United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

August 2004

Forest Resources of

the Carson National

Forest

Jim Menlove
Rocky Mountain Research Station

324 25th Street

Ogden, UT 84401

About the author __________________________

Jim Menlove is an Ecologist with the Interior West Forest Inventory and

Analysis Program, Rocky Mountain Research Station in Ogden, Utah.

Contents __________________________________

Page

Description of the Forest .....................................................................................1

Total forest land: highlights of our inventory ..................................................2

Nonreserved timberland: highlights of our inventory ...................................9

The inventory methods ......................................................................................11

Documentation ....................................................................................................13

For further information ......................................................................................13
1

Forest Resources of the Carson National Forest

Jim Menlove

The Interior West Forest Inventory and Analysis (IWFIA)

program of the USDA Forest Service, Rocky Mountain Research Station, as part of its national Forest Inventory and

Analysis (FIA) duties, conducted forest resource inventories

of the Southwestern Region (Region 3) National Forests.

This report presents highlights of the Carson National

Forest 1998 inventory, including population estimates and

summaries of commonly requested variables. Any trends

or disturbances (such as fire) that have occurred since 1998

will be discussed in future reports of the Carson National

Forest.

The information presented in this report is based solely

on the IWFIA inventory sample (USDA 1998a). The data

could be summarized in other ways for different purposes

(see “For further information” on the inside back cover for

the national FIA database and related contacts). Supplemental documentation and inventory terminology can be

found in USDA (2002a), O’Brien (2002), or on the World

Wide Web at http://www.fs.fed.us/rm/ogden. Changes in

terminology or procedures may limit comparisons with

previous estimates and summaries for this area. Additional

55% 32%

13%

Timberland

Woodland

Nonforest

Figure 1—Percent of total area by land category,

Carson National Forest.

data collected for the Carson National Forest, used separately or in combination with IWFIA data, may produce

varying results.

Description of the Forest

The Carson National Forest administers 1,491,485 acres

(USDA 1998b) of which 87 percent is classified as forest

land and 13 percent nonforest. This report describes the

characteristics of the forest land sampled on the Carson.

Forest land is land that is at least 10 percent stocked (or

formerly stocked) with live tally tree species and is greater

than 1 acre in size and 120 feet wide. Based on the tree

species present, forest land can be further subdivided into

two land categories: timberland and woodland (fig. 1).

Timberland is forest land with mostly timber species that

are typically used in the wood products industry, such as

ponderosa pine, aspen, and Douglas-fir. Woodland is

forest land with mostly woodland species that often have

a multistem growth form and are not typically used for

industrial wood products, such as pinyon pine, junipers,

and Gambel oak. On the Carson, 63 percent of the total

forest land is timberland while 37 percent is woodland.

Just over four percent of the total forest land area administered by the Carson is reserved land, such as wilderness areas, that has been withdrawn from management for

production of wood products. The first section of this report

presents summaries of timber and woodland species for

all forest land, including reserved designations. The subsequent section addresses nonreserved lands only and includes

estimates for timber species sampled on the Carson.
2

Total forest land: highlights of

our inventory

Forest type—Forest resources are often described

using a forest type classification. Forest type refers to the

prevalant tree species in a stand, based on plurality of tree

stocking. Stocking is an expression of the extent to which

growing space is effectively utilized by live trees.

Figure 2 presents the distribution of forest land area on

the Carson by forest type. The pinyon-juniper forest

type is the most common forest type, comprising 29

percent of the total forest land area. Pinyon-juniper is

followed in abundance by ponderosa pine at 18 percent,

aspen at 14 percent, and Douglas-fir at 11 percent.

Spruce-fir, white fir, and deciduous woodland oak forest types each comprise about 7 percent of the total forest land area, with Engelmann spruce comprising just

over 4 percent. The remaining 3 percent is made up of

pure juniper, blue spruce, and foxtail/bristlecone pine

forest types, each with about 1 percent of the total forest

land area.

A field plot may sample more than one condition

(stand). A forest condition is generally defined as an

area of relatively homogeneous vegetative cover that

meets the criteria for forest land. Forest type is one of

several attributes that define and separate conditions

identified on the plot. Table 1 presents the number of

conditions and the condition proportions sampled on

the Carson National Forest by forest type for 211 plots

that contained at least one forest condition.

Figure 2—Percent of total forest land area by forest type, Carson National Forest.

0% 5% 10% 15% 20% 25% 30%

Foxtail / bristlecone pine

Blue spruce

Juniper

Engelmann spruce

Deciduous woodland oak

White fir

Spruce-fir

Douglas-fir

Aspen

Ponderosa pine

Pinyon-juniper

Forest type

Percent forest land
3

0

25

50

75

100

125

150

175

200

225

250

Aspen Corkbark fir Engelmann Douglas-fir Ponderosa

spruce pine

White

fir

Other timber

species

Gambel

oak

Twoneedle

pinyon

Oneseed

juniper

Rocky

Mountain

juniper

Other

woodland

species

Timber Woodland

Species

Million trees

1.0" - 4.9"

5.0" - 10.9"

>=11.0"

Figure 3—Number of live trees 1.0 inch diameter and greater on forest land by species and diameter-size class, Carson National Forest.

Number of live trees—Forest land can also be examined

by looking at the composition of tree species. Figure 3

shows total number of live trees for all sampled tree species on the Carson for three diameter classes. Gambel oak

makes up the plurality of live trees at 33 percent, with the

vast majority of these less than 5 inches in diameter.

Aspen and common or twoneedle pinyon each make up

12 percent of the live trees on the Carson. Corkbark fir

and Engelmann spruce each make up 8 percent, and

Douglas-fir makes up 7 percent. Ponderosa pine and

white fir each made up 6 percent, oneseed juniper 4 percent,

and Rocky Mountain juniper 2 percent. The rest of the live

trees, found in more limited amounts on the Carson, are

grouped into the other timber species and other woodland

species categories. Other timber species make up 2 percent

of the live trees on the Carson and include blue spruce,

Rocky Mountain bristlecone pine, limber pine, and subalpine fir. Other woodland species make up 1 percent

and include Rocky Mountain maple and alligator juniper.

Species that are scarce may not be encountered with the

extensive sampling strategy used for this inventory.

Number and weight of dead trees—Standing and down

dead trees are important to forest ecosystems because

they provide habitat for many species of wildlife, function

as nutrient sinks, and protect the soil from erosion. Approximately 72.5 million standing dead trees (snags) and

58.1 million down dead trees (1 inch diameter and greater)

are on Carson forest land, with 56.1 snags per acre. Different size snags provide habitat components for many wildlife species. Figure 4 shows the number of snags by forest

type for three diameter classes. Of the total numbers of snags,

Table 1—Number of conditions and condition proportions

on forest land by forest type and land category,

Carson National Forest, 1998.

Number of Condition

Forest type conditionsa proportionsb

Timberland

Ponderosa pine 39 36.5

Aspen 33 28.5

Douglas-fir 23 22.6

Spruce-fir 16 15.0

White fir 15 14.3

Engelmann spruce 9 9.0

Blue spruce 2 2.0

Foxtail/bristlecone pine 2 2.0

Total Timberland 139 129.9

Woodland

Pinyon-juniper 62 57.6

Deciduous woodland oak 14 12.8

Juniper 4 2.4

Total Woodland 80 72.8

Grand Total 219 202.7

a

Number of conditions by forest type that were sampled. The sum

of these numbers is often greater than the total number of plots

because a plot may sample more than one forest condition. b

Sum of the condition proportions of plots by forest type that were

sampled. The sum of these numbers is often less than the total

number of plots because of nonforest condition proportions (from

plots containing both forest and nonforest conditions) that are not

included here.
4

72 percent are between 1 inch and 4.9 inches diameter,

with over two-thirds of these occurring within the aspen

(25 percent), Douglas-fir (17 percent), spruce-fir, and

white fir (13 percent each) forest types. Of the total numbers of snags, 22 percent are between 5 and 10.9 inches

diameter, with approximately half of these occurring

within the aspen (25 percent) and spruce-fir (24 percent)

forest types. Snags 11 inches diameter or larger make up

7 percent of the total, with 3.8 snags per acre. One third of

these large snags are found on the spruce-fir forest type;

the aspen, ponderosa pine, deciduous woodland oak, and

pinyon-juniper forest types each comprise 11 percent.

The amount of dead material can contribute significantly

to forest fuel loads and fire potential. Approximately 2.9

million tons of down dead trees and 2.6 million tons of

standing dead trees are on Carson forest land, with 2.3 tons

0

2

4

6

8

10

12

14

Aspen Spruce-fir Douglas-fir White fir Ponderosa

pine

Deciduous

woodland

oak

PinyonjuniperEngelmann

spruce spruce

Blue Juniper Foxtail / 

bristlecone

pine

Forest type

Million snags

1.0" - 4.9"

5.0" - 10.9"

>=11.0"

Figure 4—Number of standing dead trees 1.0 inch diameter and greater on forest land by forest type and diameter-size class,

Carson National Forest, 1998.

of down dead trees per acre. This estimate includes the

merchantable bole and bark of trees 5 inches diameter

and greater. Of the species contributing to down dead

trees, more than one-quarter are aspen. Ponderosa pine

(20 percent), Engelmann spruce (19 percent), and corkbark

fir (11 percent) comprise half.

Tree and stand size—The size distribution of trees is an

indicator of structural diversity. Figure 5 displays the number of live trees by 2-inch diameter class on the Carson,

combining trees from all stands. Overall, this shows a

typical diameter distribution with a higher number of small

trees than large trees.

Stand-size class is a categorization of forest land based

on the predominant diameter-size of live trees that contribute to the stocking of a stand. Stocking values for each

stand are generally summed by the following diameter

0

50

100

150

200

250

300

350

400

2 12 14 1 4 6 8 10 6 18 20 22 24 26+

Diameter class

Million trees

Figure 5—Number of live trees on

forest land by 2-inch diameter class,

Carson National Forest, 1998.
5

classes. The large diameter class includes softwoods 9

inches diameter and greater and hardwoods 11 inches

diameter and greater; the medium diameter class includes

softwoods 5 to 8.9 inches diameter and hardwoods 5 to

10.9 inches diameter; and the saplings/seedlings class

includes all trees under 5 inches diameter. Then each

stand (condition) is assigned a class according to stocking

predominance. In terms of stocking, fewer large-diameter

trees compared to small-diameter trees are required to

fully utilize a site; therefore, large-diameter trees have a

greater impact on determining stand-size class. Figure 6

displays forest land area on the Carson by stand-size class.

Approximately 66 percent of the stands have a plurality of

stocking of large trees, 17 percent of medium trees, and

12 percent of saplings and seedlings. About 5 percent are

nonstocked, such as stands that have been recently

harvested or burned .

Wood volume, biomass, and basal area of live trees—

In general, estimates of volume, basal area, and biomass

describe the amount of wood fiber in the forest. Each

estimate summarizes different portions of a tree and are

therefore more appropriate for different forest resource

applications. For example, volume relates closely to wood

as a product, basal area to forest or tree density, and biomass to forest or tree productivity. In table 2, volume

represents the amount of wood fiber in the merchantable

bole of a tree, while biomass represents the amount of

wood fiber in terms of oven-dry weight including the bole,

bark, and branches of the tree. Basal area estimates include

the cross-sectional area of a tree stem/bole at the point

0 200 400 600 800 1,000

Nonstocked

Saplings/seedlings

Medium

Large

Stand-size class

Thousand acres

Figure 6—Forest land area by stand-size

class, Carson National Forest. Large trees

include softwoods 9.0"+ and hardwoods

11.0"+; medium trees include softwoods

5.0" to 8.9" and hardwoods 5.0" to 10.9";

saplings/seedlings include trees <5.0".

Table 2—Net volume, biomass, and basal area on forest land by species, Carson National

Forest, 1998.

Volume Biomass Basal area

Species (million cubic-feet) (million tons) (million square ft.)

Ponderosa pine 347.6 6.9 19.5

Aspen 336.4 5.8 16.1

Engelmann spruce 326.6 5.1 14.8

Douglas-fir 313.4 6.2 16.5

Twoneedle pinyon 170.7 2.0 14.5

Corkbark fir 137.2 2.2 7.2

White fir 137.1 2.6 9.2

Oneseed juniper 76.6 1.0 12.2

Rocky Mountain juniper 30.1 0.4 4.0

Blue spruce 23.4 0.4 1.2

Rocky Mountain bristlecone pine 15.1 0.3 1.2

Gambel oak 8.7 0.3 1.1

Limber pine 8.0 0.1 0.5

Rocky Mountain maple 1.5 † 0.2

Subalpine fir 0.5 † ‡

Alligator juniper 0.4 † ‡

Total (all tree species) 1,933.3 33.3 118.2

† Less than 100,000 tons

‡ Less than 100,000 sq ft
6

where diameter is measured. Table 2 shows a breakdown

by species of net volume, biomass, and basal area for live

trees 5 inches diameter and larger on the Carson. Ponderosa pine, aspen, Engelmann spruce, and Douglas-fir

together make up the majority of volume (68 percent total)

and biomass (72 percent total), and account for over half

the basal area (57 percent). Although abundant in numbers

(see fig. 3), Gambel oak accounts for relatively little volume

or biomass because most trees of that species are below

5 inches in diameter.

Figure 7 shows the distribution of net volume of wood in

trees by 2-inch diameter class on Carson forest land. While

the number of trees declines with larger diameter classes

(see fig. 5), the volume increases significantly from diameter class 6 to 12 inches, where net volume peaks.

Another way to look at wood volume is by forest type,

for which per acre estimates can be computed along with

biomass and basal area (table 3). These numbers include

the many different species that can occur together within

each forest type. The highest volume per acre on the

Carson is in the spruce-fir forest type, followed by blue

spruce and Douglas-fir. These three forest types also

contain the highest basal area and biomass per acre, because these attributes are strongly correlated with volume.

Many of the forest types listed in table 3 may not be

representative due to small sample sizes (see table 1). Only

the pinyon-juniper, aspen, ponderosa pine, and Douglasfir forest types have large samples.

Stand density index—Many factors influence the rate at

which trees grow and thrive, or die. As tree size and density

0%

2%

4%

6%

8%

10%

12%

14%

16%

18%

6 12 1 8 10 4 16 18 20 22 24 26 28 30 32

Diameter class

Total volume

Figure 7—Percent of total net cubic-foot volume of live trees by 2-inch diameter class, Carson National Forest.

Table 3—Net volume, biomass, and basal area per acre on forest land by forest type,

Carson National Forest, 1998.

Volume Biomass Basal area

Forest type cubic ft. per acre tons per acre square ft. per acre

Spruce-fir 3,796 58.6 164

Blue spruce 2,895 47.6 133

Douglas-fir 2,093 40.1 112

Aspen 1,987 35.1 104

Engelmann spruce 1,796 29.4 98

White fir 1,654 31.9 100

Ponderosa pine 1,355 26.5 80

Foxtail/bristlecone pine 897 17.1 72

Pinyon-juniper 762 10.1 80

Deciduous woodland oak 320 6.7 25

Juniper 267 3.5 44

Total (all types) 1,496 25.8 91
7

increase, competition for available resources increases.

Stand density index (SDI), as developed by Reineke (1933),

is a relative measure quantifying the relationship between

trees per acre, stand basal area, average stand diameter,

and stocking of a forested stand. The concept was developed for even-aged stands, but can also be applied to

uneven-aged stands (Long and Daniel 1990; see next paragraph for an explanation of even-aged and uneven-aged

stands). SDI is usually presented as a percentage of the

maximum SDI for each forest type (USDA 1991). SDI was

computed for each location using those maximums, and

the results were grouped into six classes (fig. 8). A site is

considered to be fully occupied at 35 percent of SDI

maximum, which marks the onset of competition-related

stresses and slowed growth rates (USDA 1991). Based on

FIA sample data, 55 percent of all forest stands in the Carson

National Forest are considered to be fully occupied.

Figure 8—Area of forest land by forest type and percent stand density index, Carson National Forest.

Southwest stand structure—Stands may be categorized

on the basis of tree size, often in terms of their prevalent

diameter or height class. This works well for stands where

just one or two size classes dominate. Such stands are

called single-storied, or even-aged, because they have a

structure characterized by a single canopy layer or two

closely related layers. Stands having a structure composed

of three or more size classes are called multistoried or uneven-aged stands. Both types of structure are important in

forest diversity. Differences between single-storied stands

provide structural diversity across a landscape. Differences

between many layers within a multistoried stand provide

vertical diversity.

Figure 9 shows area of forest land by stand structure

class and diameter class for three timber softwood forest

type groups including pine, mixed conifer, and spruce-fir

timber softwood types. On the Carson, the pine category

0

25

50

75

100

125

150

0.0-0.9 1.0-4.9 5.0-11.9 12.0-17.9 18.0-23.9 24+

Single/two-storied Multi-storied

Stand structure class

Thousand acres

Pine

Mixed conifer

Spruce-fir

Figure 9—Area of forest land by stand structure class, diameter class, and timber

softwood forest type groups, Carson National Forest.

0

50

100

150

200

250

300

350

400

< 10 10.0-24.9 25.0-34.9 35.0-49.9 50.0-59.9 60 +

Thousand acres

Foxtail / bristlecone pine

Blue spruce

Juniper

Engelmann spruce

Deciduous woodland oak

White fir

Spruce-fir

Douglas-fir

Aspen

Ponderosa pine

Pinyon-juniper

Percent of maximum stand density index
8

is made up of the ponderosa pine forest type; the mixed

conifer category includes the Douglas-fir, blue spruce, and

white fir forest types; and the spruce-fir category contains

the spruce-fir, Engelmann spruce, and foxtail/bristlecone

pine forest types. The values shown are based on analysis of

SDI and tree diameter classes, a method developed by the

Southwest Region (USDA 2002b). In general, the Carson is

represented by both single-storied and multistoried stands,

with about two-thirds of the single-storied stands occurring

in the 5 to 11.9 inch diameter class.

Growth and mortality—Forest vigor can be analyzed by

measures of net annual growth and mortality. Net annual

growth is the difference between gross annual growth and

losses due to mortality. Gross annual growth is the average

annual increase in the volume of live trees while mortality

is the net volume of trees that have died over a 1-year

period based on a 5-year average. Gross annual growth

of all live trees 5 inches diameter and greater on all forest

land on the Carson is estimated to be 38 million cubic feet.

Subtracting mortality results in an estimated net annual

growth of 27 million cubic feet.

Mortality calculations estimate approximately 11 million

cubic feet of wood 5 inches diameter and greater died on

the Carson in 1997. Ponderosa pine has the highest proportion of total mortality volume at 34 percent; with aspen

at 24 percent, corkbark fir at 13 percent, and Engelmann

spruce at 11 percent. Douglas-fir makes up 8 percent of

total mortality volume, and white fir 7 percent. Blue spruce,

Rocky Mountain juniper, and twoneedle pinyon combine

to make the remaining 2 percent of mortality volume on

Carson forest land. Based on field observations, 33 percent

of the mortality on the Carson was caused by disease, 27

percent by fire, 27 percent by insects, and nearly 10 percent

by weather-related stresses. The remaining 3 percent was

attributed to suppression and unknown causes.

Figure 10 compares gross annual growth to mortality for

the nine species that included mortality trees. The largest

mortality-to-growth ratio occurs in ponderosa pine, where

mortality volume is half the gross growth. Most of the ponderosa pine mortality occurs in the deciduous woodland

oak forest type, where ponderosa pine is fairly common.

In the deciduous woodland oak forest type, ponderosa

pine mortality volume is several times its gross growth,

yielding negative net growth for ponderosa pine there.

Mortality volume in both corkbark fir and aspen is about

one-third of the gross growth on all forest land. All species

show positive net growth on all forest land.

Ponderosa pine

Aspen

Corkbark fir

Engelmann spruce

Douglas-fir

White fir

Blue spruce

Rocky Mountain juniper

Twoneedle pinyon

Species

Million cubic feet

Gross growth

Mortality

02 468

Figure 10—Gross annual growth of live trees 5.0

inches diameter and greater compared to mortality

on all forest land, Carson National Forest.
9

Understory vegetation—Understory vegetation provides

forage and cover for wildlife, contributes to forest fuel

load, and can be an indication of the successional stage

of the forest community. On each plot field crews visually

estimated crown canopy coverage for four plant groupstree seedlings/saplings, shrubs, forbs, and graminoids (see

USDA 1998a for details). Figure 11 shows the average percent cover of plant groups on forest land by forest type.

Some forest types, for example blue spruce and foxtail/

bristlecone pine, are based on relatively small samples

(see table 1).

Nonreserved timberland:

highlights of our inventory

Tree and stand size—Almost 59 percent of forest land in

the Carson National Forest is nonreserved timberland. The

area of nonreserved timberland by stand-size class is presented in figure 12. Similar to all forest land in the Carson

0

5

10

15

20

25

30

Aspen Blue spruce Deciduous

woodland oak

Douglas-fir Engelmann

spruce

Foxtail /

bristlecone pine

Juniper Pinyon-juniper Ponderosa pine Spruce-fir White fir

Forest type

Average percent cover

Trees

Shrubs

Forbs

Graminoids

Figure 11—Average percent cover of trees (seedlings/saplings), shrubs, forbs, and graminoids on

forest land by forest type,Carson National Forest.

0 100 200 300 400 500 600

Nonstocked

Saplings/seedlings

Medium

Large

Stand-size class

Thousand acres

Figure 12—Area of nonreserved timberland by standsize class, Carson National Forest.
10

(see fig. 6), most of the nonreserved timberland area has a

plurality of stocking from large trees.

Figure 13 shows the number of growing-stock trees

by 2-inch diameter class on nonreserved timberland on

the Carson. Growing-stock trees are live timber species

meeting specific standards of quality and vigor. Of all

growing-stock trees on nonreserved timberland on the

Carson, 18 percent are 9 inches diameter or greater.

Wood volume, biomass, and basal area of growing-stock

trees—Table 4 displays a breakdown of net cubic-foot

volume, tons of wood biomass, and square foot basal area

for growing-stock trees 5 inches diameter and greater by

species on nonreserved timberland for the Carson. The

total net cubic-foot volume of growing stock on nonreserved timberland is over 1.4 billion cubic feet. Together,

ponderosa pine, Douglas-fir, aspen and Engelmann spruce

account for 80 percent of this volume. The total wood

biomass is estimated at 25.3 million tons, with ponderosa

pine, Douglas-fir, aspen and Engelmann spruce combining

to make up 81 percent of this amount. Total basal area for

growing-stock trees on nonreserved timberland is estimated at 73.8 million square feet, with the combination of

ponderosa pine, Douglas-fir, aspen and Engelmann spruce

comprising 77 percent of this total.

0

20

40

60

80

100

120

2 14 1 4 6 8 10 12 6 18 20 22 24 26+

Diameter class

Million trees

Figure 13—Number of growing-stock trees on nonreserved timberland by 2-inch diameter class,

Carson National Forest.

Table 4—Net volume, biomass, and basal area of growing-stock trees 5 inches diameter and greater

on forest land by species on nonreserved timberland, Carson National Forest, 1998.

Volume Biomass Basal area

Species (million cubic feet) (million tons) (million square feet)

Ponderosa pine 307.3 6.0 17.0

Douglas-fir 301.8 5.9 15.9

Aspen 288.1 4.9 13.6

Engelmann spruce 236.0 3.7 10.7

White fir 119.2 2.3 8.1

Corkbark fir 109.4 1.8 5.9

Blue spruce 23.3 0.4 1.2

Rocky Mountain bristlecone pine 13.7 0.3 1.0

Limber pine 7.3 0.1 0.5

Subalpine fir 0.5 † ‡

Total* 1,406.8 25.3 73.8

† less than 100,000 tons

‡ less than 100,000 square feet

* numbers do not add to total due to rounding
11

The total net sawtimber volume on nonreserved timberland is estimated at 4.5 billion board feet (Scribner rule).

Sawtimber includes all growing-stock trees 9 inches and

greater for softwoods, and 11 inches diameter and greater for

hardwoods. Seventy percent of this volume consists of ponderosa pine (1.2 billion board feet), Douglas-fir (1.1 billion

board feet), and Engelmann spruce (0.8 billion board feet).

Growth and mortality—Gross annual growth of growingstock trees on nonreserved timberland on the Carson is

estimated to be 29.3 million cubic feet, while mortality is

estimated at 7.1 million cubic feet. This calculates to a net

annual growth of 22.2 million cubic feet. Mortality volume

was attributed to seven species, with over half of this total

being in aspen (37 percent) and corkbark fir (21 percent).

Gross annual growth is compared to mortality for these

seven species in figure 14. Mortality for nonreserved timberland on the Carson is about 24 percent of gross annual

growth, with relatively large mortality-to-growth ratios

occurring in corkbark fir and aspen. One notable difference

between these results and those shown in figure 10 is the

lower mortality-to-growth ratio for ponderosa pine on

nonreserved timberland. Mortality volume in ponderosa

pine is one-eighth of its gross annual growth on nonreserved

timberland, compared to one-half live ponderosa pines

5 inches diameter or greater on all forest land.

The inventory methods

About the two-phase sample design—FIA inventories

provide a statistical-based sample of forest resources

across all ownerships that can be used for planning and

analyses at local, State, regional, and national levels (for

further information about the national FIA program, refer

to the World Wide Web at http://www.fia.fs.fed.us). IWFIA

uses a two-phase sampling procedure for all inventories.

Phase one of the inventory is based on a grid of sample

points systematically located every 1,000 meters (approximately one sample point per 247 acres) across all lands in

the State. Phase one points are assigned ownership and

vegetative cover attributes using maps and remotely

sensed imagery. Field crews conduct phase two of the

inventory on a subsample of the phase one points that

occur on forest land. The sampling intensity is one field

plot every 5,000 meters (approximately one field plot per

6,178 acres), or about every 3 miles. Phase two plots are

stratified based on phase one ownership and vegetation

information, and weights are assigned to each stratum

based on the proportion of phase one points in that stratum.

Phase two plots were sampled using the mapped-plot

design. There were 235 field plots on the Carson National

Forest, of which one was determined to be inaccessible.

A total of 191 field plots sampled only forest conditions,

20 sampled both forest and nonforest conditions, and 23

sampled only nonforest conditions. A total of 219 forest

conditions (stands) were sampled on 211 plots that contain

202.7 forest and 8.3 nonforest condition proportions.

About the mapped-plot design—The mapped-plot

design was adopted by Forest Inventory and Analysis

nationwide by 1995. The predetermined subplot layout

uses boundary delineation, when necessary, to classify

differing conditions. Most plots sample a single forest

condition, therefore delineating conditions is often not

required.

Conditions were separated or mapped on differences in

any of five attributes: forest/nonforest, forest type, standsize class, stand origin, and stand density. The condition

proportion is the fraction of plot area sampled on each

Aspen

Corkbark fir

Douglas-fir

Ponderosa pine

White fir

Engelmann spruce

Blue spruce

Species

Million cubic feet

Gross growth

Mortality

02468

Figure 14—Gross annual growth of growing-stock trees 5.0 inches diameter and

greater compared to mortality on nonreserved timberland, Carson National Forest.
12

Table 5—Percent standard error for area estimate on total forest land, and percent

standard errors for estimates of net volume, net annual growth, and

annual mortality for all trees on total forest land, and growing-stock trees

on nonreserved timberland (5 inches diameter and greater), Carson

National Forest.

Percent

Land class Attribute Estimate standard error

Total forest land (acres) Area 1,292,187 ±2.3

Total forest land Volume 1,933,282,045 ±6.2

(all trees cubic feet) Growth 26,839,467 ±15.0

Mortality 11,059,381 ±32.3

Nonreserved timberland (acres) Area 761,669 ±5.5

Nonreserved timberland Volume 1,406,792,990 ±8.3

(growing-stock trees cubic feet) Growth 22,201,490 ±9.9

Mortality 7,054,301 ±25.5

condition. The sum of all condition proportions for a plot

equals 1.00. Therefore, the number and relative size of plot

conditions determines the weighted area (condition proportion multiplied by expansion factor) used for sample

expansion.

Standard errors—The two-phase sampling scheme was

designed to meet national standards for precision in State

and regional estimates of forest attributes. Standard errors,

which denote the precision of an estimate, are usually

higher for smaller subsets of data. Percent standard errors

for estimates of area, net volume, net annual growth and

annual mortality are presented in table 5. Standard errors

for other estimates are available upon request (see “For

further information” section on the inside back cover).
13

Federal Recycling Program Printed on Recycled Paper

For further information ________________

Interior West Forest Inventory and Analysis Program

Rocky Mountain Research Station

c/o Program Manager

507 25th Street

Ogden, UT 84401

Phone: 801-625-5388

FAX: 801-625-5723

World Wide Web: http://www.fs.fed.us/rm/ogden

Carson National Forest

Supervisor’s Office

208 Cruz Alta Road

Taos, NM 87571

Phone: 505-758-6200

FAX: 505-758-6213

Selected data for this Forest are part of a national database that houses

information for much of the forest land in the United States. This database

can be accessed on the Internet at the following web site:

http://www.ncrs.fs.fed.us/4801/fiadb/index.htm

Documentation _______________

Long, James N.; Daniel, Theodore W. 1990. Assessment of

growing-stock in uneven-aged stands. Western Journal

of Applied Forestry 5(3):93-96.

O’Brien, Renee A. 2002. Arizona’s Forest Resources, 1999.

Resour. Bull. RMRS-RB-2. Ogden, UT: U.S. Department of

Agriculture, Forest Service, Rocky Mountain Research

Station. 116 p.

Reineke, L.H. 1933. Perfecting a stand density index for

even-aged forests. J. Agric. Res. 46:627-638.

U.S. Department of Agriculture, Forest Service. 1991.

RMSTAND User’s Guide, Chapter 60, p. 106. Unpublished

user’s guide on file at: U.S. Department of Agriculture,

Forest Service, Southwestern Region, Albuquerque, NM.

U.S. Department of Agriculture, Forest Service. 1998a.

Forest Survey Field Procedures. Ogden, UT: USDA

Forest Service, Rocky Mountain Research Station.

U.S. Department of Agriculture, Forest Service. 1998b.

Land Areas of the National Forest System. FS-383.

U.S. Department of Agriculture, Forest Service. 2002a.

Reference documents. [Online]. Available: http://www.fs.

fed.us/rm/ogden/state_reports/arizona/az_nfs.html (also

available on file at: U.S. Department of Agriculture,

Forest Service, Rocky Mountain Research Station,

Ogden, UT).

U.S. Department of Agriculture, Forest Service. 2002b.

Region-3 Guide For Custom IW-FIA Table Set, 2002.

Unpublished report on file at: U.S. Department of

Agriculture, Forest Service, Southwestern Region,

Albuquerque, NM.
14

The Rocky Mountain Research Station develops scientific information and technology to improve management, protection,

and use of the forests and rangelands. Research is designed to meet the needs of National Forest managers, Federal and State

agencies, public and private organizations, academic institutions, industry, and individuals.

Studies accelerate solutions to problems involving ecosystems, range, forests, water, recreation, fire, resource inventory,

land reclamation, community sustainability, forest engineering technology, multiple use economics, wildlife and fish habitat,

and forest insects and diseases. Studies are conducted cooperatively, and applications may be found worldwide.

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