Forest 

Service

Mapping Pyrophilic Percentages 

across the Northeastern United States 

using Witness Trees, with Focus 

on Four National Forests

Melissa A. Thomas-Van Gundy

Gregory J. Nowacki

Charles V. Cogbill

United States Department of Agriculture

General Technical 

Report NRS-145

Northern 

Research Station February 2015
Visit our homepage at: http://www.nrs.fs.fed.us/

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February 2015 Fax: 740-368-0152

Manuscript received for publication August 2014

Abstract

Witness trees provide information fundamental for restoration ecology, often serving as baselines 

for forest composition and structure. Furthermore, when categorized by fire relations, witness trees 

can shed light on past disturbance regimes. Kriging was applied to witness-tree point data to form 

a contiguous surface of pyrophilic percentage for four national forests in the northeastern United 

States. Fire was found to be an important disturbance agent on the Allegheny and Finger Lakes 

National Forests, often corresponding to large river systems and lakesides where Native American 

activities were concentrated. In contrast, fire was relatively unimportant on the Green Mountain 

and White Mountain National Forests based on the witness-tree record. There, the cool, moist 

year-round climate, coupled with lower Native American population densities greatly subdued fire, 

supporting the local view of these as “asbestos” forests. When applying this method to town-level 

witness-tree data for the entire northeastern United States, we found a distinct east-west line 

dividing areas of high (south) and low (north) pyrophilic percentage. Known as the tension zone 

line, the undulating character of this boundary, penetrating northward along major river valleys, 

underscores the importance of Native Americans as a disturbance agent on the presettlement 

landscape. 

Authors

MELISSA A. THOMAS-VAN GUNDY is a research forester with the U.S. Forest Service, Northern 

Research Station, in Parsons, WV 26287.

GREGORY J. NOWACKI is a regional ecologist with the U.S. Forest Service, Eastern Regional 

Office, Milwaukee, WI 53202.

CHARLES V. COGBILL is an ecologist with Harvard Forest, Petersham, MA 03166.


INTRoDUCTIoN

Europeans have transformed the environment since 

their New World arrival (Mann 2005, Whitney 994). 

This effect is especially true for the Northeast (Foster 

and Motzkin 998), where Europeans have a long 

history through early settlement and interactions with 

Native cultures, perhaps dating back to the Vikings 

(Barnes 200). European influences moved across 

the continent in waves, often far in advance of their 

appearance (Richter 200). The fur trade was the first 

major European activity with far-reaching impacts, 

quickly depleting beaver (Castor canadensis Kuhl) 

populations and allowing widespread conversion of 

open riparian habitats to forests, possibly accompanied 

by increased stream incision and erosion (Innis 999, 

Parker et al. 985, Richter 200). Early encounters 

with Europeans proved devastating to Native 

American peoples through the transmission of diseases 

(Cook 973, Crosby 967, Dobyns 993, Ramenofsky 

2003), leading to mass pandemics with severe cultural 

and social upheavals and land-use repercussions 

(Mann 2005, Richter 200). As Native American 

populations waned and were forced westward, 

European populations expanded, led by a surge of 

forest clearing for timber and agriculture during the 

7th and 8th centuries (Foster and Motzkin 998). By 

the mid-800s, soil degradation and market access to 

the fertile Midwest led to the retraction of agriculture 

in New England, allowing for widespread reforestation 

as exemplified by eastern white pine (Pinus strobus L.) 

(Raup 966). Even today, with urban and suburban 

development, the region still remains largely forested, 

especially in New England (Brooks 2003). 

The forests that covered the northeastern United 

States before European settlement are long gone, but 

they can be reasonably reconstructed through the use 

of witness trees from early land warrants (Cogbill et 

al. 2002, McIntosh 972, Seischab 990, Whitney 

990). When incorporating ecophysiological and 

fire relations knowledge, we can further use witness 

trees to reconstruct past fire regimes, helping specify 

where fire was an important disturbance agent on 

the presettlement landscape (Thomas-Van Gundy 

and Nowacki 203). All forms of information, 

witness-tree-based compositions, structures, and 

disturbance regimes, are vitally important for land 

managers and conservationists involved in ecological 

restoration, with the understanding of disturbance 

regimes helping guide the return of fire back onto 

landscapes that formerly burned (Brose et al. 200, 

Nowacki et al. 2009, Nowacki and Carr 203). To 

aid this cause, we apply a recently published method 

(Thomas-Van Gundy and Nowacki 203) converting 

witness trees to pyrophilic-percentage maps to help 

identify presettlement fire gradients across four 

northeastern national forests: Allegheny (ANF), 

Finger Lakes (FLNF), Green Mountain (GMNF), and 

White Mountain (WMNF). Furthermore, town-level 

witness tree data (Thompson et al. 203) allowed us 

to project pyrophilic percentages at a regional scale, 

helping to define the division (i.e., tension zone line) 

between southern oak-pine (Quercus-Pinus) and 

northern hardwood systems bisecting the region (sensu 

Cogbill 2000, Cogbill et al. 2002) and the relationship 

of this boundary line to fire. The production of 

maps at multiple scales will help land managers, 

conservationists, and researchers understand local 

pre-European settlement fire regimes and their context 

within a larger regional perspective. 

MeThoDS

Study Areas

The national forests in this analysis cover portions 

of five states in the northeastern United States: 

Pennsylvania, New York, Vermont, New Hampshire, 

and Maine (Fig. ). The entire northeast region spans 

five ecological provinces, although only three are 

represented on the national forests. The ANF lies 

within the Northeastern Mixed Forest Province, the 
2

Figure 1.—Locations of the four national forests and five ecological provinces in the study area.
3

FLNF within the Midwest Broadleaf Forest Province, 

and the GMNF and WMNF lie within the AdirondackNew England Mixed Forest-Coniferous Forest-Alpine 

Meadow Province (Cleland et al. 2007).

The topography and surficial geology of the FLNF, 

GMNF, and WMNF were directly shaped by past 

glaciations, especially the Wisconsin glaciation. 

Over more rugged terrain (GMNF and WMNF), 

overriding glaciers were more erosional in nature, 

scouring mountains and leaving behind a thin veneer 

of locally derived sediments on ridge tops and side 

slopes with thicker accumulations on lower valley 

floors (Van Driver 987). On flat to rolling terrain 

(FLNF), glaciation was more depositional in nature, 

leaving behind thicker deposits of unconsolidated 

materials often in distinct landforms such as moraines 

and drumlin fields (Van Driver 985). Although not 

directly impacted by the Wisconsin glaciation, the 

ANF was affected by periglacial processes (freezethaw action, solifluction, nivation) due to its close 

proximity to the ice sheet leaving behind distinct 

features in some cases (talus slopes, patterned ground). 

Glacially driven land cover changes were profound 

during the Holocene, generally passing from ice 

(FLNF, GMNF, and WMNF) or tundra conditions 

(ANF) through open woodlands to forests (Davis and 

Jacobson 985). Waves of arboreal species moved 

independently across the region largely reflecting 

their mode of dispersal and sensitivity to temperature, 

with light-seeded, cold-tolerant species emerging first 

(Pielou 99). In general, Holocene vegetation shifted 

from poplar (Populus spp.) and spruce (Picea spp.) to 

pine dominance before succeeding to hemlock, maple, 

and beech (Tsuga-Acer-Fagus) communities in the 

north and oak-dominated communities in the south 

(Bernabo and Webb 977, Davis and Jacobson 985).

Witness-tree Data

Witness-tree databases with species and digital point 

locations were compiled from original land survey 

records contained in various archives by Charles 

Cogbill, funded in part by the U.S. Forest Service. 

An additional 06 points were included for the 

FLNF from a scanned map of corner trees for the 

area around Hector, NY. Two survey systems were 

represented in our study, a rectangular system similar 

to the Government Land Office (GLO) system in 

Pennsylvania (ANF) and New York (FLNF), and 

the proprietary town system in Vermont and New 

Hampshire (GMNF and WMNF). In both systems, 

witness trees were represented as corner or bearing 

trees; however, unlike in the GLO system, no 

information other than species/genera was recorded 

for each tree. 

Analysis Methods

Witness-tree point locations were converted to 

pyrophilic percentage maps following the procedures 

of Thomas-Van Gundy and Nowacki (203). First, 

witness trees were categorized as either pyrophilic 

or pyrophobic at the genus and/or species levels 

(Table ). For this analysis, we focused on species 

traits adapted (or not) to a long-term regime of 

recurrent surface fire, although many species may 

take advantage of conditions created after a single 

fire (e.g., yellow birch [Betula alleghaniensis], 

yellow-poplar [Liriodendron tulipifera], black cherry 

[Prunus serotina]). Witness trees possessing traits 

for persistence under recurring fire were considered 

pyrophilic; those possessing fire-sensitive, mesophytic 

traits were considered pyrophobic (Table ). Because 

all survey corners were represented by only one 

witness tree, the categorization resulted in points 

being either 0 or 00 percent pyrophilic. For the 

four national forests, ordinary kriging was used 

to interpolate between the points (survey corners 

with witness trees) to create a continuous surface of 

predicted pyrophilic percentages. Ordinary kriging 

is an interpolation technique where the best linear 

unbiased estimator is calculated for locations with 

unknown values and for the mean residual error to 

equal to zero (Isaaks and Srivastava 989). For all 

national forests and regional-level witness trees, a 

maximum of five and a minimum of two neighboring 

points were used for interpolation. 
4

Common name 

used in surveys Scientific name

Relationship 

to fire Vital attribute related to fire References

Ash Fraxinus americana Pyrophobic Fire-discouraging leaves, mesophyte FEIS

Basswood, linden, 

linn, linnwood, 

white wood

Tilia spp. Pyrophobic Thin bark, shallow roots, firediscouraging leaves, mesophyteFEIS

Beech, red beech Fagus grandifolia Pyrophobic Thin bark, fire discouraging leaves, 

mesophyte

FEIS

Birch Betula spp. Pyrophobic Thin bark, fire-discouraging leaves, 

poor sprouting, mesophyte

FEIS

Black ash Fraxinus nigra Pyrophobic Fire sensitive, landscape position Burns and Honkala 

1990, FEIS

Black jack Quercus velutina Pyrophilic Thick bark, sprouting, fire-encouraging 

leaves, xerophyte, tap root

FEIS

Black oak Quercus velutina Pyrophilic Thick bark, sprouting, fire-encouraging 

leaves, xerophyte, tap root

FEIS

Black spruce Picea mariana Pyrophobic Landscape position in study area Burns and Honkala 

1990, FEIS

Butternut, white 

walnut

Juglans cinerea Pyrophobic Mesophyte, fire-discouraging leaves FEIS

Buttonwood Plantanus occidentalis Pyrophobic Thin bark, mesophyte FEIS

Cedar Thuja occidentalis Pyrophobic Landsdscape position, thin bark, 

shallow roots

Burns and Honkala 

1990, FEIS

Cherry Prunus serotina Pyrophobic Thin bark, fire-discouraging leaves, 

mesophyte

FEIS

Chestnut Castanea dentata Pyrophilic Sprouting, thick bark, fire-encouraging 

leaves, tap root, rot resistance

Delcourt and 

Delcourt 1998, 

Perry and Ison 

2003

Chestnut or rock 

oak 

Quercus prinus Pyrophilic Thick bark, sprouting, fire-encouraging 

leaves, xerophyte, tap root

FEIS

Cucumber, 

elkwood

Magnolia acuminata Pyrophobic Thin bark, mesophyte Burns and Honkala 

1990

Dogwood Cornus spp. Pyrophilic Susceptible to fungal disease under 

closed canopy 

FEIS, Holzmueller 

et al. 2008

Elm, white elm, 

red elm

Ulmus spp. Pyrophobic Thin bark, fire-discouraging leaves, 

mesophyte

FEIS

Fir Abies balsamea Pyrophobic Thin bark FEIS

Gum Nyssa sylvatica Pyrophilic Thick bark Abrams 2007, 

FEIS

(Continued on next page)

Table 1.—Species listed as witness trees in early land surveys of the Northeast and their assignment as 

pyrophobic or pyrophilic
5

Common name 

used in surveys Scientific name

Relationship 

to fire Vital attribute related to fire References

Hackmatac, 

tamarack

Picea mariana or Larix 

laricinia

Pyrophobic Landscape position in study area, thin 

bark, shallow roots

Burns and Honkala 

1990, FEIS

Hard maple, 

sugar maple, 

rock maple, white 

maple

Acer saccharum Pyrophobic Thin bark, fire-discouraging leaves, 

shade tolerant, mesophyte

FEIS

Hemlock, spruce 

pine

Tsuga canadensis Pyrophobic Thin bark, shallow roots, mesophyte FEIS

Hickory Carya spp. Pyrophilic Thick bark (most species), xerophyte, 

tap root

FEIS

Hornbeam, 

ironwood, water 

beech, leverwood, 

hazel, witch hazel, 

elk horn

Ostrya virginiana, 

Carpinus caroliniana, 

Hammamelis 

virginiana, Corylus 

spp.

Pyrophobic Thin bark, shade tolerant, mesophyte, 

fire-encouraging leaves

FEIS

Juneberry/

serviceberry

Amelanchier spp. Pyrophobic Thin bark, fire-discouraging leaves FEIS

Laurel Rhododendron spp. or

Kalmia spp.

Pyrophilic Fire-encouraging leaves FEIS

Maple Acer spp. Pyrophobic Thin bark, fire-discouraging leaves, 

mesophyte, red maple increases in 

absence of fire

FEIS

Moose bush Viburnum alnifolium Pyrophobic Mesophyte, fire sensitive FEIS

Moose willow, 

moosewood

Acer pensylvanicum Pyrophobic Thin bark, fire-discouraging leaves, 

mesophyte

FEIS

Mulberry Morus spp. Pyrophobic Thin bark, fire-discouraging leaves, 

mesophyte

Oak Quercus spp. Pyrophilic Thick bark, sprouting, fire-encouraging 

leaves, xerophyte, tap root

Abrams 1990, 

Abrams 2000

Pitch pine Pinus rigida Pyrophilic Cone serotiny, sprouting, needle 

volatility, xerophyte

FEIS, Keeley 2012

Poplar, aspen Populus spp. Pyrophilic Thick bark, sprouting FEIS

Red ash Fraxinus pensylvanica Pyrophobic Landscape position FEIS

Red oak Quercus rubra Pyrophilic Thick bark, sprouting, fire-encouraging 

leaves, tap root

FEIS

Red or yellow 

birch

Betula allegheniensis Pyrophobic Thin bark, fire-discouraging leaves, 

opportunist but not fire-adapted

Burns and Honkala 

1990, FEIS

Round top Sorbus americana Pyrophobic Thin bark, landscape position FEIS

Sassafras Sassafras albidum Pyrophilic Thick bark, sprouting, xerophyte FEIS

(Continued on next page)

Table 1 (continued).
6

Common name 

used in surveys Scientific name

Relationship 

to fire Vital attribute related to fire References

Soft maple Acer rubrum Pyrophobic Thin bark, fire-discouraging leaves, 

mesophyte, red maple increases in 

absence of fire

FEIS

Spicewood Lindera benzoin Pyrophobic Landscape position, facultative 

wetland plant in many areas

NRCS 2014

Spruce Picea rubens Pyrophobic Thin bark, shallow roots, mesophyte FEIS, White and 

Pickett 1985

Water birch Betula nigra or lenta Pyrophobic Thin bark, fire-discouraging leaves, 

mesophyte

Burns and Honkala 

1990

White birch Betula papyrifera Pyrophilic Sprouting, re-seeds post fire, 

flammable bark

FEIS

White oak Quercus alba Pyrophilic Thick bark, sprouting, fire-encouraging 

leaves, xerophyte, tap root

FEIS

White pine Pinus strobus Pyrophilic Thick bark on older trees, seedbed 

requirements, needle volatility

Abrams 2001, 

FEIS, Keeley 2012

Table 1 (continued).

We estimated user resolution of the interpolated 

pyrophilic percentage data by employing average 

nearest neighbor analysis (Mitchell 2005). Nearest 

neighbor distances were averaged from pairwise 

comparisons of witness-tree points in ArcMap 0 

using the Spatial Statistics tool (ESRI 200). The 

average nearest neighbor distance was then squared 

to determine an estimate of user resolution for each 

interpolated pyrophilic percentage map for the four 

national forests; the recommended user resolution for 

the regional witness tree data came from Thompson et 

al. (203). 

To investigate the role of Native Americans on forest 

dynamics in the Northeast, we mapped known Native 

American settlements, represented spatially as points, 

from published literature (Table 2). These settlements 

were transferred to digital maps using descriptions in 

the published literature and modern maps as guides. 

These point locations were buffered by 5 and 0 

km to analyze Native American relations to species 

composition (Black et al. 2006). Mean pyrophilic 

percentages were calculated on a 500 m grid for the 

continuous surface of predicted percentages. From 

this grid, mean pyrophilic percentages were calculated 

for the area within and outside of 5 and 0 km radii 

from Native American settlements; the area in lakes 

was removed from the binomial analysis. We used 

a generalized linear model via PROC GLIMMIX 

(SAS 203) to compare pyrophilic percentages within 

and beyond 5 and 0 km of Native American sites. 

Because the data were percentages, we used the beta 

distribution with the logit link function. Distance 

from American Indian settlement was the only fixed 

effect in the model. We used LSMEANS to compare 

the results; all analyses were conducted at α = 0.05 

significance.

For the regional product, we used the witness-tree 

data from a set of 70 proprietary towns covering 

Maine, New Hampshire, Vermont, Massachusetts, 

Connecticut, New York, Rhode Island, Pennsylvania, 

and New Jersey (Harvard Forest Dataset HF20; 

Thompson et al. 203). For each proprietary town, the 

relative abundances for each genera or species were 

calculated. The species or genera were categorized as 

either pyrophilic or pyrophobic as explained above. 

The percentage of pyrophilic witness trees was 

calculated for each town by summing the relative 

abundances for blackgum (Nyssa sylvatica), American 
7

National forest

Site 

number Site name General location References

Allegheny 1 Buckaloons Mouth of Brokenstraw Creek; 

near present-day Irvine.

Sipe 1930, Kent et al. 1981, 

Ruffner and Abrams 2002, Black 

et al. 2006

2 Conewango Mouth of Conewango Creek; 

near present-day Warren.

Sipe 1930, Deardorff 1946, Kent 

et al. 1981, Black et al. 2006

3 Genesinguhta, 

Old Town, 

Tiozinossongochta 

(NY)

Nine miles above 

Jenuchshadega on northwest 

side of Allegheny River in New 

York State.

Wallace 1952, Deardorff 1946

4 Goschgoschunk, 

Goschgoschink, 

Goshgoshing, 

Damascus, 

Conenugayaa

Locations spread from mouth of 

West Hickory Creek to the mouth 

of Tionesta Creek; from presentday communities of West Hickory 

to Tionesta.

Sipe 1930, Deardorff 1941, 

Deardorff 1946, Kent et al. 1981

5 Lawunakhannek, 

Hickory Townb

Mouth of Hickory Creek; near 

present-day East Hickory.

Sipe 1930, Deardorff 1946, Kent 

et al. 1981

6 Jenuchshadega, 

Cornplanter, 

Dionesadage

On Allegheny River; 6 mi east of 

present-day Scandia.

Sipe 1930, Deardorff 1941, 

Wallace 1952, Kent et al. 1981

7 Tidioute On the Allegheny River; near 

present-day Tidioute.

Deardorff 1941; Deardorff 1946, 

Black et al. 2006.

Finger Lakes 8 Kendaia, Appletown East shore of Lake Seneca. Jordan 2010, Marks and Gardescu 

1992, Sullivan Expedition Mapc

9 Kanadesaga, 

Kanasadega

Northwest corner of Lake 

Seneca.

Jordan 2010, Sullivan Expedition 

Mapc

Green Mountain 10 Skitchewaug West side of Connecticut River 

near present-day Windsor, VT.

Chilton 2002, Petersen and Cowie 

2002

11 Fort Hill East side (NH) of Connecticut 

River across from present-day 

Brattleboro, VT.

Chilton 2002, Petersen and Cowie 

2002

White Mountain 12 Winnepesaukee 

(near center of 

Winnepesaukee 

population)

West of Lake Winnipesaukee 

near present-day Meredith 

Center, NH.

Cook 1976, Calloway 1990

13 Cowass (center of 

Coosuc population)

Mouth of the Ammonoosuc River 

near present-day Woodville.

Cook 1976, Calloway 1990

14 Ossipee (center of 

Ossipee population)

West side of Ossipee Lake. Cook 1976, Calloway 1990

15 Pigwacket, Pequaket On the Saco River near presentday Fryeburg, ME.Cook 1976, Calloway 1990

16 Conway Located along the Saco River 

near present-day Intervale Park, 

Conway, NH.

Calloway 1990, Boisvert 1999

17 Randolph Located along the Moose River 

near present-day Randolph, NH.

Boisvert 1999

18 Mt. Jasper Near Berlin, NH. Boisvert 1999

19 Israel River Complex Near present-day Jefferson, NH. Boisvert 1999

Table 2.—Documented Native American settlements near the Allegheny, Finger Lakes, Green Mountain, 

and White Mountain National Forests

a Actually consists of three towns (Upper Town, Middle Town, Lower Town) along six river miles (Deardorff 1946).

b Village known by both names (Kent et al. 1981).

c http://sullivanclinton.com/maps/images/iroquoisinvasion.jpg
8

chestnut (Castanea dentata), hickory (Carya), 

oak, pine, and poplar. Ordinary kriging was used 

to interpolate pyrophilic percentage between town 

polygons. 

ReSULTS

The density of witness trees varied by survey 

(Table 3), but being rectangular or town-based, this 

variation is not completely tied to the underlying 

topography like metes-and-bounds surveys elsewhere. 

Land surveys in the areas that later became the 

individual national forests largely took place from the 

late 700s through the early 800s. Compiled town 

surveys across the entire Northeast region spanned 

a longer time period from roughly 670 to 890 

(Thompson et al. 203). Witness-tree samples were 

most densely clustered on the FLNF (averaging 

.35 trees/mi2 ) and least on the WMNF 

(0.6 trees/mi2 ).

A broad mix of pyrophobic and pyrophilic witness 

trees was present on the ANF and FLNF (Table 4). 

Spatially, pyrophilic trees were concentrated within the 

western sectors of both national forests immediately 

adjacent to water bodies, specifically the Allegheny 

River on the ANF and Seneca Lake on the FLNF 

(Figs. 2, 3). In contrast, witness trees were 

overwhelmingly pyrophobic on the GMNF and 

WMNF (Table 4; Figs. 4, 5).

National forest Survey type

Survey time 

period (not 

inclusive)

No. of witness 

trees/towns

Study area* 

(mi2)

Avg. no. of 

witness trees/

mi2 (range)

Estimated 

user resolution 

of pyrophilic 

percentage map

Allegheny Rectangular 1790-1889 3,003 2,594 1.15 (0 - 12) 109 ac

Finger Lakes Rectangular 1790-1796 585 433 1.35 (0 - 5) 173 ac

Green Mountain Town 1770-1870 1,007 2,834 0.35 (0 - 15) 91 ac

White Mountain Town 1751-1798 748 4,562 0.16 (0 – 11) 227 ac

Northeast Region Public land 

surveys, 

rectangular 

surveys, and 

deeds 

1672-1890 701 160,175 N/A 39 mi2

Table 3.—Descriptive parameters of witness tree data used in local (national forest) and regional analyses

* Study area = area of kriged surface; see individual NF maps for reference. Generally these are the square extent of the witness tree points 

used as input to kriging, minus larger bodies of water.

Witness tree type Allegheny Finger Lakes Green Mountain White Mountain

Tsuga 485 14 68 75

Acer 375 107 101 67

Fagus 955 118 387 204

Other pyrophobe 445 106 447 373

All pyrophobes 2,260 (75%) 345 (59%) 1,003 (≈100%) 719 (96%)

Pinus 138 41 2 13

Quercus 360 146 0 5

Carya 50 22 0 0

Other pyrophobe 195 31 2 11

All pyrophiles 743 (25%) 240 (41%) 4 (<1%) 29 (4%)

Total 3,003 585 1,007 748

Table 4.—Witness tree counts (percentages in parentheses) by pyrogenicity for four national forests in 

the northeastern United States
9

Figure 2.—Witness tree locations by indicator class for the Allegheny National Forest.
0

Figure 3.—Witness tree locations by indicator class for the Finger Lakes National Forest.


Figure 4.—Witness tree locations by indicator class for the Green Mountain National Forest.
2

Figure 5.—Witness tree locations by indicator class for the White Mountain National Forest.
3

The distributional patterns displayed by witness-tree 

points (Figs. 2 through 5) were transformed into 

continuous surfaces of pyrophilic percentages through 

kriging (Figs. 6 through 9). Accordingly, pyrophilic 

percentages were high (≥51%) along most of the 

course of the Allegheny River (Fig. 6) and along 

Seneca Lake (Fig. 7), the latter actually enveloping 

the south half of the FLNF within Hector Falls and 

Tug Hollow Creek drainages. The FLNF was the most 

pyrogenic in terms of pyrophilic tree representation 

(41%; Table 4) and areal coverage in pyprophilic 

percentages above 50 percent (59%; Table 5). On the 

ANF, 25 percent of the witness trees were categorized 

as pyrophilic (Table 4), resulting in 7 percent of 

the area having pyrophilic percent class above 50 

percent (Table 5). Because very few witness trees were 

categorized as pyrophilic on the GMNF 

and WMNF (<1% and 4%, respectively; Table 4), 

low pyrophilic percentages (≤ 20%) predominated in 

these national forests and surrounding areas (Table 5; 

Figs. 8, 9).

Possible Native American influence on pyrogenicity 

is apparent in the analysis of least square mean 

pyrophilic percent within set distances of known 

Native American settlements (Table 6). Least square 

mean pyrophilic percentages within 5 and 0 km 

of known Native American sites on the ANF were 

significantly higher than means outside those radii 

(61% vs. 37% and 52% vs. 32%, respectively). For 

the FLNF, pyrophilic percentages were significantly 

different only within 5 km of known Native American 

sites (59% within vs. 45% beyond; Table 6). There 

were too few locations and grid cells within the 

analysis area for meaningful analysis of the GMNF. 

On the WMNF, the relationship found on the ANF 

and FLNF is reversed with increased arithmetic mean 

pyrophilic percentages beyond 5 and 0 km; however, 

the least square means followed the trend on the 

ANF and FLNF, suggesting the differences may be 

ecologically insignificant. Although the arithmetic 

mean differences are statistically significant on the 

WMNF, all pyrophilic percentage means are less than 

25 percent, so regardless of distance from Native 

American settlement, the landscape is overwhelmingly 

pyrophobic. 

At the regional level, the tension zone described by 

Cogbill (2000) is clearly demarcated by the abrupt 

change in pyrophilic percentages across the Northeast 

(roughly along the 50 percent break point as shown in 

Fig. 0). Northward protrusions of the tension zone 

line (TZL) were affiliated with major river valleys, 

including the Allegheny (PA), Susquehanna (West and 

Main branches, PA), Delaware (PA and NY), Hudson 

(NY), Connecticut (MA), and Merrimack (NH). All 

four national forests are located north of this line, 

except for the southwest quadrant of the ANF, which 

skirts it. This regional depiction corroborates the high 

level of pyrophobicity found on the national forests. 

However, an island of slightly elevated pyrophilicity 

is located in the western portion of the Finger Lakes 

Region (yellow area; Fig. 0), which corresponds 

to the pyrophilic percentage map derived from local 

witness-tree data (Fig. 7).
4

Figure 6.— Pyrophillic percentage interpolated from witness trees on the Allegheny National Forest. Refer to Table 2 for Native 

American site names and information.
5

Figure 7.—Pyrophilic percentage interpolated from witness trees on the Finger Lakes National Forest. Refer to Table 2 for 

Native American site names and information.
6

Figure 8.— Pyrophilic percentage interpolated from witness trees on the Green Mountain National Forest. Refer to Table 2 for 

Native American site names and information.
7

Figure 9.—Pyrophilic percentage interpolated from witness trees on the White Mountain National Forest. Refer to Table 2 for 

Native American site names and information.
8

Allegheny Finger Lakes Green Mountain White Mountain

% pyrophilic class area (ac) % area (ac) % area (ac) % area (ac) %

0-10 464,024.9 63.2 2,124.9 13.0 640,972.1 98.5 768,972.5 82.1

10-20 49,868.3 6.8 765.8 4.7 9,948.9 1.5 107,806.2 11.5

20-30 32,387.1 4.4 1,145.6 7.0 33.6 0.0 55,258.4 5.9

30-40 34,127.7 4.7 1,160.7 7.1 0.0 0.0 4,226.0 0.5

40-50 28,292.3 3.9 1,474.5 9.0 0.0 0.0 0.0 0.0

50-60 35,409.7 4.8 1,549.1 9.5 0.0 0.0 0.0 0.0

60-70 40,741.2 5.6 2,071.7 12.7 0.0 0.0 0.0 0.0

70-80 35,456.1 4.8 1,476.5 9.1 0.0 0.0 0.0 0.0

80-90 12,624.1 1.7 1,614.6 9.9 0.0 0.0 0.0 0.0

90-100 844.9 0.1 2,916.3 17.9 0.0 0.0 0.0 0.0

Total 733,775.8 16,299.5 650,954.4 936,263.3 

Table 5.—Area by percent pyrophilic class for each national forest; area within national forest 

proclamation boundaries only (or within stands for the Finger Lakes)

Arithmetic (and least square) mean pyrophilic percentage

Within 5 km Beyond 5 km Within 10 km Beyond 10 km 

of Native of Native of Native of Native 

National Forest American sites American sites P-value American sites American sites P-value

Allegheny 60.7 (58.0) 36.7 (37.2) <0.0001 51.8 (51.0) 32.2 (33.3) <0.0001

Finger Lakes 59.2 (57.0) 44.6 (44.6) <0.0001 45.7 (45.1) 44.9 (44.9) 0.8085

Green Mountain 0 0 NA 0 0 NA

White Mountain 18.6 (26.0) 23.4 (22.9) <0.0001 19.7 (24.3) 24.1 (22.9) 0.0007

Table 6.—Arithmetic and least square mean pyrophilic percentage scores in relation to distances to 

Native American sites and results of linear mixed model

DISCUSSIoN

Ecosystem management, especially embedded 

restoration efforts (Society for Ecological Restoration 

International Science & Policy Working Group 2004), 

is predicated on understanding biotic compositions, 

structures, and dynamics of the past (Grumbine 

994, Landres et al. 999). Thus, information on 

past disturbance regimes—formative processes that 

contributed to long-term vegetation expression—is 

critical (Engstrom et al. 999, Pickett and White 985, 

White et al. 999). Although they represent a snapshot in time and are not the only source of information 

for determining restoration activities, witness trees 

have been successfully used to reconstruct former 

vegetation conditions and document change across 

the eastern United States (Abrams and Ruffner 995, 

Bourdo 956, Friedman and Reich 2005, Schulte et 

al. 2007, Thompson et al. 203, Wang et al. 2009, 

Whitney 987). Furthermore, they have been used to 

document past disturbance types and regimes, either 

directly (Canham and Loucks 984, Lorimer 977, 

Seischab and Orwig 99, Zhang et al. 999) or 

indirectly (Thomas-Van Gundy and Nowacki 203). 

By using the latter method, we were able to convert 

witness trees into pyro-indicators to gain perspective 

on past fire regimes at two spatial scales in the 

Northeast. However, nothing in this analysis should 

preclude the use of prescribed fire as a silvicultural 

tool at the site level where supported by other means. 
9

Figure 10.—Pyrophilic percentage as interpolated from town-level witness trees across the northeastern United States. 

Tension zone line is the 50 percent pyrophilic contour.
20

Overall, presettlement fire regimes were generally 

subdued on the four national forests studied. 

Pyrogenic signals embedded in witness trees were 

largely undetected on the national forests furthest 

east (WMNF and GMNF). This finding is not 

surprising given that, north of the TZL, “asbestos” 

conifer-northern hardwood communities historically 

dominated, largely comprised of thin-barked 

pyrophobic species such as maple, beech, and hemlock 

(Bormann and Likens 979, Niering 992, O’Keefe 

and Foster 998). However, given the resolution 

of our pyrophilic percentages maps (9 to 227 ac; 

Table 3) and patchiness of the distribution of witness 

trees themselves, small areas with recurrent localized 

fires may have existed on these national forests. 

Indeed, there is precedence for fires on dry, pinedominated ridges in northern Vermont (Engstrom 

and Mann 99). However, they tended to be small 

due to the occurrence of natural firebreaks such as 

bedrock outcrops and cliffs. Native Americans might 

have augmented ignitions, but their populations 

were sparse due to marginal living conditions. 

Here, the harsh climate and mountainous terrain 

greatly curtailed agriculture and burning normally 

associated with it (compared to more productive 

and pyrogenic landscapes to the south; Nowacki 

et al. 202). Altogether, low Native populations, 

their non-agricultural (hunting and gathering) basis 

of subsistence, and the persistently cool and damp 

climate greatly limited the number and effectiveness 

of their ignitions on the GMNF and WMNF. 

Although residing within a similar climate regime 

supporting conifer-northern hardwoods, the FLNF 

and ANF possessed pyrophilic vegetation in certain 

locations, conspicuously adjacent to water bodies. 

This, coupled with the overall unfavorable fire climate 

(moist, humid conditions) and mesophytic character of 

this biome, strongly points toward humans as primary 

agents of fire. It is well documented that the Allegheny 

River and associated tributaries were actively used 

by Native Americans as travel corridors, lined with 

many shore villages (Chartier’s Town, Kittanning, 

Venango, Goschgoschunk, Lawunakhannek, 

Tidioute, Buckaloons, Conewango, Jenuchshadega, 

Genesinguhta; Sipe 930; Deardorff 94, 946; 

Wallace 952; Kent et al. 98). In 775, the Seneca 

populated northern portions of the river (above 

present-day Warren, PA), whereas the Delaware and 

Shawnee settled in villages southward (Deardorff 

94). 

The inferred association among Native Americans, 

fire, and pyrophilic vegetation is not new but has 

been proffered by others. For instance, Marquis 

(975) attributed the oak type along the Allegheny 

River directly to Native American burning. Through 

dendrochronological research, Ruffner and Abrams 

(2002) documented that frequent, low intensity fires 

burned near the Buckaloons during Seneca Indian 

occupation, precisely the type of disturbance regime 

that would support local oak-hickory forests 

(see Fig. 6). The lack of a climatic signal in tree-ring 

growth is particularly telling, indicating that fire 

was driving vegetation dynamics in presettlement 

times and thus preventing the expression of the 

climatic climax (i.e., conifer-northern hardwoods). 

By establishing zones of Native American influence 

(NAI) from archaeological data and inference, Black et 

al. (2006) provided definitive linkages between Native 

Americans and the presence of pyrogenic oak-hickorychestnut communities in northwest Pennsylvania. The 

fact that NAI was by far the most significant predictor 

of oak-hickory-chestnut occurrence compared to 

edaphic factors (geology, landform, elevation, etc.) 

further underscores the importance of human controls 

over certain presettlement landscapes of the ANF. 

This link is also evident in our comparative analysis 

of arithmetic and least square mean pyrophilic 

percentages within and beyond fixed distances from 

known Native American settlements on the ANF 

(Table 6).

The same phenomenon is thought to have occurred 

on the FLNF, with Native American villages, travel 

corridors, and activities concentrated along the eastern 

shores of Seneca Lake (see Fig. .3 of Marks and 

Gardescu 992). Here, with prevailing westerly winds, 
2

fires lit near shoreline waypoints, encampments, 

and villages would effectively sweep eastward up 

slopes and valley draws. The latter may explain the 

prevalence of pyrophilic trees within the larger Hector 

Falls and Tug Hollow Creek drainages on FLNF’s 

south side, including Burnt Hill. Note that an abrupt 

change from pyrophilic to pyrophobic vegetation 

coincides with an N-S ridgeline (Hector Backbone), 

a natural fire break that bisects the FLNF (Fig. 7). 

Regionally across the Military Tract (6,800 km2

), burn 

patches were recorded in survey notes, concentrated 

around the western portion of the Finger Lakes where 

FLNF is located (Marks and Gardescu 992). Here, 

an old road ran up the eastside of Seneca Lake replete 

with “Indian clearings.” Marks and Gardescu (992) 

further reported that two-thirds of the witness trees 

located on west/southwest banks (east sides) of the 

Finger Lakes were pyrophilic oak, pine, and hickory; 

whereas pyrophobic hemlock, beech, and maple were 

most common on east-northeast banks (west sides 

of lakes). This finding adds support to the idea that 

Native American activities on east of lakes had a more 

profound effect on landscape vegetation (vs. west 

sides), with fires burning most effectively up drier 

west/southwest-facing terrain driven by prevailing 

westerlies. This relationship is further supported by 

our analysis of mean pyrophilic percentages within 

and beyond 5 km from known Native American 

settlements on the FLNF (Table 6).

Native American controls on pyrophytic distribution 

at the local scale (ANF and FLNF) seem to hold 

at the regional scale as well, given the crenulated 

configuration of the TZL. The conversion of witness 

trees to a pyroindicator function allowed this signal to 

be clearly visible (Fig. 0) and provided evidence that 

the TZL is driven by factors other than just climate 

or edaphics. Specifically, the tendrils of pyrophilic 

dominance extending up major river systems and 

along the Atlantic coast deep into the conifernorthern hardwood biome most closely adheres to 

the distribution of Native American populations and 

their related activities (Abrams and Nowacki 2008, 

Doolittle 2000, Mann 2005, Patterson and Sassaman 

988, Richter 200). Indeed, with landscape fire 

removed from much of the eastern landscape, shadetolerant, fire-sensitive northern hardwoods have 

greatly increased in importance south of the TZL 

(Nowacki and Abrams 2008). The TZL has great 

relevance in land management (Nowacki and Abrams 

204), generally depicting where fire can be broadly 

and routinely applied for ecosystem restoration (south 

of TZL) and where fire may be applied more sitespecifically where local information documenting past 

fire exists (north of TZL). The FLNF and ANF are 

good examples of the latter, whereby local witnesstree data support the use of fire in specific areas for 

restoration purposes. 

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Thomas-Van Gundy, Melissa A.; Nowacki, Gregory J.; Cogbill, Charles V. 2015. 

Mapping pyrophilic percentages across the northeastern United States 

using witness trees, with focus on four national forests. Gen. Tech. Rep. 

NRS-145. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, 

Northern Research Station. 26 p.

Witness trees provide information fundamental for restoration ecology, often serving 

as baselines for forest composition and structure. Furthermore, when categorized 

by fire relations, witness trees can shed light on past disturbance regimes. Kriging 

was applied to witness-tree point data to form a contiguous surface of pyrophilic 

percentage for four national forests in the northeastern United States. Fire was 

found to be an important disturbance agent on the Allegheny and Finger Lakes 

National Forests, often corresponding to large river systems and lakesides where 

Native American activities were concentrated. In contrast, fire was relatively 

unimportant on the Green Mountain and White Mountain National Forests based 

on the witness-tree record. There, the cool, moist year-round climate, coupled with 

lower Native American population densities, greatly subdued fire, supporting the 

local view of these as “asbestos” forests. When applying this method to town-level 

witness-tree data for the entire northeastern United States, we found a distinct eastwest line dividing areas of high (south) and low (north) pyrophilic percentage. Known 

as the tension zone line, the undulating character of this boundary, penetrating 

northward along major river valleys, underscores the importance of Native 

Americans as a disturbance agent on the presettlement landscape. 

KEY WORDS: fire, presettlement disturbance regimes, Native Americans
Northern Research Station

www.nrs.fs.fed.us