix M. Monroe Mountain, Fishlake National Forest (MON).................................................. 133

Appendix N. Abajo Mountains, Manti-La Sal National Forest (ABM) .............................................. 134

Topography............................................................................................................................ 134

Tree Demography .................................................................................................................. 134

Historical and Current Forest Structure and Composition ....................................................... 134

Fire Scars............................................................................................................................... 134

Post-Fire Cohorts.................................................................................................................... 135

Spatial Variation in Fire Regimes............................................................................................ 135

Appendix O. Wasatch Plateau, Manti-La Sal National Forest (EPH) ................................................ 146

Topography............................................................................................................................ 146

Tree Demography .................................................................................................................. 146

Historical and Current Forest Structure and Composition ....................................................... 146

Fire Scars............................................................................................................................... 146

Post-Fire Cohorts.................................................................................................................... 147

Spatial Variation in Fire Regimes............................................................................................ 147

Appendix P. Western Uinta Mountains, Ashley National Forest (WUN).......................................... 155

Topography............................................................................................................................ 155

Tree Demography .................................................................................................................. 155

Historical and Current Forest Structure and Composition ....................................................... 155

Fire Scars............................................................................................................................... 155

Post-Fire Cohorts.................................................................................................................... 156

Spatial Variation in Fire Regimes............................................................................................ 156

Appendix Q. Central Uinta Mountains, Ashley National Forest (MUR)........................................... 164

Topography............................................................................................................................ 164

Tree Demography .................................................................................................................. 164

Historical and Current Forest Structure and Composition ....................................................... 164

Fire Scars............................................................................................................................... 164

Post-Fire Cohorts.................................................................................................................... 165

Spatial Variation in Fire Regimes............................................................................................ 165

Appendix R. Eastern Uinta Mountains, Ashley National Forest (BRO) ............................................ 174

Topography............................................................................................................................ 174

Tree Demography .................................................................................................................. 174

Historical and Current Forest Structure and Composition ....................................................... 174

Fire Scars............................................................................................................................... 174

Post-Fire Cohorts.................................................................................................................... 175

Spatial Variation in Fire Regimes............................................................................................ 175

Appendix S. Wasatch Range, Uinta-Wasatch-Cache National Forest (WCH) .................................. 185

Topography............................................................................................................................ 185

Tree Demography .................................................................................................................. 185

Historical and Current Forest Structure and Composition ....................................................... 185

Fire Scars............................................................................................................................... 185

Post-Fire Cohorts.................................................................................................................... 186

Spatial Variation in Fire Regimes............................................................................................ 186

iii

USDA Forest Service RMRS-GTR-261WWW. 2011. 1

Introduction

Diverse forest and woodland ecosystems occur across landscape, elevational, and climatic gradients in Utah and eastern Nevada (Mauk and Henderson 1984; Youngblood and Mauk 1985). 

However, quantitative data on historical fire regimes are generally lacking for most of these ecosystems (but see Kitchen 2010; Madany and West 1983; Stein 1988; Wadleigh and Jenkins 1996). 

Furthermore, we have little information on the effect that variation in historical fire regimes had on 

the composition and structure of forests and woodlands or on the effect that recent fire exclusion 

may have had on current composition and structure. Such information is critical for forest management, especially regarding when and where fuel treatments, fire, or ecological restoration are 

needed or appropriate (for example, Allen and others 2002; Covington and others 1997; Falk 2006; 

Schoennagel and others 2004). This information is also crucial for inferring the drivers of regional 

variation in fire regimes through time and across space. Such drivers include climate, forest type, 

topography, and land use (for example, Brown and others 2008a).

We reconstructed crossdated (annually accurate) fire and forest histories from systematically 

sampled grids of plots at 13 sites in Utah and 1 site in eastern Nevada. In addition, we reconstructed 

fire histories and some forest histories at another five sites in Utah, some sampled systematically 

and others targeted only for a history of low-severity fires. The 19 sites include a broad range of 

forest types (pinyon-juniper woodlands to spruce-fir forests) and fire regime types. We have already 

used these histories to infer the drivers of variation in fire through time and space across the region 

(Brown and others 2008a; Kitchen 2010). While these studies are useful for managing fire and forests at regional scales, the site specific details of fire and forest history that we have not previously 

published will help other researchers and land managers understand and manage forests and fire at 

local scales. For example, understanding the departure of current forests from historical conditions 

can support management plans for specific areas to land management agencies and the public. Also, 

the local-scale properties of historical fire regimes, such as mean fire interval, can be compared to 

modern regimes to understand how they may have changed over the past century.

Our objective is to provide site-specific fire and forest histories that can be used for land management or additional research. We describe the study area and methods in a single section that applies 

to all sites, but we provide detailed results for each site in separate appendices. For each site, we include site and fire maps, interpret chronologies of fire and tree recruitment, estimate time-averaged 

properties of past fire regimes (frequency and severity), and show how these characteristics varied 

across the site by forest type and topography.

Methods

Study Area

We sampled sites in forests and woodlands across the Colorado Plateau of southern and central 

Utah, the Wasatch Plateau in central Utah, the Wah Wah Mountains and Snake Range in the eastern 

Great Basin, and the Uinta and northern Wasatch Range (fig. 1; table 1). The region is a complex 

of valleys, canyons, mountains, plateaus, and mesas that range in elevation from 2950 to 13,528 ft.

Sampling Design for Gridded Sites

We distributed 14 gridded sites across Utah, generally outside wilderness areas, on public lands 

managed by the USDA Forest Service, Bureau of Land Management, or National Park Service. We 

selected sites that covered a range of topography and forest type in an area that had road access but 

minimal forest management and no recent fires. We identified potential sampling sites based on local knowledge and selected final sampling sites during field reconnaissance.

Prior to sampling, we mapped plot locations for each site on a 0.31-mile grid oriented in the 

cardinal directions, using Universal Transverse Mercator coordinates (UTMs). In the field, we navigated to each plot using handheld global positioning system receivers. However, some plots were 

in areas we could not sample because they occurred in streams; on dramatic changes in slope such 

as ridges; roads; skid-trails; mudslides; or in areas that could not be safely sampled such as cliffs. 

In these cases, moving 164 ft along a random azimuth generally relocated plot center to an area we 
2 USDA Forest Service RMRS-GTR-261WWW. 2011.

could sample. We sampled 24 to 30 plots at most of the gridded sites (average 28 plots) but 44 plots 

at one site (Beaver River [RBC]; table 1) and 15 plots at another (Mytoge Mountains [UFR]). We 

sampled a total of 395 plots over 28,263 acres (table 1). The sites ranged from 1391 to 2837 acres 

and encompassed all of the plots plus a buffer of 0.16 mile, equal to one-half the average distance 

between plots. We were unable to sample 48 plots, either because we could not relocate plot center 

to a place we could sample or because the plot lacked trees ≥8 inches in diameter at breast height 

(DBH, 4.5 ft). Our final plots were 0.31 mile apart on average but ranged from 0.16 to 0.44 mile 

apart.

At each sampled plot, we recorded UTMs, elevation, slope, and aspect. At most plots, we took 

four photographs (one in each cardinal direction). We visually estimated ground cover for each 

plot as the percentage of rock, litter, bare ground, forbs, grasses, and shrubs, and we recorded 

the dominant understory plants for most plots. To compute an index of soil moisture at each plot 

(Topographic Relative Moisture Index; Parker 1982), we recorded topographic position (valley bottom, lower slope, middle slope, upper slope, or ridge top) and slope shape (concave, convex, or 

straight). In the office, we evaluated whether the topography of the sampled plots was representative 

of the topography of the site by comparing the distribution of plots among three topographic parameters (elevation, slope, and aspect) to that of the land area at the site. We derived the topographic 

characteristics of the land area from a digital elevation model (98 ft resolution; Utah AGRC 2004).

0 75 150 miles

"

"

"

" " "

"

"

"

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37°N

gridded site

non-gridded site

Nevada Utah

111°W

42°N WCH

PSG

BMC

WAH

RBC BOM

HNR

ABM

EPH

BCL

WUN BRO

MUR

MON

INC

OWP

RAY

TVP

UFR

N

Figure 1—Locations of our fire and forest history sites in Utah and eastern Nevada against a 

background of elevation. Characteristics of each site are given in table 1.
USDA Forest Service RMRS-GTR-261WWW. 2011.

3

Table 1—Amount of evidence used to reconstruct fire and forest histories. The number of crossdated, fire-scarred sections does not include trees with fire dates that did not 

occur on at least two trees at the site. Of the 889 crossdated fire-scarred trees sampled at gridded sites, 301 were trees that we also sampled for recruitment date. Trees at MON were sampled for a previous study (Chappell 1997) but were crossdated for this study. All Universal Transverse Mercator (UTM) coordinates are relative to the 1927 North American Datum (NAD27) and lie in UTM zone 12, except for the Snake Range site (BMC), which is in zone 11.

Trees in plots Fire-scarred trees Location of

Center of

National Forest Number Number Number Site

or other Area Area of plots Number cross- Number crossSite code Site name land ownership (acres) (ha) sampled sampled dated sampled dated UTM E UTM N

Gridded

ABM Abajo Mountain Manti-La Sal 2223 897 26 737 697 76 55 636081 4192853BCL Book Cliffs Bureau Land Mgmt. 1788 722 29 883 707 30 11 636624 4379720BMC Snake Range Great Basin Natl. Park 1569 633 24 674 507 128 103 735944 4323652BOM Boulder Mountain Dixie 1963 792 30 892 788 114 95 463505 4227120BRO Brownie Creek Ashley 1842 744 30 841 731 74 69 604433 4500480EPH Ephraim Canyon Manti-La Sal 1876 757 29 856 724 38 26 457943 4353018HNR Henry Mountains Bureau Land Mgmt. 2280 920 30 868 626 25 18 514716 4213697MUR Central Uinta Mountains Ashley 2218 895 30 810 610 97 83 576529 4498031PSG Paunsaugunt Plateau Dixie 2262 913 29 844 661 73 46 385172 4142590RBC Beaver Creek Fishlake 2837 1145 44 1332 913 194 164 373558 4231772UFR Mytoge Mountains Fishlake 1391 562 15 447 402 22 13 442816 4269737WAH Wah Wah Mountains Bureau Land Mgmt. 1593 643 24 730 610 130 125 276630 4276601WCH Bear River Range Uinta-Wasatch-Cache 2166 874 30 909 564 18 16 458199 4637430WUN Western Uinta Mountains Ashley 2255 910 25 745 524 74 65 531727 4489112

TOTAL 28,263 11,410 395 11,568 9064 1093 889Non-gridded

INC Indian Creek Fishlake 624 252 6 182 146 36 34 368989 4254123MON Monroe Mountain Fishlake --- --- 0 0 0 11 11 414263 4260309OWP Old Woman Plateau Fishlake 49 20 0 0 0 17 16 463477 4305011RAY Ray Mesa Bureau Land Mgmt. 15 6 4 118 97 19 16 664652 4241779TVP East Tavaputs Plateau Bureau Land Mgmt. 10 4 0 0 0 19 16 621022 4363832

TOTAL 698 282 10 300 243 102 94
4 USDA Forest Service RMRS-GTR-261WWW. 2011.

Tree Demography at Gridded Sites

At each plot, we used n-tree density-adapted sampling to reconstruct tree demography (recruitment and death dates) and historical and current forest structure (Jonsson and others 1992; Lessard 

and others 2002). This method allowed us to sample the same number of trees in every plot (roughly 

30) regardless of tree density, which varied greatly across the study area. This method has been 

successfully used elsewhere (Brown and others 2008b; Brown and Wu 2005; Heyerdahl and others 2006). At each plot, we sampled live or dead trees that were ≥8 inches DBH and closest to plot 

center, up to a maximum of 35 trees (minimum 6 trees, average 29 trees; fig. 2). We estimated plot 

size using the distance between plot center and the farthest tree sampled (area of plot = � × [distance 

to farthest tree]2). The farthest tree was 20 to 207 ft from plot center (average 73 ft). Consequently, 

plot size ranged from 0.03 to 3.09 acres with an average of 0.38 acres.

For each tree in the plot, we noted species, measured diameter with calipers at breast height 

(DBH) and sampling height (4 to 6 inches, and recorded the azimuth and distance from plot center. 

From live trees, we removed increment cores 4 to 6 inches above ground level. All heights were 

measured along the slope contour. We attempted to obtain increment cores that were no more than 

a field-estimated 10 rings from pith but removed a maximum of four cores from any given tree and 

retained the one that was closest to pith. From dead trees (logs, snags, and stumps) that were sound 

enough to sample, we used a chain saw to remove a full or partial cross section that included pith 

from what would have been approximately 4 to 6 inches above ground level. From dead trees that 

were not sound enough to sample, we did not remove a section but instead tallied them and noted 

whether or not they were charred.

All cores and sections were sanded until the cell structure was visible with a binocular microscope. We assigned calendar years to tree rings using a combination of mainly visual crossdating of 

ring widths and occasional cross-correlation of measured ring-width series (Grissino-Mayer 2001; 

Holmes 1983). For crossdating, we used ring-width chronologies that we developed for our sites 

and the species we sampled as well as chronologies that we downloaded from the International 

Tree-Ring Data Bank (http://www.ncdc.noaa.gov/paleo/treering.html). Crossdating is the process of 

matching climatically driven patterns of wide and narrow rings or other ring features, such as latewood width, from trees within and among sites to identify and account for false or partially absent 

rings (Stokes and Smiley 1968). Crossdating is possible because year-to-year variation in ring width 

or density is determined in part by year-to-year variation in climate, which was generally homogeneous across large parts of the region (Meko and others 1993).

distance from plot center (ft)

-260 -195 -130 -65 0 65 130 195 260

distance from plot center (ft)

-260

-195

-130

-65

0

65

130

195

260

+

+

+

+

+

+

X

live tree

+ dead, fire-scarred tree

dead tree

X

extent of plot

plot center

Figure 2—Schematic map of trees 

sampled at plot BOM17L. The 

diameter of the green and black 

symbols is proportional to 

DBH. We sampled the 30 trees 

that were ≥8 inches DBH and 

closest to plot center (whether 

living [green symbol] or dead 

[black symbol]). The size of this 

plot (the area within the blue 

circle) is 0.5 acres. In addition, 

we searched within 260 ft of 

plot center and found four firescarred trees (black symbols 

outside the blue circle).
USDA Forest Service RMRS-GTR-261WWW. 2011. 5

Slowly varying trends in ring width, such as those generated by stand dynamics, occurred in our 

samples in addition to the year-to-year variation that was driven by climate, but these trends did not 

affect our ability to crossdate individual live or dead trees. If we were unable to visually match the 

ring-width patterns from a sample to a ring-width chronology, we measured the width of the rings on 

the sample and statistically compared them to the chronology. This statistical comparison suggested 

possible dates for the rings on our samples, which we then verified on the wood to obtain final, exact 

calendar years for every tree ring. A total of 11,568 trees occurred in our plots and we removed wood 

samples from 10,284 of them (table 1). Of those, we were able to crossdate samples from 9064 trees. 

We excluded samples that we could not crossdate from analyses that relied on dates, such as fire 

frequency, but included them in analyses that did not, such as modern tree density and composition.

We estimated tree-recruitment dates from pith dates at sampling height (4 to 6 inches above 

ground level. Samples from most trees (70 percent) did not intersect the pith, so we estimated the 

number of years to pith based on the curvature of the innermost rings sampled (Applequist 1958; 

Duncan 1989) and subtracted this number from the innermost crossdated ring date. The average correction was eight years with a standard deviation of eight years. We did not correct for the number 

of years to reach sampling height because accurately measuring sampling height is challenging, especially where ground level may have changed at the base of trees that are several hundred years old 

and because the rate of vertical tree growth can vary through time. Therefore, we report recruitment 

dates—in other words, the date at which the tree reached a height of 4 to 6 inches.

Historical and Current Forest Structure and Composition

We assigned each plot to a category of historical (1860) and modern (2000) vegetation roughly 

following classifications developed for the LANDFIRE zones that cover our study area (zones 16, 

17, and 23; table 2; fig. 3; Comer and others 2003; LANDFIRE 2006; Rollins and Frame 2006). 

We classified historical vegetation into rough approximations of LANDFIRE Biophysical Settings 

(BpS). BpS categories represent the vegetation communities that would exist under given environmental conditions (climate, soils, and landscape physiography) and historical disturbance regimes. 

Table 2—Forest types that we assigned to plots and the names and codes of the LANDFIRE Biophysical Setting (BpS) and 

Existing Vegetation Type (EVT) categories from which our forest types are roughly derived (Comer and others 2003; 

LANDFIRE 2006).

Forest type used BpS EVT

in this study Category used in LANDFIRE BpS and EVT code code

spruce-fir Rocky Mountain Subalpine Dry-Mesic Spruce-Fir Forest and Woodland 10550 2055

spruce-fir Rocky Mountain Subalpine Mesic-Wet Spruce-Fir Forest and Woodland 10560 2056

limber-bristlecone Inter-Mountain Basins Subalpine Limber-Bristlecone Pine Woodland 10200 2020

lodgepole Rocky Mountain Lodgepole Pine Forest 10500 2050

aspen Rocky Mountain Aspen Forest and Woodland 10110 2011

aspen-mixed conifer Inter-Mountain Basins Aspen-Mixed Conifer Forest and Woodland 10610 2061

mixed conifer Southern Rocky Mountain Dry-Mesic Montane Mixed Conifer Forest 10510 2051

and Woodland

mixed conifer Southern Rocky Mountain Mesic Montane Mixed Conifer Forest 10520 2052

and Woodland

ponderosa pine Southern Rocky Mountain Ponderosa Pine Woodland 10540 2054

ponderosa pine Southern Rocky Mountain Ponderosa Pine Savanna 11170 2117

mountain mahogany Inter-Mountain Basins Curl-Leaf Mountain Mahogany Woodland 10620 2062

and Shrubland

pinyon-juniper Colorado Plateau Pinyon-Juniper Shrubland 11020 2102

pinyon-juniper Colorado Plateau Pinyon-Juniper Woodland 10160 2016

pinyon-juniper Great Basin Pinyon-Juniper Woodland 10190 2019

oak Rocky Mountain Gambel Oak-Mixed Montane Shrubland 11070 2107

sagebrush Inter-Mountain Basins Montane Sagebrush Steppe 11260 2126

shrubland Rocky Mountain Lower Montane-Foothill Shrubland 10860 2086
6 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure 3—Photographs of the range of forest types sampled for this study (table 2). Site and plot 

identifiers and cardinal direction in which the photograph was taken (north [N], south [S], east [E], 

or west [W]) are provided to the right of each photo. All photographs were taken between 2002 

and 2005.
USDA Forest Service RMRS-GTR-261WWW. 2011. 7

Figure 3—Continued.
8 USDA Forest Service RMRS-GTR-261WWW. 2011.

BpS is similar in concept to potential natural vegetation (Schmidt and others 2002). We assigned 

BpS categories to each plot based on the species and numbers of trees that we estimated were alive 

in that plot in 1860. Based on our crossdated samples, some plots (66 plots or 16 percent) lacked live 

trees in 1860. For these plots, we assigned BpS based on the dominant understory vegetation recorded at the plot. For example, in several plots, there was evidence that woody vegetation had expanded 

into what we inferred were historically sagebrush or grassland ecosystems. Similarly, we classified 

modern vegetation into rough approximations of LANDFIRE Existing Vegetation Types (EVT). We 

assigned EVT categories to each plot based on the species and number of trees present in that plot 

in 2000. Our plots fell into 17 different BpS and EVT categories but we combined some to form 12 

forest-type categories that were consistent across the region (table 2). For example, we combined 

“Southern Rocky Mountain Ponderosa Pine Woodland” with “Southern Rocky Mountain Ponderosa 

Pine Savanna” to form a single “ponderosa pine” category and “Colorado Plateau Pinyon-Juniper 

Woodland” with “Great Basin Pinyon-Juniper Woodland” to form a single “pinyon-juniper” category. The classes we assigned to plots in this study (table 2) follow general BpS and EVT categories 

but are not directly comparable to them (see also Swetnam and Brown 2010). We report tree density 

by modern forest type but otherwise analyze only historical forest type.

For each site, we estimated changes in forest structure and composition over time by estimating 

the historical (1900) and modern (2000) density of trees ≥8 inches DBH at each plot and pooling 

them by forest type. To compute density at a plot in 1900, we divided the number of all dated trees 

that were alive in that plot in 1900 by the area of the plot. Note that the density of trees in 1900 

does not include trees we were unable to crossdate or from which we were unable to remove a wood 

sample. Therefore, we have likely underestimated density in 1900 in some plots. To compute density in 2000, we divided the number of all trees that were alive when we sampled a plot (regardless 

of whether or not we removed a wood sample and crossdated it) by the area of that plot.

Fire Scars at Gridded Sites

We reconstructed a history of surface fires by using a chain saw to remove one to several partial 

cross sections from 1093 fire-scarred trees (table 1; Arno and Sneck 1977). Most of these trees 

(668 trees) were in our plots. This includes 364 of the trees that we sampled for recruitment date plus 

304 trees that we searched for in a larger plot—in other words, we searched within approximately 

260 ft of plot center, corresponding to an area of 5 acres (fig. 2). We sampled the remaining 461 

fire-scarred trees as we encountered them between plots. We sanded and crossdated these samples, 

as previously described, for recruitment date samples and, again, we excluded any samples that we 

could not crossdate from further analyses.

We identified the calendar year of the tree ring in which each scar formed to determine the year 

of fire occurrence. We identified the position of each scar within a ring (ring boundary, early-earlywood, middle-earlywood, late-earlywood, latewood, or unknown; fig. 4) because this information 

could be used to infer the season of fire occurrence (Dieterich and Swetnam 1984). In addition to 

fire scars, we obtained a small amount of supporting evidence of surface fires (8 percent of fire records), mostly from eroded fire scars (ones for which much or all of the overlapping, curled rings 

were destroyed by subsequent fires or rot) but also from abrupt changes in the width of annual rings. 

However, because factors other than surface fires can cause abrupt changes in cambial growth, 

we used ring-width changes as evidence of surface fire only when they were synchronous with a 

fire scar on other samples at the same site. In the northern hemisphere, the season of cambial dormancy (the period corresponding to the ring boundary) spans two calendar years—from the time the 

cambium stops growing in the fall of one year until it resumes in the spring of the following year. 

For the southern sites (Abajo Mountain [ABM], Snake Range [BMC], Boulder Mountain [BOM], 

Ephraim Canyon [EPH], Henry Mountains [HNR], Indian Creek [INC], Monroe Mountain [MON], 

Old Woman Plateau [OWP], Paunsaugunt Plateau [PSG], RBC, UFR, and Wah Wah Mountains 

[WAH]), we assigned ring-boundary scars to the following calendar year because most modern fires 

in southern Utah burn early in the cambial growing season (Barrows 1978; Kitchen and McArthur 

2003; Swetnam 1990). In contrast, the remaining sites are to the north (Wasatch Range [WCH], 

Western Uinta Mountains [WUN], Central Uinta Mountains [MUR], Brownie Creek [BRO], Book 

Cliffs [BCL], and East Tavaputs Plateau [TVP]), and so we assigned ring-boundary scars to the preceding calendar year because most modern fires in northern Utah burn late in the cambial growing 

season (Brown and others 2008a). Occasionally however, some late-season fires occur in southern 
USDA Forest Service RMRS-GTR-261WWW. 2011. 9

Utah and some early season fires occur in northern Utah. In addition, scars from a given fire can 

have a range of intra-annual positions because the timing of radial growth varies across the landscape (Fritts 1976) and because fires may burn for several months (Parsons and van Wagtendonk 

1996). Therefore, when a site had many ring-boundary scars but some late-season scars at southern 

sites (or early-season scars at northern sites), we assigned all of the scars to the preceding year (or 

the following year at northern sites; 134, or 4 percent, of scar dates changed). We were unable to 

determine the intra-ring position of some scars (26 percent) because they were obscured by rot or 

insect galleries or because the rings were very narrow. For each site, we report the distribution of 

fire scars by intra-ring position of species for which at least 20 fire scars occurred during the period 

from 1650 to 1900.

Cohorts at Gridded Sites

For each plot, we inferred a history of severe fires (fires that killed some or all of the overstory 

trees) based on the occurrence of cohorts of trees and occasionally on tree death dates (Brown and 

others 2008b; Heyerdahl and others 2001). We assumed all of the cohorts we identified were recruited in response to high-severity fires, although it is likely that some of these cohorts were recruited 

after trees were killed by other disturbances such as insect outbreaks, wind, drought, or interactions 

among these disturbances (Brown 2006; DeRose and Long 2007; Kulakowski and Veblen 2002). 

Furthermore, while tree death dates can accurately indicate fire dates, estimated recruitment dates 

of trees in cohorts are not accurate fire dates because tree-ring determination of recruitment dates is 

not exact and trees may establish in fire-created openings over a period of years (Oliver and Larsen 

1990).

We identified a cohort of trees at a plot when five or more trees were recruited within 20 years. 

More than one cohort could be identified at a plot but we required that every cohort date be preceded 

by at least 30 years with no recruitment to avoid identifying cohorts from continuous recruitment. 

We also identified severe fires at a plot when five or more trees died in the same year. We were not always able to obtain both pith and death dates for the dead trees we sampled because the sapwood of 

many tree species decays more rapidly than the heartwood. In identifying cohorts, we only included 

dates from trees whose outer rings were not decayed. We excluded the death dates of stumps even 

Figure 4—Examples of fire scars on ponderosa pine trees that differ in their intra-ring 

positions, which can be combined with information on cambial phenology to indicate 

the season in which a fire burned.
10 USDA Forest Service RMRS-GTR-261WWW. 2011.

though trees killed by fire may have subsequently been harvested because we did not have harvesting dates. We estimated the year of the fire that created the opening in which a cohort established as 

the earliest recruitment date within that cohort. Although cohorts and scars occurred in the same or 

neighboring plots and may have been created by the same fire, we did not assign cohorts to fire-scar 

dates because low-severity fires were generally too frequent for us to unequivocally associate each 

cohort with a single fire-scar date. We present chronologies of fire scars and cohorts in fire charts 

(Grissino-Mayer 1995).

Plot-Composite Fire Regimes at Gridded Sites

Fire Intervals (Low-Severity Fires Only)

During the analysis period (1650 to 1900) for each plot, we estimated plot-composite fire intervals as the interval between years in which fire scarred two or more trees at the site (Dieterich 1980). 

We assumed that scar dates recorded on two or more trees were unlikely to have been created by 

factors other than fire, for example lightning or falling trees or branches. We report plot-composite 

intervals, pooled by forest type, for those forest types with 10 or more intervals at a site.

Fire Severity

To infer fire severity at plots before 1900, we assumed that fire-scar dates are evidence of lowseverity fire, cohorts are evidence of high-severity fire, and a combination of the two is evidence of 

mixed-severity fire (table 3). We assigned low severity to plots that had three or more fire-scar dates 

but no cohorts and high severity to plots that had no fire-scar dates, a single cohort, and no trees 

recruited prior to the cohort (with the exception of trees killed by the fire that resulted in the cohort). 

More than one cohort can be present in a plot if a fire does not kill all the overstory trees but leaves 

some residual trees (Turner 2010). For example, if a cohort established in 1619 in response to a fire 

that killed all the trees in a plot, a second cohort could have established in 1899 in response to a fire 

that killed some, but not all of the trees in the 1619 cohort. Therefore, we assigned mixed severity

to plots that had (1) one or more fire-scar dates and one or more cohorts or (2) a cohort plus trees 

that were recruited prior to the cohort. We were able to infer historical fire severity at most plots 

(55 percent) using these criteria.

Table 3—Criteria used to assign historical fire severity to plots at gridded sites. Note that plots could 

be assigned to mixed severity if they contained either of two kinds of evidence. Twelve of the 395 

plots were classified as not historically forested because they lacked both trees recruited before 

1900 and undated remnant trees. Another 26 were unclassified because they did not meet the 

criteria for any of our categories of fire severity.

Number of

fire-scar Number of Additional 

Fire severity datesa cohortsb evidence

Assumed no fire 0 0 No charred remnants; pre-1900 trees dominatedc

over the period of by species with non-winged seeds (pinyons,

record junipers), lack serotinous cones, or do not sprout

High 0 1 No recruitment pre-dates the cohort

Assumed high 0 0 Pre-1900 trees dominated by Engelmann spruce, 

white fir, subalpine fir, quaking aspen, or lodgepole

 pine

Mixed 0 ≥1 Recruitment pre-dates at least one of the cohorts

Mixed ≥1 ≥1

Assumed mixed <3 0 Pre-1900 trees dominated by ponderosa pine, 

Douglas-fir, Great Basin bristlecone pine, or 

limber pine

Low ≥3 0

a

 Recorded on ≥2 trees at a site.

b

 Five or more trees with recruitment and/or death dates within 20 years, preceded by 30 years with no 

recruitment. Death dates can be from snags or logs but not from stumps. Cohorts that initiated after 1900 are 

not included. c

 Defined here as ≥50 percent of the trees at a plot were recruited before 1900.
USDA Forest Service RMRS-GTR-261WWW. 2011. 11

The remaining plots did not have sufficient fire scars and/or cohorts to meet our criteria for low, 

high, or mixed severity, so instead, we inferred severity from the life-history strategies of the trees 

occurring in those plots. We assigned assumed mixed severity to plots with fewer than three firescar dates and no cohorts whose pre-1900 trees were dominated (in other words, at least half of the 

trees were recruited by 1900) by ponderosa pine (scientific names and authorities for overstory species are provided in table 4), Douglas-fir, Great Basin bristlecone pine, or limber pine (Agee 1993; 

Brown and Smith 2000; Wright and Bailey 1982). These species have relatively thick bark and 

generally high crowns and, therefore, tend to be adapted to low-severity fire regimes. We assigned 

assumed high severity to plots that lacked both fire scars and cohorts, and whose pre-1900 trees were 

dominated by Engelmann spruce, white fir, subalpine fir, quaking aspen, or lodgepole pine. These 

species have winged seeds (in the case of spruce and fir), predominately serotinous cones (lodgepole 

pine), or can sprout (aspen), all of which are characteristics that allow them to recolonize an area 

relatively fast after high-severity fire. We assigned assumed no fire to plots with (1) no fire-scar 

dates or cohorts, (2) no charred dead trees, and (3) pre-1900 trees dominated by species that have 

non-winged seeds (pinyon or juniper), lack serotinous cones, and do not sprout. A few plots did not 

fit the requirements for any of our categories and were not assigned an historical fire severity (6 percent), and a few were assumed to be not historically forested (3 percent) because they lacked both 

trees before 1900 and undated dead trees. While plots in the last three categories (assumed no fire, 

unclassified, and not historically forested) may have sustained fire in the past, we found no evidence 

of fire over the period of record.

Relative Fire Extent (Low-Severity Fires Only)

For every fire year that was recorded by a scar or fire-caused injury on two or more trees at a site, 

we used the location of fire-scarred trees sampled in and between plots to estimate the relative extent 

of low-severity fires. It is likely that we underestimated the extent of most of the fires that we reconstructed because they intersected the boundaries of our study sites. Therefore, we term our estimates 

“relative fire extent” to indicate that we are not able to reconstruct a complete fire-size distribution. 

To estimate relative fire extent, we divided each site into cells containing a single plot, where the 

boundaries of each cell lay halfway between a plot and its nearest neighbors (Mark 1987). The cells 

containing sampled plots averaged 63 acres in area and ranged from 37 to 101 acres. We estimated 

relative fire extent as the sum of the area of all cells with evidence of fire in that year. Because many 

fires intersected the boundaries of the sites and because not all trees were recording during every 

fire year (in other words, the trees at some plots were too young to show evidence of fire or the trees 

were not susceptible to scarring), we also computed relative fire extent as a percentage of recording 

area (area of cells with evidence of fire divided by area of cells with recording trees). We sampled 

a few trees outside of the cells (one tree each at EPH, HNR, and MUR) and mapped fire-scar dates 

Table 4—Common and scientific names of the species mentioned in the text. Nomenclature follows 

Welsh and others (1993) and USDA NRCS (2002).

Common name Scientific name

Colorado pinyon Pinus edulis Engelmann

common juniper Juniperus communis Linnaeus

curl-leaf mountain mahogany Cercocarpus ledifolius Nuttall in Torrey & Gray

Douglas-fir Pseudotsuga menziesii (Mirbel) Franco

Engelmann spruce Picea engelmannii Parry ex Engelmann

Gambel oak Quercus gambelii Nuttall

Great Basin bristlecone pine Pinus longaeva D.K. Bailey

limber pine Pinus flexilis James

lodgepole pine Pinus contorta Douglas ex Loudon

ponderosa pine Pinus ponderosa Douglas ex Lawson & Lawson

quaking aspen Populus tremuloides Michaux

Rocky Mountain juniper Juniperus scopulorum Sargent

Rocky Mountain maple Acer glabrum Torrey

singleleaf pinyon Pinus monophylla Torrey & Frémont

subalpine fir Abies lasiocarpa (Hooker) Nuttall

Utah juniper Juniperus osteosperma (Torrey) Little

white fir Abies concolor (Gordon & Glendinning) Lindley ex Hildebrand
12 USDA Forest Service RMRS-GTR-261WWW. 2011.

from these trees but did not include them in our estimates of relative fire extent. While it is likely 

that many of the fires we reconstructed included small patches to extensive areas of high-severity 

fire, we unfortunately could not map the extent of these higher-severity fires because we generally 

could not reconstruct them with annual accuracy.

Spatial Variation in Fire Regimes within Gridded Sites

At each site, we graphically compared fire frequency at each plot to elevation, forest type, and an 

index of soil moisture at that plot—the topographic relative moisture index (TRMI; Parker 1982). 

This index of soil moisture is the sum of indices of four slope parameters that we measured in the 

field: aspect, slope, topographic position, and slope configuration. Our measure of fire frequency 

was the number of fire dates we reconstructed from fire scars and cohorts of trees from 1650 to 1900.

Non-Gridded Sites

In addition to the 14 gridded sites, we report fire history from five sites in Utah. We sampled two 

of these sites on grids in a manner similar to that used for the gridded sites but including only a few 

plots (Ray Mesa [RAY] and INC). At the remaining three sites, we only sampled fire-scarred trees 

(TVP, OWP, and MON). All tree-ring samples collected at these sites were sanded and crossdated, 

as previously described for the gridded sites.

The East Tavaputs Plateau (TVP) is approximately 24 miles southwest of BCL in woodland 

dominated by ponderosa pine and pinyon-juniper with scattered Douglas-fir. We sampled this site 

because it was one of the few locations on the Tavaputs Plateau with the concentration of firescarred trees that we needed for our regional study of the climate drivers of fire (Brown and others 

2008a). We sampled 19 fire-scarred trees (15 ponderosa pine and 4 Douglas-fir) over an area of 

approximately 10 acres.

Ray Mesa (RAY) is located on the south side of the La Sal Mountains. The site is dominated by 

sagebrush meadows and pinyon-juniper woodlands and forests. We intended to sample a grid of 

plots in this area but did not find a suitable location. Instead, we sampled four plots in a manner similar to that used for the gridded sites to provide information for a project that was being conducted 

by the Bureau of Land Management. The ponderosa pine we sampled occurred mainly in drainages 

or rocky areas on the mesa. In four plots spread over 15 acres, we sampled 118 trees for recruitment dates and 11 trees for fire scars. We also removed partial cross sections from eight targeted 

fire-scarred ponderosa pine trees over an area of 4 acres, approximately 2.5 miles east of the plots.

Indian Creek (INC) is dominated by ponderosa pine, mixed conifer, aspen, and curlleaf mountain 

mahogany and is approximately 14 miles north of RBC. Similar to RAY, we intended to sample a 

grid of plots in this area but were not able to find a suitable environmental gradient over which to 

sample. Instead, we sampled six plots over 624 acres in a manner similar to that used for the gridded sites. We sampled 82 trees for recruitment dates and 15 trees for fire scars. We also sampled 21 

fire-scarred trees that we encountered between plots.

Old Woman Plateau (OWP) is a relatively flat mesa bounded by steep canyons and cliffs to the 

east, north, and south and is dominated by ponderosa pine. We searched a portion of the mesa for 

trees with multiple fire scars and removed partial cross sections from 17 ponderosa pine trees over 

an area of 49 acres. Similar to TVP, we collected fire-scarred trees from this site for use in our analysis of the regional climate drivers of fire (Brown and others 2008a).

Monroe Mountain (MON) was sampled in a previous study conducted by the Fishlake National 

Forest (Chappell 1997). Fire-scarred and recruitment-date sections were removed from approximately 40 trees at approximately 16 locations. We were able to crossdate fire-scarred sections from 

10 of these trees (6 ponderosa pine, 2 Douglas-fir, 1 quaking aspen, and 1 Colorado pinyon). The 

trees are spread along an approximately 35-mile north-south transect (in areas 2, 3, 5, 11, 15, 22, and 

23, sampled by Chappell [1997]) but we lack exact locations for the individual trees.

Results and Discussion

Our fire and forest history tree-ring collection from Utah and eastern Nevada is the largest of its 

type from a single region for a single study. We sampled over 11,000 trees and were able to crossdate 

samples from more than 9000 of them. In this section, we briefly describe several overall aspects of 
USDA Forest Service RMRS-GTR-261WWW. 2011. 13

these data and briefly review studies from which we inferred some of the causes of regional variation. In Appendices A through S, we provide details of the fire and forest histories we reconstructed 

for each site.

Many of our plots had evidence of a range of fire severities through time, but it is also likely that 

individual fires were of mixed severity across space, as has been documented elsewhere for modern 

fires (Lentile and others 2005). For example, at BRO we found evidence of a widespread fire in 1871 

in the form of fire scars in 15 of the 16 cells that were recording that year (fig. H-7). We also identified nine cohorts with initial recruitment dates between 1871 and 1879, two of which occurred in 

plots that lacked fire scars in 1871. It is likely that these cohorts established in response to the same 

fire that created the scars. However, this site is unusual among our sites in that it had relatively few 

low-severity fires. At other sites, low-severity fires were generally more frequent, so a given cohort 

may have established in response to one of several low-severity fires.

It is challenging to reconstruct fire severity from tree rings. Our ability to identify cohorts of 

trees is limited by the accuracy with which we can reconstruct recruitment dates. Even though our 

fire-scar dates are annually accurate and we can date each tree ring on our recruitment samples to 

the correct calendar year, we cannot obtain annually accurate fire years from recruitment dates alone 

because there may have been climate driven delays in post-fire establishment. These inaccuracies 

interact with our rules for identifying cohorts and, thus, it is likely that we failed to identify some 

cohorts. Furthermore, we assumed that all of the cohorts we identified established in response to fire, 

but it is likely that some of these cohorts established after trees were killed by other disturbances 

such as insect outbreaks, wind, drought, or interactions among these factors (Brown 2006; DeRose 

and Long 2007; Kulakowski and Veblen 2002).

We were unable to assign fire severity to some of our plots (6 percent), but this does not imply 

that they necessarily lacked fire during the period of record. In fact, we found a few fire scars in 

some of these plots and others were surrounded by plots that sustained fire in the past. For example, 

the tree-ring evidence from plot BRO 14E (fig. R-1) did not meet our criteria for any category of 

fire severity. However, in most of the surrounding plots we reconstructed between one and four fire 

dates from both fire scars and cohorts. Given that the earliest recruitment date in plot BRO 14E post 

dates fire dates from most of the surrounding plots (fig. R-7), it is likely that this plot sustained a 

high-severity fire in the recent past.

We obtained death dates for 1121 trees, many of which occurred on or before 1900 (87 percent), 

but we were surprised that we were able to associate only a few of these death dates with highseverity fires based on our criterion of five or more trees dying in the same year. We suggest that 

trees died as a result of factors other than fire.

It was also challenging to estimate tree density and fire extent. Our estimates of tree density are 

conservative. We probably underestimated tree density in 1900 because some trees may have established before 1900 but had died and been consumed by fire or rot since then and because we were 

able to obtain pith dates for only 71 percent of the trees that occurred in our plots. In addition, our 

estimates of modern tree density did not include very small trees because the estimates were made 

only from trees that were at least 8 inches DBH when sampled. Another challenge to determining 

modern tree density was that the number of years it took for trees that were ≥8 inches DBH to reach 

sampling height (4 to 6 inches) likely varied both within and among our sites. For example, trees at 

the relatively mesic WCH site that were 8 to 9 inches DBH when sampled were recruited between 

1782 and 1959, whereas trees of the same size at the relatively dry WAH site were recruited between 

1243 and 1893, indicating that growth was generally slower at the dry WAH site. We estimated the 

extent of low-severity fires within our sites but did not capture the full distribution of relative fire 

extents that burned the landscape in the past. Many of the low-severity fires we reconstructed intersected the site boundary so the full extent of these fires was not reconstructed. For example, from 

1650 to 1900 at BMC, most fire years (74 percent) burned in at least one cell on the boundary of the 

site (fig. F-12).

The season during which a fire burns can have ecological consequences for forest structure or 

understory composition (Harrington 1993; Kerns and others 2006; Knapp and others 2009). We 

report the intra-ring position of fire scars that could be used to infer the seasonal timing of past fires, 

but such inferences require data on the phenology of cambial growth, in other words, the seasonal 

timing of radial growth. Unfortunately, very little is known about cambial phenology in this region. 

In the future, we may be able to estimate the seasonal timing of past fires using the results of phenology studies that are now underway.
14 USDA Forest Service RMRS-GTR-261WWW. 2011.

We present details of the spatial and temporal variation we found at our sites in appendices to 

this report, but we have inferred the causes of that variation in three other studies so far. First, we 

used fire-scar dates from 18 of the sites reported here (all except BCL) in an analysis of the climate 

drivers of regional-fire years between 1630 and 1900 (Brown and others 2008a). We found that 

years when fires were widespread across the region (31 years with fire at ≥20 percent of sites) had 

drier than average summers, whereas years with no fires at any site (100 years) were wetter than 

average. In addition, prior wet summers were associated with regional fire years in mixed-conifer 

and ponderosa pine forest types, possibly by increasing fine fuel amount and continuity, but prior 

wet summers were not associated with regional-fire years in spruce-fir or pinyon-juniper forests. We 

also found associations between fire and El Niño-Southern Oscillation (ENSO). Regional-fire years 

tended to occur during La Niña years when dry conditions prevailed across most of the study area, 

whereas non-fire years tended to occur during El Niño years when wet conditions prevailed across 

most of the study area. However, while dry conditions were associated with ponderosa pine and 

mixed-conifer forests throughout the study area, ENSO forcing was seen only in southeastern sites, 

which supports a hypothesis that a geographic pivot line in Pacific Basin teleconnections occurs at 

approximately latitude 40 ̊ N.

Second, Kitchen (2010) used fire chronologies from six new sites in combination with fire histories from four of our gridded sites (BMC, INC, RBC, and WAH) to explore in greater detail three 

aspects of historical fire patterns in the eastern Great Basin. First, using fire-scar data from four sites, 

he evaluated the competing risks for over- and under-estimation of point mean fire interval using 

individual-tree and composite fire chronologies. He recommended estimating mean fire interval 

from multiple-tree chronologies derived from sample areas of approximately 1.2 acres for heterogeneous landscapes. He also suggested that a correction factor be applied to mean fire intervals 

calculated from single-tree chronologies. Second, he found that the climate drivers of fire at 10 sites 

scattered just south of latitude 40 ̊ N were similar to those found in our broader study (Brown and 

others 2008a). Years of widespread fire were drier than average, whereas years with no fires were 

wetter than average. Widespread fires were more likely to occur in La Niña years and just after wetto-dry transitions in multi-year precipitation oscillations. Local fire years occurred under a broad 

range of conditions. Kitchen (2010) cited a bimodal seasonality pattern as evidence of the influence of Native American ignitions on the fire regime. Third, spatial and temporal variation in the 

frequency, severity, and size of fires and tree recruitment patterns were explored for two sites. Point 

mean fire interval varied 10-fold within sites demonstrating strong topographic control of the fire 

regime. Surface fire was predominant at upper-elevation sub-alpine stands; however, intervals were 

longer than at lower-elevation mixed-conifer stands. Most fires were small and together accounted 

for only a minor proportion of area burned. Recruitment pulses varied spatially from stand to landscape scales and were often synchronous with fire-quiescent periods, consistent with the notion of a 

dynamic mixed-severity fire regime especially at mid-elevations.

Third, Swetnam and Brown (2010) compared vegetation characteristics derived through simulation modeling for use in fire regime condition class (FRCC; Hann and Bunnell 2001; Hardy and 

others 2001; Schmidt and others 2002) and LANDFIRE with those we reconstructed from tree rings 

at 11 of our gridded sites (WCH, MUR, WUN, UFR, WAH, INC, BOM, RBC, HNR, ABM, and 

PSG). First, the BpS categories assigned to plots did not differ significantly from the composition of 

the plot in 1880 that was derived from tree rings for ponderosa pine, aspen, and mixed-conifer BpS, 

but they did differ significantly for spruce-fir, pinyon-juniper, and lodgepole pine BpS. Second, 

LANDFIRE map data were approximately 58 percent accurate for BpS and approximately 60 percent accurate for EVT. These results suggest that the reference condition definitions used in FRCC 

assessments could be improved by additional sampling to determine the relationship of tree age to 

size. Additionally, more empirical data are needed to better parameterize FRCC vegetation models, 

especially in low-frequency fire types.

Management Implications

The site specific data we report here are important for managing fire and forests, especially at the 

broad spatial and temporal scales we present. While the fire and forest histories we report provide 

a foundation for management, many other factors are critical to determining actual management 

actions and desired conditions (Allen and others 2002; Hood and Miller 2007; Keeley and others 
USDA Forest Service RMRS-GTR-261WWW. 2011. 15

2009). Restoring the regimes we reconstructed may not be feasible if it would conflict with other 

objectives such as reducing invasive species. Nonetheless, quantitative data on fire and forest history provides a baseline for identifying recent changes that are unusual and perhaps incompatible 

with protecting specific species or habitats (Keeley and others 2009). These data are still valuable 

in the face of changing climate (Fulé 2008). The Forest Service’s recent directive “Ecological restoration and resilience” (Interim Directive No. 2020-2010-1; March 3, 2010; http://www.fs.fed.us/

im/directives/fsm/2000/id_2020-2010-1.doc) recognizes that “Ecosystems are dynamic and change 

is inevitable,” and that “Knowledge of past and current ecosystem dynamics, current and desired 

conditions, climate change projections, and human uses is fundamental to planning restoration activities.” The data we present here can also be used as reference dynamics for process-centered 

restoration (Falk 2006).

For More Information

Our fire-scar and tree-recruitment dates and associated metadata are available from the 

International Multiproxy Paleofire Database (IMPD), a permanent, public archive maintained by 

the Paleoclimatology Program of the National Oceanic and Atmospheric Administration in Boulder, 

Colorado (http://www.ncdc.noaa.gov/paleo/impd/paleofire.html). The wood samples we collected 

are permanently archived and their current location(s) are provided in the metadata that are archived 

at the IMPD.

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USDA Forest Service RMRS-GTR-261WWW. 2011. 19

Appendix A. Henry Mountains, Bureau of Land 

Management (HNR)

Topography

We sampled 30 plots over 2280 acres near Willow and Dugout Creeks on the west side of Mount 

Ellen, Kanab Field Office, Bureau of Land Management, in Garfield County, Utah (figs. 1 and A-1). 

The plots were separated by 0.29 miles on average (range 0.22 to 0.33 miles) and averaged 0.95 

acres in area (range 0.14 to 2.13 acres). Plots were sampled within cells that averaged 63 acres and 

ranged from 52 to 74 acres. Plots ranged in elevation from 7892 to 10,289 ft (fig. A-2). They ranged 

in slope from 5 to 64 percent, but all except one plot had slopes less than 50 percent. The plots were 

sampled on a range of aspects, but most were on south or west aspects (83 percent). The distribution of the plots by elevation or aspect did not differ from the distribution of the landscape by more 

than 10 percent in any category except for gentle and moderate slopes, which were under and over 

sampled, respectively (fig. A-2). We took four photographs each at 12 of the plots.

Tree Demography

Of the 868 trees that occurred in the plots, most (97 percent) were Utah juniper, Colorado pinyon, 

ponderosa pine, Douglas-fir, quaking aspen, or limber pine, but 10 subalpine fir and 13 Engelmann 

spruce trees also occurred (fig. A-3). Most of these trees were living (94 percent) and the rest were 

snags (3 percent) or logs (3 percent). We were able to remove and crossdate wood samples from 

most of these trees (626 trees or 72 percent) and obtained actual or estimated pith dates for 621 of 

them. These pith dates ranged from 1325 to 1972, but many post-dated 1900 (296 trees; fig. A-4). 

The death dates we obtained for one snag and one log were 1961 and 1900, respectively.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (sagebrush, pinyon-juniper, 

ponderosa pine, mixed conifer, aspen, and spruce-fir; table A-1). Some plots changed forest type 

between 1860 and 2000: three sagebrush and one ponderosa pine plot converted to mixed conifer. 

In 1900, tree density averaged 18 trees per acre and ranged from 0 to 79 trees per acre (fig. A-5). In 

2000, tree density averaged 50 trees per acre and ranged from 13 to 218 trees per acre. However, we 

likely underestimated historical tree density because we could not obtain recruitment or earliest-ring 

dates for 242 of the 868 trees that occurred in the plots and only an earliest-ring date for another 

5 trees.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 18 trees. Only 3 of these trees 

were sampled in 2 of the 30 plots at this site. We sampled the 15 other fire-scarred trees as we 

encountered them between plots over 1057 acres throughout the site (fig. A-6). Most of the 18 firescarred trees were ponderosa pine (89 percent), and the rest were limber pine. Most were living 

(67 percent) and the rest were snags or stumps. These 18 trees yielded 97 fire scars and 7 eroded 

fire scars or abrupt changes in ring width (figs. A-4 and A-7), none of which was recorded on only 

a single tree. We were able to assign an intra-ring position to 94 percent of the 77 fire scars that occurred during the analysis period (1650 to 1900). Of the scars that occurred on ponderosa pine trees, 

most (62 percent) occurred on the boundary between two rings (fig. A-8).
20 USDA Forest Service RMRS-GTR-261WWW. 2011.

Post-Fire Cohorts

We identified 12 cohorts of trees from estimated recruitment dates at 11 of the plots. Six of these 

cohorts were recruited before 1900 (1626 to 1853) and were identified from 39 trees (5 to 8 trees per 

cohort), about half of which were ponderosa pine (49 percent) and the rest were Colorado pinyon 

(18 percent), Engelmann spruce (15 percent), Douglas-fir (13 percent) or limber pine (5 percent; 

figs. A-4 and A-7). The cohorts recruited before 1900 occurred in plots with a range of forest types: 

ponderosa pine (50 percent of cohorts), spruce-fir (17 percent), and mixed conifer (17 percent), and 

pinyon-juniper (17 percent).

Spatial Variation in Fire Regimes

We reconstructed too few fire intervals in plots during the analysis period (1650 to 1900) to compute plot-composite fire intervals by forest type at this site. The tree-ring record before 1900 was 

less than 100 years long for 6 of the 30 plots at this site (fig. A-9).

We inferred that five pinyon-juniper plots did not sustain fire over the period of record (table 

A-2). Two plots were not historically forested, and we could not infer historical fire severity at two 

others because they did not meet our requirements for any of the severity categories. We assigned 

the remaining plots to the mixed or high fire severity categories.

From 1650 to 1900, the 22 low-severity fires we reconstructed within our 2280-acre sampling 

area averaged 109 acres and ranged from 59 to 195 acres (fig. A-10), equivalent to 24 to 100 percent 

of the recording area (in other words, the combined area of cells containing recording, fire-scarred 

trees during a given year). Recording area varied among fire years, ranging from 121 to 374 acres. 

We likely underestimated the extent of low-severity fires because most fires intersected the boundary of the site (fig. A-11).

Table A-2—Distribution of plots at HNR by historical forest type (1860; table 2) and fire severity 

(table 3).

Assumed Assumed Assumed Not historically

Forest type High high Mixed mixed no fire forested Unclassified

Spruce-fir 1

Aspen 2

Mixed conifer 1 4

Ponderosa pine 3 7 1 1

Pinyon-juniper 1 5 1

Sagebrush 2 1

Total 1 2 5 13 5 2 2

Table A-1—Distribution of plots at HNR by historical (1860) and modern (2000) forest types 

(table 2).

Modern forest type (2000)

Historical forest Spruce- Mixed Ponderosa Pinyon- Total plots

type (1860) fir Aspen conifer pine juniper in 1860

Spruce-fir 1 1

Aspen 2 2

Mixed conifer 5 5

Ponderosa pine 1 11 12

Pinyon-juniper 7 7

Sagebrush 3 3

Total plots in 2000 1 2 9 11 7 30
USDA Forest Service RMRS-GTR-261WWW. 2011. 21

Figure A-1—Locations of plots and crossdated fire-scarred trees that were sampled outside plots. 

Two of the fire-scarred trees were sampled within plots and are not mapped individually. Plots are 

identified by column and row, in other words, the northwestern most plot is 3C, the next plot to the 

east is 3D, and so forth.

Figure A-2—Distribution of 

sampled plots and land 

area at HNR by topography. 

Aspect classes are 90o wide, 

beginning with 46o for east 

(E). Land area was derived 

from a digital elevation 

model (Utah AGRC 2004).

Figure A-3—Distribution by 

species of the 868 live and 

dead trees ≥8 inches DBH 

that occurred in plots at HNR, 

regardless of whether or not 

we removed wood samples 

and crossdated them. Not 

shown are 10 subalpine fir and 

13 Engelmann spruce trees.

C D E F G H I J K

3

4

5

6

7

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

none (no trees 8 inches DBH)

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles

Dugout Creek

Willow Creek

7900

10900

9900

8900
22 USDA Forest Service RMRS-GTR-261WWW. 2011.

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

(a) fire scars and cohorts composited at plots

aspen

ponderosa pine

mixed conifer

spruce-fir

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

sagebrush

pinyon-juniper

(e) Colorado pinyon

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

number of trees recruite

d

0

10

20

(d) ponderosa pine

0

10

20

(c) Douglas-fir

0

10

20

year

(b) limber pine

0

10

20

30

Figure A-4—Chronologies of fire and tree recruitment at HNR. In (a), horizontal lines are plotcomposite fire-scar and cohort dates by forest type. Non-recorder years precede the first scar, 

whereas recorder years generally follow it, but non-recorder years can also occur when the catface 

margin is consumed by subsequent fires or rot. In (b) through (e), recruitment dates are given 

for species comprising ≥10 percent of trees with such dates. The latter part of the distribution is 

incomplete because we only cored trees that were ≥8 inches DBH. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 23

density (trees/acre)

0 100 200 300 400 500

forest type

sagebrush

pinyon-juniper

ponderosa pine

mixed conifer

aspen

spruce-fir

0 100 200 300 400 500

(a) 1900 (b) 2000

Figure A-5—Density of trees ≥8 inches DBH that were alive at each plot at HNR (a) in 1900 and (b) in 

2000, by forest type (table 2).

fire scars on trees sampled between plots

ponderosa pine

tree

species

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

year

Figure A-6—Chronology of low-severity fires recorded on the 15 trees sampled between plots, over 

approximately 1057 acres at HNR.
24 USDA Forest Service RMRS-GTR-261WWW. 2011.

03C

high

03G

mixed

03H

mixed

03I

assumed

mixed

03J

assumed

mixed

03K

mixed

04C

unclassified

04D

assumed

mixed

04E

unclassified

04F

mixed

04H

not

historically

forested

05E

not

historically

forested

05F

assumed

mixed

05D

assumed

no fire

04K

assumed

mixed

04I

assumed

mixed

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

year

quaking aspen Douglas-fir

Engelmann spruce ponderosa pine

subalpine fir limber pine

Utah juniper Colorado pinyon

fire scar cohort HNR

inner date pith date

outer date bark date

recorder years non-recorder years

Figure A-7—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies of 

tree demography (recruitment and death), fire scars, and cohorts at each plot. Bark dates on four 

stumps are shown as outer dates. Inferred fire severity (table 3) is indicated to the left of each 

panel. Plot 6G is not shown because it contained only quaking aspen with center rot from which 

we could not obtain recruitment dates.
USDA Forest Service RMRS-GTR-261WWW. 2011. 25

06F

assumed

mixed

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

07F

assumed

mixed

07E

assumed

no fire

07D

assumed

no fire

07C

assumed

no fire

1500 1600 1700 1800 1900 2000

year

1500 1600 1700 1800 1900 2000

year

06C

assumed

no fire

05K

assumed

mixed

06E

assumed

mixed

06D

assumed

mixed

05J

assumed

mixed

05I

assumed

high

05H

mixed

05G

assumed

mixed

quaking aspen Douglas-fir

Engelmann spruce ponderosa pine

subalpine fir limber pine

Utah juniper Colorado pinyon

fire scar cohort HNR

inner date pith date

outer date bark date

recorder years non-recorder years

Figure A-8—Intra-ring position of fire scars 

sampled in and between plots at HNR 

from 1650 to 1900, as a percentage 

of the number of scars for which the 

position could be determined (given in 

parentheses). Not shown is the intraring position for one fire scar on a 

limber pine tree.

Figure A-7—Continued.
26 USDA Forest Service RMRS-GTR-261WWW. 2011.

number of fire years

(1650 to 1900)

024

topographic relative

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

forest type

sagebrush

pinyon-juniper

ponderosa pine

mixed conifer

aspen

spruce-fir

100 or more years

fewer than 100 years

length of record

Figure A-9—Variation in fire among 

plots at HNR with topography, 

forest type, and relative soil 

moisture availability (Parker 1982). 

Number of fire years includes both 

fire-scar and cohort dates. Plots 

with no reconstructed fires during 

this period fall on the dotted line.

Figure A-10—Relative extent of 

low-severity fires within the 

2280-acre HNR site from 1650 

to 1900, as area (top) and as a 

percentage of the recording area 

(in other words, the combined 

area of cells containing 

recording, fire-scarred trees 

during each year; bottom). 

Commonly used fire-size classes 

are indicated at the top (NWCG 

2007).
USDA Forest Service RMRS-GTR-261WWW. 2011. 27

Figure A-11—Maps of years with evidence of low-severity fires in three or more cells at HNR. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped.
28 USDA Forest Service RMRS-GTR-261WWW. 2011.

Appendix B. Wah Wah Mountains, Bureau of Land 

Management (WAH)

Topography

We sampled 24 plots over 1593 acres near Lawson Cove Canyon, Fillmore Field Office, Bureau 

of Land Management in Millard County, Utah (figs. 1 and B-1). The plots were separated by 0.29 

miles on average (range 0.16 to 0.36 miles) and averaged 0.43 acres in area (range 0.21 to 1.11 acres). 

Plots were sampled within cells that averaged 61 acres and ranged from 32 to 70 acres. Plots ranged 

in elevation from 7197 to 8806 ft (fig. B-2) and ranged in slope from 12 to 58 percent. They were 

sampled on a range of aspects, but most were on north or east aspects (83 percent). The distribution of the plots by elevation, aspect, or slope did not differ from the distribution of the landscape 

by more than 10 percent in any category except north and east aspects, which were over and under 

sampled, respectively (fig. B-2). We took between one and four photographs each at 22 of the plots.

Tree Demography

Of the 730 trees that occurred in the plots, all were Utah juniper, singleleaf pinyon, Rocky 

Mountain juniper, ponderosa pine, white fir, Douglas-fir, or Great Basin bristlecone pine, except 

3 trees we could not identify (fig. B-3). Most of these trees were living (74 percent) and the rest were 

snags (9 percent), logs (16 percent), or stumps (1 percent). We were able to remove and crossdate 

wood samples from most of these trees (610 trees or 84 percent) and obtained actual or estimated 

pith dates for 576 of them. These pith dates ranged from 558 to 1893 (fig. B-4). The death dates we 

obtained for 98 logs and snags ranged from 1419 to 2003.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (pinyon-juniper, mixed conifer, 

and limber-bristlecone; table B-1). One limber-bristlecone plot converted to mixed conifer between 

1860 and 2000. In 1900, tree density averaged 61 trees per acre and ranged from 22 to 112 trees per 

acre (fig. B-5). In 2000, tree density averaged 61 trees per acre and ranged from 21 to 112 trees per 

acre. However, we likely underestimated historical tree density because we could not obtain recruitment or earliest-ring dates for 120 of the 730 trees that occurred in the plots and only an earliest-ring 

date for another 34 trees.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 129 trees, 4 of which had only 

scars that were recorded on a single tree and so were excluded from further analyses. Of the remaining 125 trees, about half (65 trees) were sampled in 19 of the 24 plots at this site (1 to 14 trees per 

plot, average 3 trees). We sampled the 60 other fire-scarred trees as we encountered them between 

plots over 1163 acres throughout the site (fig. B-6). Most of the 125 fire-scarred trees were ponderosa pine (74 percent) and the rest were Great Basin bristlecone pine, white fir, singleleaf pinyon, 

Utah juniper, and Rocky Mountain juniper. Most were snags, logs, and stumps (66 percent) and 

the rest were live trees. These 125 trees yielded 369 fire scars and 79 eroded fire scars or abrupt 

changes in ring width (figs. B-4 and B-7). However, four of these scar dates were eliminated from 

further analyses because they were recorded on only a single tree at the site. We were able to assign 

an intra-ring position to 87 percent of the 271 fire scars that occurred during the analysis period 

(1650 to 1900). Of the scars that occurred on ponderosa pine trees, half (52 percent) occurred on the 

boundary between two rings (fig. B-8).
USDA Forest Service RMRS-GTR-261WWW. 2011. 29

Post-Fire Cohorts

We identified eight cohorts of trees from estimated recruitment dates at eight of the plots. All 8 

cohorts were recruited before 1900 (1527 to 1786) and were identified from 56 trees (5 to 11 trees 

per cohort), most of which were white fir (66 percent), ponderosa pine (16 percent), and Utah juniper (11 percent) with a few Douglas-fir and singleleaf pinyon trees (figs. B-4 and B-7). Most of 

the cohorts occurred in plots of the mixed conifer forest type (88 percent of cohorts) with the rest 

occurring in pinyon-juniper plots (12 percent).

Spatial Variation in Fire Regimes

During the analysis period (1650 to 1900), plot-composite low-severity fire intervals that were 

pooled among mixed conifer plots averaged 20 years (range 2 to 86 years; fig. B-9). The tree-ring 

record before 1900 was longer than 100 years for all 24 plots at this site (fig. B-10).

We inferred that one pinyon-juniper plot did not sustain fire over the period of record (table B-2). 

We could not infer historical fire severity at four plots because they did not meet our requirements 

for any of the severity categories. We assigned the remaining plots to the low, mixed, or high fire 

severity categories.

From 1650 to 1900, the 50 low-severity fires we reconstructed within our 1593-acre sampling 

area averaged 172 acres and ranged from 61 to 604 acres (fig. B-11), equivalent to 5 to 53 percent 

of the recording area (in other words, the combined area of cells containing recording, fire-scarred 

trees during a given year). Recording area varied among fire years, ranging from 845 to 1279 acres. 

We likely underestimated the extent of low-severity fires because most fires intersected the boundary of the site (fig. B-12).

Table B-2—Distribution of plots at WAH by historical forest type (1860; table 2) and fire 

severity (table 3).

Assumed Assumed Assumed

Forest type high Mixed mixed Low no fire Unclassified

Limber-bristlecone 1

Mixed conifer 5 7 1 3 1

Pinyon-juniper 1 1 1 3

Total 5 8 1 5 1 4

Table B-1—Distribution of plots at WAH by historical (1860) and modern (2000) 

forest types (table 2).

Modern forest type (2000)

Historical forest 

type (1860) Mixed conifer Pinyon-juniper Total plots in 1860

Limber-bristlecone 1 1

Mixed conifer 17 17

Pinyon-juniper 6 6

Total plots in 2000 18 6 24
30 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure B-1—Locations of plots and 

crossdated fire-scarred trees that 

were sampled outside of plots. 

About half of the fire-scarred 

trees were sampled within plots 

and are not mapped individually. 

Plots are identified by column 

and row, in other words, the 

northwestern most plot is 2A, the 

next plot to the east is 2B, and 

so forth.

Figure B-2—Distribution of 

sampled plots and land area 

at WAH by topography. 

Aspect classes are 90o wide, 

beginning with 46o for east 

(E). Land area was derived 

from a digital elevation 

model (Utah AGRC 2004). 

One percent of the land area 

was below 7000 ft and is not 

shown here.

A B C D E

2

3

4

5

6

7

8

9

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

too hazardous to sample

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles Lawson CoveCanyon

6900

7900

6900

6900
USDA Forest Service RMRS-GTR-261WWW. 2011. 31

percentage of trees

occurring at plots

0 10 20 30 40 50

tree species

Utah juniper

singleleaf pinyon

Rocky Mountain juniper

ponderosa pine

white fir

Douglas-fir

Great Basin bristlecone

mixed conifer

limberbristlecone

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

pinyon-juniper

(a) fire scars and cohorts composited at plots

1200 1300 1400 1500 1600 1700 1800 1900 2000

(b) white fir

0

10

20

(d) singleleaf pinyon

year

1200 1300 1400 1500 1600 1700 1800 1900 2000

0

10

(c) ponderosa pine

number of trees recruite

d

0

10

Figure B-3—Distribution by 

species of the 730 live and 

dead trees ≥8 inches DBH 

that occurred in plots at 

WAH, regardless of whether 

or not we removed wood 

samples and crossdated 

them. Not shown are three 

trees of unknown species.

Figure B-4—Chronologies of fire and tree recruitment at WAH. In (a), horizontal lines are plotcomposite fire-scar and cohort dates by forest type. Non-recorder years precede the first scar, 

whereas recorder years generally follow it, but non-recorder years can also occur when the catface 

margin is consumed by subsequent fires or rot. In (b) through (d), recruitment dates are given 

for species comprising ≥10 percent of trees with such dates. The latter part of the distribution is 

incomplete because we only cored trees that were ≥8 inches DBH.
32 USDA Forest Service RMRS-GTR-261WWW. 2011.

density (trees/acre)

0 100 200 300 400 500

forest type

pinyon-juniper

mixed conifer

limber-bristlecone

0 100 200 300 400 500

(a) 1900 (b) 2000

Figure B-6—Chronology of low-severity fires recorded on the 60 trees sampled between plots over 

approximately 1163 acres at WAH.

Figure B-5—Density of trees ≥8 inches DBH that were alive at each plot at WAH (a) in 1900 and (b) in 

2000, by forest type (table 2).

fire scars on trees sampled between plots

ponderosa pine

tree

species

year

1200 1300 1400 1500 1600 1700 1800 1900 2000

juniper

singleleaf pinyon

white fir

Great Basin

bristlecone pine

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date
USDA Forest Service RMRS-GTR-261WWW. 2011. 33

02A

unclassified

02C

unclassified

03A

mixed

03B

mixed

03C

low

04A

low

04B

mixed

04D

assumed

no fire

04E

mixed

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

06A

mixed

05D

unclassified

05C

assumed

high

05B

low

05A

mixed

1500 1600 1700 1800 1900 2000

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years WAH

1500 1600 1700 1800 1900 2000

year

Douglas-fir ponderosa pine

white fir single-leaf pinyon

Great Basin bristlecone pine

Rocky Mountain or Utah juniper

Figure B-7—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies of 

tree demography (recruitment and death), fire scars, and cohorts at each plot. Bark dates on 20 

stumps are shown as outer dates. Not shown are 60 fire-scarred trees sampled between plots. 

Inferred fire severity (table 3) is indicated to the left of each panel. Most of the trees (60 percent) in 

the combined Rocky Mountain and Utah juniper category are Utah juniper.
34 USDA Forest Service RMRS-GTR-261WWW. 2011.

09X

assumed

high

09B

assumed

mixed

08B

low

07E

mixed

07D

mixed

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

1500 1600 1700 1800 1900 2000

year

07C

low

07B

assumed

high

06D

assumed

high

06C

assumed

high

06B

unclassified

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years WAH

Douglas-fir ponderosa pine

white fir single-leaf pinyon

Great Basin bristlecone pine

Rocky Mountain or Utah juniper

Figure B-7—Continued.

Figure B-8—Intra-ring position of fire 

scars sampled in and between plots 

at WAH from 1650 to 1900, as a 

percentage of the number of scars 

for which the position could be 

determined (given in parentheses). 

Not shown are intra-ring positions 

for 18 fire scars on Utah juniper, 

singleleaf pinyon, Rocky Mountain 

juniper, white fir, and Great Basin 

bristlecone pine trees.
USDA Forest Service RMRS-GTR-261WWW. 2011. 35 forest type

pinyon-juniper

mixed conifer limber-bristlecone

number of fire years

(1650 to 1900)

0 5 10 15 20

topographic relative

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure B-9—Plot-composite 

intervals between low-severity 

fires in mixed conifer plots 

at WAH from 1650 to 1900. 

Plots averaged 0.43 acres. 

The box (top panel) encloses 

the 25th to 75th percentiles 

and the whiskers enclose the 

10th to 90th percentiles of the 

distribution of intervals. The 

vertical line indicates the median 

fire interval, and all values 

falling outside the 10th to 90th 

percentiles are shown as circles. 

In the histogram (bottom panel), 

the same intervals are plotted in 

10-year bins (1 to 10 years, 11 to 

20 years, and so forth).

Figure B-10—Variation in fire among 

plots at WAH with topography, 

forest type, and relative soil 

moisture availability (Parker 1982). 

Number of fire years includes both 

fire-scar and cohort dates. Plots 

with no reconstructed fires during 

this period fall on the dotted line.

6 mixed conifer plots (27 intervals)

fire interval (years)

number of intervals

0 20 40 60 80 100

0

5

10
36 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure B-11—Relative extent of 

low-severity fires within the 

1593-acre WAH site, from 

1650 to 1900, as area (top) 

and as a percentage of the 

recording area (in other words, 

the combined area of cells 

containing recording, firescarred trees during each year; 

bottom). Commonly used firesize classes are indicated at the 

top (NWCG 2007).
USDA Forest Service RMRS-GTR-261WWW. 2011. 37

Figure B-12—Maps of years with evidence of low-severity fires in three or more cells at WAH. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped.
38 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure B-12—Continued.
USDA Forest Service RMRS-GTR-261WWW. 2011. 39

Figure B-12—Continued.
40 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure B-12—Continued.
USDA Forest Service RMRS-GTR-261WWW. 2011. 41

Figure B-12—Continued.
42 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure B-12—Continued.
USDA Forest Service RMRS-GTR-261WWW. 2011. 43

Figure B-12—Continued.
44 USDA Forest Service RMRS-GTR-261WWW. 2011.

Appendix C. Book Cliffs, Bureau of Land Management 

(BCL)

Topography

We sampled 29 plots over 1788 acres near Pine Spring and Hideout Creeks, Vernal Field Office, 

Bureau of Land Management in Uintah County, Utah (figs. 1 and C-1). The plots were separated 

by 0.30 miles on average (range 0.25 to 0.31 miles) and averaged 0.36 acres in area (range 0.15 to 

1.01 acres). Plots were sampled within cells that averaged 62 acres and ranged from 56 to 72 acres. 

Plots ranged in elevation from 6957 to 7357 ft (fig. C-2). They ranged in slope from 0 to 71 percent, but all except two plots had slopes less than 50 percent. The plots were sampled on a range of 

aspects. The distribution of the plots by elevation, aspect, or slope differed from the distribution of 

the landscape by more than 10 percent only for north and south aspects, which were over and under 

sampled, respectively (fig. C-2). We took between two and four photographs each at 10 of the plots.

Tree Demography

All of the 883 trees that occurred in the plots were Utah juniper, Colorado pinyon, Rocky Mountain 

juniper, ponderosa pine, or Douglas-fir, except 2 trees that we could not identify (fig. C-3). Most 

of these trees were living (73 percent) and the rest were snags (14 percent), logs (12 percent), or 

stumps (1 percent). We were able to remove and crossdate wood samples from most of these trees 

(707 trees or 80 percent) and we obtained actual or estimated pith dates for 616 of them. These pith 

dates ranged from 1220 to 1978, including 30 trees that post-dated 1900 (fig. C-4). The death dates 

we obtained for 100 logs and snags ranged from 1660 to 2004.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (pinyon-juniper, ponderosa 

pine, and mixed conifer; table C-1). Some plots changed forest type between 1860 and 2000: one 

pinyon-juniper and one ponderosa pine plot converted to mixed conifer plots. In 1900, tree density 

averaged 74 trees per acre and ranged from 15 to 147 trees per acre (fig. C-5). In 2000, tree density 

averaged 81 trees per acre and ranged from 24 to 166 trees per acre. However, we likely underestimated historical tree density because we could not obtain recruitment or earliest-ring dates for 176 

of the 883 trees that occurred in the plots and only an earliest-ring date for another 91 trees. Three 

of these trees had earliest-ring dates between 1901 and 1920 and therefore may have been living 

before 1900.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 20 trees, 9 of which had only 

scars that were recorded on a single tree and so were excluded from further analyses. Of the remaining 11 trees, 5 were sampled in 4 of the 29 plots at this site. We sampled the six other fire-scarred 

trees as we encountered them between plots, over 245 acres at the north end of the site (fig. C-6). 

Most of the 11 fire-scarred trees were ponderosa pine (82 percent) and the rest were Douglas-fir 

trees. Nearly half were logs or snags (45 percent) and the rest were live trees. These 11 trees yielded 

23 fire scars (figs. C-4 and C-7). However, 11 of these scar dates were eliminated from further analyses because they were recorded on only a single tree at the site. Only two of these scars occurred 

during the analysis period (1650 to 1900) and we were not able to assign an intra-ring position to 

either of them.
USDA Forest Service RMRS-GTR-261WWW. 2011. 45

Post-Fire Cohorts

We identified six cohorts of trees from estimated recruitment dates at six of the plots. All of the 

cohorts were recruited before 1900 (1532 to 1728) and were identified from 34 trees (5 to 8 trees per 

cohort), all of which were Utah juniper (47 percent), Colorado pinyon (38 percent), or Douglas-fir 

(15 percent; figs. C-4 and C-7). The cohorts recruited before 1900 occurred in plots with one of two 

forest types: pinyon-juniper (88 percent of cohorts) and mixed conifer (17 percent).

Spatial Variation in Fire Regimes

We reconstructed only a single low-severity fire during analysis period (1650 to 1900) and so did 

not compute plot-composite fire intervals by forest type at this site. This fire occurred in 1759 and 

was 122 acres in extent, equivalent to 48 percent of the recording area. All the plots at this site had 

a record longer than 100 years (fig. C-8).

We inferred that half of the plots at this site did not sustain fire over the period of record, including 14 pinyon-juniper plots and 1 mixed conifer plot (table C-2). We could not infer historical fire 

severity at two plots because they did not meet our requirements for any of the severity categories. 

We assigned the remaining plots to the mixed or high fire severity categories.

From 1650 to 1900, we reconstructed only a single low-severity fire within our 1788-acre 

site that was 122 acres in extent, equivalent to 48 percent of the 252-acre recording area (in other 

words, the combined area of cells containing recording, fire-scarred trees during a given year). We 

likely underestimated the extent of this low-severity fire because it intersected the boundary of the 

site (fig. C-9).

Table C-2—Distribution of plots at BCL by historical forest type (1860; table 2) and fire 

severity (table 3).

Forest type High Mixed Assumed mixed Assumed no fire Unclassified

Mixed conifer 1 5 1 2

Ponderosa pine 1

Pinyon-juniper 2 3 14

Total 2 4 6 15 2

Table C-1—Distribution of plots at BCL by historical (1860) and modern 

(2000) forest types (table 2).

Modern forest type (2000)

Historical forest 

type (1860) Mixed conifer Pinyon-juniper Total plots in 1860

Mixed conifer 9 9

Ponderosa pine 1 1

Pinyon-juniper 2 17 19

Total plots in 2000 12 17 29
46 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure C-1—Locations of plots and crossdated fire-scarred trees that were sampled outside plots. 

About half of the fire-scarred trees were sampled within plots and are not mapped individually. 

Plots are identified by column and row, in other words, the northeastern most plot is 10I, the next 

plot to the west is 10H, and so forth.

Figure C-2—Distribution of 

sampled plots and land area 

at BCL by topography. Aspect 

classes are 90o wide, beginning 

with 46o for east (E). Land area 

was derived from a digital 

elevation model (Utah AGRC 

2004). Nineteen percent of the 

land area and 24 percent of 

the plots were sampled below 

7000 ft and are not shown 

here.

C D E F G H I

10

11

12

13

14

15

Evidence from crossdated trees:

recruitment dates

fire scars

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles

Dugout Canyon

Pine Spring Canyon

Hideout Canyon

6900

6900

6900
USDA Forest Service RMRS-GTR-261WWW. 2011. 47

percentage of trees

occurring at plots

0 10 20 30 40 50 60

tree species

Utah juniper

Colorado pinyon

Rocky Mountain juniper

ponderosa pine

Douglas-fir

ponderosa pine

mixed conifer

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

pinyon-juniper

(a) fire scars and cohorts composited at plots

1200 1300 1400 1500 1600 1700 1800 1900 2000

(d) Utah juniper

year

number

1200 1300 1400 1500 1600 1700 1800 1900 2000

of trees recruite

d

0

10

(c) Colorado pinyon

0

10

(b) Douglas-fir

0

10

Figure C-4—Chronologies of fire and tree recruitment at BCL. In (a), horizontal lines are plotcomposite fire-scar and cohort dates by forest type. Non-recorder years precede the first scar, 

whereas recorder years generally follow it, but non-recorder years can also occur when the 

catface margin is consumed by subsequent fires or rot. In (b) through (d), recruitment dates are 

given for species comprising ≥10 percent of trees with such dates. The latter part of the distribution 

is incomplete because we only cored trees that were ≥8 inches DBH.

Figure C-3—Distribution by species 

of the 883 live and dead trees 

≥8 inches DBH that occurred 

in plots at BCL, regardless of 

whether or not we removed 

wood samples and crossdated 

them. Not shown are two trees of 

unknown species.
48 USDA Forest Service RMRS-GTR-261WWW. 2011.

density (trees/acre)

0 100 200 300 400 500

forest type

pinyon-juniper

ponderosa pine

mixed conifer

0 100 200 300 400 500

(a) 1900 (b) 2000

ponderosa pine

tree

species fire scars on trees sampled between plots

Douglas-fir

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

1200 1300 1400 1500 1600 1700 1800 1900 2000

year

Figure C-5—Density of trees ≥8 inches DBH that were alive at each plot at BCL (a) in 1900 and (b) in 

2000, by forest type (table 2).

Figure C-6—Chronology of low-severity fires recorded on the six trees sampled between plots over 

approximately 245 acres in the eastern portion of the BCL site.
USDA Forest Service RMRS-GTR-261WWW. 2011. 49

10G

unclassified

10H

assumed

no fire

10I

high

11E

assumed

no fire

11F

assumed

mixed

11G

assumed

no fire

11H

assumed

no fire

11I

assumed

no fire

12D

mixed

1500 1600 1700 1800 1900 2000

12F

assumed

mixed

12G

high

12H

assumed

mixed

12I

assumed

mixed

13D

assumed

mixed

13E

unclassified

12E

mixed

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year 1500 1600 1700 1800 1900 2000 year

Douglas-fir ponderosa pine

Colorado pinyon

Rocky Mountain or Utah juniper

BCL

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

Figure C-7—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies of 

tree demography (recruitment and death), fire scars, and cohorts at each plot. Bark dates on 13 

stumps are shown as outer dates. Not shown are six fire-scarred trees sampled between plots. 

Inferred fire severity (table 3) is indicated to the left of each panel. Most of the trees (84 percent) in 

the combined Rocky Mountain and Utah juniper category are Utah juniper.
50 USDA Forest Service RMRS-GTR-261WWW. 2011.

13I

assumed

no fire

14D

assumed

no fire

14C

assumed

no fire

14E

assumed

no fire

14F

assumed

no fire

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

14G

assumed

no fire

14H

assumed

no fire

15D

mixed

15E

mixed

15F

assumed

no fire

1500 1600 1700 1800 1900 2000

year

13G

assumed

no fire

13H

assumed

mixed

13F

assumed

no fire

Douglas-fir ponderosa pine

Colorado pinyon

Rocky Mountain or Utah juniper

BCL

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

Figure C-7—Continued.
USDA Forest Service RMRS-GTR-261WWW. 2011. 51 forest type

pinyon-juniper

ponderosa pine mixed conifer

number of fire years

(1650 to 1900)

-1 012345

topographic relative

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure C-8—Variation in fire among 

plots at BCL with topography, 

forest type, and relative soil 

moisture availability (Parker 

1982). Number of fire years 

includes both fire-scar and 

cohort dates. Plots with no 

reconstructed fires during this 

period fall on the dotted line.
52 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure C-9—Maps of years with evidence of low-severity fires in three or more cells at BLC. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped.
USDA Forest Service RMRS-GTR-261WWW. 2011. 53

Appendix D. East Tavaputs Plateau, Bureau of Land 

Management (TVP)

In 2004, we removed fire-scarred partial cross sections from 19 trees (15 ponderosa pine and 

4 Douglas-fir) over an area of approximately 10 acres on the Tavaputs Plateau, approximately 24 miles southwest of BCL, near Pine Springs Canyon, Vernal Field Office, Bureau of Land 

Management, in Uintah County, Utah (fig. 1). We sampled in woodland dominated by ponderosa 

pine and pinyon-juniper with scattered Douglas-fir. We sampled this site because it was one of the 

few locations on the Tavaputs Plateau where we found a concentration of fire-scarred trees for our 

regional study of the climate drivers of fire (Brown and others 2008a). All but one of these trees 

were dead when sampled. We were able to crossdate samples from 16 of them (12 ponderosa pine 

and 4 Douglas-fir). Three fire years were recorded by fire scars on two or more trees at this site 

(fig. D-1). We were able to assign an intra-ring position to more than half (54 percent) of the fire 

scars, but there were too few of these to report the distribution of scars by this feature (16 on ponderosa pine trees and 5 on Douglas-fir trees).

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

ponderosa pine

tree

species

year

Figure D-1—Chronology of low-severity fires from trees sampled over 10 acres at TVP. Each 

horizontal line indicates the length of record for a single tree. Non-recorder years precede the first 

scar at a plot, whereas recorder years generally follow it. However, non-recorder years also occur 

when the margin of the catface is consumed by subsequent fires or rot.
54 USDA Forest Service RMRS-GTR-261WWW. 2011.

Appendix E. Ray Mesa, Bureau of Land Management (RAY)

Topography

We sampled 4 plots over 15 acres on Ray Mesa, Monticello Field Office, Bureau of Land 

Management in San Juan County, Utah (figs. 1 and E-1). The plots were separated by 0.13 miles on 

average (range 0.08 to 0.27 miles) and averaged 0.40 acres in area (range 0.19 to 0.59 acres. Plots 

ranged in elevation from 7377 to 7475 ft. They ranged in slope from 0 to 10 percent. We did not take 

photographs at this site.

Tree Demography

All of the 118 trees that occurred in the plots were Utah juniper, Colorado pinyon, or ponderosa 

pine (fig. E-2). Most of these trees were living (78 percent) and the rest were snags (6 percent), logs 

(13 percent), or stumps (3 percent). We were able to remove and crossdate wood samples from most 

of these trees (97 trees or 82 percent), and we obtained actual or estimated pith dates for 85 of them. 

These pith dates ranged from 1566 to 1926 and only three of them post-dated 1900 (fig. E-3). The 

death dates we obtained for nine logs and snags ranged from 1795 to 2000.

Historical and Current Forest Structure and Composition

The plots included two historical and modern forest types (pinyon-juniper and ponderosa pine; 

table E-1). No plots changed forest type between 1860 and 2000 at this site. In 1900, tree density 

averaged 64 trees per acre and ranged from 41 to 101 trees per acre (fig. E-4). In 2000, tree density 

averaged 71 trees per acre and ranged from 38 to 133 trees per acre. However, we likely underestimated historical tree density because we could not obtain recruitment or earliest-ring dates for 21 

of the 118 trees that occurred in the plots and only an earliest-ring date for another 12 trees. Five 

of these trees had earliest-ring dates between 1901 and 1920 and therefore may have been living 

before 1900.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 19 trees. Three of these trees 

had only scars that were recorded on a single tree and so were excluded from further analyses. Of the 

remaining 16 trees, 8 were sampled in two of the four plots at this site. The eight other fire-scarred 

trees were sampled over an area of 4 acres, approximately 2.5 miles east of the plots (figs. E-1 and 

E-5). All of the 16 fire-scarred trees were ponderosa pine. Most were logs or stumps (63 percent) 

and the rest were live trees. They yielded 68 fire scars (figs. E-3 and E-6). However, 20 of these 

scar dates were eliminated from further analyses because they were recorded on only a single tree 

at the site. During the analysis period (1650 to 1900), we were able to assign an intra-ring position 

to 51 percent of the 45 fire scars. The fire scars were roughly equally distributed among intra-ring 

positions (fig. E-7).

Post-Fire Cohorts

We identified three cohorts of trees from estimated recruitment dates at two of the plots. All of 

these cohorts were recruited before 1900 (1580 to 1748) and were identified from 19 trees (5 to 9 

trees per cohort), of which half was Colorado pinyon (53 percent) and half was ponderosa pine (47 

percent; figs. E-5 and E-6). The cohorts that were recruited before 1900 occurred in two pinyonjuniper plots and one ponderosa pine plot.
USDA Forest Service RMRS-GTR-261WWW. 2011. 55

Spatial Variation in Fire Regimes

We reconstructed too few fire intervals in plots during the analysis period (1650 to 1900) to 

compute plot-composite fire intervals by forest type at this site (fig. E-8). We assigned two plots 

to the mixed fire severity categories but we could not infer historical fire severity at the other two 

plots because they did not meet our requirements for any of the severity categories (table E-2). We 

sampled too few plots at this site to estimate fire extent.

Table E-2—Distribution of plots at RAY by historical 

forest type (1860; table 2) and fire severity (table 3).

Forest type Mixed Unclassified

Ponderosa pine 1

Pinyon-juniper 1 2

Total 2 2

Table E-1—Distribution of plots at RAY by historical (1860) and 

modern (2000) forest types (table 2).

Modern forest type (2000)

Historical forest 

type (1860) Ponderosa pine Pinyon-juniper Total

Ponderosa pine 1 1

Pinyon-juniper 3 3

Total 1 3 4

Figure E-1—Locations of plots and crossdated fire-scarred trees that were sampled outside of plots. 

Half the fire-scarred trees were sampled within plots and are not mapped individually. Plots at this 

site are identified by numbers only, as indicated on the map.

2

3

4

5

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles

6900
56 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure E-2—Distribution by species 

of the 118 live and dead trees ≥8 

inches DBH that occurred in plots 

at RAY, regardless of whether or 

not we removed wood samples 

and crossdated them.

(a) fire scars and cohorts composited at plots

ponderosa pine

pinyon-juniper

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

(b) Colorado pinyon

0

2

4

6

(c) ponderosa pine

year

1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

n

u

mber of trees recruite

d

0

2

4

Figure E-3—Chronologies of fire and tree recruitment at RAY. In (a), horizontal lines show plotcomposite dates of fire scars and cohorts by forest type. Non-recorder years precede the first scar at 

a plot, whereas recorder years generally follow it, but non-recorder years can also occur when the 

margin of the catface is consumed by subsequent fires or rot. In (b) and (c), recruitment dates are 

given for species comprising ≥10 percent of trees with such dates. Utah juniper is not given beause 

the samples from many trees of this species (10 percent) could not be crossdated. The latter part of 

the distribution is incomplete because we only cored trees that were ≥8 inches DBH.
USDA Forest Service RMRS-GTR-261WWW. 2011. 57

Figure E-4—Density of trees ≥8 inches DBH that were alive at each plot at RAY (a) in 1900 and (b) in 

2000, by forest type (table 2).

fire scars on trees sampled outside plots

ponderosa pine

tree

species

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

Figure E-5—Chronology of low-severity fires recorded on the eight trees sampled between plots over 

4 acres east of the plots at RAY.

density (trees/acre)

0 100 200 300 400 500

forest type

pinyon-juniper

ponderosa pine

0 100 200 300 400 500

(a) 1900 (b) 2000
58 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure E-7—Intra-ring position of fire 

scars on 16 trees sampled in and to 

the east of plots at RAY from 1650 to 

1900, as a percentage of the number 

of scars for which the position could 

be determined (given in parentheses).

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

ponderosa pine

Colorado pinyon

Utah juniper

RAY

2

unclassified

3

mixed

4

unclassified

5

mixed

year

Figure E-6—Fire-demography 

diagrams (FDDs, Brown 

and others 2008b) showing 

chronologies of tree demography 

(recruitment and death), fire 

scars, and cohorts at each plot. 

Bark dates on four stumps are 

shown as outer dates. Not shown 

are eight fire-scarred trees that 

were sampled over 4 acres, 

approximately 2.5 miles east of 

the plots. Inferred fire severity 

(table 3) is indicated to the left of 

each panel.
USDA Forest Service RMRS-GTR-261WWW. 2011. 59

Figure E-8—Maps of years with evidence of low-severity fires in three or more cells at RAY. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped.
60 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure E-8—Continued.
USDA Forest Service RMRS-GTR-261WWW. 2011. 61

Appendix F. Snake Range, Great Basin National Park (BMC)

Topography

We sampled 24 plots over 1569 acres near Mill Creek in Great Basin National Park, White Pine 

County, Nevada (figs. 1 and F-1). The plots were separated by 0.30 miles on average (range 0.27 to 

0.31 miles) and averaged 0.52 acres in area (range 0.10 to 1.18 acres). Plots were sampled within 

cells that averaged 61 acres and ranged from 49 to 75 acres. Plots ranged in elevation from 7757 to 

10,596 ft (fig. F-2) and in slope from 19 to 57 percent. They were sampled on a range of aspects, but 

most were on north or east aspects (96 percent). The distribution of the plots by elevation, aspect, or 

slope differed from the distribution of the landscape by more than 10 percent only for moderate and 

steep slopes, which were over and under sampled, respectively (fig. F-2). We took between three and 

four photographs each at 18 of the plots.

Tree Demography

Of the 674 trees that occurred in the plots, most (99 percent) were singleleaf pinyon, curl-leaf 

mountain mahogany, ponderosa pine, white fir, Douglas-fir, limber pine, or Engelmann spruce, but 

2 Utah juniper and 4 quaking aspen trees also occurred plus 3 trees we could not identify (fig. F-3). 

Most of these trees were living (79 percent) and the rest were snags (11 percent), logs (8 percent), or 

stumps (2 percent). We were able to remove and crossdate wood samples from most of these trees 

(507 trees or 75 percent), and we obtained actual or estimated pith dates for 470 of them. These pith 

dates ranged from 1154 to 1958, but many post-dated 1900 (119 trees; fig. F-4). The death dates we 

obtained for 52 logs and snags ranged from 1689 to 2003.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (sagebrush, shrubland, mountain mahogany, pinyon-juniper, ponderosa pine, mixed conifer, limber-bristlecone, and spruce-fir; 

table F-1). Some plots changed forest type between 1860 and 2000: one sagebrush plot converted 

to mountain mahogany; one sagebrush, one shrubland, and one mountain mahogany plot converted 

to pinyon-juniper; and two sagebrush, one mountain mahogany, and one ponderosa pine plot converted to mixed conifer. In 1900, tree density averaged 63 trees per acre and ranged from 0 to 

242 trees per acre (fig. F-5). In 2000, tree density averaged 75 trees per acre and ranged from 5 to 

235 trees per acre. However, we likely underestimated historical tree density because we could not 

obtain recruitment or earliest-ring dates for 167 of the 674 trees that occurred in the plots and only 

an earliest-ring date for another 37 trees.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 110 trees, 7 of which had only 

scars that were recorded on a single tree and so were excluded from further analyses. Of the remaining 103 trees, 67 were sampled in 13 of the 24 plots at this site (1 to 16 trees per plot, average 

5 trees). We sampled the 36 other fire-scarred trees as we encountered them between plots, over 

614 acres throughout the site (fig. F-6). Most of the 103 fire-scarred trees were limber pine (45 percent) or ponderosa pine (30 percent) and the rest were white fir, Douglas-fir, singleleaf pinyon, and 

trees of unknown species. Most were live trees (59 percent) and the rest were logs, snags, or stumps. 

These 103 trees yielded 372 fire scars and 55 eroded fire scars or abrupt changes in ring width (figs. 

F-4 and F-7). However, 10 of the scar dates and 1 of the non-scar dates were eliminated from further 

analyses because they were recorded on only a single tree at the site. We were able to assign an intraring position to 79 percent of the 321 fire scars that occurred during the analysis period (1650 to 
62 USDA Forest Service RMRS-GTR-261WWW. 2011.

1900). Of the scars that occurred on ponderosa pine, Douglas-fir, and limber pine trees, many (39, 

44, and 51 percent, respectively) occurred on the boundary between two rings (fig. F-8).

Post-Fire Cohorts

We identified 12 cohorts of trees from estimated recruitment dates at 12 of the plots. Nine of 

these cohorts were recruited before 1900 (1643 to 1826) and were identified from 64 trees (5 to 

15 trees per cohort), which were ponderosa pine (23 percent), white fir (23 percent), singleleaf pinyon (22 percent), limber pine (16 percent), Douglas-fir (13 percent), and a few Engelmann spruce 

(figs. F-4 and F-7). The cohorts that were recruited before 1900 occurred in plots with a range of historical forest types: mixed conifer (56 percent of cohorts), pinyon-juniper (22 percent), ponderosa 

pine (11 percent), and spruce-fir (11 percent).

Spatial Variation in Fire Regimes

During the analysis period (1650 to 1900), plot-composite, low-severity fire intervals averaged 

11 years (range 2 to 22 years) when pooled among ponderosa pine plots and averaged 19 years 

(range 1 to 62 years; fig. F-9) when pooled among mixed conifer plots. The tree-ring record before 

1900 was less than 100 years long for 7 of the 24 plots at this site (fig. F-10).

Three plots were not historically forested and we could not infer historical fire severity at four 

others because they did not meet our requirements for any of the severity categories (table F-2). We 

assigned the remaining plots to the low, mixed, or high fire severity categories.

From 1650 to 1900, the 50 low-severity fires we reconstructed within our 1569-acre sampling 

area averaged 146 acres and ranged from 59 to 370 acres (fig. F-11), equivalent to 6 to 37 percent 

of the recording area (in other words, the combined area of cells containing recording, fire-scarred 

trees during a given year). Recording area varied among fire years, ranging from 619 to 990 acres. 

We likely underestimated the extent of low-severity fires because most fires intersected the boundary of the site (fig. F-12).

Table F-1—Distribution of plots at BMC by historical (1860) and modern (2000) forest types (table 2).

Modern forest type (2000)

Historical forest Spruce- Limber- Mixed Pinyon- Mountain Total plots

type (1860) fir bristlecone conifer juniper mahogany in 1860

Spruce-fir 1 1

Limber-bristlecone 4 4

Mixed conifer 8 8

Ponderosa pine 1 1

Pinyon-juniper 2 2

Mountain mahogany 1 1 1 3

Shrubland 1 1

Sagebrush 2 1 1 4

Total plots in 2000 1 4 12 5 2 24
USDA Forest Service RMRS-GTR-261WWW. 2011. 63

Table F-2—Distribution of plots at BMC by historical forest type (1860; table 2) and fire severity (table 3).

Assumed Assumed Not historically

Forest type High high Mixed mixed Low forested Unclassified

Spruce-fir 1

Limber-bristlecone 1 3

Mixed conifer 1 2 4 1

Ponderosa pine 1

Pinyon-juniper 2

Mountain mahogany 1 2

Shrubland 1

Sagebrush 3 1

Total 1 2 8 2 4 3 4

Figure F-1—Locations of plots and crossdated fire-scarred trees that were sampled outside of plots. 

More than half of the fire-scarred trees were sampled within plots and are not mapped individually. 

Plots are identified by column and row, in other words, the northwestern most plot is 11C, the next 

plot to the east is 11D, and so forth. 

C D E F G H I J

11

12

13

14

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

none (no trees 8 inches DBH)

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles

Mill Creek

8900

7900

9900

10900
64 USDA Forest Service RMRS-GTR-261WWW. 2011.

percentage of trees

occurring at plots

0 5 10 15 20 25 30 35

tree species

singleleaf pinyon

mountain mahagony

ponderosa pine

white fir

Douglas-fir

limber pine

Engelmann spruce

(a) fire scars and cohorts composited at plots

mountain

mahogany

ponderosa pine

mixed conifer

spruce-fir

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

sagebrush

limberbristlecone

shrubland

pinyon-juniper

1400 1500 1600 1700 1800 1900 2000

(b) limber pine

number of trees recruite

d

0

10

(d) white fir

0

10

(c) Douglas-fir

0

10

(e) singleleaf pinyon

year

1400 1500 1600 1700 1800 1900 2000

0

10

Figure F-2—Distribution of sampled plots and land area 

at BMC by topography. Aspect classes are 90o wide, 

beginning with 46o for east (E). Land area was derived 

from a digital elevation model (Utah AGRC 2004). 

Figure F-3—Distribution by species of the 674 live and 

dead trees ≥8 inches DBH that occurred in plots at 

BMC, regardless of whether or not we removed wood 

samples and crossdated them. Not shown are two 

Utah juniper and four quaking aspen trees plus three 

trees of unknown species. 

Figure F-4—Chronologies of fire and tree recruitment at BMC. In (a), horizontal lines are plot-composite fire-scar 

and cohort dates by forest type. Non-recorder years precede the first scar, whereas recorder years generally 

follow it, but non-recorder years can also occur when the catface margin is consumed by subsequent fires or 

rot. In (b) through (e), recruitment dates are given for species comprising ≥10 percent of trees with such dates. 

The latter part of the distribution is incomplete because we only cored trees that were ≥8 inches DBH. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 65

density (trees/acre)

0 100 200 300 400 500

forest type

sagebrush

shrubland

mountain mahogany

pinyon-juniper

ponderosa pine

mixed conifer

limber-bristlecone

spruce-fir

0 100 200 300 400 500

(a) 1900 (b) 2000

Figure F-5—Density of trees ≥8 inches DBH that were alive at each plot at BMC (a) in 1900 and (b) in 

2000, by forest type (table 2). 

fire scars on trees sampled between plots

ponderosa pine

tree

species

unknown

Douglas-fir

limber pine

year

1400 1500 1600 1700 1800 1900 2000

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

Figure F-6—Chronology of low-severity fires recorded on the 36 trees sampled between plots over 

approximately, 614 acres throughout the BMC site. 
66 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure F-7—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies of tree 

demography (recruitment and death), fire scars, and cohorts at each plot. Bark dates on 21 stumps 

are shown as outer dates. Not shown are 36 fire-scarred trees sampled between plots. Inferred 

fire severity (table 3) is indicated to the left of each panel. Most of the trees (92 percent) in the 

combined limber pine and curl-leaf mountain mahogany category are limber pine. 

12I

unclassified

12H

unclassified

12G

not

historically

forested

12F

low

12E

assumed

high

12C

low

11J

mixed

11I

not

historically

forested

11H

not

historically

forested

11E

mixed

11D

mixed

11C

low

12D

assumed

mixed

13C

low

13D

assumed

mixed

13E

mixed

13F

high

12J

mixed

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

year

quaking aspen Douglas-fir

Engelmann spruce ponderosa pine

white fir single-leaf pinyon

limber pine or curl-leaf mountain mahogany

fire scar cohort BMC

inner date pith date

outer date bark date

recorder years non-recorder years
USDA Forest Service RMRS-GTR-261WWW. 2011. 67

14F

assumed

high

14G

mixed

1500 1600 1700 1800 1900 2000

14H

mixed

1500 1600 1700 1800 1900 2000

year

13G

unclassified

13H

mixed

13I

unclassified

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

quaking aspen Douglas-fir

Engelmann spruce ponderosa pine

white fir single-leaf pinyon

limber pine or curl-leaf mountain mahogany

fire scar cohort BMC

inner date pith date

outer date bark date

recorder years non-recorder years

Figure F-7—Continued. 

Figure F-8—Intra-ring position of fire scars 

sampled in and between plots at BMC 

from 1650 to 1900, as a percentage of the 

number of scars for which the position 

could be determined (given in parentheses). 

Not shown are intra-ring positions for 13 

fire scars on singleleaf pinyon, white fir, and 

trees of unknown species. 
68 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure F-9—Plot-composite intervals 

between low-severity fires in mixed 

conifer and ponderosa pine plots 

at BMC from 1650 to 1900. Plots 

averaged 0.52 acres. The boxes (top 

panels for each forest type) enclose 

the 25th to 75th percentiles and the 

whiskers enclose the 10th to 90th

percentiles of the distribution of 

intervals. The vertical lines indicate 

the median fire interval, and all 

values falling outside the 10th

to 90th percentiles are shown as 

circles. In the histogram (bottom 

panels for each forest type), the 

same intervals are plotted in 10-

year bins (1 to 10 years, 11 to 20 

years, and so forth). 

1 ponderosa pine plot (20 intervals)

fire interval (years)

number of intervals

0 20 40 60 80 100

0

5

10

4 mixed conifer plots (27 intervals)

fire interval (years)

number of intervals

0 20 40 60 80 100

0

5

10
USDA Forest Service RMRS-GTR-261WWW. 2011. 69 forest type

sagebrush

shrubland

mahogany

pinyon-juniper

ponderosa pine

mixed conifer

limber-bristlecone

spruce-fir

number of fire years

(1650 to 1900)

0 5 10 15 20 25

topographic relativ

e

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure F-10—Variation in fire among 

plots at BMC with topography, 

forest type, and relative soil 

moisture availability (Parker 1982). 

Number of fire years includes both 

fire-scar and cohort dates. Plots 

with no reconstructed fires during 

this period fall on the dotted line.

Figure F-11—Relative extent of lowseverity fires within the 1569-acre 

BMC site, from 1650 to 1900, as 

area (top) and as a percentage of the 

recording area (in other words, the 

combined area of cells containing 

recording fire-scarred trees during 

each year; bottom). Commonly used 

fire-size classes are indicated at the 

top (NWCG 2007).
70 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure F-12—Maps of years with evidence of low-severity fires in three or more cells at BMC. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 71

Figure F-12—Continued. 
72 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure F-12—Continued. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 73

Figure F-12—Continued. 
74 USDA Forest Service RMRS-GTR-261WWW. 2011.

Appendix G. Paunsaugunt Plateau, Dixie National Forest 

(PSG)

Topography

We sampled 29 plots over 2262 acres in Meadow and Pipeline Canyons on the Powell Ranger 

District of the Dixie National Forest in Kane County, Utah (figs. 1 and G-1). The plots were separated by 0.30 miles on average (range 0.23 to 0.33 miles) and averaged 0.69 acres in area (range 

0.24 to 3.09 acres). Plots were sampled within cells that averaged 62 acres and ranged from 52 to 

68 acres. Plots ranged in elevation from 7571 to 8972 ft (fig. G-2) and in slope from 4 to 75 percent. 

They were sampled on a range of aspects, but most were on south or east aspects (72 percent). The 

distribution of the plots by elevation, aspect, or slope differed from the distribution of the landscape 

by more than 10 percent only for moderate slopes, which were under sampled (fig. G-2). We took 

between three and four photographs each at five of the plots.

Tree Demography

Of the 844 trees that occurred in the plots, most (99 percent) were Utah juniper, Rocky Mountain 

juniper, ponderosa pine, white fir, Douglas-fir, quaking aspen, limber pine, or Engelmann spruce, 

but 9 Colorado pinyon trees also occurred plus 1 tree we could not identify (fig. G-3). Most of these 

trees were living (87 percent) and the rest were snags (6 percent), logs (2 percent), or stumps (5 percent). We were able to remove and crossdate wood samples from most of these trees (661 trees or 

78 percent), and we obtained actual or estimated pith dates for 654 of them. These pith dates ranged 

from 1418 to 1974, but more than half of these post-dated 1900 (383 trees; fig. G-4). The death dates 

we obtained for 32 logs and snags ranged from 1939 to 2003.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (shrubland, pinyon-juniper, ponderosa pine, mixed conifer, aspen, and spruce-fir; table G-1). Nearly half the plots changed forest 

type between 1900 and 2000: nine shrubland, five ponderosa pine, and two aspen plots converted to 

mixed conifer. In 1900, tree density averaged 20 trees per acre and ranged from 0 to 81 trees per acre 

(fig. G-5). In 2000, tree density averaged 53 trees per acre and ranged from 6 to 121 trees per acre. 

However, we likely underestimated historical tree density because we could not obtain recruitment or 

earliest-ring dates for 183 of the 844 trees that occurred in the plots and only an earliest-ring date for 

another 7 trees. One of these had an earliest-ring date between 1901 and 1920 and therefore may have 

been living before 1900.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 52 trees, 6 of which had only 

scars that were recorded on a single tree and so were excluded from further analyses. Of the remaining 46 trees, about 18 were sampled in 11 of the 29 plots at this site (1 to 3 trees per plot). 

We sampled the 28 other fire-scarred trees as we encountered them between plots over 1126 acres 

throughout the site (fig. G-6). Most of the 46 fire-scarred trees were ponderosa pine (76 percent) and 

the rest were Douglas-fir, limber pine, white fir, and Engelmann spruce. Most were logs, snags, or 

stumps (67 percent) and the rest were live trees. These 46 trees yielded 147 fire scars and 11 eroded 

fire scars or abrupt changes in ring width (figs. G-4 and G-7). However, six of these scar dates were 

eliminated from further analyses because they were recorded on only a single tree at the site. We 

were able to assign an intra-ring position to 81 percent of the 134 fire scars that occurred during the 
USDA Forest Service RMRS-GTR-261WWW. 2011. 75

analysis period (1650 to 1900). Of the scars that occurred on ponderosa pine trees, over half (62 percent) occurred on the boundary between two rings (fig. G-8).

Post-Fire Cohorts

We identified 16 cohorts of trees from estimated recruitment dates at 15 of the plots. Eight 

of these cohorts were recruited before 1900 (1809 to 1897) and were identified from 58 trees (5 

to 15 trees per cohort) composed of white fir (41 percent), ponderosa pine (24 percent), Rocky 

Mountain juniper (13 percent), limber pine (10 percent), and Douglas-fir (10 percent; figs. G-4 and 

G-7). The cohorts recruited before 1900 occurred in plots with a range of forest types: mixed conifer 

(38 percent of cohorts), aspen (25 percent), shrubland (25 percent), and ponderosa pine (13 percent).

Spatial Variation in Fire Regimes

We reconstructed too few fire intervals in plots during the analysis period (1650 to 1900) to compute plot-composite fire intervals by forest type at this site. The tree-ring record before 1900 was 

less than 100 years long for 12 of the 29 plots (fig. G-9).

We inferred that one shrubland plot did not sustain fire over the period of record (table G-2). 

Four plots were not historically forested, and we could not infer historical fire severity at four others because they did not meet our requirements for any of the severity categories. We assigned the 

remaining plots to the low, mixed, or high fire severity categories.

From 1650 to 1900, the 26 low-severity fires we reconstructed within our 2262-acre sampling 

area averaged 213 acres and ranged from 62 to 743 acres (fig. G-10), equivalent to 8 to 74 percent 

of the recording area (in other words, the combined area of cells containing recording, fire-scarred 

trees during a given year). Recording area varied among fire years, ranging from 244 to 1001 acres. 

We likely underestimated the extent of low-severity fires because most fires intersected the boundary of the site (fig. G-11).

Table G-2—Distribution of plots at PSG by historical forest type (1860; table 2) and fire severity (table 3).

Assumed Assumed Assumed Not historically

Forest type High high Mixed mixed Low no fire forested Unclassified

Spruce-fir 2

Aspen 2

Mixed conifer 1 1 2 3 1

Ponderosa pine 1 2 2 1 1

Pinyon-juniper 1

Shrubland 2 1 1 3 2

Total 3 3 5 6 3 1 4 4

Table G-1—Distribution of plots at PSG by historical (1860) and modern (2000) 

forest types (table 2).

Modern forest type (2000)

Historical forest Spruce- Mixed Ponderosa Pinyon- Total plots

type (1860) fir conifer pine juniper in 1860

Spruce-fir 2 2

Aspen 2 2

Mixed conifer 8 8

Ponderosa pine 5 2 7

Pinyon-juniper 1 1

Shrubland 9 9

Total plots in 2000 2 24 2 1 29
76 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure G-1—Locations of plots 

and crossdated fire-scarred 

trees that were sampled outside 

of plots. About one-third of 

the fire-scarred trees were 

sampled within plots and 

are not mapped individually. 

Plots are identified by column 

and row, in other words, the 

northwestern most plot is 3C, 

the next plot to the east is 3D, 

and so forth. 

Figure G-2—Distribution of 

sampled plots and land 

area at PSG by topography. 

Aspect classes are 90o wide, 

beginning with 46o for east 

(E). Land area was derived 

from a digital elevation model 

(Utah AGRC 2004). 

B H C D E F G

3

4

5

6

7

8

9

Meadow Canyon

Pipeline Canyon

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

none (no trees 8 inches DBH)

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles

7900

7900

8900

8900

8900
USDA Forest Service RMRS-GTR-261WWW. 2011. 77

percentage of trees

occurring at plots

0 10 20 30 40 50

tree species

Utah juniper

Rocky Mountain juniper

ponderosa pine

white fir

Douglas-fir

quaking aspen

limber pine

Engelmann spruce

aspen

ponderosa pine

mixed conifer

spruce-fir

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

shrubland

pinyon-juniper

(a) fire scars and cohorts composited at plots

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

(b) Douglas-fir

0

25

50

(d) ponderosa pine

year

number

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

of trees recruite

d

0

25

(c) white fir

0

25

Figure G-3—Distribution by species 

of the 844 live and dead trees ≥8 

inches DBH that occurred in plots 

at PSG, regardless of whether or 

not we removed wood samples and 

crossdated them. Not shown are 

nine Colorado pinyon trees plus 

one tree of unknown species. 

Figure G-4—Chronologies of fire and tree recruitment at PSG. In (a), horizontal lines are plotcomposite fire-scar and cohort dates by forest type. Non-recorder years precede the first scar, 

whereas recorder years generally follow it, but non-recorder years can also occur when the catface 

margin is consumed by subsequent fires or rot. In (b) through (d), recruitment dates are given 

for species comprising ≥10 percent of trees with such dates. The latter part of the distribution is 

incomplete because we only cored trees that were ≥8 inches DBH. 
78 USDA Forest Service RMRS-GTR-261WWW. 2011.

density (trees/acre)

0 100 200 300 400 500

forest type

shrubland

pinyon-juniper

ponderosa pine

mixed conifer

aspen

spruce-fir

0 100 200 300 400 500

(a) 1900 (b) 2000

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

ponderosa pine

tree

species fire scars on trees sampled between plots

Douglas-fir

limber pine

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

year

Figure G-5—Density of trees ≥8 inches DBH that were alive at each plot at PSG (a) in 1900 and (b) in 

2000, by forest type (table 2). 

Figure G-6—Chronology of low-severity fires recorded on the 28 trees sampled between plots over 

approximately, 1126 acres throughout the PSG site. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 79

03C

assumed

high

03D

assumed

high

03E

high

03F

assumed

mixed

04C

mixed

04D

assumed

mixed

04E

mixed

04F

unclassified 06E

not

historically

forested

06D

not

historically

forested

06C

assumed

high

06B

mixed

05G

assumed

mixed

05F

not

historically

forested

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

year

05C

high

05D

assumed

mixed

05E

assumed

no fire

quaking aspen Douglas-fir

Engelmann spruce ponderosa pine

white fir limber pine

Colorado pinyon

Rocky Mountain or Utah juniper PSG

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

Figure G-7—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies 

of tree demography (recruitment and death), fire scars, and cohorts at each plot. Bark dates on 

34 stumps are shown as outer dates. Not shown are 28 fire-scarred trees sampled between plots. 

Inferred fire severity (table 3) is indicated to the left of each panel. Most of the trees (81 percent) in 

the combined Rocky Mountain and Utah juniper category are Rocky Mountain juniper. 
80 USDA Forest Service RMRS-GTR-261WWW. 2011.

07D

unclassified

08F

mixed

08E

mixed

08D

not

historically

forested

07H

assumed

mixed

08G

high

08H

unclassified

09E

assumed

mixed

07F

unclassified

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

1500 1600 1700 1800 1900 2000

year

07C

low

07B

low

06F

low

quaking aspen Douglas-fir

Engelmann spruce ponderosa pine

white fir limber pine

Colorado pinyon

Rocky Mountain or Utah juniper PSG

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

Figure G-7—Continued. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 81

Figure G-8—Intra-ring position of fire scars 

sampled in and between plots at PSG 

from 1650 to 1900, as a percentage 

of the number of scars for which the 

position could be determined (given in 

parentheses). Not shown are intra-ring 

positions for nine fire scars on white fir, 

Douglas-fir, and limber pine trees. 

forest type

shrubland

pinyon-juniper

ponderosa pine

mixed conifer

aspen

spruce-fir

number of fire years

(1650 to 1900)

0246 8

topographic relative

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure G-9—Variation in fire among 

plots at PSG with topography, 

forest type, and relative soil 

moisture availability (Parker 

1982). Number of fire years 

includes both fire-scar and 

cohort dates. Plots with no 

reconstructed fires during this 

period fall on the dotted line.
82 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure G-10—Relative extent of lowseverity fires within the 2262-acre 

PSG site, from 1650 to 1900, as 

area (top) and as a percentage of the 

recording area (in other words, the 

combined area of cells containing 

recording, fire-scarred trees during 

each year; bottom). Commonly 

used fire-size classes are indicated 

at the top (NWCG 2007). 
USDA Forest Service RMRS-GTR-261WWW. 2011. 83

Figure G-11—Maps of years with evidence of low-severity fires in three or more cells at PSG. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped.
84 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure G-11—Continued.
USDA Forest Service RMRS-GTR-261WWW. 2011. 85

Figure G-11—Continued.
86 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure G-11—Continued.
USDA Forest Service RMRS-GTR-261WWW. 2011. 87

Appendix H. Boulder Mountain, Dixie National Forest 

(BOM)

Topography

We sampled 30 plots over 1963 acres near Spring Creek on the Teasdale Ranger District of 

the Dixie National Forest in Wayne County, Utah (figs. 1 and H-1). The plots were separated by 

0.31 miles on average (range 0.27 to 0.31 miles) and averaged 0.35 acres in area (range 0.08 to 

0.90 acres). Plots were sampled within cells that averaged 65 acres and ranged from 58 to 74 acres. 

Plots ranged in elevation from 7887 to 11,071 ft (fig. H-2) and in slope from 0 to 47 percent. They 

were sampled on a range of aspects, but most were on north and east aspects (77 percent). The distribution of the plots by elevation, aspect, or slope did not differ from the distribution of the landscape 

by more than 10 percent in any category except gentle and moderate slopes, which were under and 

over sampled, respectively (fig. H-2). We took four photographs each at three of the plots.

Tree Demography

All of the 892 trees that occurred in the plots were Utah juniper, Colorado pinyon, Rocky 

Mountain juniper, ponderosa pine, Douglas-fir, quaking aspen, subalpine fir, or Engelmann spruce 

(fig. H-3). Most of these trees were living (75 percent) and the rest were snags (11 percent), logs 

(7 percent), or stumps (8 percent). We were able to remove and crossdate wood samples from most 

of these trees (788 trees or 88 percent), and we obtained actual or estimated pith dates for 696 of 

these. These pith dates ranged from 1346 to 1971 and many of these post-dated 1900 (244 trees; 

fig. H-4). The death dates we obtained for 117 logs and snags ranged from 1510 to 2004.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (pinyon-juniper, ponderosa pine, 

mixed conifer, aspen-mixed conifer, aspen, and spruce-fir; table H-1). Some plots changed forest 

type between 1860 and 2000: one ponderosa pine and two aspen plots converted to aspen-mixed 

conifer. In 1900, tree density averaged 86 trees per acre and ranged from 2 to 290 trees per acre (fig. 

H-5). In 2000, tree density averaged 110 trees per acre and ranged from 19 to 322 trees per acre. 

However, we likely underestimated historical tree density because we could not obtain recruitment 

or earliest-ring dates for 104 of the 892 trees that occurred in the plots and only an earliest-ring date 

for another 92 trees. Twelve of these trees had earliest-ring dates between 1901 and 1920 and therefore may have been living before 1900.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 104 trees, 9 of which had only 

scars that were recorded on a single tree and so were excluded from further analyses. Of the remaining 95 trees, most (68 trees) were sampled in 22 of the 30 plots at this site (1 to 7 trees per plot, 

average 3 trees). We sampled the 27 other fire-scarred trees as we encountered them between plots 

over 1344 acres throughout the site (fig. H-6). Most of the 95 fire-scarred trees were ponderosa pine 

(60 percent) or Engelmann spruce (20 percent) and the rest were Douglas-fir, Colorado pinyon, 

quaking aspen, and Utah juniper. Most were logs, snags or stumps (80 percent) and the rest were live 

trees. These 95 trees yielded 441 fire scars and 3 eroded fire scars or abrupt changes in ring width 

(figs. H-4 and H-7). However, 10 of these scar dates were eliminated from further analyses because 

they were recorded on only a single tree at the site. We were able to assign an intra-ring position to 

60 percent of the 380 fire scars that occurred during the analysis period (1650 to 1900). Of the scars 

that occurred on ponderosa pine trees, many (42 percent) occurred in the early- or middle-earlywood 

(fig. H-8).
88 USDA Forest Service RMRS-GTR-261WWW. 2011.

Post-Fire Cohorts

We identified 19 cohorts of trees from estimated recruitment dates at 17 of the plots. Sixteen of 

these cohorts were recruited before 1900 (1605 to 1875) and were identified from 112 trees (5 to 11 

trees per cohort), most of which were quaking aspen (35 percent), Engelmann spruce (29 percent), 

ponderosa pine (24 percent), or Douglas-fir (6 percent), but there were also a few Utah juniper, 

Colorado pinyon, and Rocky Mountain juniper (figs. H-4 and H-7). The cohorts that were recruited 

before 1900 occurred in plots with a range of forest types: spruce-fir (44 percent of cohorts), pinyonjuniper (6 percent of cohorts) and ponderosa pine, mixed conifer, aspen-mixed conifer, and aspen 

forest types (each 13 percent of cohorts).

Spatial Variation in Fire Regimes

During the analysis period (1650 to 1900), plot-composite, low-severity fire intervals averaged 26 years (range 7 to 26 years) when pooled among pinyon-juniper plots; 16 years (range 1 to 

64 years) when pooled among ponderosa pine plots; 30 years (range 5 to 110 years) when pooled 

among mixed conifer plots; and 13 years (range 3 to 40 years) when pooled among aspen plots 

(fig. H-9). More fires occurred in mixed conifer, ponderosa pine, and pinyon-juniper plots than in 

spruce-fir, aspen, and aspen-mixed conifer plots (fig. H-10). The tree-ring record before 1900 was 

less than 100 years long for 4 of the 30 plots at this site.

We inferred that one ponderosa pine plot did not sustain fire over the period of record (table H-2). 

We could not infer historical fire severity at two plots because they did not meet our requirements 

for any of the severity categories. We assigned the remaining plots to the low, mixed, or high fire 

severity categories.

From 1650 to 1900, the 50 low-severity fires we reconstructed within our 1963-acre sampling 

area averaged 258 acres and ranged from 62 to 795 acres (fig. H-11), equivalent to 5 to 75 percent 

of the recording area (in other words, the combined area of cells containing recording, fire-scarred 

trees during a given year). Recording area varied among fire years, ranging from 784 to 1453 acres. 

We likely underestimated the extent of low-severity fires because most fires intersected the boundary of the site (fig. H-12). 

Table H-1—Distribution of plots at BOM by historical (1860) and modern (2000) forest types (table 2).

Modern forest type (2000)

Historical forest Spruce- Aspen-mixed Mixed Ponderosa Pinyon- Total plots

type (1860) fir Aspen conifer conifer pine juniper in 1860

Spruce-fir 6 6

Aspen 1 2 3

Aspen-mixed conifer 3 3

Mixed conifer 6 6

Ponderosa pine 1 7 8

Pinyon-juniper 4 4

Total plots in 2000 6 1 6 6 7 4 30
USDA Forest Service RMRS-GTR-261WWW. 2011. 89

Table H-2—Distribution of plots at BOM by historical forest type (1860; table 2) and fire severity (table 3).

Assumed Assumed Assumed

Forest type High high Mixed mixed Low no fire Unclassified

Spruce-fir 1 4 1

Aspen 2 1

Aspen-mixed conifer 2 1

Mixed conifer 2 2 2

Ponderosa pine 2 1 4 1

Pinyon-juniper 1 1 2

Total 3 1 11 3 9 1 2

Figure H-2—Distribution of 

sampled plots and land area 

at BOM by topography. 

Aspect classes are 90o wide, 

beginning with 46o for east 

(E). Land area was derived 

from a digital elevation model 

(Utah AGRC 2004). Five 

percent of the land area and 

7 percent of the plots were 

sampled above 11,000 ft and 

are not shown here. 

Figure H-1—Locations of plots and crossdated fire-scarred trees that were sampled outside of plots. 

About three-fourths of the fire-scarred trees were sampled within plots and are not mapped 

individually. Plots are identified by column and row, in other words, the southwestern most plot is 

20A, the next plot to the east is 20B, and so forth. 

A B C D E F G H I J K L M N O

15

16

17

18

19

20 Spring Creek

Fish Creek

Carcass Creek

7900

8900

9900

10900

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles
90 USDA Forest Service RMRS-GTR-261WWW. 2011.

percentage of trees

occurring at plots

0 5 10 15 20 25 30

tree species

Utah juniper

Colorado pinyon

Rocky Mountain juniper

ponderosa pine

Douglas-fir

quaking aspen

Engelmann spruce

aspen

ponderosa pine

mixed conifer

spruce-fir

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

aspenmixed conifer

pinyon-juniper

(a) fire scars and cohorts composited at plots

1400 1500 1600 1700 1800 1900 2000

(b) Engelmann spruce

0

10

20

30

(e) ponderosa pine

0

10

20

(c) quaking aspen

0

10

20

(f) Colorado pinyon

year

1400 1500 1600 1700 1800 1900 2000

number of trees recruite

d

0

10

20

(d) Douglas-fir

0

10

20

30

Figure H-3—Distribution by 

species of the 892 live and 

dead trees ≥8 inches DBH 

that occurred in plots at BOM, 

regardless of whether or not we 

removed wood samples and 

crossdated them. Not shown are 

16 subalpine fir trees. 

Figure H-4—Chronologies of fire and tree recruitment at BOM. In (a), horizontal lines are plotcomposite fire-scar and cohort dates by forest type. Non-recorder years precede the first scar, 

whereas recorder years generally follow it, but non-recorder years can also occur when the catface 

margin is consumed by subsequent fires or rot. In (b) through (f), recruitment dates are given 

for species comprising ≥10 percent of trees with such dates. The latter part of the distribution is 

incomplete because we only cored trees that were ≥8 inches DBH. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 91

density (trees/acre)

0 100 200 300 400 500

forest type

pinyon-juniper

ponderosa pine

mixed conifer

aspen-mixed conifer

aspen

spruce-fir

0 100 200 300 400 500

(a) 1900 (b) 2000

ponderosa pine

tree fire scars on trees sampled between plots species

Engelmann

spruce

Colorado pinyon

Utah juniper

1400 1500 1600 1700 1800 1900 2000

year

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

Figure H-5—Density of trees ≥8 inches DBH that were alive at each plot at BOM (a) in 1900 and 

(b) in 2000, by forest type (table 2). 

Figure H-6—Chronology of low-severity fires recorded on the 27 trees sampled between plots over 

approximately 1344 acres throughout the BOM site. 
92 USDA Forest Service RMRS-GTR-261WWW. 2011.

17L

low

17M

low

17N

unclassified

18C

mixed

18D

low

17K

assumed

mixed

17J

assumed

no fire

17I

mixed

17H

assumed

mixed

17G

low

16O

mixed

16N

unclassified

16M

mixed

15O

low

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

year

quaking aspen Douglas-fir

Engelmann spruce ponderosa pine

subalpine fir Colorado pinyon

Rocky Mountain or Utah juniper BOM

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

Figure H-7—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies 

of tree demography (recruitment and death), fire scars, and cohorts at each plot. Bark dates on 

73 stumps are shown as outer dates. Not shown are 27 fire-scarred trees sampled between plots. 

Inferred fire severity (table 3) is indicated to the left of each panel. Most of the trees (74 percent) in 

the combined Rocky Mountain and Utah juniper category are Utah juniper. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 93

18J

low

18K

low

18L

low

19A

mixed

19B

assumed

high

19C

high

20B

mixed

20A

mixed

19F

high

19E

mixed

19D

mixed

18I

mixed

18H

mixed

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

1500 1600 1700 1800 1900 2000

year

18E

high

18F

low

18G

assumed

mixed

quaking aspen Douglas-fir

Engelmann spruce ponderosa pine

subalpine fir Colorado pinyon

Rocky Mountain or Utah juniper BOM

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

Figure H-7—Continued.
94 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure H-8—Intra-ring position of fire scars 

sampled in and between plots at BOM 

from 1650 to 1900, as a percentage 

of the number of scars for which the 

position could be determined (given in 

parentheses). Not shown are intra-ring 

positions for 36 fire scars on Utah juniper, 

Colorado pinyon, Douglas-fir, aspen, and 

Engelmann spruce trees. 

Figure H-9—Plot-composite intervals 

between low-severity fires by 

forest type at BOM from 1650 to 

1900. Plots averaged 0.35 acres. 

The boxes (top panels for each 

forest type) enclose the 25th to 

75th percentiles and the whiskers 

enclose the 10th to 90th percentiles 

of the distribution of intervals. The 

vertical lines indicate the median 

fire interval, and all values falling 

outside the 10th to 90th percentiles 

are shown as circles. In the 

histogram (bottom panels for each 

forest type), the same intervals are 

plotted in 10-year bins (1 to 10 

years, 11 to 20 years, and so forth).

1 aspen-mixed conifer plot (14 intervals)

0 20 40 60 80 100

number of intervals

0

5

10

4 mixed conifer plots (27 intervals)

0 20 40 60 80 100

number of intervals

0

5

10

5 ponderosa pine plots (61 intervals)

0 20 40 60 80 100

number of intervals

0

10

20

30

2 pinyon-juniper plots (12 intervals)

fire interval (years)

0 20 40 60 80 100

number of intervals 0

2

4
USDA Forest Service RMRS-GTR-261WWW. 2011. 95 forest type

pinyon-juniper

ponderosa pine

mixed conifer

aspen-mixed conifer

aspen

spruce-fir

number of fire years

(1650 to 1900)

0 5 10 15 20 25

topographic relativ

e

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

11000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure H-10—Variation in fire 

among plots at BOM with 

topography, forest type, and 

relative soil moisture availability 

(Parker 1982). Number of fire 

years includes both fire-scar 

and cohort dates. Plots with no 

reconstructed fires during this 

period fall on the dotted line.

Figure H-11—Relative extent of 

low-severity fires within the 

1963-acre BOM site, from 1650 

to 1900, as area (top) and as a 

percentage of the recording area 

(in other words, the combined 

area of cells containing 

recording, fire-scarred trees 

during each year; bottom). 

Commonly used fire-size classes 

are indicated at the top (NWCG 

2007).
96 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure H-12—Maps of years with evidence of low-severity fires in three or more cells at BOM. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped.
USDA Forest Service RMRS-GTR-261WWW. 2011. 97

Figure H-12—Continued. 
98 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure H-12—Continued. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 99

Appendix I. Beaver River, Tushar Mountains, Fishlake 

National Forest (RBC)

Topography

We sampled 44 plots (half again as many plots as we sampled at the other gridded sites) over 2837 

acres along the Beaver River, on the Beaver Ranger District of the Fishlake National Forest in Beaver 

County, Utah (figs. 1 and I-1). The plots were separated by 0.30 miles on average (range 0.27 to 0.33 

miles) and averaged 0.24 acres in area (range 0.07 to 0.82 acres). Plots were sampled within cells that 

averaged 63 acres and ranged from 55 to 76 acres. Plots ranged in elevation from 7732 to 10,091 ft 

and in slope from 2 to 56 percent (fig. I-2). They were sampled on a range of aspects, but most were 

on north and east aspects (70 percent). The distribution of the plots by elevation, aspect, or slope did 

not differ from the distribution of the landscape by more than 10 percent in any category except west 

aspects, which were under sampled (fig. I-2). We took two to four photographs each at 41 of the plots.

Tree Demography

Of the 1332 trees that occurred in the plots, most were ponderosa pine, white fir, Douglas-fir, 

quaking aspen, subalpine fir, or Engelmann spruce, but 5 Rocky Mountain juniper also occurred (fig. 

I-3). Most of these trees were living (77 percent) and the rest were snags (14 percent), logs (8 percent), or stumps (2 percent). We were able to remove and crossdate wood samples from most of these 

trees (913 trees or 69 percent) and we obtained actual or estimated pith dates for 881 of them. These 

pith dates ranged from 1535 to 1955, but many post-dated 1900 (252 trees; fig. I-4). The death dates 

we obtained for 128 logs and snags ranged from 1830 to 2002.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (ponderosa pine, mixed conifer, aspen-mixed conifer, aspen, and spruce-fir; table I-1). Nearly half the plots changed forest type 

between 1860 and 2000: five ponderosa pine and four aspen plots converted to mixed conifer; one 

mixed conifer, five aspen, and four spruce fir plots converted to aspen-mixed conifer; and one aspenmixed conifer plot converted to spruce-fir. In 1900, tree density averaged 82 trees per acre and ranged 

from 0 to 242 trees per acre (fig. I-5). In 2000, tree density averaged 127 trees per acre and ranged 

from 28 to 349 trees per acre. However, we likely underestimated historical tree density because we 

could not obtain recruitment or earliest-ring dates for 419 of the 1332 trees that occurred in the plots 

and only an earliest-ring date for another 32 trees. Five of these trees had earliest-ring dates between 

1901 and 1920 and therefore may have been living before 1900.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 164 trees. We sampled 112 of 

these trees in 24 of the 44 plots at this site (1 to 16 trees per plot, average 5 trees). We sampled the 

52 other fire-scarred trees as we encountered them between plots over 2005 acres throughout the 

site (fig. I-6). Most of the 164 fire-scarred trees were ponderosa pine (41 percent) or Douglas-fir (38 

percent), and the rest were Engelmann spruce, subalpine fir, white fir, quaking aspen, or trees we 

could not identify. Most were logs, snags or stumps (65 percent), and the rest were live trees. These 

164 trees yielded 620 fire scars and 46 eroded fire scars or abrupt changes in ring width (figs. I-4 and 

I-7). However, two of the non-scar dates were eliminated from further analyses because they were 

recorded on only a single tree at the site. We were able to assign an intra-ring position to 69 percent of 

the 568 fire scars that occurred during the analysis period (1650 to 1900). Of the scars that occurred 

on ponderosa pine trees, most (44 percent) occurred in the late-earlywood or latewood. In contrast, 

most of those that occurred on Douglas-fir trees (60 percent) were on the boundary between two 

rings (fig. I-8).
100 USDA Forest Service RMRS-GTR-261WWW. 2011.

Post-Fire Cohorts

We identified 28 cohorts of trees from estimated recruitment dates at 25 of the plots. Twenty-four 

of these cohorts were recruited before 1900 (1619 to 1897) and were identified from 191 trees (5 to 

15 trees per cohort), most of which were quaking aspen (25 percent), Douglas-fir (24 percent), subalpine fir (16 percent), Engelmann spruce (15 percent), or ponderosa pine (12 percent) but included 

a few Rocky Mountain juniper and white fir (figs. I-4 and I-7). The cohorts that were recruited before 1900 occurred in plots with a range of forest types: aspen (33 percent of cohorts), mixed conifer 

(29 percent), spruce-fir (21 percent), and ponderosa pine (17 percent).

Spatial Variation in Fire Regimes

During the analysis period (1650 to 1900), plot-composite, low-severity fire intervals averaged 

12 years (range 1 to 31 years) when pooled among ponderosa pine plots; 34 years (range 2 to 

100 years) when pooled among mixed conifer plots; 18 years (range 7 to 49 years) when pooled 

among aspen-mixed conifer plots; and 32 years (range 4 to 116 years) when pooled among sprucefir plots (fig. I-9). There were more fire years in ponderosa pine and aspen-mixed conifer plots than 

in plots of other forest types (fig. I-10). There were also more fire years in low-elevation plots than 

in high-elevation plots. The tree-ring record before 1900 was less than 100 years long for 19 of the 

44 plots.

We could not infer historical fire severity at one plot because it did not meet our requirements 

for any of the severity categories (table I-2). We assigned the remaining plots to the low, mixed, or 

high fire severity categories.

From 1650 to 1900, the 59 low-severity fires we reconstructed within our 2837-acre sampling 

area averaged 220 acres and ranged from 58 to 1209 acres (fig. I-11), equivalent to 5 to 86 percent 

of the recording area (in other words, the combined area of cells containing recording, fire-scarred 

trees during a given year). Recording area varied among fire years, ranging from 380 to 1419 acres. 

We likely underestimated the extent of low-severity fires because most fires intersected the boundary of the site (fig. I-12).

Table I-1—Distribution of plots at RBC by historical (1860) and modern (2000) forest types (table 2).

Modern forest type (2000)

Historical forest Spruce- Aspen-mixed Mixed Ponderosa Total plots

type (1860) fir Aspen conifer conifer pine in 1860

Spruce-fir 10 4 14

Aspen 1 5 4 10

Aspen-mixed conifer 1 2 3

Mixed conifer 1 10 11

Ponderosa pine 5 1 6

Total plots in 2000 11 1 12 19 1 44

Table I-2—Distribution of plots at RBC by historical forest type (1860; table 2) and fire 

severity (table 3).

Assumed Assumed

Forest type High high Mixed mixed Low Unclassified

Spruce-fir 2 8 3 1

Aspen 5 2 3

Aspen-mixed conifer 2 1

Mixed conifer 1 6 1 2 1

Ponderosa pine 3 3

Total 7 13 15 1 7 1
USDA Forest Service RMRS-GTR-261WWW. 2011. 101

Figure I-1—Locations of plots and crossdated fire-scarred trees that were sampled outside of plots. 

More than half of the fire-scarred trees were sampled within plots and are not mapped individually. 

Plots are identified by column and row, in other words, the northwestern most plot is 9A, the next 

plot to the east is 9B, and so forth. 

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

Willow

Lake

Lower

Kents Lake

Kents

Lake

Birch

Lake

Upper Kents Lake

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles

A B C D E F G H I J K

7900

9900

8900

8900

South Fork Beaver River
102 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure I-2—Distribution of 

sampled plots and land area 

at RBC by topography. Aspect 

classes are 90o wide, beginning 

with 46o for east (E). Land area 

was derived from a digital 

elevation model (Utah AGRC 

2004). 

Figure I-3—Distribution by species 

of the 1332 live and dead trees 

≥8 inches DBH that occurred 

in plots at RBC, regardless of 

whether or not we removed 

wood samples and crossdated 

them. Not shown are five Rocky 

Mountain juniper trees. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 103

(a) fire scars and cohorts composited at plots

aspen

ponderosa pine

mixed conifer

spruce-fir

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

aspenmixed conifer

(b) Engelmann spruce

0

25

50

(d) quaking aspen

0

25

(c) subalpine fir

0

25

(f) white fir

year

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

number of trees recruite

d

0

25

(e) Douglas-fir

0

25

Figure I-4—Chronologies of fire and tree recruitment at RBC. In (a), horizontal lines are plotcomposite fire-scar and cohort dates by forest type. Non-recorder years precede the first scar, 

whereas recorder years generally follow it, but non-recorder years can also occur when the catface 

margin is consumed by subsequent fires or rot. In (b) through (f), recruitment dates are given 

for species comprising ≥10 percent of trees with such dates. The latter part of the distribution is 

incomplete because we only cored trees that were ≥8 inches DBH. 
104 USDA Forest Service RMRS-GTR-261WWW. 2011.

density (trees/acre)

0 100 200 300 400 500

forest type

ponderosa pine

mixed conifer

aspen-mixed conifer

aspen

spruce-fir

0 100 200 300 400 500

(a) 1900 (b) 2000

white fir

tree

species fire scars on trees sampled between plots

ponderosa pine

Douglas-fir

Engelmann

spruce

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

year

Figure I-6—Chronology of low-severity fires recorded on the 52 trees sampled between plots over 

approximately 2005 acres throughout the RBC site. 

Figure I-5—Density of trees ≥8 inche DBH that were alive at each plot at RBC (a) in 1900 and (b) in 

2000, by forest type (table 2). 
USDA Forest Service RMRS-GTR-261WWW. 2011. 105

11D

low

11C

mixed

11B

low

10C

mixed

10B

high

10A

low

09B

low

09A

mixed

12D

assumed

high

12C

mixed

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

13D

unclassified

13E

assumed

high

13F

assumed

mixed

14E

mixed

14F

high

14G

mixed

12E

low

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

quaking aspen Douglas-fir

Engelmann spruce ponderosa pine

subalpine or white fir Rocky Mountain juniper

fire scar cohort RBC

inner date pith date

outer date bark date

recorder years non-recorder years

16F

mixed

15F

high

15G

mixed

15H

assumed

high

Figure I-7—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies of tree demography 

(recruitment and death), fire scars, and cohorts at each plot. Bark dates on 55 stumps are shown as outer dates. Not shown 

are 52 fire-scarred trees sampled between plots. Inferred fire severity (table 3) is indicated to the left of each panel. The 

trees in the combined subalpine/white fir category are evenly divided between those two species. 
106 USDA Forest Service RMRS-GTR-261WWW. 2011.

18I

high

19I

mixed

18J

assumed

high

19H

assumed

high

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

19J

assumed

high

20H

high

20I

assumed

high

22J

assumed

high

22I

assumed

high

21K

mixed

21J

assumed

high

21I

low

20J

assumed

high

1500 1600 1700 1800 1900 2000

year

1500 1600 1700 1800 1900 2000

year

17G

low

17H

mixed

17I

high

18H

mixed

16H

mixed

16G

mixed

23K

high

23J

assumed

high

23I

mixed

22K

assumed

high

Figure I-7—Continued. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 107

Figure I-8—Intra-ring position of fire scars 

sampled in and between plots at RBC 

from 1650 to 1900, as a percentage 

of the number of scars for which the 

position could be determined (given 

in parentheses). Not shown are intraring positions for nine fire scars on 

Engelmann spruce, subalpine fir, white 

fir, and trees of unknown species. 

Figure I-9—Plot-composite intervals between 

low-severity fires by forest type at RBC 

from 1650 to 1900. Plots averaged 

0.24 acres. The boxes (top panels for 

each forest type) enclose the 25th to 75th

percentiles and the whiskers enclose the 

10th to 90th percentiles of the distribution 

of intervals. The vertical lines indicate the 

median fire interval and all values falling 

outside the 10th to 90th percentiles are 

shown as circles. In the histogram (bottom 

panels for each forest type), the same 

intervals are plotted in 10-year bins (1 to 

10 years, 11 to 20 years, and so forth).

3 spruce-fir plots (10 intervals)

0 20 40 60 80 100

number of intervals

0

2

4

1 aspen-mixed conifer plot (11 intervals)

0 20 40 60 80 100

number of intervals

0

2

4

6

7 mixed conifer plots (13 intervals)

0 20 40 60 80 100

number of intervals

0

2

4

6

5 ponderosa pine plots (83 intervals)

fire interval (years)

0 20 40 60 80 100

number of intervals

0

10

20

30

40
108 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure I-11—Relative extent of 

low-severity fires within the 

2837-acre RBC site, from 1650 

to 1900, as area (top) and as a 

percentage of the recording area 

(in other words, the combined 

area of cells containing 

recording, fire-scarred trees 

during each year; bottom). 

Commonly used fire-size classes 

are indicated at the top (NWCG 

2007).

forest type

ponderosa pine

mixed conifer

aspen-mixed conifer

aspen

spruce-fir

number of fire years

(1650 to 1900)

0 5 10 15 20 25 30

topographic relative

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure I-10—Variation in fire 

among plots at RBC with 

topography, forest type, and 

relative soil moisture availability 

(Parker 1982). Number of fire 

years includes both fire-scar 

and cohort dates. Plots with no 

reconstructed fires during this 

period fall on the dotted line.
USDA Forest Service RMRS-GTR-261WWW. 2011. 109

Figure I-12—Maps of years with evidence of low-severity fires in three or more cells at RBC. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped.
110 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure I-12—Continued.
USDA Forest Service RMRS-GTR-261WWW. 2011. 111

Figure I-12—Continued.
112 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure I-12—Continued.
USDA Forest Service RMRS-GTR-261WWW. 2011. 113

Figure I-12—Continued.
114 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure I-12—Continued.
USDA Forest Service RMRS-GTR-261WWW. 2011. 115

Appendix J. Indian Creek, Tushar Mountains, Fishlake 

National Forest (INC)

Topography

We sampled only six plots over 624 acres along Indian Creek, on the Beaver Ranger District 

of the Fishlake National Forest in Beaver County, Utah (figs. 1 and J-1). The plots were separated 

by 0.30 miles on average (range 0.28 to 0.33 miles) and averaged 0.42 acres in area (range 0.22 

to 0.57 acres). Plots were sampled within cells that averaged 104 acres and ranged from 55 to 

167 acres. Plots ranged in elevation from 7752 to 8257 ft. They ranged in slope from 7 to 60 percent 

and were sampled on a range of aspects. There were too few plots to compare with the distribution 

of land area by topography. We took four photographs at each of the six plots.

Tree Demography

Of the 182 trees that occurred in the plots, most (96 percent) were ponderosa pine, white fir, 

Douglas-fir, and quaking aspen, but two Rocky Mountain juniper, one curl-leaf mountain mahogany, and five limber pine also occurred (fig. J-2). Most of these trees were living (84 percent) and 

the rest were snags (5 percent), logs (3 percent), or stumps (7 percent). We were able to remove and 

crossdate wood samples from most of these trees (146 trees or 80 percent), and we obtained actual 

or estimated pith dates for 140 of them. These pith dates ranged from 1479 to 1947 and 26 of them 

post-dated 1900 (fig. J-3). The death dates we obtained for four logs and snags ranged from 1986 

to 1999.

Historical and Current Forest Structure and Composition

The plots included three historical and modern forest types (ponderosa pine, mixed conifer, and 

aspen-mixed conifer; table J-1). Half the plots changed forest type between 1860 and 2000: one 

of the ponderosa pine plots converted to mixed conifer and two others converted to aspen-mixed 

conifer. In 1900, tree density averaged 49 trees per acre and ranged from 30 to 95 trees per acre 

(fig. J-4). In 2000, tree density averaged 70 trees per acre and ranged from 35 to 114 trees per acre. 

However, we likely underestimated historical tree density because we could not obtain recruitment 

or earliest-ring dates for 36 of the 182 trees that occurred in the plots and only an earliest-ring date 

for another 6 trees, 1 of which had an earliest-ring date between 1901 and 1920 and therefore may 

have been living before 1900.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 35 trees, 1 of which had only 

scars that were recorded on a single tree and so was excluded from further analyses. Of the remaining 34 trees, 14 were sampled in five of the six plots at this site (1 to 5 trees per plot). We sampled 

the 20 other fire-scarred trees as we encountered them between plots, over 359 acres throughout 

the site (fig. J-5). Most of the 34 fire-scarred trees were ponderosa pine (88 percent), and the rest 

were Douglas-fir and white fir. Most were logs, snags or stumps (59 percent), and the rest were live 

trees. These 34 trees yielded 153 fire scars and 28 eroded fire scars or abrupt changes in ring width 

(figs. J-3 and J-6). However, five of these scar dates were eliminated from further analyses because 

they were recorded on only a single tree at the site. We were able to assign an intra-ring position 

to 76 percent of the 128 fire scars that occurred during the analysis period (1650 to 1900). Of the 

scars that occurred on ponderosa pine trees, most (58 percent) occurred in the early- and middleearlywood (fig. J-7).
116 USDA Forest Service RMRS-GTR-261WWW. 2011.

Post-Fire Cohorts

We identified three cohorts of trees from estimated recruitment dates at three of the plots. All 

of these cohorts were recruited before 1900 (1838 to 1866) and were identified from 22 trees (5 to 

16 trees per cohort), most of which were quaking aspen (32 percent), ponderosa pine (32 percent), 

white fir (18 percent), Douglas-fir (14 percent), and limber pine trees (5 percent, figs. J-3 and J-6). 

The cohorts occurred in plots of two forest types: ponderosa pine (67 percent of cohorts) and mixed 

conifer (33 percent).

Spatial Variation in Fire Regimes

During the analysis period (1650 to 1900), plot-composite, low-severity fire intervals averaged 30 years (range 6 to 81 years) when pooled among ponderosa plots and 28 years (range 6 to 

75 years) when pooled among mixed-conifer plots (fig. J-8). The tree-ring record before 1900 was 

longer than 100 years for all six plots at this site (fig. J-9). We assigned half of the six plots to the 

low fire severity category and half to the mixed fire severity category (table J-2).

From 1650 to 1900, the 27 low-severity fires we reconstructed within our 624-acre sampling 

area averaged 240 acres and ranged from 61 to 568 acres (fig. J-10), equivalent to 11 to 100 percent 

of the recording area (in other words, the combined area of cells containing recording, fire-scarred 

trees during a given year). Recording area varied among fire years, ranging from 507 to 568 acres. 

We likely underestimated the extent of low-severity fires because most fires intersected the boundary of the site (fig. J-11).

Table J-2—Distribution of plots at INC by 

historical forest type (1860; table 2) and fire 

severity (table 3).

Forest type Mixed Low

Mixed conifer 1 1

Ponderosa pine 2 2

Total 3 3

Table J-1—Distribution of plots at INC by historical (1860) and modern (2000) 

forest types (table 2).

Modern forest type (2000)

Historical forest Aspen- Mixed Ponderosa Total plots

type (1860) mixed conifer conifer pine in 1860

Mixed conifer 2 2

Ponderosa pine 1 2 1 4

Total plots in 2000 1 4 1 6
USDA Forest Service RMRS-GTR-261WWW. 2011. 117

Figure J-1—Locations of plots and 

crossdated fire-scarred trees that 

were sampled outside of plots. 

Nearly half of the fire-scarred 

trees were sampled within 

plots and are not mapped 

individually. Plots are identified 

by column and row, in other 

words, the northwestern most 

plot is 5E, the next plot to the 

east is 5F, and so forth. 

Figure J-2—Distribution by species 

of the 182 live and dead trees 

≥8 inches DBH that occurred 

in plots at INC, regardless of 

whether or not we removed 

wood samples and crossdated 

them. Not shown are two Rocky 

Mountain juniper and one curlleaf mountain mahogany tree. 

Indian Creek Reservoir

E F G J K

5

6

Manderfield

Reservoir

Indian Creek

7900

8900

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles
118 USDA Forest Service RMRS-GTR-261WWW. 2011.

ponderosa pine

mixed conifer

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

(a) fire scars and cohorts composited at plots

(b) quaking aspen

0

5

10

15

(e) ponderosa pine

year

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

number of trees recruite

d

0

5

10

(d) white fir

0

5

10

(c) Douglas-fir

0

5

10

Figure J-3—Chronologies of fire and tree recruitment at INC. In (a), horizontal lines are plotcomposite fire-scar and cohort dates by forest type. Non-recorder years precede the first scar, 

whereas recorder years generally follow it, but non-recorder years can also occur when the catface 

margin is consumed by subsequent fires or rot. In (b) through (e), recruitment dates are given 

for species comprising ≥10 percent of trees with such dates. The latter part of the distribution is 

incomplete because we only cored trees that were ≥8 inches DBH. 

density (trees/acre)

0 100 200 300 400 500

forest type

ponderosa pine

mixed conifer

aspen-mixed conifer

0 100 200 300 400 500

(a) 1900 (b) 2000

Figure J-4—Density of trees ≥8 inches DBH that were alive at each plot at INC (a) in 1900 and (b) in 

2000, by forest type (table 2). 
USDA Forest Service RMRS-GTR-261WWW. 2011. 119

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

ponderosa pine

tree

species fire scars on trees sampled between plots

Douglas-fir

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

year

Figure J-5—Chronology of low-severity fires recorded on the 20 trees sampled between plots over 

approximately, 359 acres throughout the INC site. 
120 USDA Forest Service RMRS-GTR-261WWW. 2011.

05G

low

05F

mixed

05E

low

1500 1600 1700 1800 1900 2000

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

quaking aspen Douglas-fir

ponderosa pine white fir

limber pine Rocky Mountain juniper

INC

06G

mixed

05K

mixed

05J

low

1500 1600 1700 1800 1900 2000

year

Figure J-6—Fire-demography 

diagrams (FDDs, Brown 

and others 2008b) showing 

chronologies of tree demography 

(recruitment and death), fire scars, 

and cohorts at each plot. Bark 

dates on 19 stumps are shown 

as outer dates. Not shown are 

20 fire-scarred trees sampled 

between plots. Inferred fire 

severity (table 3) is indicated to 

the left of each panel. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 121

Figure J-7—Intra-ring position of fire scars 

sampled in and between plots at INC 

from 1650 to 1900, as a percentage 

of the number of scars for which the 

position could be determined (given in 

parentheses). Not shown are intra-ring 

positions for six fire scars on Douglas-fir 

trees. 

Figure J-8—Plot-composite 

intervals between lowseverity fires by forest type 

at INC from 1650 to 1900. 

Plots averaged 0.42 acres. 

The boxes (top panels for 

each forest type) enclose 

the 25th to 75th percentiles 

and the whiskers enclose 

the 10th to 90th percentiles 

of the distribution of 

intervals. The vertical lines 

indicate the median fire 

interval, and all values 

falling outside the 10th to 

90th percentiles are shown 

as circles. In the histogram 

(bottom panels for each 

forest type), the same 

intervals are plotted in 10-

year bins (1 to 10 years, 11 

to 20 years, and so forth).

2 ponderosa pine plots (12 intervals)

fire interval (years)

number of intervals

0 20 40 60 80 100

0

2

4

2 mixed conifer plots (12 intervals)

fire interval (years)

number of intervals

0 20 40 60 80 100

0

2

4
122 USDA Forest Service RMRS-GTR-261WWW. 2011. forest type ponderosa pine

mixed conifer

number of fire years

(1650 to 1900)

0 5 10 15

topographic relative

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure J-9—Variation in fire among 

plots at INC with topography, forest 

type, and relative soil moisture 

availability (Parker 1982). Number 

of fire years includes both fire-scar 

and cohort dates. The dotted line 

indicates no fires from 1650 to 1900.

Figure J-10—Relative extent of lowseverity fires within the 624-acre 

INC site, from 1650 to 1900, as 

area (top) and as a percentage 

of the recording area (in other 

words, the combined area of cells 

containing recording, fire-scarred 

trees during each year; bottom). 

Commonly used fire-size classes 

are indicated at the top (NWCG 

2007).
USDA Forest Service RMRS-GTR-261WWW. 2011. 123

Figure J-11—Maps of years with evidence of low-severity fires in three or more cells at INC. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped.
124 USDA Forest Service RMRS-GTR-261WWW. 2011.

Appendix K. Upper Fremont River, Mytoge Mountains, 

Fishlake National Forest (UFR)

Topography

We sampled 15 plots over 1391 acres surrounding the northern Crater Lake, near the north end 

of Fish Lake, on the Loa Ranger District of the Fishlake National Forest in Sevier County, Utah 

(figs. 1 and K-1). We sampled half as many plots here as at the other gridded sites because the 

Fishlake National Forest managers needed data from this area to address wildland-urban interface 

issues near Fish Lake, but the area lacked strong gradients in elevation or forest type. The plots were 

separated by 0.31 miles on average (range 0.28 to 0.31 miles) and averaged 0.25 acres in area (range 

0.12 to 0.55 acres). Plots were sampled within cells that averaged 71 acres and ranged from 56 to 

101 acres. Plots ranged in elevation from 9180 to 9964 ft (fig. K-2). They ranged in slope from 4 to 

65 percent, but most had slopes less than 20 percent (87 percent of plots). They were sampled on a 

range of aspects. The distribution of the plots by elevation, aspect, or slope did not differ from the 

distribution of the landscape by more than 10 percent except for gentle and moderate slopes (over 

and under sampled, respectively) and north aspects, which were over sampled (fig. K-2). We took 

two photographs at one of the plots.

Tree Demography

Of the 447 trees that occurred in the plots, most (99 percent) were Douglas-fir, quaking aspen, 

subalpine fir, or Engelmann spruce, but 1 curl-leaf mountain mahogany also occurred as well as 2 

trees we could not identify (fig. K-3). Most of these trees were living (73 percent) and the rest were 

snags (15 percent) and logs (12 percent). We were able to remove and crossdate wood samples from 

most of these trees (402 trees or 90 percent), and we obtained actual or estimated pith dates for 299 

of them. These pith dates ranged from 1511 to 1964 and 62 of these post-dated 1900 (fig. K-4). The 

death dates we obtained for 83 logs and snags ranged from 1853 to 2003.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (mixed conifer, aspen-mixed 

conifer, aspen, and spruce-fir; table K-1). Some plots changed forest type between 1860 and 2000: 

three mixed conifer, one aspen, and one spruce-fir plot converted to aspen-mixed conifer. In 1900, 

tree density averaged 87 trees per acre and ranged from 22 to 204 trees per acre (fig. K-5). In 2000, 

tree density averaged 112 trees per acre and ranged from 40 to 219 trees per acre. However, we 

likely underestimated historical tree density because we could not obtain recruitment or earliestring dates for 45 of the 447 trees that occurred in the plots and only an earliest-ring date for another 

103 trees. Twenty of these trees had earliest-ring dates between 1901 and 1920 and therefore may 

have been living before 1900.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 16 trees, 3 of which had only 

scars that were recorded on a single tree and so were excluded from further analyses. Of the remaining 13 trees, 6 were sampled in 5 of the 15 plots at this site (1 to 2 trees per plot). We sampled the 

seven other fire-scarred trees as we encountered them between plots over 225 acres throughout the 

site (fig. K-6). Most of the 13 fire-scarred trees were ponderosa pine (92 percent) and the rest were 

Engelmann spruce. They were nearly equally divided among snags (38 percent), logs (31 percent), 

and live trees (31 percent). The fire-scarred trees yielded 24 fire scars and 1 abrupt change in ring 

width (figs. K-4 and K-7). However, five of these scar dates were eliminated from further analyses 
USDA Forest Service RMRS-GTR-261WWW. 2011. 125

because they were recorded on only a single tree at the site. We were able to assign an intra-ring 

position to 42 percent of the 12 fire scars that occurred during the analysis period (1650 to 1900).

Post-Fire Cohorts

We identified eight cohorts of trees from estimated recruitment dates at seven of the plots. All 

of these cohorts were recruited before 1900 (1730 to 1890) and were identified from 59 trees (5 

to 12 trees per cohort), most of which were Douglas-fir (46 percent), aspen (39 percent), or subalpine fir (12 percent), but there were also a few Engelmann spruce (figs. K-4 and K-7). The cohorts 

occurred in plots with a range of forest types: mixed conifer (63 percent of cohorts), aspen (25 percent), and spruce-fir (13 percent).

Spatial Variation in Fire Regimes

We reconstructed too few fire intervals in plots during the analysis period (1650 to 1900) to compute plot-composite fire intervals by forest type at this site. The tree-ring record before 1900 was 

less than 100 years long for 1 of the 15 plots at this site (fig. K-8). We assigned the remaining plots 

to the mixed or high fire severity categories (table K-2).

From 1650 to 1900, the three low-severity fires we reconstructed within our 1391-acre sampling 

area averaged 137 acres and ranged from 62 to 230 acres, equivalent to 33 to 65 percent of the 

recording area (in other words, the combined area of cells containing recording, fire-scarred trees 

during a given year). Recording area varied among fire years, ranging from 185 to 353 acres. We 

likely underestimated the extent of low-severity fires because most fires intersected the boundary of 

the site (fig. K-9).

Table K-2—Distribution of plots at UFR by historical forest 

type (1860; table 2) and fire severity (table 3).

Forest type High Assumed high Mixed

Spruce-fir 2 1

Aspen 1

Aspen-mixed conifer 2

Mixed conifer 3 4 2

Total 3 8 4

Table K-1—Distribution of plots at UFR by historical (1860) and modern (2000) 

forest types (table 2).

Modern forest type (2000)

Historical forest Spruce- Aspen-mixed Mixed Total plots

type (1860) fir conifer conifer in 1860

Spruce-fir 2 1 3

Aspen 1 1

Aspen-mixed conifer 2 2

Mixed conifer 3 6 9

Total plots in 2000 2 7 6 15
126 USDA Forest Service RMRS-GTR-261WWW. 2011.

percentage of trees

occurring at plots

0 5 10 15 20 25 30 35

tree species

Douglas-fir

quaking aspen

subalpine fir

Engelmann spruce

Figure K-1—Locations of plots and 

crossdated fire-scarred trees that were 

sampled outside plots. About half of 

the fire-scarred trees were sampled 

within plots and are not mapped 

individually. Plots are identified by 

column and row, in other words, the 

northwestern most plot is 10H, the 

next plot to the east is 11H, and so 

forth. Note that at most other sites, the 

rows are identified by number and the 

columns by letter.

Figure K-2—Distribution of 

sampled plots and land 

area at UFR by topography. 

Aspect classes are 90o wide, 

beginning with 46o for east 

(E). Land area was derived 

from a digital elevation 

model (Utah AGRC 2004).

Figure K-3—Distribution by 

species of the 447 live and 

dead trees ≥8 inches DBH 

that occurred in plots at UFR, 

regardless of whether or not 

we removed wood samples 

and crossdated them. Not 

shown are one curl-leaf 

mountain mahogany and two 

trees of unknown species.

10 11 12 13 14 15

G

H

I

J

K

L

Fish Lake

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

none (no trees 8 inches DBH)

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles

8900

9900

9900

Crater

Lakes
USDA Forest Service RMRS-GTR-261WWW. 2011. 127

aspen

mixed conifer

spruce-fir

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

aspenmixed conifer

(a) fire scars and cohorts composited at plots

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

(b) Engelmann spruce

0

5

10

15

(e) Douglas-fir

year

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

0

5

10

(d) quaking aspen

0

5

10

(c) subalpine fir

number of trees recruite

d

0

5

10

Figure K-4—Chronologies of fire and tree recruitment at UFR. In (a), horizontal lines are plotcomposite fire-scar and cohort dates by forest type. Non-recorder years precede the first scar, 

whereas recorder years generally follow it, but non-recorder years can also occur when the catface 

margin is consumed by subsequent fires or rot. In (b) through (e), recruitment dates are given 

for species comprising ≥10 percent of trees with such dates. The latter part of the distribution is 

incomplete because we only cored trees that were ≥8 inches DBH. 
128 USDA Forest Service RMRS-GTR-261WWW. 2011.

density (trees/acre)

0 100 200 300 400 500

forest type

mixed conifer

aspen-mixed conifer

aspen

spruce-fir

0 100 200 300 400 500

(a) 1900 (b) 2000

Figure K-5—Density of trees ≥8 inches DBH that were alive at each plot at UFR (a) in 1900 and (b) in 

2000, by forest type (table 2).

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

Douglas-fir

tree

species fire scars on trees sampled between plots Engelmann

spruce

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

year

Figure K-6—Chronology of low-severity fires recorded on the seven trees sampled between plots over 

approximately, 225 acres at southern and western edges of the UFR site.
USDA Forest Service RMRS-GTR-261WWW. 2011. 129

10H

assumed

high

10I

assumed

high

11H

assumed

high

11I

mixed

11J

assumed

high

12I

assumed

high

12L

high

13H

high

15H

mixed

14L

mixed

14K

mixed

14H

assumed

high

14G

high

13L

assumed

high

13K

assumed

high

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

quaking aspen Douglas-fir

Engelmann spruce subalpine fir

unknown

UFR

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

year

Figure K-7—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies of tree 

demography (recruitment and death), fire scars, and cohorts at each plot. Not shown are seven firescarred trees sampled between plots. Inferred fire severity (table 3) is indicated to the left of each 

panel. There is only one tree for which the species is unknown. 
130 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure K-9—Maps of years with evidence of lowseverity fires in three or more cells at UFR. 

“Recording, no evidence of fire” indicates at least 

one tree was alive at that location during that year 

but did not have a fire scar or fire-caused injury. 

Empty cells indicate that no fire-scarred trees were 

recording in that cell during that year. Cohort dates 

are not mapped.

forest type

mixed conifer aspen-mixed conifer aspen

spruce-fir

number of fire years

(1650 to 1900)

-1 01234

topographic relative

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure K-8—Variation in fire among plots 

at UFR with topography, forest type, and 

relative soil moisture availability (Parker 

1982). Number of fire years includes both 

fire-scar and cohort dates. Plots with no 

reconstructed fires during this period fall 

on the dotted line.
USDA Forest Service RMRS-GTR-261WWW. 2011. 131

Appendix L. Wasatch Plateau, Fishlake National Forest 

(OWP)

In 2003, we removed fire-scarred partial cross sections from 17 ponderosa pine trees over an area 

of 49 acres on Old Woman Plateau on the Richfield Ranger District of the Fishlake National Forest 

in Sevier County, Utah (fig. 1). The forest was a relatively open ponderosa pine/sagebrush ecosystem on a flat sandy bench. We sampled here at the request of the Fishlake National Forest because it 

is near both the wildland-urban interface (it is close to a summer cabin subdivision and other developed areas) and a Research Natural Area (approximately 6 miles to the southeast). All of the trees 

were dead when sampled (nine stumps, two logs, and six snags). We were able to crossdate samples 

from all but one of them, from which we identified 96 fire scars and no fire-caused injuries (fig. L-1). 

From the composite fire-scar record of 12 intervals over the analysis period (1650 to 1900), a fire occurred somewhere in the 49-acre sampling area every 20 years on average (range 4 to 39 years; fig. 

L-2) and these fires scarred an average of 52 percent of the sampled trees that were recording (range 

18 to 89 percent). We were able to assign an intra-ring position to most (62 percent) of the scars that 

were formed during the analysis period (1650 to 1990). Of the scars to which we could assign an 

intra-ring position, about half were created by fires that burned when the cambium was dormant (58 

percent ring-boundary scars; fig. L-3). The rest were created during the growing season (18 percent 

in early- plus middle-earlywood versus 24 percent in late-earlywood plus latewood).

year

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

tree

species

ponderosa pine

Figure L-1—Chronology of surface fires from trees sampled over 49 acres at OWP. Each horizontal 

line indicates the length of record for a single tree. Non-recorder years precede the first scar at a 

plot, whereas recorder years generally follow it. However, non-recorder years also occur when the 

margin of the catface is consumed by subsequent fires or rot.
132 USDA Forest Service RMRS-GTR-261WWW. 2011.

ponderosa pine (12 intervals)

fire interval (years)

number of intervals

0 10 20 30 40

0

1

2

Figure L-3—Intra-ring position of fire 

scars on ponderosa pine trees at OWP 

from 1650 to 1900, as a percentage 

of the number of scars for which the 

position could be determined (given in 

parentheses).

Figure L-2—Composite fire 

intervals at OWP, determined 

as the intervals between years 

with fire scars on two or more 

ponderosa pine trees over 

the 49-acre sampling area 

during the period from 1650 to 

1900. The box (top) encloses 

the 25th to 75th percentiles 

and the whiskers enclose 

the 10th to 90th percentiles of 

the distribution of intervals. 

The vertical line across the 

box indicates the median 

fire interval, and all values 

falling outside the 10th to 

90th percentiles are shown 

as circles. In the histogram 

(bottom), the same intervals are 

plotted in 2-year bins. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 133

Appendix M. Monroe Mountain, Fishlake National Forest 

(MON)

We crossdated fire-scarred sections from 10 trees that had been sampled on Monroe Mountain 

on the Richfield Ranger District of the Fishlake National Forest in Sevier and Paiute Counties, Utah 

(fig. 1). The trees were sampled along an approximately 35-mile north-south transect for a previous 

study (Chappell 1997). Although we lack exact locations for each tree, they occurred between 8350 

and 9600 ft on easterly to northerly slopes. All, but one was living when sampled. We identified 36 

fire scars and 4 fire-caused injuries (fig. M-1). We were able to assign an intra-ring position to all, 

but 2 of the 26 scars that formed on the six ponderosa pine trees during the analysis period (1650 

to 1900). We did not compute fire intervals for this site because the trees were sampled over a very 

large area of unknown size. Of the scars to which we could assign an intra-ring position, over half 

were created by fires burning when the cambium was dormant (59 percent ring-boundary scars; 

fig. M-2). The remaining scars were created during the growing season (29 percent in early- plus 

middle-earlywood versus 13 percent in late-earlywood plus latewood).

Figure M-2—Intra-ring position of 

fire scars on ponderosa pine trees 

at MON from 1650 to 1900, as a 

percentage of the number of scars 

for which the position could be 

determined (given in parentheses). 

year

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

tree

species

ponderosa pine

Figure M-1—Chronology of surface fires at MON, sampled over an approximately 35-mile north-south 

transect. Each horizontal line indicates the length of record for a single tree. Non-recorder years 

precede the first scar at a plot, whereas recorder years generally follow it. However, non-recorder years 

also occur when the margin of the catface is consumed by subsequent fires or rot.
134 USDA Forest Service RMRS-GTR-261WWW. 2011.

Appendix N. Abajo Mountains, Manti-La Sal National Forest 

(ABM)

Topography

We sampled 26 plots over 2223 acres along North Canyon Creek and Pine Ridge on the east side 

of the Abajo Mountains, on the Monticello Ranger District of the Manti-La Sal National Forest in San 

Juan County, Utah (figs. 1 and N-1). The plots were separated by 0.31 miles on average (range 0.27 to 

0.44 miles) and averaged 0.41 acres in area (range 0.06 to 1.64 acres). Plots were sampled within cells 

that averaged 68 acres and ranged from 54 to 86 acres. Plots ranged in elevation from 8387 to 10,598 

ft, but most (77 percent) were below 9500 ft (fig. N-2). They ranged in slope from 1 to 69 percent and 

were sampled on a range of aspects, but most were on north or east aspects (77 percent). The distribution of the plots by elevation, aspect, or slope did not differ from the distribution of the landscape by 

more than 10 percent in any category (fig. N-2). We took between one and four photographs each at 

10 of the plots.

Tree Demography

Of the 737 trees that occurred in the plots, most (98 percent) were Gambel oak, ponderosa pine, 

Douglas-fir, quaking aspen, subalpine fir, or Engelmann spruce, but 3 white fir and 2 Colorado pinyon 

also occurred (fig. N-3). Most of these trees were living (76 percent) and the rest were snags (15 percent), logs (7 percent), or stumps (2 percent). We were able to remove and crossdate wood samples 

from most of these trees (697 trees or 95 percent), and we obtained actual or estimated pith dates for 

559 of them. These pith dates ranged from 1326 to 1973, but many post-dated 1900 (208 trees; fig. 

N-4). The death dates we obtained for 109 logs and snags ranged from 1825 to 2003.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (oak, ponderosa pine, mixed conifer, aspen-mixed conifer, aspen, and spruce-fir; table N-1). Some plots changed forest type between 

1860 and 2000: one aspen-mixed conifer and two aspen plots converted to mixed conifer; and one 

ponderosa pine and two aspen plots converted to aspen-mixed conifer. In 1900, tree density averaged 

80 trees per acre and ranged from 6 to 250 trees per acre (fig. N-5). In 2000, tree density averaged 126 

trees per acre and ranged from 18 to 511 trees per acre. However, we likely underestimated historical 

tree density because we could not obtain recruitment or earliest-ring dates for 40 of the 737 trees that 

occurred in the plots and only an earliest-ring date for another 138 trees. Some of these trees (24 trees) 

had earliest-ring dates between 1901 and 1920 and therefore may have been living before 1900.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 68 trees, 13 of which had only 

scars that were recorded on a single tree and so were excluded from further analyses. Of the remaining 

55 trees, about half (28 trees) were sampled in 10 of the 26 plots at this site (1 to 10 trees per plot, average 3 trees). We sampled the 27 other fire-scarred trees as we encountered them between plots, over 

547 acres, at the north end of the site (fig. N-6). Most of the 55 fire-scarred trees were ponderosa pine 

(96 percent) and the rest were Engelmann spruce and Gambel oak. Most were logs, snags, or stumps 

(70 percent) and the rest were live trees. These 55 trees yielded 198 fire scars and 3 eroded fire scars or 

abrupt changes in ring width (figs. N-4 and N-7). However, 15 of these scar dates were eliminated from 

further analyses because they were recorded on only a single tree at the site. We were able to assign an 

intra-ring position to 57 percent of the 151 fire scars that occurred during the analysis period (1650 to 

1900). Of the scars that occurred on ponderosa pine trees, half (48 percent) occurred on the boundary 

between two rings (fig. N-8).
USDA Forest Service RMRS-GTR-261WWW. 2011. 135

Post-Fire Cohorts

We identified 17 cohorts of trees from estimated recruitment dates at 16 of the plots. Thirteen of 

these cohorts were recruited before 1900 (1326 to 1896) and were identified from 101 trees (5 to 

15 trees per cohort), most of which were quaking aspen (56 percent), ponderosa pine (26 percent), 

Engelmann spruce (8 percent), or subalpine fir (6 percent), but there were also a few Douglas-fir and 

white fir (figs. N-4 and N-7). The cohorts that were recruited before 1900 occurred in plots with a range 

of forest types: aspen (38 percent of cohorts), ponderosa pine (38 percent), spruce-fir (15 percent), and 

mixed conifer (8 percent).

Spatial Variation in Fire Regimes

During the analysis period (1650 to 1900), plot-composite low-severity fire intervals pooled among 

ponderosa pine plots averaged 31 years (range 3 to 107 years; fig. N-9). There were more fire years in 

plots below versus above 9000 ft in ponderosa pine than in other forest types, and with higher relative 

soil moisture (fig. N-10). The tree-ring record before 1900 was less than 100 years long for 7 of the 26 

plots at this site.

We could not infer historical fire severity at one plot because it did not meet our requirements for 

any of the severity categories (table N-2). We assigned the remaining plots to the low, mixed, or high 

fire severity categories.

From 1650 to 1900, the 30 low-severity fires we reconstructed within our 2223-acre sampling area 

averaged 187 acres and ranged from 71 to 398 acres (fig. N-11), equivalent to 14 to 75 percent of the 

recording area (in other words, the combined area of cells containing recording, fire-scarred trees during a given year). Recording area varied among fire years, ranging from 384 to 628 acres. We likely 

underestimated the extent of low-severity fires because most fires intersected the boundary of the site 

(fig. N-12).

Table N-1—Distribution of plots at ABM by historical (1860) and modern (2000) forest types (table 2).

Modern forest type (2000)

Historical forest Spruce- Aspen-mixed Mixed Ponderosa Total plots

type (1860) fir Aspen conifer conifer pine Oak in 1860

Spruce-fir 5 5

Aspen 3 2 2 7

Aspen-mixed conifer 1 1

Mixed conifer 2 2

Ponderosa pine 1 9 10

Oak 1 1

Total plots in 2000 5 3 3 5 9 1 26

Table N-2—Distribution of plots at ABM by historical forest type (1860; table 2) and fire 

severity (table 3).

Assumed Assumed

Forest type High high Mixed mixed Low Unclassified

Spruce-fir 3 2

Aspen 5 2

Aspen-mixed conifer 1

Mixed conifer 1 1

Ponderosa pine 4 2 4

Oak 1

Total 5 7 7 2 4 1
136 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure N-1—Locations of plots 

and crossdated fire-scarred 

trees that were sampled 

outside plots. About half of 

the fire-scarred trees were 

sampled within plots and 

are not mapped individually. 

Plots are identified by column 

and row, in other words, the 

southwestern most plot is S17, 

the next plot to the east is 

S18, and so forth. Note that at 

most other sites, the rows are 

identified by number and the 

columns by letter. 

17 18 19 20 21 22 23

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

none (no trees 8 inches DBH)

fire scars sampled between plots ABM

Contour interval=100 ft

0 1 2 miles

Hart's Draw

Spring

Creek

Clay Draw

North Canyon

Bankhead

Creek

10900

10900

8900

9900
USDA Forest Service RMRS-GTR-261WWW. 2011. 137

Figure N-2—Distribution of 

sampled plots and land 

area at ABM by topography. 

Aspect classes are 90o wide, 

beginning with 46o for east 

(E). Land area was derived 

from a digital elevation 

model (Utah AGRC 2004). 

Figure N-3—Distribution by 

species of the 737 live and 

dead trees ≥8 inches DBH 

that occurred in plots at 

ABM, regardless of whether 

or not we removed wood 

samples and crossdated 

them. Not shown are two 

Colorado pinyon and three 

white fir trees. 
138 USDA Forest Service RMRS-GTR-261WWW. 2011.

(a) fire scars and cohorts composited at plots

aspen

ponderosa pine

mixed conifer

spruce-fir

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

oak

1400 1500 1600 1700 1800 1900 2000

aspenmixed conifer

(e) ponderosa pine

year

1400 1450 1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

0

10

20

(d) quaking aspen

0

10

20

(c) subalpine fir

number of trees recruite

d

0

10

20

(b) Engelmann spruce

0

10

20

30

Figure N-4—Chronologies of fire and tree recruitment at ABM. In (a), horizontal lines are plotcomposite fire-scar and cohort dates by forest type. Non-recorder years precede the first scar, 

whereas recorder years generally follow it, but non-recorder years can also occur when the catface 

margin is consumed by subsequent fires or rot. In (b) through (e), recruitment dates are given 

for species comprising ≥10 percent of trees with such dates. The latter part of the distribution is 

incomplete because we only cored trees that were ≥8 inches DBH. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 139

(a) 1900

0 100 200 300 400 500

forest type

oak

ponderosa pine

mixed conifer

aspen-mixed conifer

aspen

spruce-fir

(b) 2000

0 100 200 300 400 500

density (trees/acre)

fire scars on trees sampled between plots

ponderosa pine

tree

species

1400 1500 1600 1700 1800 1900 2000

year

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

Figure N-5—Density of trees ≥8 inches DBH that were alive at each plot at ABM (a) in 1900 and (b) in 

2000, by forest type (table 2). 

Figure N-6—Chronology of low-severity fires recorded on the 27 trees sampled between plots over 

approximately, 547 acres at the northern end of the ABM site. 
140 USDA Forest Service RMRS-GTR-261WWW. 2011.

20F

low

21H

mixed

20N

assumed

high

20H

assumed

high

20G

assumed

mixed

1500 1600 1700 1800 1900 2000

17R

assumed

high

17S

mixed

18R

mixed

18S

assumed

high

19G

mixed

19O

assumed

high

19P

assumed

high

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

1500 1600 1700 1800 1900 2000

year

19Q

mixed

20E

low

20J

unclassified

quaking aspen Douglas-fir

Engelmann spruce ponderosa pine

Gambel oak Colorado pinyon

subalpine or white fir ABM

fire scar cohort

inner date

outer date

pith date

bark date

recorder years non-recorder years

Figure N-7—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies of 

tree demography (recruitment and death), fire scars, and cohorts at each plot. Bark dates on 16 

stumps are shown as outer dates. Not shown are 27 fire-scarred trees sampled between plots. Plot 

identifier and inferred fire severity (table 3) are indicated to the left of each panel. Most of the trees 

(96 percent) in the combined subalpine/white fir category are subalpine fir. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 141

22G

low

21N

assumed

high

21M

high

22H

assumed

mixed

22I

low

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

22L

high

22M

high

23G

mixed

22K

high

year

1500 1600 1700 1800 1900 2000

year

21K

high

21I

mixed

quaking aspen Douglas-fir

Engelmann spruce ponderosa pine

Gambel oak Colorado pinyon

subalpine or white fir ABM

fire scar cohort

inner date

outer date

pith date

bark date

recorder years non-recorder years

Figure N-7—Continued. 
142 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure N-8—Intra-ring position of fire scars on trees 

sampled in and between plots at ABM from 1650 

to 1900, as a percentage of the number of scars for 

which the position could be determined (given in 

parentheses). Not shown is the intra-ring position for 

one fire scar on an Engelmann spruce tree. forest type

oak

ponderosa pine

mixed conifer

aspen-mixed conifer

aspen

spruce-fir

number of fire years

(1650 to 1900)

0 5 10 15 20

topographic relative

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure N-9—Plot-composite intervals between low-severity fires 

in ponderosa pine plots at ABM from 1650 to 1900. Plots 

averaged 0.41 acres. The box (top) encloses the 25th to 75th

percentiles and the whiskers enclose the 10th to 90th percentiles 

of the distribution of intervals. The vertical line indicates the 

median fire interval, and all values falling outside the 10th to 

90th percentiles are shown as circles. In the histogram (bottom), 

the same intervals are plotted in 10-year bins (1 to 10 years, 11 

to 20 years, and so forth).

Figure N-10—Variation in fire 

among plots at ABM with 

topography, forest type, 

and relative soil moisture 

availability (Parker 1982). 

Number of fire years includes 

both fire-scar and cohort dates. 

Plots with no reconstructed 

fires during this period fall on 

the dotted line.

5 ponderosa pine plots (30 intervals)

fire interval (years)

number of intervals

0 20 40 60 80 100

0

5

10
USDA Forest Service RMRS-GTR-261WWW. 2011. 143

Figure N-12—Maps of years with evidence of low-severity fires in three or more cells at ABM. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped.

Figure N-11—Relative extent of 

low-severity fires within the 

2223-acre ABM site, from 

1650 to 1900, as area (top) 

and as a percentage of the 

recording area (in other words, 

the combined area of cells 

containing recording firescarred trees during each year; 

bottom). Commonly used firesize classes are indicated at the 

top (NWCG 2007).
144 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure N-12—Continued.
USDA Forest Service RMRS-GTR-261WWW. 2011. 145

Figure N-12—Continued.
146 USDA Forest Service RMRS-GTR-261WWW. 2011.

Appendix O. Wasatch Plateau, Manti-La Sal National Forest 

(EPH)

Topography

We sampled 29 plots over 1876 acres near Maple and Cottonwood Creeks on the Sanpete Ranger 

District of the Manti-La Sal National Forest in Sanpete County, Utah (figs. 1 and O-1). The plots 

were separated by 0.30 miles on average (range 0.25 to 0.31 miles) and averaged 0.43 acres in 

area (range 0.07 to 1.16 acres). Plots were sampled within cells that averaged 63 acres and ranged 

from 54 to 72 acres. Plots ranged in elevation from 7601 to 9196 ft (fig. O-2) and in slope from 3 

to 63 percent. They were sampled on a range of aspects, but most were on north and west aspects 

(79 percent). The distribution of the plots by elevation, aspect, or slope did not differ from the 

distribution of the landscape by more than 10 percent in any category (fig. O-2). We took four photographs each at 28 of the plots.

Tree Demography

Of the 856 trees that occurred in the plots, most (99 percent) were Rocky Mountain juniper, 

Gambel oak, white fir, Douglas-fir, quaking aspen, subalpine fir, or Engelmann spruce, but 2 bigtooth maple, 1 ponderosa pine, and 5 limber pine also occurred (fig. O-3). Most of these trees were 

living (85 percent) and the rest were snags (11 percent), logs (3 percent), or stumps (1 percent). We 

were able to remove and crossdate wood samples from most of these trees (724 trees or 85 percent), 

and we obtained actual or estimated pith dates for 680 of them. These pith dates ranged from 1593 

to 1983 and many post-dated 1900 (310 trees; fig. O-4). The death dates we obtained for 72 logs and 

snags ranged from 1962 to 2004.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (oak, mixed conifer, aspen-mixed 

conifer, aspen, and spruce-fir; table O-1). Most plots changed forest type between 1860 and 2000: 

one oak plot converted to pinyon-juniper; three oak and eight aspen-mixed conifer plots converted 

to mixed conifer; six aspen plots converted to aspen-mixed conifer; and two mixed conifer and one 

aspen plot converted to spruce-fir. In 1900, tree density averaged 57 trees per acre and ranged from 

4 to 200 trees per acre (fig. O-5). In 2000, tree density averaged 92 trees per acre and ranged from 

18 to 400 trees per acre. However, we likely underestimated historical tree density because we could 

not obtain recruitment or earliest-ring dates for 132 of the 856 trees that occurred in the plots and 

only an earliest-ring date for another 44 trees. Eleven of these trees had earliest-ring dates between 

1901 and 1920 and therefore may have been living before 1900.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 30 trees, 4 of which had only 

scars that were recorded on a single tree and so were excluded from further analyses. Of the remaining 26 trees, 11 were sampled in 5 of the 29 plots at this site (1 to 4 trees per plot). We sampled the 

15 other fire-scarred trees as we encountered them between plots, over 453 acres at the southeastern 

end of the site (fig. O-6). Most of the 26 fire-scarred trees were white fir (35 percent), limber pine 

(31 percent), or Douglas-fir (27 percent) and the rest were Engelmann spruce or subalpine fir. Most 

were live trees (62 percent) and the rest were snags (27 percent), stumps (8 percent), or logs (4 percent). These 26 trees yielded 48 fire scars and 12 eroded fire scars or abrupt changes in ring width 

(figs. O-4 and O-7). However, six of these scar dates were eliminated from further analyses because 
USDA Forest Service RMRS-GTR-261WWW. 2011. 147

they were recorded on only a single tree at the site. We were able to assign an intra-ring position to 

76 percent of the 33 fire scars that occurred during the analysis period (1650 to 1900).

Post-Fire Cohorts

We identified 17 cohorts of trees from estimated recruitment dates at 16 of the plots. All of these 

cohorts were recruited before 1900 (1794 to 1896) and were identified from 158 trees (5 to 17 trees 

per cohort), most of which were quaking aspen (55 percent), white fir (20 percent), Douglas-fir (11 

percent), as well as a few Gambel oak, subalpine fir, and Engelmann spruce (figs. O-4 and O-7). The 

cohorts that were recruited before 1900 occurred in plots with a range of forest types: aspen (29 percent of cohorts), aspen-mixed conifer (29 percent), mixed conifer (29 percent), and oak (12 percent).

Spatial Variation in Fire Regimes

We reconstructed too few fire intervals in plots during the analysis period (1650 to 1900) to compute plot-composite fire intervals by forest type at this site. The tree-ring record before 1900 was 

less than 100 years long for 21 of the 29 plots at this site (fig. O-8).

We could not infer historical fire severity at two plots because they did not meet our requirements 

for any of the severity categories (table O-2). We assigned the remaining plots to the low, mixed, or 

high fire severity categories.

From 1650 to 1900, the 12 low-severity fires we reconstructed within our 1876-acre sampling 

area averaged 126 acres and ranged from 61 to 199 acres (fig. O-9), equivalent to 17 to 100 percent 

of the recording area (in other words, the combined area of cells containing recording, fire-scarred 

trees during a given year). Recording area varied among fire years, ranging from 116 to 497 acres. 

We likely underestimated the extent of low-severity fires because most fires intersected the boundary of the site (fig. O-10).

Table O-2—Distribution of plots at EPH by historical forest type (1860; table 2) 

and fire severity (table 3).

Forest type High Assumed high Mixed Low Unclassified

Spruce-fir 2

Aspen 3 5 2

Aspen-mixed conifer 3 2 2 1

Mixed conifer 3 1 1

Oak 1 1 2

Total 10 10 6 1 2

Table O-1—Distribution of plots at EPH by historical (1860) and modern (2000) forest types 

(table 2).

Modern forest type (2000)

Historical forest Spruce- Aspen-mixed Mixed Pinyon- Total plots

type (1860) fir Aspen conifer conifer juniper in 1860

Spruce-fir 2 2

Aspen 1 3 6 10

Aspen-mixed conifer 8 8

Mixed conifer 2 3 5

Oak 3 1 4

Total plots in 2000 5 3 6 14 1 29
148 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure O-1—Locations of plots and crossdated fire-scarred trees that were sampled outside of plots. 

Nearly half of the fire-scarred trees were sampled within plots and are not mapped individually. 

Plots are identified by column and row, in other words, the northwestern most plot is 10C, the next 

plot to the east is 10D, and so forth. 

Figure O-2—Distribution of 

sampled plots and land 

area at EPH by topography. 

Aspect classes are 90o wide, 

beginning with 46o for east 

(E). Land area was derived 

from a digital elevation model 

(Utah AGRC 2004). 

C D E F G H I J

10

11

12

13

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

none (no trees 8 inches DBH)

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles

6900

7900

8900

9900

9900

Maple Creek

Cottonwood Spring

White Fork

Cottonwood Creek

Left Fork
USDA Forest Service RMRS-GTR-261WWW. 2011. 149

percentage of trees

occurring at plots

0 5 10 15 20 25 30 35

tree species

Gambel oak

Rocky Mountain juniper

white fir

Douglas-fir

quaking aspen

subalpine fir

Engelmann spruce

Figure O-3—Distribution by 

species of the 856 live and 

dead trees ≥8 inches DBH 

that occurred in plots at EPH, 

regardless of whether or not we 

removed wood samples and 

crossdated them. Not shown 

are two bigtooth maple, one 

ponderosa pine, and five limber 

pine trees. 

(a) fire scars and cohorts composited at plots

aspen

mixed conifer

spruce-fir

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

oak

aspenmixed conifer

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

(b) subalpine fir

0

20

(d) white fir

year

number

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

of trees recruite

d

0

20

(c) quaking aspen

0

20

Figure O-4—Chronologies of fire and tree recruitment at EPH. In (a), horizontal lines are plotcomposite fire-scar and cohort dates by forest type. Non-recorder years precede the first scar, 

whereas recorder years generally follow it, but non-recorder years can also occur when the catface 

margin is consumed by subsequent fires or rot. In (b) through (d), recruitment dates are given 

for species comprising ≥10 percent of trees with such dates. The latter part of the distribution is 

incomplete because we only cored trees that were ≥8 inches DBH.
150 USDA Forest Service RMRS-GTR-261WWW. 2011.

density (trees/acre)

0 100 200 300 400 500

forest type

oak

pinyon-juniper

mixed conifer

aspen-mixed conifer

aspen

spruce-fir

0 100 200 300 400 500

(a) 1900 (b) 2000

Figure O-5—Density of trees ≥8 inches DBH that were alive at each plot at EPH (a) in 1900 and (b) in 

2000, by forest type (table 2). 

fire scars on trees sampled between plots

Douglas-fir

tree

species

white fir

limber pine

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

year

Figure O-6—Chronology of low-severity fires recorded on the 15 trees sampled between plots over 

approximately, 453 acres at the southeastern end of EPH. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 151

10C

unclassified

10D

mixed

10E

high

10F

assumed

high

10G

assumed

high

10H

low

10I

high

11C

unclassified

11D

assumed

high

11E

high

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

11F

mixed

12C

high

11I

assumed

high

11H

mixed

11G

high

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

quaking aspen Douglas-fir

Engelmann spruce ponderosa pine

subalpine white fir Rocky Mountain juniper

Gambel oak, limber pine, bigtooth maple

or

or

fire scar cohort EPH

inner date pith date

outer date bark date

recorder years non-recorder years

Figure O-7—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies of 

tree demography (recruitment and death), fire scars, and cohorts at each plot. Bark dates on four 

stumps are shown as outer dates. Not shown are 15 fire-scarred trees sampled between plots. 

Inferred fire severity (table 3) is indicated to the left of each panel. Most of the trees (62 percent) 

in the combined subalpine/white fir category are white fir. Most of the trees (85 percent) in the 

combined Gambel oak, limber pine, and bigtooth maple category are Gambel oak. 
152 USDA Forest Service RMRS-GTR-261WWW. 2011.

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

13E

mixed

13I

assumed

high

13H

assumed

high

13G

high

13F

mixed

1500 1600 1700 1800 1900 2000

year

12I

assumed

high

12H

high

12G

assumed

high

13C

high

13D

mixed

12J

high

12F

high

12E

assumed

high

12D

assumed

high

quaking aspen Douglas-fir

Engelmann spruce ponderosa pine

subalpine white fir Rocky Mountain juniper

Gambel oak, limber pine, bigtooth maple

or

or

fire scar cohort EPH

inner date pith date

outer date bark date

recorder years non-recorder years

Figure O-7—Continued. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 153 forest type

oak

ponderosa pine

mixed conifer

aspen-mixed conifer

aspen

spruce-fir

number of fire years

(1650 to 1900)

0 5 10 15 20

topographic relative

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure O-8—Variation in fire 

among plots at EPH with 

topography, forest type, and 

relative soil moisture availability 

(Parker 1982). Number of fire 

years includes both fire-scar 

and cohort dates. Plots with no 

reconstructed fires during this 

period fall on the dotted line.

Figure O-9—Relative extent of 

low-severity fires within the 

1876-acre EPH site, from 

1650 to 1900, as area (top) 

and as a percentage of the 

recording area (in other words, 

the combined area of cells 

containing recording, firescarred trees during each year; 

bottom). Commonly used firesize classes are indicated at the 

top (NWCG 2007).
154 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure O-10—Maps of years with evidence of low-severity fires in three or more cells at EPH. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped.
USDA Forest Service RMRS-GTR-261WWW. 2011. 155

Appendix P. Western Uinta Mountains, Ashley National 

Forest (WUN)

Topography

We sampled 25 plots over 2255 acres in Miners Gulch, just south of the High Uintas Wilderness 

on the Duchesne Ranger District of the Ashley National Forest in Duchesne County, Utah (figs. 1 

and P-1). The plots were separated by 0.30 miles on average (range 0.27 to 0.32 miles and averaged 

0.48 acres in area (range 0.14 to 1.35 acres). Plots were sampled within cells that averaged 62 acres 

and ranged from 56 to 69 acres. Plots ranged in elevation from 7352 to 10,437 ft (fig. P-2) and 

ranged in slope from 5 to 65 percent, but most had slopes between 26 and 50 percent (68 percent of 

plots). They were sampled on a range of aspects, but most were on south and east aspects (88 percent). The distribution of plots differed from that of land area by more than 10 percent for several 

categories of topography. Plots were oversampled from elevations of 9000 to 10,000 ft, on moderate 

slopes, and on east aspects, and plots were undersampled for elevations from 8000 to 9000 ft, on 

steep slopes and on west aspects (fig. P-2). We took four photographs at each of the plots.

Tree Demography

Of the 745 trees that occurred in the plots, most (99 percent) were ponderosa pine, Douglas-fir, 

quaking aspen, lodgepole pine, subalpine fir, or Engelmann spruce, but 1 Colorado pinyon and 7 

Rocky Mountain juniper also occurred plus 3 trees we could not identify (fig. P-3). Most of these 

trees were living (84 percent) and the rest were snags (6 percent), logs (10 percent), or stumps 

(1 percent). We were able to remove and crossdate wood samples from most of these trees (524 trees 

or 70 percent), and we obtained actual or estimated pith dates for 504 of them. These pith dates 

ranged from 1514 to 1961 and 103 of them post-dated 1900 (fig. P-4). The death dates we obtained 

for 49 logs and snags ranged from 1840 to 2003.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (ponderosa pine, mixed conifer, 

lodgepole, and spruce-fir; table P-1). One lodgepole plot converted to mixed conifer between 1860 

and 2000. In 1900, tree density averaged 49 trees per acre and ranged from 1 to 153 trees per acre 

(fig. P-5). In 2000, tree density averaged 69 trees per acre and ranged from 17 to 167 trees per acre. 

However, we likely underestimated historical tree density because we could not obtain recruitment 

or earliest-ring dates for 221 of the 745 trees that occurred in the plots and only an earliest-ring date 

for another 20 trees. One tree had an earliest-ring date between 1901 and 1920 and therefore may 

have been living before 1900.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 65 trees. Most of these (54 

trees) were sampled in 16 of the 25 plots at this site (1 to 10 trees per plot, average 3 trees). We 

sampled the 11 other fire-scarred trees as we encountered them between plots, over 287 acres at the 

southwestern end of the site (fig. P-6). Most of the 65 fire-scarred trees were lodgepole pine (45 percent) and ponderosa pine (37 percent) and the rest were Douglas-fir and Rocky Mountain juniper. 

About half were live trees (52 percent), and the rest were logs and snags. These 65 trees yielded 94 

fire scars and 19 eroded fire scars or abrupt changes in ring width (figs. P-4 and P-7). We were able 

to assign an intra-ring position to 56 percent of the 87 fire scars that occurred during the analysis 

period (1650 to 1900). Of the scars that occurred on lodgepole pine trees, half (50 percent) occurred 

on the boundary between two rings (fig. P-8). In contrast, of the scars that occurred on ponderosa 

pine trees, half (44 percent) occurred in the early- and middle-earlywood.
156 USDA Forest Service RMRS-GTR-261WWW. 2011.

Post-Fire Cohorts

We identified 13 cohorts of trees from estimated recruitment dates at 10 of the plots. Twelve of 

these cohorts were recruited before 1900 (1840 to 1863) and were identified from 109 trees (5 to 

21 trees per cohort), most of which were lodgepole (39 percent), ponderosa pine (29 percent), or 

Douglas-fir (26 percent), but a few quaking aspen, Rocky Mountain juniper, and subalpine fir also 

occurred (figs. P-4 and P-7). The cohorts that were recruited before 1900 occurred in plots with a 

range of forest types: ponderosa pine (40 percent of cohorts), lodgepole (30 percent), and mixed 

conifer (30 percent).

Spatial Variation in Fire Regimes

We reconstructed too few fire intervals in plots during the analysis period (1650 to 1900) to compute plot-composite fire intervals by forest type at this site. The tree-ring record before 1900 was 

less than 100 years long for 3 of the 25 plots at this site (fig. P-9).

We could not infer historical fire severity at one plot because it did not meet our requirements for 

any of the severity categories (table P-2). We assigned the remaining plots to the mixed or high fire 

severity categories.

From 1650 to 1900, the 14 low-severity fires we reconstructed within our 2255-acre sampling 

area averaged 145 acres and ranged from 56 to 813 acres (fig. P-10), equivalent to 8 to 100 percent 

of the recording area (in other words, the combined area of cells containing recording, fire-scarred 

trees during a given year). Recording area varied among fire years, ranging from 131 to 815 acres. 

We likely underestimated the extent of low-severity fires because most fires intersected the boundary of the site (fig. P-11).

Table P-1—Distribution of plots at WUN by historical (1860) and modern (2000) 

forest types (table 2).

Modern forest type (2000)

Historical forest Spruce- Mixed Ponderosa Total plots

type (1860) fir Lodgepole conifer pine in 1860

Spruce-fir 3 3

Lodgepole 7 1 8

Mixed conifer 10 10

Ponderosa pine 4 4

Total plots in 2000 3 7 11 4 25

Table P-2—Distribution of plots at WUN by historical forest type (1860; table 2) 

and fire severity (table 3).

Forest type Assumed high Mixed Assumed mixed Unclassified

Spruce-fir 3

Lodgepole 4 3 1

Mixed conifer 2 3 5

Ponderosa pine 4

Total 9 10 5 1
USDA Forest Service RMRS-GTR-261WWW. 2011. 157

Figure P-1—Locations of plots 

and crossdated fire-scarred 

trees that were sampled 

outside of plots. Most of 

the fire-scarred trees were 

sampled within plots and 

are not mapped individually. 

Plots are identified by 

column and row, in other 

words, the northwestern most 

plot is 10C, the next plot to 

the east is 10D, and so forth. 

Figure P-2—Distribution of 

sampled plots and land area 

at WUN by topography. 

Aspect classes are 90o wide, 

beginning with 46o for east 

(E). Land area was derived 

from a digital elevation 

model (Utah AGRC 2004). 

C D E F G H I

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

none (no trees 8 inches DBH)

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles

Rock Creek

Miners Gulch

7900

7900

8900

9900

10900

10900
158 USDA Forest Service RMRS-GTR-261WWW. 2011.

ponderosa pine

mixed conifer

spruce-fir

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

lodgepole

(a) fire scars and cohorts composited at plots

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

(e) ponderosa pine

year

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

number of trees recruite

d

0

10

20

(d) Douglas-fir

0

10

20

(c) lodgepole pine

0

10

20

(b) subalpine fir

0

10

20

Figure P-3—Distribution by 

species of the 745 live and 

dead trees ≥8 inches DBH that 

occurred in plots at WUN, 

regardless of whether or not we 

removed wood samples and 

crossdated them. Not shown 

are one Colorado pinyon and 

seven Rocky Mountain juniper 

plus three trees of unknown 

species. 

Figure P-4—Chronologies of fire and tree recruitment at WUN. In (a), horizontal lines are plotcomposite fire-scar and cohort dates by forest type. Non-recorder years precede the first scar, 

whereas recorder years generally follow it, but non-recorder years can also occur when the catface 

margin is consumed by subsequent fires or rot. In (b) through (e), recruitment dates are given 

for species comprising ≥10 percent of trees with such dates. The latter part of the distribution is 

incomplete because we only cored trees that were ≥8 inches DBH. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 159

density (trees/acre)

0 100 200 300 400 500

forest type

ponderosa pine

mixed conifer

lodgepole

spruce-fir

0 100 200 300 400 500

(a) 1900 (b) 2000

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

ponderosa pine

tree

species fire scars on trees sampled between plots

Douglas-fir

lodgepole

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

year

Figure P-5—Density of trees ≥8 inches DBH that were alive at each plot at WUN (a) in 1900 and (b) 

in 2000, by forest type (table 2). 

Figure P-6—Chronology of low-severity fires recorded on the 11 trees sampled between plots over 

approximately, 287 acres at the southern end of WUN. 
160 USDA Forest Service RMRS-GTR-261WWW. 2011.

10F

assumed

high

11C

assumed

high

11D

assumed

high

11E

assumed

high

11F

mixed

12C

assumed

high

12D

mixed

12E

mixed

12G

assumed

mixed

13C

mixed

13D

assumed

mixed

13E

assumed

mixed

13F

assumed

high

14H

assumed

high

14G

assumed

mixed

14F

assumed

high

14E

unclassified

14D

mixed

13G

assumed

high

quaking aspen Douglas-fir

Engelmann spruce lodgepole pine

ponderosa pine subalpine fir

Rocky Mountain juniper WUN

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year 1500 1600 1700 1800 1900 2000

year

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

Figure P-7—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies of 

tree demography (recruitment and death), fire scars, and cohorts at each plot. Bark dates on three 

stumps are shown as outer dates. Not shown are 11 fire-scarred trees sampled between plots. 

Inferred fire severity (table 3) is indicated to the left of each panel.
USDA Forest Service RMRS-GTR-261WWW. 2011. 161

Figure P-7—Continued. 

15H

assumed

mixed

15G

mixed

1500 1600 1700 1800 1900 2000

16E

mixed

1500 1600 1700 1800 1900 2000

year

15E

mixed

15D

mixed

15C

mixed

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

quaking aspen Douglas-fir

Engelmann spruce lodgepole pine

ponderosa pine subalpine fir

Rocky Mountain juniper WUN

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

Figure P-8—Intra-ring position of fire scars 

sampled in and between plots at WUN 

from 1650 to 1900, as a percentage 

of the number of scars for which the 

position could be determined (given in 

parentheses). Not shown are intra-ring 

positions for four fire scars on Douglasfir trees. 
162 USDA Forest Service RMRS-GTR-261WWW. 2011. forest type mixed conifer aspen

lodgepole

spruce-fir

number of fire years

(1650 to 1900)

0 5

topographic relative

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure P-9—Variation in fire among 

plots at WUN with topography, 

forest type, and relative soil 

moisture availability (Parker 1982). 

Number of fire years includes both 

fire-scar and cohort dates. Plots 

with no reconstructed fires during 

this period fall on the dotted line.

Figure P-10—Relative extent of 

low-severity fires within the 

2255-acre WUN site, from 1650 

to 1900, as area (top) and as a 

percentage of the recording area 

(in other words, the combined 

area of cells containing 

recording, fire-scarred trees 

during each year; bottom). 

Commonly used fire-size classes 

are indicated at the top (NWCG 

2007).
USDA Forest Service RMRS-GTR-261WWW. 2011. 163

Figure P-11—Maps of years with evidence of low-severity fires in three or more cells at WUN. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped.
164 USDA Forest Service RMRS-GTR-261WWW. 2011.

Appendix Q. Central Uinta Mountains, Ashley National 

Forest (MUR)

Topography

We sampled 30 plots over 2218 acres near Pole and Big Elk Creeks, just south of the High 

Uintas Wilderness on the Roosevelt Ranger District of the Ashley National Forest in Duchesne 

County, Utah (figs. 1 and Q-1). The plots were separated by 0.31 miles on average (range 0.30 

to 0.32 miles) and averaged 0.33 acres in area (range 0.03 to 1.22 acres). Plots were sampled 

within cells that averaged 67 acres and ranged from 59 to 81 acres. Plots ranged in elevation from 

7567 to 10,656 ft (fig. Q-2) and in slope from 0 to 68 percent, but most were less than 25 percent 

(63 percent). They were sampled on a range of aspects, but most were on south and east aspects 

(77 percent). The distribution of the plots by elevation, aspect, or slope did not differ from the 

distribution of the landscape by more than 10 percent in any category (fig. Q-2). We took four 

photographs each at 24 of the plots.

Tree Demography

Of the 810 trees that occurred in the plots, most (99 percent) were ponderosa pine, subalpine 

fir, Douglas-fir, quaking aspen, lodgepole pine, or Engelmann spruce, but 8 Utah juniper also occurred (fig. Q-3). Most of these trees were living (73 percent) and the rest were snags (8 percent), 

logs (9 percent), or stumps (10 percent). We were able to remove and crossdate wood samples 

from most of these trees (610 trees or 75 percent), and we obtained actual or estimated pith dates 

for 484 of them. These pith dates ranged from 1410 to 1974 and 146 of them post-dated 1900 (fig. 

Q-4). The death dates we obtained for 46 logs and snags ranged from 1806 to 2004.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (ponderosa pine, aspen-mixed 

conifer, aspen, lodgepole, and spruce-fir; table Q-1). Some plots changed forest type between 

1860 and 2000: one aspen plot converted to mixed conifer; and one ponderosa pine, one lodgepole, and three aspen plots converted to aspen-mixed conifer. In 1900, tree density averaged 85 

trees per acre and ranged from 0 to 716 trees per acre (fig. Q-5). In 2000, tree density averaged 

127 trees per acre and ranged from 16 to 1038 trees per acre. However, we likely underestimated 

historical tree density because we could not obtain recruitment or earliest-ring dates for 200 of 

the 810 trees that occurred in the plots and only an earliest-ring date for another 126 trees. Sixteen 

of these trees had earliest-ring dates between 1901 and 1920 and therefore may have been living 

before 1900.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 84 trees, 1 of which had only 

scars that were recorded on a single tree and so was excluded from further analyses. Of the remaining 83 trees, about half (47 trees) were sampled in 16 of the 30 plots at this site (1 to 8 trees 

per plot, average 3 trees). We sampled the 36 other fire-scarred trees as we encountered them 

between plots, over 2460 acres throughout the site (fig. Q-6). Most of the 83 fire-scarred trees 

were lodgepole pine (47 percent) and ponderosa pine (41 percent) and the rest were Engelmann 

spruce and Douglas-fir. Most were logs, snags, or stumps (64 percent) and the rest were live trees. 

These 83 trees yielded 167 fire scars and 9 eroded fire scars or abrupt changes in ring width (figs. 

Q-4 and Q-7). However, one of these scar dates was eliminated from further analyses because 

it was recorded on only a single tree at the site. We were able to assign an intra-ring position to 
USDA Forest Service RMRS-GTR-261WWW. 2011. 165

67 percent of the 148 fire scars that occurred during the analysis period (1650 to 1900). Of the 

scars that occurred on ponderosa pine trees, half (48 percent) occurred in the late-earlywood or 

the latewood (fig. Q-8). In contrast, of the scars that occurred on lodgepole pine trees, most (94 

percent) occurred either on the boundary between two rings or in the late-earlywood or latewood.

Post-Fire Cohorts

We identified 16 cohorts of trees from estimated recruitment dates at 15 of the plots. Thirteen 

of these cohorts were recruited before 1900 (1410 to 1898) and were identified from 98 trees (5 to 

13 trees per cohort), most of which were quaking aspen (33 percent), lodgepole pine (30 percent), 

Engelmann spruce (22 percent), or ponderosa pine (12 percent), but a few Douglas-fir and Utah juniper trees also occurred (figs. Q-4 and Q-7). The cohorts that were recruited before 1900 occurred 

in plots with a range of forest types: lodgepole (31 percent of cohorts), spruce-fir (31 percent), aspen 

(23 percent), and ponderosa pine (15 percent).

Spatial Variation in Fire Regimes

During the analysis period (1650 to 1900), plot-composite, low-severity fire intervals that were 

pooled among ponderosa pine plots averaged 42 years (range 5 to 178 years; fig. Q-9). There were 

more fire years in low-elevation than in high-elevation plots (fig. Q-10). The tree-ring record before 

1900 was less than 100 years long for 11 of the 30 plots at this site.

We inferred that one lodgepole plot was not historically forested (table Q-2). We assigned the 

remaining plots to the low, mixed, or high fire severity categories.

From 1650 to 1900, the 15 low-severity fires we reconstructed within our 2218-acre sampling 

area averaged 240 acres and ranged from 58 to 976 acres (fig. Q-11), equivalent to 6 to 94 percent 

of the recording area (in other words, the combined area of cells containing recording, fire-scarred 

trees during a given year). Recording area varied among fire years, ranging from 312 to 1042 acres. 

We likely underestimated the extent of low-severity fires because most fires intersected the boundary of the site (fig. Q-12).

Table Q-2—Distribution of plots at MUR by historical forest type (1860; table 2) and fire 

severity (table 3).

Assumed Assumed Low Not historically 

Forest type High high Mixed mixed forested

Spruce-fir 2 4 2

Lodgepole 2 3 1 1

Aspen 2 5 1

Aspen-mixed conifer 1

Ponderosa pine 2 2 2

Total 4 12 8 2 3 1

Table Q-1—Distribution of plots at MUR by historical (1860) and modern (2000) forest types (table 2).

Modern forest type (2000)

Historical forest Spruce- Aspen-mixed Mixed Ponderosa Total plots

type (1860) fir Lodgepole Aspen conifer conifer pine in 1860

Spruce-fir 8 8

Lodgepole 6 1 7

Aspen 4 3 1 8

Aspen-mixed conifer 1 1

Ponderosa pine 1 5 6

Total plots in 2000 8 6 4 6 1 5 30
166 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure Q-1—Locations of plots 

and crossdated fire-scarred 

trees that were sampled 

outside of plots. More than 

half of the fire-scarred trees 

were sampled within plots and 

are not mapped individually. 

Plots are identified by column 

and row, in other words, the 

southwestern most plot is 4A, 

the next plot to the east is 5A, 

and so forth. Note that at 

most other sites, the rows are 

identified by number and the 

columns by letter. 

Figure Q-2—Distribution of 

sampled plots and land 

area at MUR by topography. 

Aspect classes are 90o wide, 

beginning with 46o for east (E). 

Land area was derived from a 

digital elevation model (Utah 

AGRC 2004).

4 5 6 7 8 9 10

O

N

M

L

K

J

I

H

G

F

E

D

C

B

A

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

none (no trees 8 inches DBH)

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles Pole Creek

Bull Elk Creek

Clover Creek

Big

Bend

8900

7900

9900
USDA Forest Service RMRS-GTR-261WWW. 2011. 167

percentage of trees

occurring at plots

0 5 10 15 20 25 30 35

tree species

ponderosa pine

Douglas-fir

quaking aspen

lodgepole pine

subalpine fir

Engelmann spruce

aspen

ponderosa pine

spruce-fir

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

lodgepole

aspenmixed conifer

(a) fire scars and cohorts composited at plots

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

(e) ponderosa pine

year

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

number of trees recruite

d

0

25

50

(d) quaking aspen

0

25

50

(c) lodgepole pine

0

25

50

(b) Engelmann spruce

0

25

50

Figure Q-3—Distribution by 

species of the 810 live and 

dead trees ≥8 inches DBH 

that occurred in plots at MUR, 

regardless of whether or not 

we removed wood samples 

and crossdated them. Not 

shown are eight Utah juniper 

trees. 

Figure Q-4—Chronologies of fire and tree recruitment at MUR. In (a), horizontal lines are plotcomposite fire-scar and cohort dates by forest type. Non-recorder years precede the first scar, 

whereas recorder years generally follow it, but non-recorder years can also occur when the catface 

margin is consumed by subsequent fires or rot. In (b) through (e), recruitment dates are given 

for species comprising ≥10 percent of trees with such dates. The latter part of the distribution is 

incomplete because we only cored trees that were ≥8 inches DBH. 
168 USDA Forest Service RMRS-GTR-261WWW. 2011.

density (trees/acre)

0 100 200 300 400 500

forest type

ponderosa pine

mixed conifer

aspen-mixed conifer

aspen

lodgepole

spruce-fir

0 100 200 300 400 500

(a) 1900 (b) 2000

Douglas-fir

tree

species

fire scars on trees sampled between plots

year

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

lodgepole

Engelmann spruce

ponderosa pine

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

Figure Q-5—Density of trees ≥8 inches DBH that were alive at each plot at MUR (a) in 1900 and (b) 

in 2000, by forest type (table 2). Not shown is one lodgepole plot (MUR10K), which had a density 

of 716 trees/acre in 1900 and 1038 trees in 2000.

Figure Q-6—Chronology of low-severity fires recorded on the 36 trees sampled between plots over 

approximately, 2460 acres throughout the MUR site.
USDA Forest Service RMRS-GTR-261WWW. 2011. 169

09I

mixed

09H

assumed

high

09G

mixed

09F

mixed

08F

high

04A

low

04B

mixed

05B

low

06A

assumed

mixed

06B

mixed

07B

assumed

high

07C

assumed

mixed

07D

assumed

high

07E

high

08D

assumed

high

08E

assumed

high

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

year year

quaking aspen Douglas-fir

Engelmann spruce lodgepole pine

ponderosa pine subalpine fir

Utah juniper MUR

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

Figure Q-7—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies of 

tree demography (recruitment and death), fire scars, and cohorts at each plot. Bark dates on 31 

stumps are shown as outer dates. Not shown are 36 fire-scarred trees sampled between plots. 

Inferred fire severity (table 3) is indicated to the left of each panel. 
170 USDA Forest Service RMRS-GTR-261WWW. 2011.

10I

low

10J

assumed

high

10N

mixed

10M

assumed

high

10L

mixed

10K

mixed

10H

assumed

high

10G

assumed

high

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

1500 1600 1700 1800 1900 2000

year

09O

assumed

high

09N

high

09M

assumed

high

09L

high

09K

assumed

high

09J

not

historically

forested

quaking aspen Douglas-fir

Engelmann spruce lodgepole pine

ponderosa pine subalpine fir

Utah juniper MUR

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

Figure Q-7—Continued. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 171

Figure Q-8—Intra-ring position of fire 

scars on trees sampled in and between 

plots at MUR from 1650 to 1900, 

as a percentage of the number of 

scars for which the position could be 

determined (given in parentheses). Not 

shown are intra-ring positions for two 

fire scars on Douglas-fir trees. 

Figure Q-9—Plot-composite 

intervals between low-severity 

fires in ponderosa pine plots 

at MUR from 1650 to 1900. 

Plots averaged 0.33 acres. 

The box (top) encloses the 

25th to 75th percentiles and the 

whiskers enclose the 10th to 90th

percentiles of the distribution 

of intervals. The vertical line 

indicates the median fire interval, 

and all values falling outside the 

10th to 90th percentiles are shown 

as circles. In the histogram 

(bottom), the same intervals are 

plotted in 10-year bins (1 to 10 

years, 11 to 20 years, and so 

forth).

5 ponderosa pine plots (18 intervals)

fire interval (years)

number of intervals

0 20 40 60 80 100

0

2

4
172 USDA Forest Service RMRS-GTR-261WWW. 2011. forest type

ponderosa pine

aspen-mixed conifer

aspen

lodgepole

spruce-fir

number of fire years

(1650 to 1900)

0 5 10

topographic relative

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure Q-10—Variation in fire among 

plots at MUR with topography, forest 

type, and relative soil moisture 

availability (Parker 1982). Number 

of fire years includes both fire-scar 

and cohort dates. Plots with no 

reconstructed fires during this period 

fall on the dotted line.

Figure Q-11—Relative extent 

of low-severity fires within 

the 2218-acre MUR site, 

from 1650 to 1900, as area 

(top) and as a percentage of 

the recording area (in other 

words, the combined area of 

cells containing recording, 

fire-scarred trees during each 

year; bottom). Commonly used 

fire-size classes are indicated 

at the top (NWCG 2007).
USDA Forest Service RMRS-GTR-261WWW. 2011. 173

Figure Q-12—Maps of years with evidence of low-severity fires in three or more cells at MUR. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped.
174 USDA Forest Service RMRS-GTR-261WWW. 2011.

Appendix R. Eastern Uinta Mountains, Ashley National 

Forest (BRO)

Topography

We sampled 30 plots over 1842 acres along Brownie Creek, on the Vernal Ranger District of 

the Ashley National Forest in Uintah County, Utah (figs. 1 and R-1). The plots were separated by 

0.30 miles on average (range 0.25 to 0.31 miles) and averaged 0.38 acres in area (range 0.15 to 

1.22 acres). Plots were sampled within cells that averaged 61 acres and ranged from 55 to 70 acres. 

Plots ranged in elevation from 7778 to 9667 ft (fig. R-2) and in slope from 2 to 72 percent. They were 

sampled on a range of aspects, but most were on south and west aspects (70 percent). The distribution of the plots by elevation, aspect, or slope did not differ from the distribution of the landscape 

by more than 10 percent in any category except south and west aspects, which were under and over 

sampled, respectively (fig. R-2). We took between two and four photographs at each of the plots.

Tree Demography

Of the 841 trees that occurred in the plots, most (98 percent) were Rocky Mountain juniper, 

ponderosa pine, Douglas-fir, quaking aspen, lodgepole pine, subalpine fir, or Engelmann spruce, but 

15 limber pine trees also occurred (fig. R-3). Most of these trees were living (80 percent) and the 

rest were snags (11 percent), logs (8 percent), or stumps (1 percent). We were able to remove and 

crossdate wood samples from most of the trees (731 trees or 87 percent), and we obtained actual or 

estimated pith dates for 669 of them. These pith dates ranged from 1400 to 1973 and many of these 

post-dated 1900 (196 trees; fig. R-4). The death dates we obtained for 116 logs and snags ranged 

from 1802 to 2004.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (sagebrush, shrubland, pinyonjuniper, ponderosa pine, mixed conifer, aspen-mixed conifer, aspen, lodgepole, and spruce-fir; table 

R-1). Some plots changed forest type between 1860 and 2000: one sagebrush plot converted to 

pinyon-juniper; two sagebrush, one shrubland, two pinyon-juniper, and one ponderosa pine plot 

converted to mixed conifer; and one aspen plot converted to aspen-mixed conifer. In 1900, tree 

density averaged 65 trees per acre and ranged from 0 to 194 trees per acre (fig. R-5). In 2000, tree 

density averaged 83 trees per acre and ranged from 11 to 194 trees per acre. However, we likely 

underestimated historical tree density because we could not obtain recruitment or earliest-ring dates 

for 110 of the 841 trees that occurred in the plots and only an earliest-ring date for another 62 trees. 

Ten of these trees had earliest-ring dates between 1901 and 1920 and therefore may have been living before 1900.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 73 trees, 4 of which had only 

scars that were recorded on a single tree and so were excluded from further analyses. Of the remaining 69 trees, about half (38 trees) were sampled in 17 of the 30 plots at this site (1 to 4 trees per plot). 

We sampled the 31 other fire-scarred trees as we encountered them between plots, over 688 acres 

throughout the site (fig. R-6). Most of the 69 fire-scarred trees were ponderosa pine (54 percent) 

and Douglas-fir (23 percent) and the rest were lodgepole pine, Engelmann spruce, subalpine fir, and 

Rocky Mountain juniper. About 90 percent were live trees (46 percent) or snags (45 percent) and the 

rest were logs. These 69 trees yielded 114 fire scars and 20 eroded fire scars or abrupt changes in ring 

width (figs. R-4 and R-7). However, five of these scar dates were eliminated from further analyses 
USDA Forest Service RMRS-GTR-261WWW. 2011. 175

because they were recorded on only a single tree at the site. We were able to assign an intra-ring 

position to 80 percent of the 94 fire scars that occurred during the analysis period (1650 to 1900). Of 

the scars that occurred on ponderosa pine trees, half (55 percent) occurred on the boundary between 

two rings (fig. R-8).

Post-Fire Cohorts

We identified 19 cohorts of trees from estimated recruitment dates at 18 of the plots. Seventeen of 

these cohorts were recruited before 1900 (1806 to 1895) and were identified from 243 trees (5 to 26 

trees per cohort), most of which were lodgepole pine (51 percent), Douglas-fir (20 percent), quaking aspen (14 percent), or Engelmann spruce (9 percent), but a few ponderosa pine and subalpine fir 

also occurred (figs. R-4 and R-7). The cohorts recruited before 1900 occurred in plots with a range 

of forest types: lodgepole (41 percent of cohorts), aspen (18 percent), mixed conifer (18 percent), 

spruce-fir (12 percent), aspen-mixed conifer (6 percent), and pinyon-juniper (6 percent).

Spatial Variation in Fire Regimes

We reconstructed too few fire intervals in plots during the analysis period (1650 to 1900) to compute plot-composite fire intervals by forest type at this site. The tree-ring record before 1900 was 

less than 100 years long for 13 of the 30 plots at this site (fig. R-9). We inferred that two plots were 

not historically forested, and we could not infer historical fire severity at two others because they did 

not meet our requirements for any of the severity categories (table R-2). We assigned the remaining 

plots to the low, mixed, or high fire severity categories.

From 1650 to 1900, the 10 low-severity fires we reconstructed within our 1842-acre sampling 

area averaged 284 acres and ranged from 61 to 910 acres (fig. R-10), equivalent to 11 to 94 percent 

of the recording area (in other words, the combined area of cells containing recording, fire-scarred 

trees during a given year). Recording area varied among fire years, ranging from 548 to 968 acres. 

We likely underestimated the extent of low-severity fires because most fires intersected the boundary of the site (fig. R-11).

Table R-1—Distribution of plots at BRO by historical (1860) and modern (2000) forest types (table 2).

Modern forest type (2000)

Historical forest Spruce- Aspen-mixed Mixed Pinyon- Total plots

type (1860) fir Lodgepole Aspen conifer conifer juniper in 1860

Spruce-fir 4 4

Lodgepole 7 7

Aspen 1 3 4

Aspen-mixed conifer 1 1

Mixed conifer 7 7

Ponderosa pine 1 1

Pinyon-juniper 2 2

Shrubland 1 1

Sagebrush 2 1 3

Total plots in 2000 4 7 1 4 13 1 30
176 USDA Forest Service RMRS-GTR-261WWW. 2011.

Table R-2—Distribution of plots at BRO by historical forest type (1860; table 2) and fire severity (table 3).

Assumed Assumed Not historically

Forest type High high Mixed mixed Low forested Unclassified

Spruce-fir 1 2 1

Lodgepole 2 5

Aspen 3 1

Aspen-mixed conifer 1

Mixed conifer 3 3 1

Ponderosa pine 1

Pinyon-juniper 1 1

Shrubland 1

Sagebrush 2 1

Total 6 3 11 4 2 2 2

D E F G

Brownie Creek

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

fire scars sampled between plots

Contour interval=100 ft

0 1 2 miles

7900

7900

9900

8900

8900

8900

Figure R-1—Locations of plots and 

crossdated fire-scarred trees 

that were sampled outside of 

plots. About half of the firescarred trees were sampled 

within plots and are not mapped 

individually. Plots are identified 

by column and row, in other 

words, the northwestern most 

plot is 8D, the next plot to the 

east is 8E, and so forth. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 177

percentage of trees

occurring at plots

0 5 10 15 20 25 30 35

tree species

Rocky Mountain juniper

ponderosa pine

Douglas-fir

quaking aspen

lodgepole pine

subalpine fir

Engelmann spruce

Figure R-2—Distribution of 

sampled plots and land 

area at BRO by topography. 

Aspect classes are 90o wide, 

beginning with 46o for east 

(E). Land area was derived 

from a digital elevation 

model (Utah AGRC 2004). 

Figure R-3—Distribution by 

species of the 841 live and 

dead trees ≥8 inches DBH 

that occurred in plots at BRO, 

regardless of whether or not we 

removed wood samples and 

crossdated them. Not shown 

are 15 limber pine trees. 
178 USDA Forest Service RMRS-GTR-261WWW. 2011.

(a) fire scars and cohorts composited at plots

aspen

ponderosa pine

mixed conifer

spruce-fir

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

shrubland

lodgepole

aspenmixed conifer

pinyon-juniper

sagebrush

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

(e) Douglas-fir

year

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

number of trees recruite

d

0

25

50

(d) quaking aspen

0

25

50

(c) lodgepole pine

0

25

50

(b) Engelmann spruce

0

25

50

75

Figure R-4—Chronologies of fire and tree recruitment at BRO. In (a), horizontal lines are plotcomposite fire-scar and cohort dates by forest type. Non-recorder years precede the first scar, 

whereas recorder years generally follow it, but non-recorder years can also occur when the catface 

margin is consumed by subsequent fires or rot. In (b) through (e), recruitment dates are given 

for species comprising ≥10 percent of trees with such dates. The latter part of the distribution is 

incomplete because we only cored trees that were ≥8 inches DBH. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 179

density (trees/acre)

0 100 200 300 400 500

forest type

sagebrush

shrubland

pinyon-juniper

ponderosa pine

mixed conifer

aspen-mixed conifer

aspen

lodgepole

spruce-fir

0 100 200 300 400 500

(a) 1900 (b) 2000

fire scars on trees sampled between plots tree species

juniper

ponderosa pine

Douglas-fir

year

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

fire scar

pith date inner date

recorder years non-recorder years

bark date outer date

Figure R-5—Density of trees ≥8 inches DBH that were alive at each plot at BRO (a) in 1900 and (b) in 

2000, by forest type (table 2). 

Figure R-6—Chronology of low-severity fires recorded on the 31 trees sampled between plots over 

approximately, 688 acres at the southern end of BRO. 
180 USDA Forest Service RMRS-GTR-261WWW. 2011.

08D

high

08E

mixed

09D

assumed

high

09E

assumed

high

10D

mixed

10E

mixed

11D

mixed

11E

mixed

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

11F

low

1500 1600 1700 1800 1900 2000

year 1500 1600 1700 1800 1900 2000

year

11G

mixed

12G

assumed

mixed

12F

not historically forested

12E

mixed

12D

assumed

mixed

quaking aspen Douglas-fir

Engelmann spruce lodgepole pine

ponderosa pine subalpine fir

limber pine Rocky Mountain juniper

fire scar cohort BRO

inner date pith date

outer date bark date

recorder years non-recorder years

Figure R-7—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies of 

tree demography (recruitment and death), fire scars, and cohorts at each plot. Bark dates on two 

stumps are shown as outer dates. Not shown are 31 fire-scarred trees sampled between plots. 

Inferred fire severity (table 3) is indicated to the left of each panel. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 181

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

15E

unclassified

15F

assumed

high

15G

high

17F

unclassified

16F

mixed

16E

high

16D

assumed

mixed

1500 1600 1700 1800 1900 2000

year

15D

low

14G

mixed

year

1500 1600 1700 1800 1900 2000

14F

high

14E

high

14D

mixed

13G

mixed

13F

high

13E

not historically forested

13D

assumed

mixed

quaking aspen Douglas-fir

Engelmann spruce lodgepole pine

ponderosa pine subalpine fir

limber pine Rocky Mountain juniper

fire scar cohort BRO

inner date pith date

outer date bark date

recorder years non-recorder years

Figure R-7—Continued. 
182 USDA Forest Service RMRS-GTR-261WWW. 2011. forest type

sagebrush

shrubland

pinyon-juniper

ponderosa pine

mixed conifer

aspen-mixed conifer

aspen

lodgepole

spruce-fir

number of fire years

(1650 to 1900)

0246

topographic relative

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure R-8—Intra-ring position of fire 

scars on trees sampled in and between 

plots at BRO from 1650 to 1900, as a 

percentage of the number of scars for 

which the position could be determined 

(given in parentheses). Not shown are 

intra-ring positions for 22 fire scars on 

Rocky Mountain juniper, Douglas-fir, 

and lodgepole pine trees.

Figure R-9—Variation in fire 

among plots at BRO with 

topography, forest type, 

and relative soil moisture 

availability (Parker 1982). 

Number of fire years includes 

both fire-scar and cohort dates. 

Plots with no reconstructed 

fires during this period fall on 

the dotted line.
USDA Forest Service RMRS-GTR-261WWW. 2011. 183

Figure R-11—Maps of years with evidence of low-severity fires in three or more cells at BRO. 

“Recording, no evidence of fire” indicates at least one tree was alive at that location during that 

year but did not have a fire scar or fire-caused injury. Empty cells indicate that no fire-scarred trees 

were recording in that cell during that year. Cohort dates are not mapped.

Figure R-10—Relative extent of 

low-severity fires within the 

1842-acre BRO site, from 

1650 to 1900, as area (top) 

and as a percentage of the 

recording area (in other words, 

the combined area of cells 

containing recording, firescarred trees during each year; 

bottom). Commonly used firesize classes are indicated at the 

top (NWCG 2007).
184 USDA Forest Service RMRS-GTR-261WWW. 2011.

Figure R-11—Continued.
USDA Forest Service RMRS-GTR-261WWW. 2011. 185

Appendix S. Wasatch Range, Uinta-Wasatch-Cache 

National Forest (WCH)

Topography

We sampled 30 plots over 2166 acres near Little Bear Creek in Logan Canyon on the Logan 

Ranger District of the Uinta-Wasatch-Cache National Forest in Cache County, Utah (figs. 1 and 

S-1). The plots were separated by 0.30 miles on average (range 0.28 to 0.40 miles) and averaged 

0.33 acres in area (range 0.09 to 1.39 acres). Plots were sampled within cells that averaged 62 acres 

and ranged from 56 to 68 acres. Plots ranged in elevation from 7393 to 8484 ft (fig. S-2) and in slope 

from 5 to 55 percent, but most were less than 25 percent (73 percent of plots). They were sampled 

on a range of aspects. The distribution of the plots by elevation, aspect, or slope did not differ from 

the distribution of the landscape by more than 10 percent in any category (fig. S-2). We took three 

or four photographs at each of the plots.

Tree Demography

All of the 909 trees that occurred in the plots were Douglas-fir, quaking aspen, lodgepole pine, 

subalpine fir, limber pine, or Engelmann spruce (fig. S-3). Most of these trees were living (79 percent) and the rest were snags (15 percent), logs (4 percent), or stumps (2 percent). We were able 

to remove and crossdate wood samples from fewer trees at this site than at others (564 trees or 62 

percent) largely because this site had a higher proportion of trees with rot (29 percent) than any of 

the other sites. We obtained actual or estimated pith dates for 544 of the crossdated trees. These pith 

dates ranged from 1679 to 1959 and many post-dated 1900 (179 trees; fig. S-4). The death dates we 

obtained for 22 logs and snags ranged from 1904 to 2005.

Historical and Current Forest Structure and Composition

The plots included a range of historical and modern forest types (mixed conifer, aspen, lodgepole, and spruce-fir; table S-1). Some plots changed forest type between 1860 and 2000: 3 aspen and 

1 spruce-fir plot converted to mixed conifer; three aspen and one spruce-fir plot converted to aspenmixed conifer; and two aspen plots converted to spruce-fir. In 1900, tree density averaged 58 trees 

per acre and ranged from 2 to 202 trees per acre (fig. S-5). In 2000, tree density averaged 108 trees 

per acre and ranged from 14 to 245 trees per acre. However, we likely underestimated historical 

tree density because we could not obtain recruitment or earliest-ring dates for 345 of the 909 trees 

that occurred in the plots and only an earliest-ring date for another 20 trees. Nine of these trees had 

earliest-ring dates between 1901 and 1920 and therefore may have been living before 1900.

Fire Scars

We were able to remove and crossdate fire-scarred samples from 16 trees, all of which were 

sampled in 5 of the 30 plots at this site (1 to 9 trees per plot, average 3 trees). We did not sample 

any fire-scarred trees between plots at this site. Most of the fire-scarred trees were lodgepole pine 

(88 percent) and the rest were Douglas-fir. Most were live trees (88 percent) and the rest were logs. 

These 16 trees yielded 18 fire scars (figs. S-4 and S-6). We were able to assign an intra-ring position 

to each of the four fire scars that occurred during the analysis period (1650 to 1900).
186 USDA Forest Service RMRS-GTR-261WWW. 2011.

Post-Fire Cohorts

We identified 10 cohorts of trees from estimated recruitment dates at 10 of the plots. Eight of 

these cohorts were recruited before 1900 (1748 to 1885) and were identified from 64 trees (5 to 16 

trees per cohort) composed of subalpine fir (38 percent), Douglas-fir (38 percent), lodgepole pine 

(9 percent), quaking aspen (8 percent), or limber pine (8 percent) (figs. S-4 and S-6). The cohorts 

that were recruited before 1900 occurred in plots with a range of forest types: aspen (63 percent of 

cohorts), mixed conifer (25 percent), and lodgepole pine (13 percent).

Spatial Variation in Fire Regimes

We reconstructed too few fire intervals in plots during the analysis period (1650 to 1900) to compute plot-composite fire intervals by forest type at this site. The tree-ring record before 1900 was 

less than 100 years long for 18 of the 30 plots at this site (fig. S-7).

We could not infer historical fire severity at one plot because it did not meet our requirements for 

any of the severity categories (table S-2). We assigned the remaining plots to the mixed or high fire 

severity categories.

From 1650 to 1900, we reconstructed only two low-severity fires within our 2166-acre sampling 

area. One was 120 acres and the other was 126 acres, equivalent to 66 and 100 percent of the recording area, respectively (in other words, the combined area of cells containing recording, fire-scarred 

trees during a given year). Recording area during these fire years was 181 and 126 acres, respectively. We likely underestimated the extent of these low-severity fires because both intersected the 

boundary of the site (fig. S-8).

Table S-2—Distribution of plots at WCH by historical forest type (1860; 

table 2) and fire severity (table 3).

Assumed Assumed

Forest type High high Mixed mixed Unclassified

Spruce-fir 6

Lodgepole 5 1

Aspen 4 3 1 1

Mixed conifer 2 1 6

Total 6 15 2 6 1

Table S-1—Distribution of plots at WCH by historical (1860) and modern (2000) forest types (table 2).

Modern forest type (2000)

Historical forest Spruce- Aspen-mixed Mixed Total plots

type (1860) fir Lodgepole Aspen conifer conifer in 1860

Spruce-fir 4 1 1 6

Lodgepole 6 6

Aspen 2 1 3 3 9

Mixed conifer 9 9

Total plots in 2000 6 6 1 4 13 30
USDA Forest Service RMRS-GTR-261WWW. 2011. 187

C D E F G H I J K

5

6

7

8

9

Evidence from crossdated trees:

recruitment dates

recruitment dates and fire scars

none (no trees 8 inches DBH)

Contour interval=100 ft

0 1 2 miles

6900

7900

Little Bear Creek

7900

7900

Figure S-1—Locations of plots and crossdated fire-scarred trees that were sampled outside plots. 

All of the fire-scarred trees were sampled within plots and are not mapped individually. Plots are 

identified by column and row, in other words, the southwestern most plot is 9C, the next plot to 

the east is 9D, and so forth. 

Figure S-2—Distribution of sampled 

plots and land area at WCH by 

topography. Aspect classes are 

90o wide, beginning with 46o for 

east (E). Land area was derived 

from a digital elevation model 

(Utah AGRC 2004). 
188 USDA Forest Service RMRS-GTR-261WWW. 2011.

percentage of trees

occurring at plots

0 10 20 30 40 50

tree species

Douglas-fir

quaking aspen

lodgepole pine

subalpine fir

limber pine

Engelmann spruce

(a) fire scars and cohorts composited at plots

aspen

mixed conifer

spruce-fir

forest type

fire scar

pith date inner date

cohort recorder years non-recorder years

bark date outer date

lodgepole

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

(b) subalpine fir

0

10

20

30

(e) Douglas-fir

year

1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000

number of trees recruite

d

0

10

20

(c) lodgepole pine

0

10

20

(d) quaking aspen

0

10

20

Figure S-3—Distribution by species 

of the 909 live and dead trees 

≥8 inches DBH that occurred 

in plots at WCH, regardless of 

whether or not we removed 

wood samples and crossdated 

them. 

Figure S-4—Chronologies of fire and tree recruitment at WCH. In (a), horizontal lines are plot-composite fire-scar 

and cohort dates by forest type. Non-recorder years precede the first scar, whereas recorder years generally follow 

it, but non-recorder years can also occur when the catface margin is consumed by subsequent fires or rot. In (b) 

through (e), recruitment dates are given for species comprising ≥10 percent of trees with such dates. The latter 

part of the distribution is incomplete because we only cored trees that were ≥8 inches DBH. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 189

density (trees/acre)

0 100 200 300 400 500

forest type

mixed conifer

aspen-mixed conifer

aspen

lodgepole

spruce-fir

0 100 200 300 400 500

(a) 1900 (b) 2000

Figure S-5—Density of trees ≥8 inches DBH that were alive at each plot at WCH (a) in 1900 and (b) in 

2000, by forest type (table 2). 
190 USDA Forest Service RMRS-GTR-261WWW. 2011.

05E

high

05F

assumed

high

05G

assumed

high

05H

assumed

mixed

05I

assumed

mixed

06D

assumed

high

06F

high

06G

high

06J

assumed

high

06K

assumed

high

07E

high

07H

assumed

high

07I

assumed

high

07J

assumed

high

08G

assumed

mixed

08F

assumed

mixed

08E

assumed

mixed

07K

assumed

high

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

1500 1600 1700 1800 1900 2000

year

quaking aspen Douglas-fir

Engelmann spruce lodgepole pine

subalpine fir limber pine

WCH

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

Figure S-6—Fire-demography diagrams (FDDs, Brown and others 2008b) showing chronologies of tree 

demography (recruitment and death), fire scars, and cohorts at each plot. The bark date on one stump 

is shown here as an outer date. Inferred fire severity (table 3) is indicated to the left of each panel. 
USDA Forest Service RMRS-GTR-261WWW. 2011. 191

09J

assumed

high

09H

assumed

high

09I

mixed

09G

mixed

09F

assumed

high

1500 1600 1700 1800 1900 2000 1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

year

year

09E

assumed

mixed

09D

high

09C

unclassified

08K

assumed

high

08J

assumed

high

08I

assumed

high

08H

high

quaking aspen Douglas-fir

Engelmann spruce lodgepole pine

subalpine fir limber pine

WCH

fire scar cohort

inner date pith date

outer date bark date

recorder years non-recorder years

Figure S-6—Continued. 
192 USDA Forest Service RMRS-GTR-261WWW. 2011. forest type mixed conifer aspen

lodgepole

spruce-fir

number of fire years

(1650 to 1900)

0 5

topographic relative

moisture index

0

10

20

30

40

50

elevation (ft)

7000

8000

9000

10000

xeric mesic

100 or more years

fewer than 100 years

length of record

Figure S-8—Map of the one 

year with evidence of lowseverity fires in three or more 

cells at WCH. “Recording, 

no evidence of fire” 

indicates at least one tree 

was alive at that location 

during that year but did 

not have a fire scar or firecaused injury. Empty cells 

indicate that no fire-scarred 

trees were recording in that 

cell during that year. Cohort 

dates are not mapped.

Figure S-7—Variation in fire among 

plots at WCH with topography, 

forest type, and relative soil 

moisture availability (Parker 1982). 

Number of fire years includes both 

fire-scar and cohort dates. Plots 

with no reconstructed fires during 

this period fall on the dotted line.
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 Research Station

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