United States

Department of

Agriculture

Forest Service

Northeastern

Research Station

Resource Bulletin NE-156

William H. McWilliams

Carol A. Alerich

Daniel A. Devlin

Tonya W. Lister

Stephen L. Sterner

James A. Westfall

Annual Inventory Report

for Pennsylvania’s Forests:

Results from the First Two Years

Pennsylvania

Department of Conservation

and Natural Resources

Bureau of Forestry
Published by: For additional copies:

USDA FOREST SERVICE USDA Forest Service

11 CAMPUS BLVD SUITE 200 Publications Distribution

NEWTOWN SQUARE PA 19073-3294 359 Main Road

Delaware, OH 43015-8640

November 2002 Fax: (740)368-0152

Visit our homepage at: http://www.fs.fed.us/ne

Abstract

In 2000, the USDA Forest Service’s Forest Inventory and Analysis (FIA) program

implemented a new system for inventory and monitoring Pennsylvania’s forest

resources. The most salient feature of the new inventory process will be a nearly

threefold improvement in timeliness. This report summarizes the results of the first

2 years of annual inventory measurements. The area of forest land in Pennsylvania

has remained stable since a previous inventory in 1989. The Keystone State’s

forests continue to mature as larger trees and an increase in inventory volume were

recorded. A separate study of tree seedlings revealed a general lack of

regeneration in one-third to one-half of stands in which regeneration should be

adequate.

The Authors

WILLIAM H. MCWILLIAMS, CAROL A. ALERICH, TONYA W. LISTER, and JAMES

A. WESTFALL are researchers with the Northeastern Research Station’s Forest

Inventory and Analysis unit at Newtown Square, Pennsylvania. DANIEL A. DEVLIN

and STEPHEN L. STERNER are foresters with the Pennsylvania Department of

Conservation, Bureau of Forestry, at Harrisburg, Pennsylvania.

Manuscript received for publication 27 August 2002
1

Executive Summary

In 2000, the USDA Forest Service’s Forest Inventory and Analysis (FIA) program implemented

a new system for inventory and monitoring Pennsylvania’s forest resources. The most salient

benefit of the new inventory system will be a nearly threefold improvement in timeliness. Also,

the extension of the sample to include a broader range of measurements will help analysts

understand the relationships between resource change and underlying ecological variables.

According to the first two panels of inventory data, Pennsylvania has 16,649,800 acres of forest

land (confidence interval of ± 266, 397 acres). This compares to the 1989 estimate of

16,704,400 forested acres (± 100,226 acres). These two confidence intervals overlap, so there is

no discernable trend.

The distribution of forest land by forest-type group has been stable over the past decade, but

that is likely given that Pennsylvania’s forests have been maturing gradually over time. The

distribution of the specific oak types also is relatively stable. The only trend that is evident is

that red-maple forest types increased substantially, perhaps by as much as one-third. More

detailed shifts in specific types are not discernable with only two panels of inventory data.

The distribution of forest land by stand-size class highlights a long-term trend that has been

developing in Pennsylvania for some time—the gradual maturing of a tremendously diverse and

valuable resource. This maturing is highlighted by a decrease in seedling-sapling stands and an

increase in sawtimber stands. The decrease in the young seedling-sapling class is problematic

because this trend has become long-term and negative. The situation bears close monitoring

because of the impacts on young successional forest-dependant wildlife species. The other

striking trend is the continued increase in sawtimber stands. This trend supports the conclusion

that Pennsylvania’s forests contain more timber today than at any time since the late 1800’s.

The total sound-wood volume of live trees increased from 27.5 to 33.7 billion cubic feet, a

23-percent increase. This compares to a 10-percent increase in the volume of growing-stock

trees. Increases occurred for both softwood and hardwood inventory volumes. Significant

increases occurred for 8 of the 10 most abundant species (exceptions were sugar maple and

eastern hemlock). It is important to note red maple’s increasing share of the State’s total volume.

Currently, this species accounts for one-fifth of the volume of live trees. Red maple also

contributed 60 percent of the increase in volume statewide.

The total volume of sawtimber increased from 72.8 billion board feet (International 1⁄4-inch

rule) in 1989 to 85.8 billion board feet in 2001, an increase of 18 percent. Increases were noted

for both softwoods and hardwoods. Again, except for sugar maple and eastern hemlock,

Pennsylvania’s top 10 species had significant increases in sawtimber volume.

By every measure, the prospective regeneration picture in Pennsylvania is bleak based on the

findings for the first panel of regeneration measurements. If commercial species were deemed

acceptable for purposes of future management, one-third to one-half of the forest land likely

would fail to regenerate without the additional stocking that comes from other sources

following disturbance. The small number of samples used does not allow detailed comparisons

of various forest types or other stand descriptors. Also, the analytical framework for evaluating

regeneration is in review and may change slightly. However, it is appropriate based on available

evidence to say that poor regeneration is common across Pennsylvania rather than specific to a

particular owner or forest type.
2

Annual Data: The Future

of Forest Monitoring

The USDA Forest Service’s, Forest Inventory and Analysis

(FIA) program has been conducting forest inventories in

Pennsylvania since the 1950’s. Periodic reports on the

status of and changes in forest conditions were completed

for 1955 (Ferguson 1955), 1965 (Ferguson 1968), 1978

(Considine and Powell 1980), and 1989 (Alerich 1993).

In 2000, FIA implemented a new system for inventorying

and monitoring of Pennsylvania’s forest resources. In the

past, “periodic” inventories were conducted in the State

every 10 to 15 years. As the value of the Keystone State’s

forested ecosystem continued to increase and questions

concering the condition and health of this valuable

resource mounted, it became clear that more timely data

gathering and monitoring were needed. In conjunction

with the Pennsylvania Bureau of Forestry, FIA has adapted

an annual inventory system under which the length of the

inventory cycle has been shortened to 5 years and

measurements are collected continually across the State.

This report covers the first 2 years of measurement.

Annual Inventory Design

The annual inventory system combines features of the

periodic system with a new systematic grid of sample plots

and incorporates measurements from the Forest Health

Monitoring (FHM) program. The inventory consists of

these three phases:

Phase 1. Traditionally, aerial photography or remote

sensing is used to characterize the acreage of forest and

nonforest. In Pennsylvania, satellite-based remote sensing

will replace aerial photography. Phase 1 estimation will

not begin until the third year of measurements is

complete.

Phase 2. Field measurements are conducted at sample

locations distributed systematically about every 3 miles

across the landscape (Fig. 1). Sample locations are situated

within individual cells of a hexagonal grid laid across the

State. Each year, 20 percent of the sample locations are

measured, that is, it takes 5 years to complete the

inventory. Each year’s sample is referred to as an

Figure 1.—Distribution of the first two panels of FIA sample locations in Pennsylvania by ecoregion

and inventory panel (ecoregions and numerical designations are from Bailey 1995).

Boundaries

Western Glaciated Allegheny Plateau Section (221F)

Southern Unglaciated Allegheny Plateau Section (221E)

Laurentian Mixed Forest Province (212)

Northern Glaciated Allegheny Plateau Section (212F)

Northern Unglaciated Allegheny Plateau Section (212G)

Central Appalachian Broadleaf Forest - Coniferous Forest - Meadow Province (M221 A-D)

Eastern Broadleaf Forest (Oceanic) Province (221)

Warm Continental Division (210):

Hot Continental Division (220):

Other (221 A-D)

Eastern Broadleaf Forest (Continental) Province (222)

Erie and Ontario Lake Plain Section (222 I)

State

Ecological Division

Ecological Province

Ecological Section

Sampled FIA Inventory Plots

. Panels 2 and 3

Boundaries

Western Glaciated Allegheny Plateau Section (221F)

Southern Unglaciated Allegheny Plateau Section (221E)

Laurentian Mixed Forest Province (212)

Northern Glaciated Allegheny Plateau Section (212F)

Northern Unglaciated Allegheny Plateau Section (212G)

Central Appalachian Broadleaf Forest - Coniferous Forest - Meadow Province (M221 A-D)

Eastern Broadleaf Forest (Oceanic) Province (221)

Warm Continental Division (210):

Hot Continental Division (220):

Other (221 A-D)

Eastern Broadleaf Forest (Continental) Province (222)

Erie and Ontario Lake Plain Section (222 I)

State

Ecological Division

Ecological Province

Ecological Section

Sampled FIA Inventory Plots

. Panels 2 and 3

221F

221E

212G 212F

221 A-D
3

“inventory panel.” The overall design is referred to as an

“interpenetrating design” because within each inventory

panel, no cell is adjacent to another. As a result, each

panel provides an unbiased representation of conditions

across the State. Until the implementation of Phase 1

procedures, each sample location is weighted according to

the area of a single hexagonal cell, or about 6,000 acres of

land. The new design also incorporates a change to a foursubplot cluster.1

 At each location, a suite of variables is

measured that characterizes the land and trees associated

with the sample.

Phase 3. On a limited number of Phase 2 locations, more

extensive forest health measurements are conducted

during a 10-week period in summer. The measurements

are grouped into five general categories of indicators:

crown conditions, vegetation diversity and structure,

down woody debris, soil condition, and lichen

communities. The intensity of the Phase 3 sample is one

sample location per 95,000 acres of land.

To better address the issue of regeneration in the State, the

Pennsylvania Bureau of Forestry is funding a study to

quantify the composition, abundance, and quality of tree

seedlings and other understory vegetation on Phase 2

sample plots. The Pennsylvania Regeneration Study (PRS)

is part of a larger research initiative undertaken by the

Pennsylvania Bureau of Forestry, two Northeastern

Research Station silvicultural research labs, and the School

of Forest Resources of The Pennsylvania State University.

The northeastern FIA samples complement research at

these cooperating institutions that are developing site- and

species-specific stocking guidelines and management

criteria. The PRS began the first year of data collection in

2001 following a one-year pilot study designed to evaluate

techniques for measuring tree seedlings and other understory

vegetation on FIA sample locations. All established tree

seedlings at least 2 inches tall are being tallied by species,

seedling source, and height class on a subset of sample

locations measured during the leaf-on season (referred to

as a subpanel). Other understory vegetation also is being

measured. Along with other Phase 2 measurements, these

samples will help scientists gauge the forest’s regenerative

capacity and the impact of other vegetation.

Under the annual inventory system, field crews within the

State measure Phase 2 and 3 samples continually. Once

the first 5 years of data are complete, a comprehensive

report covering forest resources will be generated.

Following that, each year’s measurements will replace the

oldest year’s data to provide new estimates each year.

Limitations: Caution in Early Years

of Implementation

While the new system is being implemented, several

aspects of the inventory results will require careful

scrutiny. Because of the interpenetrating design of the new

sample grid, each year’s inventory panel provides unbiased

estimates of resource location. However, until the first 5

years of measurements are complete, sampling errors will

be larger, making it more difficult to detect changes in

inventory. The issue of sampling error is particularly acute

for evaluating estimates for subregions of the State, for

example, Ecological Sections. As a result, a table

containing sampling errors accompanies each 2001

resource table in the Appendix. When analyzing the

statistics for a change in conditions, one should examine

the mean and confidence intervals of estimates. If

confidence intervals do not overlap, there is sufficient

evidence to suggest true resource change; if they overlap,

resource change is questionable. The sampling errors were

computed for the 67-percent level of confidence, or two

chances in three. Note that 67-perent confidence intervals

provide liberal bounds on the estimates.

During the early years of installation, several of the more

commonly used land-base indicators of forest resource

change will not be available. The Phase 1 forest/nonforest

map will not be generated until the third year of the

inventory cycle. Until then, estimates of land area are

based on simple random sampling, that is, each sample

location represents an equal area of forest. The Phase 1

sample will improve the accuracy of estimates by assigning

a more representative number of acres to each sample

location.

Analysis of certain plot-characterization variables will

require scrutiny during the early years of implementation.

An example is the analysis of changes in the distribution

of forest land by forest-type group and stand-size class.

The current algorithm for determining these variables has

changed since 1989 and during the next several years will

undergo modifications to comply with national standards

and procedures. For this report, the 1989 sample data

were recompiled with the current algorithm used by the

northeastern FIA unit. A set of the revised 1989 tables is

included in the Appendix. Estimates of the distribution of

forest land by forest-type group are presented for only the

two most recent inventory dates due to the vagaries

associated with compilation procedures prior to 1989. For

pre-1989 inventories, estimates of the distribution of

forest land by stand-size class should be comparable

because these compilation procedures are simpler than

those for forest-type group. Estimates for older inventories

were prorated to provide comparable statistics for

graphical analysis; previous reports were for “timberland”

1

Northeast field guide, field manual version 1.6. On file with

the Northeastern Research Station, Forest Inventory and

Analysis, 11 Campus Blvd., Suite 200, Newtown Square, PA

19073.
4

and contemporary analyses are for “forest land.”

Timberland represents that portion of forest land that is

capable of producing more than 20 cubic feet per acre per

year and that is not withdrawn from timber utilization.

The more extensive land class, forest land, includes tracts

of land that are at least 1 acre in size, at least 120 feet

wide, and not developed for a nonforest land use.

Evaluation of long-term trends in the numbers of trees is

based on trees measured on timberland because only trees

on timberland were reported in older inventories. The

distribution of live trees per acre of forest land is a

valuable indicator of broad structural changes affecting

the entire forest. However, these data are available only for

the 1989 and 2001 inventories. Trends as far back as the

1965 inventory are available for growing-stock trees that

are larger than 5.0 inches in diameter. This furthers limits

one’s ability to examine the entire forest structure because

sapling, rough, rotten, and standing dead trees are

excluded.

The components of inventory change—growth, removals,

and mortality—are the primary indicators of flux and

sustainability of forest land. However, estimates of these

components will be of limited use during the early years

of the annual inventory process. Two factors that affect

the estimation of change components are the percentage

of sample locations and trees that are remeasured. The

hexagonal grid system used for the new annual inventory

replaces the grid of stratified random locations used for

the 1989 inventory. During the installation of the

hexagonal grid, each cell was examined to determine

whether it contained a previously measured FHM or FIA

sample. About 55 percent of the hexagons contained

previously measured samples. On remeasured sample

locations, the new four-subplot cluster is centered over the

1/5th-acre sample design used in 1989. At individual

sample locations, only trees on the central 1/20th-acre

center subplot that is overlaid on the old 1/5th-acre design

are being remeasured. As such, about 13 percent of the

sample trees will be remeasured during the first 5-year

cycle that began in 2000 and will be completed in 2004.

This means that sampling errors will be particularly high

for estimates of components of change. As each new

measurement panel is completed during the second 5-year

cycle that will be completed in 2009, sampling errors will

be reduced dramatically.

Overall “net change” in inventory is a useful surrogate

indicator of sustainability during the early years. Net

change in inventory expressed in net cubic feet2

 and board

feet3

 summarizes the effects of growth, removals, and

mortality. Net growth is equal to gross growth minus

mortality. Net change is equal to net growth minus

removals. Positive changes in inventory volume reflect

conditions such that net growth exceeds removals.

Negative changes reflect situations in which removals

exceed net growth—a key indication of unsustainable

conditions in the near term. Change in inventory volume

is a useful indicator of trends for the major species groups

within Pennsylvania. Although only the 1989 and 2001

inventories are examined, it is important to note that

examining more than two points in time is recommended.

For example, evaluating three points in time may reveal

that a positive net change followed a negative change of

similar magnitude, supporting little overall change for the

period examined.

Benefits: More Rapid and Complete

Resource Analyses

Perhaps the most salient benefit of the new inventory

system will be the nearly threefold improvement in

timeliness. A complete, new inventory will be available in

3 years (the end of the first 5-year cycle) with updates on

conditions available yearly thereafter. The installation of a

single remeasured sample design across the State will

greatly improve the quality of information on change in

resource extent, status, and condition. The use of this

national sample design will facilitate resource assessments

that straddle traditional regional and state boundaries to

include Pennsylvania’s results within the Mid-Atlantic

region, as well as national and international assessments.

The extension of the sample to include a broader range of

measurements will help analysts understand the

relationships between resource change and underlying

ecological variables. In particular, the implementation of a

suite of forest health variables (Phase 3) will foster a better

understanding of conditions on Phase 2 plots. The results

of the PRS will aid in evaluating forest composition over

the longer term.

The hiring of permanent field crews is a significant

advantage over the use of temporary crews. Under the new

design, crew members will be visiting sample locations

within their region year after year, enhancing their ability

to locate samples, obtain permission from landowners,

identify local species, evaluate tree quality, understand

forest composition and management activities, and

2

Net cubic-foot volume of the central stem of trees at least

5.0 inches in diameter at breast height from a 1-foot stump

to a 4-inch top or a point where the stem breaks into limbs.

3

Net board-foot volume of the central stem of softwood trees

at least 9.0 inches in diameter and hardwood trees at least

11.0 inches in diameter from a 1-foot stump to a 7.0-inch

top for softwoods and a 9.0-inch top for hardwoods or to a

point above which a sawlog cannot be produced.
5

measure the forces affecting resource change in their

region.

All of the improvements in the inventory system have

been accompanied by technological improvements since

the 1989 inventory, for example, the ability to conduct

sophisticated geospatial analyses. Geographic Information

Systems, improved database management systems, and

satellite-based land-classification systems will provide

map-based products, links to auxiliary datasets, and

improved geospatial modeling. Of particular interest is the

ability to portray resource statistics for geographic regions

of interest, e.g., ecoregions, geophysical regions, climate

zones, watersheds, pest outbreak zones, large disturbance

areas, and congressional districts.

The Annual Inventory:

Results From The First Two Years

Forest Land

Pennsylvania’s landscape is characterized by a complex mix

of land uses with forest land typically the residual land

use, or the use for which there is no higher economic

demand. Land use, physiography, climate, and pest/

pathogens have intermingled in creating different forest

conditions across the State. The result is a diverse mix of

issues and concerns that is being addressed by the forest

inventory. For example, alternate food sources for deer

populations ease the pressure on forest regeneration in

regions of the State where forests are mixed with

agricultural land. In heavily forested regions, few sources

of available food and high deer populations have

obliterated tree seedlings in the forest understory over

large areas.

A useful way to partition the State is by ecoregions (Bailey

1995) that supplement FIA inventory regions. Ecoregions

often correspond with natural phenomena that forge

forest composition, structure, and function. It is

important to scale the analysis of forest land to an area

that will yield a statistically reliable estimate of forest

condition. Ecological Divisions, Provinces, and Sections

of interest in Pennsylvania are shown in Figure 1. These

ecoregions contain sufficient forested plots for a

reasonable estimate of forest area. As new inventory panels

are completed, more detailed resource statistics can be

analyzed by ecoregion.

The northern tier of Pennsylvania contains the major

boundary between the Warm and Hot Continental

Divisions. The Laurentian Mixed Forest Province is

separated into Glaciated and Unglaciated Sections. The

Eastern Broadleaf Forest (Oceanic) Province comprises

several Sections that were combined on the map. This

Province is split in the middle by the Central Appalachian

Broadleaf Forest – Coniferous Forest – Meadow Province

(the Appalachian Mountains). A prominent feature of the

Province and Section boundaries is the line of glaciation

that weaves across the State’s northern tier.

As shown in the tabulation that follows, the most recent

inventory panels indicate that Pennsylvania has

16,649,800 acres of forest land (confidence interval of ±

266,397 acres). This compares to the 1989 estimate of

16,704,400 acres (± 100,226 acres). These two confidence

intervals overlap, so there is no discernable trend.

Estimates below the State level have even larger sampling

errors, though a general indication of prospective changes

can be discerned by using large ecoregions. For example,

the data suggest slight increases in forest land in the

northern and some central regions, and decreases in the

southwestern, southeastern, and portions of the central

part of the State. It is interesting to contrast recent leveling

of the forest-land base in Pennsylvania with the more

violent changes that occurred earlier in the previous

century (Fig. 2). The total area of forest land in the State

has been relatively stable since the mid-1960’s.

The forest types and groupings used by FIA are useful for

tracking changes through time. In fact, FIA has used the

same forest-type naming and grouping system over the

Ecoregion 1989a 2001a

Warm Continental Division

Laurentian Mixed Forest Prov.

North. Glaciated Allegheny

Plateau Section 2,411.6 2,447.8

North. Unglaciated Allegheny

Plateau Section 3,113.7 3,244.4

Subtotal 5,525.3 5,692.2

Hot Continental Division

East. Broadleaf Forest (Oceanic) Prov.

Southern Unglaciated Allegheny

Plateau Section 2,660.7 2,840.4

West. Glaciated Allegheny

Plateau Sectionb 1,230.6 1,135.3

Other 836.5 728.9

Subtotal 4,727.8 4,704.6

Cen. Appalachian Broadleaf Forest/

Coniferous Forest/Meadow Prov.c 6,451.2 6,253.0

Total 16,704.4 16,649.8

a

Sampling errors range from 8.5 percent to 0.6 percent.

b

Includes 151,800 and 153,900 acres of the Erie and Ontario Lake

Plain Section.

c

See Bailey (1995).
6

years to ensure the best trend information possible.

Although the goal has been to track forest types over

decades, there are inherent difficulties. For example,

because the data are not in digital form, we cannot use the

new classification algorithms to reconfigure past inventory

data to current standards. As a result, information on

forest-type group is shown for only the 1989 and 2001

inventories (Fig. 3). It is clear that the distribution of

forest land by forest-type group has been stable over the

past decade, but this is likely because Pennsylvania’s forests

have been maturing gradually. At this level of data use,

FIA inventories generally monitor only major disturbance

events or other shifts in composition. Thus, no sweeping

changes would be anticipated. The oak-hickory group

decreased by 2 percent since 1989, but this change

probably is smaller than would be expected. Also, the

current acreage of oak-hickory probably is greater than in

the 1978 inventory even though a precise estimate for that

inventory is not reliable due to computational differences.

The distribution of the specific oak types also seems

relatively stable. The only other trend that is evident from

forest-type information is that red maple types increased

substantially, perhaps by as much as one-third. More

detailed shifts in specific types cannot be discerned with

only two panels of inventory data. It will be useful to

examine the more detailed forest-type data generated by

FIA as they become available.

As with forest-type groups, the distribution of forest land

by stand-size class points out the gradual maturing of

forest land (Fig. 4). This maturing has been marked by a

decrease in seedling-sapling stands and an increase in

sawtimber stands. Stand-size classes are not strictly

defined by age but they are indicative of stages of stand

development (successional stage). Seedling-sapling stands

are young, early successional stands while sawtimber

stands are older stands that are approaching financial

maturity. The decrease in the seedling-sapling class is of

concern because this is a long-term and negative trend.

The situation bears close monitoring because of potential

adverse impacts on a variety of wildlife species that are

dependent on young successional stands. The trend of

increasing sawtimber stands further supports the

conclusion that Pennsylvania’s forests contain more timber

today than at any time since the late 1800’s. It is

interesting that this trend is concurrent with the

unprecedented use of the State’s forest land for recreation

and other uses.

Numbers of Trees

The distribution of live trees by various measures is a

valuable indicator of broad structural changes that are

occurring in Pennsylvania’s forests. Data on numbers of

trees per acre should be examined without relating specific

numbers to known silvicultural standards for various

cover types because the FIA results represent averages for

the entire State. As such, they should be reviewed for

relative changes over time and within species and size

classes.

Year

1630 1907 1938 1955 1965 1978 1989 2001

Millions of Acres

0

5

10

15

20

25

30

Figure 2.—Area of forest land, Pennsylvania, for selected

years (estimates for years prior to 1995 from Smith and

others 2001). Except the difference between 1989 and

2001, all differences between bars are statistically

significant at 67-percent level.

Forest-Type Group

Thousands of Acres

0

2000

4000

6000

8000

10000

1989

2001

White/Red Pine

Elm-Ash-Red maple

Northern Hardwoods

Aspen/Birch

Oak/Hickory

Other Conifer and Oak-Pine

Figure 3.—Distribution of forest land in Pennsylvania by

forest-type group, 1989 and 2001 (error bars reflect 67-

percent confidence intervals).
7

Figure 5 shows the breakdown of the total population of

live and dead trees by tree class and for growing-stock

poletimber4

 and sawtimber trees.5 The distribution for the

two points in time are similar except for a slight increase

in the number of dead trees. In Figure 6, the broad

changes in the numbers of growing-stock trees by

diameter class (the stock table) are depicted for all

previous inventories except the 1955 inventory. The sharp

rotation of the stock table between 1965 and 1975

illustrates a dramatic shift toward larger trees. The stock

table then continues to shift but at a slower rate. The most

recent changes suggest a gradual but steady shift toward

larger sawtimber-size trees, particularly in the larger

classes. These most recent changes also are reflected in

Figure 7, which shows the distribution of all live trees

Forest Land (%)

0

10

20

30

Forest Land (%)

0

20

40

60

Forest Land (%)

0

10

20

30

40

50

60

70

1955 1965 1978 1989 2001

1955 1965 1978 1989 2001 1955 1965 1978 1989 2001 1955 1965 1978 1989 2001 1955 1965 1978 1989 2001

Figure 4.—Distribution of forest land by

stand-size class, Pennsylvania, 1955, 1965,

1978, 1989 and 2001. Error bars reflect 67

percent confidence intervals. Sampling errors

are not available for years prior to 1989.

0

20

40

60

80

100

1989 2001

Percent

NonSalv Dead

Salv Dead

Rotten

Rough

GS Sawtimber

GS Poletimber

Figure 5.—Distribution of live

and dead trees (5.0 inches and

larger) by tree class and size class

(poletimber and sawtimber),

Pennsylvania, 1989 and 2001.

4

Growing-stock trees from 5.0 inches in diameter to 9.0 and

11.0 inches in diameter for softwood and hardwood species,

respectively.

5

Growing-stock trees at least 9.0 and 11.0 inches in diameter

for softwood and hardwood species, respectively.

Seedling-Sapling Poletimber

Sawtimber
8

down to the 2-inch diameter class. Note that the apparent

increase in the number of trees in this class is not

statistically significant.

Inventory Volume

As mentioned earlier, the depth of the analysis of change

in volume will be limited during the early years of the

annual inventory. Net change in inventory volume

expressed in cubic and board feet for the top species will

highlight the more salient trends. Overall, total inventory

volume increased, as did the volume of live trees and

growing stock. The total volume of live trees increased

from 27.5 to 33.7 billion cubic feet, a 23-percent increase.

This compares to a 10-percent increase in the volume of

growing stock trees. Inventory volume increased for both

softwoods and hardwoods. Changes in inventory are

depicted in Figure 8, which illustrates changes in the total

volume of growing-stock per acre since 1955. Long-term

historical increases continue but at a slightly slower rate

than in the past. The rapid increase in red maple volume

per acre since 1955 is shown in Figure 9.

Examining the top 10 tree species in Pennsylvania offers

additional insight into volume trends (Fig. 10). Based on

the volume of live trees, they include red maple, black

Diameter Class (inches)

4 6 8 10 12 14 16 18 20 22

Growing-Stock Trees/Acre of Timberland (no.)

0

10

20

30

40

50

60

70

1965

1978

1989

2001

Figure 6.—Distribution of growing-stock trees (5.0 inches

and larger) per acre of timberland, Pennsylvania, 1965,

1978, 1989, and 2001.

Diameter Class (inches)

2 4 6 8 10 12 14 16 18 20 22

Number of Trees/Acre

0

50

100

150

200

250

300

1989

2001

Figure 7.—Distribution of live trees (1.0 inch and larger)

per acre of forest land in Pennsylvania by diameter class,

1989 and 2001. Error bars reflect 67-percent confidence

intervals.

0

500

1000

1500

2000

1955 1965 1978 1989 2001

Cubic Feet

Figure 8.—Volume of growing stock per acre of

timberland in Pennsylvania by inventory date, 1955,

1965, 1978, 1989, and 2001. All differences between

bars are statistically significant at 67-percent level.

0

100

200

300

400

1955 1965 1978 1989 2001

Cubic Feet

Figure 9.—Volume of red maple growing stock per acre of

timberland in Pennsylvania by inventory date, 1955,

1965, 1978, 1989, and 2001. All differences between

bars are statistically significant at 67-percent level.
9

cherry, northern red oak, sugar maple, chestnut oak, white

oak, white ash, other oaks, yellow-poplar, and eastern

hemlock. Currently, red maple makes up 20 percent of the

total volume of live trees in the State and accounts for 60

percent of the increase in volume statewide. It is

interesting that the top 5 tree species account for more

than half of the inventory volume and the top 10 account

for 75 percent of the total volume. Increases were

significant for 8 of the top 10 species (exceptions were

sugar maple and eastern hemlock).

The results for sawtimber volume also are positive. The

total volume of sawtimber increased from 72.8 billion

board feet (International 1⁄4-inch rule) in 1989 to 85.8

billion board feet in 2001, an increase of 18 percent.

Increases were noted for both softwoods and hardwoods.

The buildup in sawtimber volume over time is shown in

Figure 11. Increases are clearly evident, but at a slower rate

than in the two previous inventory periods. Again, except

for sugar maple and hemlock, Pennsylvania’s top 10 tree

species increased in sawtimber volume (Fig.12). Yellowpoplar had the largest increase on a proportional basis (65

percent).

Understory Diversity and Abundance

Tree seedlings

Past studies have shown that advance regeneration often is

absent in stands across Pennsylvania and that oak

regeneration is especially rare. With over half the State’s

forest land in sawtimber stands, regeneration is the most

pressing issue in discussions about the long-term

sustainability of Pennsylvania’s forested landscape. To

date, only a single subpanel of regeneration measurements

has been collected, though preliminary results suggest a

slight improvement in regeneration since data collected

during the 1980’s.

It is difficult to fully interpret regeneration data due to a

dearth of information from other studies reporting similar

data for Mid-Atlantic States. A study of advance treeseedling regeneration during the 1989 inventory revealed

low regeneration levels (McWilliams and others 1995a).

In this study, stands within the range of stocking where

advance regeneration should be present (40 to 75 percent)

were examined. The methods used differ from those used

in the current study, so comparisons should be made with

Red Maple

Black Cherry

N. Red Oak

Sugar MapleChestnut Oak

White OakWhite Ash

Other Oaks

Yellow-Poplar

Eastern Hemlock

Million Cubic Feet

0

2000

4000

6000

8000

1989

2001

Figure 10.—Volume of live trees on forest land for the 10

most abundant species in Pennsylvania, 1989, and 2001.

Error bars reflect 67-percent confidence intervals.

0

1000

2000

3000

4000

5000

6000

1955 1965 1978 1989 2001

Board Feet (International 1/4-inch Rule Figure 11.—Volume of sawtimber per acre of timberland

in Pennsylvania by inventory date, 1955, 1965, 1978,

1989, and 2001. All differences between bars are

statistically significant at 67-percent level.

Red Maple

Black Cherry

N. Red Oak

Yellow-Poplar

Sugar Maple

Chestnut Oak

White Oak

Other Oaks

White Ash

Eastern Hemlock

Million Board Feet

0

2000

4000

6000

8000

10000

12000

14000

16000

1989

2001

Figure 12.—Volume of sawtimber on forest land for the

10 most abundant species in Pennsylvania, 1989, and

2001. Error bars reflect 67-percent confidence intervals.
10

caution. Methods used for the study implemented in

2001 were tested in a pilot study conducted during the

2000 field season to determine the most efficient sampling

procedure for Pennsylvania’s forests (McWilliams and

others 2002). Another study in 1990 focused on oak

regeneration following disturbance. Results showed that

regeneration occurs but that oaks are rare in the

understory of heavily disturbed stands (McWilliams and

others 1995b). Regeneration stocking generally improved

following disturbance, primarily due to red maple, sweet

birch, black cherry, and other species that were not

apparent as advance regeneration but came from existing

seed sources and seedbanks.

The 1989 and 2001 tree-seedling studies are compared in

the two charts in Figure 13 that show the percentage of

samples that met regeneration criteria for desirable,

commercial, and woody species groups. The 1989 study

region included counties that were measured during the

summer window without spatial dispersion. Many of the

samples were in mountainous ecoregions where

regeneration was known to be less abundant. The 2001

study samples were distributed spatially across

Pennsylvania by the same interpenetrating design used for

the standard FIA sample grid. Also, previous estimates

were analyzed by evaluating whether four of five

regeneration plots met regeneration criteria. It is not

possible to recreate this approach with the current fourmicroplot system. Using all forested sample conditions as

the sample population should improve the reliability of

the results. The most notable difference in results between

the two studies is the more favorable abundance of tree

seedlings in the understory in 2001. However, it is not

known whether this difference is due to differences in

study design or “real” change.

The analysis of regeneration levels depends on how species

are divided among composition groups, assumptions

related to requirements for regeneration stocking, and the

tree sizes included in the analysis. Both standard and strict

regeneration criteria were used to account for the diversity

of conditions across Pennsylvania. Of the species

groupings mentioned, desirable species reflect timber

markets, commercial species are associated with custodial

management, and all woody species reflect overall site

occupancy. The comparison in Figure 13 was limited to

seedlings only. The effect of including saplings and larger

trees on the results is shown in Figure 14. Seedlings and

saplings are the preferred sizes for representing

regeneration status within the forest understory.

Incorporating older trees, typically those within a higher

forest canopy, affects the results but detracts from focusing

on more important components of regeneration. Also,

larger trees have only a minor impact on the analysis.

Thus, in subsequent analyses, seedlings and saplings are

used as the regeneration measure.

Figure 13.—Percentage of samples satisfying regeneration

criteria by species composition grouping and regeneration

criteria using seedlings only, Pennsylvania, 1989 and

2001. The sample data means are subject to sampling

errors of 4.9 percent.

Figure 14.—Percentage of samples satisfying regeneration criteria by species composition

grouping, regeneration criteria, and tree size, Pennsylvania, 2001. The sample data means

are subject to sampling errors of 4.9 percent.

47

65 69

59

75 80

0

20

40

60

80

100

Percent

Strict Standard

31

51 56

48

66

72

0

20

40

60

80

100

Percent

Strict Standard

    

17

28 31

39

52 58

0

20

40

60

80

100

Percent

Strict Standard

        	 

Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group

47

65 69

59

75 80

0

20

40

60

80

100

Percent

Strict Standard

31

51 56

48

66

72

0

20

40

60

80

100

Percent

Strict Standard

    

17

28 31

39

52 58

0

20

40

60

80

100

Percent

Strict Standard

        	 

Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group

17

28 31

39

52 58

0

20

40

60

80

100

Percent

Strict Standard

4 6 10

20

28

41

0

20

40

60

80

100

Percent

Strict Standard

Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group



Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group
11

The impact of red maple is of interest for additional

evaluation of the study results. If red maple regeneration is

heavily influencing regeneration-stocking levels, then

removing the species from the analysis should reveal its

impact. Results using seedlings only, and seedlings and

saplings are illustrated in Figure 15. The impact of red

maple is strong for both regeneration components and

might partially explain differences in the 1989 and 2001

study results had the development of this species been

accelerated between studies.

The results for larger ecoregions are shown in Figure 16. It

would seem that the Plateau and eastern portions of the

Eastern Broadleaf Forest Province have slightly lower

17

28 31 39

52 58

0

20

40

60

80

100

Percent

Strict Standard

  

12

23 26 30

46 52

0

20

40

60

80

100

Percent

Strict Standard

   

Desirable

Commercial

Woody

Species Composition Group

31

51 56 48

66 72

0

20

40

60

80

100

Percent

Strict Standard

  

Desirable

Commercial

Woody

Species Composition Group

24

45 52

37

58 65

0

20

40

60

80

100

Percent

Strict Standard

    

  

  

17

28 31 39

52 58

0

20

40

60

80

100

Percent

Strict Standard

  

12

23 26 30

46 52

0

20

40

60

80

100

Percent

Strict Standard

   

Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group

31

51 56 48

66 72

0

20

40

60

80

100

Percent

Strict Standard

  

Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group

24

45 52

37

58 65

0

20

40

60

80

100

Percent

Strict Standard

    

  

  

Figure 15.—Percentage of samples satisfying

regeneration criteria by species composition

grouping and regeneration criteria with and

without red maple, Pennsylvania, 2001. The

sample data means are subject to sampling

errors of 4.9 percent.

Figure 16.—Percentage of samples satisfying

regeneration criteria by species composition

grouping, regeneration criteria, and ecoregion

using seedlings and saplings, Pennsylvania, 2001.

The sample data means are subject to sampling

errors of 4.9 percent.

Desirable

Commercial

Woody

Species Composition Group

24

45 46 47

65 68

0

20

40

60

80

100

Percent

Strict Standard

 

30

52 58

44

64 72

0

20

40

60

80

100

Percent

Strict Standard

Desirable

Commercial

Woody

Species Composition Group

   

Desirable

Commercial

Woody

Species Composition Group

45

57

66

58

69 77

0

20

40

60

80

100

Percent

Strict Standard

 	   


Desirable

Commercial

Woody

Species Composition Group

22

39

50 50

61

67

0

20

40

60

80

100

Percent

Strict Standard

 	   

Desirable

Commercial

Woody

Species Composition Group

24

45 46 47

65 68

0

20

40

60

80

100

Percent

Strict Standard

 

Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group

24

45 46 47

65 68

0

20

40

60

80

100

Percent

Strict Standard

 

30

52 58

44

64 72

0

20

40

60

80

100

Percent

Strict Standard

Desirable

Commercial

Woody

Species Composition Group

   

30

52 58

44

64 72

0

20

40

60

80

100

Percent

Strict Standard

Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group

   

Desirable

Commercial

Woody

Species Composition Group

45

57

66

58

69 77

0

20

40

60

80

100

Percent

Strict Standard

 	   


Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group

45

57

66

58

69 77

0

20

40

60

80

100

Percent

Strict Standard

 	   


Desirable

Commercial

Woody

Species Composition Group

22

39

50 50

61

67

0

20

40

60

80

100

Percent

Strict Standard

 	   

Desirable

Commercial

Woody

Species Composition Group

Desirable

Commercial

Woody

Species Composition Group

22

39

50 50

61

67

0

20

40

60

80

100

Percent

Strict Standard

 	   12

percentages of samples that met the regeneration criteria.

Additional sample data are needed for detailed spatial

analyses.

Because of the uncertainty surrounding the regenerative

capacity of Pennsylvania’s forests, it is difficult to

formulate succinct statements concerning regeneration

abundance and quality. The most fundamental findings

are those for the three species-composition groups using

the stocking of seedlings and saplings (Fig. 14). Put

simply, the results suggest that under a general goal of

managing for a desirable species mix, 32 to 48 percent of

Pennsylvania’s forest land supports favorable levels of

advance regeneration. Under a more liberal goal of

managing for commercial species, 51 to 66 percent meets

regeneration criteria. Setting a goal of establishing any

woody vegetation improves the results only slightly (56 to

72 percent).

By every measure, the regeneration picture in

Pennsylvania is bleak based on the findings for the first

panel of regeneration measurements. Even if commercial

species were deemed acceptable, one-third to one-half of

the forest land would likely fail to regenerate without the

additional stocking from other sources following

disturbance. The small number of samples used prevents

detailed comparisons of forest types or other stand

variables. Also, the analytical framework for evaluating

regeneration is being reviewed and might be revised

slightly. Still, on the basis of available evidence, we can

state that poor regeneration is common across

Pennsylvania rather than specific to a particular

landowner or forest type.

Associated understory vegetation

Broad relationships between tree-seedling abundance and

the occurrence of other understory vegetation are

illustrated by examining the relative abundance of

understory vegetation for the major species encountered

in the samples. Figure 17 includes results for the major

components of understory vegetation for sampled

conditions that did and did not meet regeneration criteria.

The samples that failed to meet the criteria had higher

levels of associated understory occupying sample plots.

Care is needed in interpreting the magnitude of

























 

  

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

























 

  

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

























 

  

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

























 

  

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

























 

  

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

























 

  

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

     

   

    

























 

  

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

























 

  

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

























 

  

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

























 

  

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

























 

  

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

























 

  

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

Fern

Fern, Grass,

& Herb.

Shrub & Vine

All Understory

     

   

    

Figure 17.—Mean percent cover by regeneration criteria and understory vegetation component,

Pennsylvania, 2001.
13

understory cover for various vegetation components

because they represent averages across the entire sample,

i.e., a wide range of conditions. As a result, the relative

differences are of prime interest. Differences between

levels for samples that did and did not meet the

regeneration criteria are most apparent for the fern, and

for fern, grass, and other herbs combined.

Results of existing silvicultural research provide guidelines

for evaluating what the study results reveal about

relationships between tree-seedling abundance and the

occurrence of other understory vegetation. These

relationships, in turn, provide insight into the

establishment and development of tree seedlings. It is

difficult to apply guidelines intended for site- or standspecific silvicultural prescriptions because of the

numerous stand conditions encountered at FIA sample

locations. However, it has been found that maple-beechbirch and mixed-oak stands under even-age management

that have stocking of nontree vegetation that exceeds 30

percent are candidates for stand preparation treatments to

remove vegetation that competes with tree seedlings

(Marquis 1994). The strong relationship between samples

that met regeneration criteria and levels of associated

vegetation is shown in Figure 18.

       	 
      

All

Understory 

Shrub 

and

Vine

Fern,

Grass, 

and

Herbs Criteria Fern

Standard -Woody 16.6 45.7 43.0 66.7

Strict - Woody 10.8 34.7 34.2 52.3

Standard - Commercial 15.2 41.6 39.9 61.4

Strict - Commercial 10.5 31.3 30.8 47.4

Standard - Desirable 10.8 32.5 31.5 45.5

Strict - Desirable 6.1 21.5 21.0 30.3

All

Understory 

Shrub 

and

Vine

Fern,

Grass, 

and

Herbs Criteria Fern

Standard -Woody 16.6 45.7 43.0 66.7

Strict - Woody 10.8 34.7 34.2 52.3

Standard - Commercial 15.2 41.6 39.9 61.4

Strict - Commercial 10.5 31.3 30.8 47.4

Standard - Desirable 10.8 32.5 31.5 45.5

Strict - Desirable 6.1 21.5 21.0 30.3

All

Understory 

Shrub 

and

Vine

Fern,

Grass, 

and

Herbs

Fern

Criteria

Standard -Woody 8.3 21.3 15.2 26.7

Strict - Woody 14.2 32.3 24.0 41.1

Standard - Commercial 9.8 25.4 18.3 32.0

Strict - Commercial 14.4 35.7 27.4 46.0

Standard - Desirable 14.2 34.5 26.7 47.9

Strict - Desirable 18.8 45.5 37.2 63.1

All

Understory 

Shrub 

and

Vine

Fern,

Grass, 

and

Herbs

Fern

Criteria

Standard -Woody 8.3 21.3 15.2 26.7

Strict - Woody 14.2 32.3 24.0 41.1

Standard - Commercial 9.8 25.4 18.3 32.0

Strict - Commercial 14.4 35.7 27.4 46.0

Standard - Desirable 14.2 34.5 26.7 47.9

Strict - Desirable 18.8 45.5 37.2 63.1

Figure 18.—Percentage of understory vegetation samples with at least 30 percent cover by understory

vegetation component and regeneration criteria, Pennsylvania, 2001.
14

Literature Cited

Alerich, Carol A. 1993. Forest statistics for

Pennsylvania—1978 and 1989. Resour. Bull. NE-126.

Radnor, PA: U.S. Department of Agriculture, Forest

Service, Northeastern Forest Experiment Station. 244 p.

Bailey, Robert G. 1995. Description of the ecoregions of

the United States. 2nd ed. Misc. Publ. 1391 (rev.).

Washington, DC: U.S. Department of Agriculture,

Forest Service. 108 p.

Considine, Thomas J., Jr.; Powell, Douglas S. 1980.

Forest statistics for Pennsylvania—1978. Resour.

Bull. NE-65. Broomall, PA: U.S. Department of

Agriculture, Forest Service, Northeastern Forest

Experiment Station. 88 p.

Ferguson, Roland H. 1955. The timber resources of

Pennsylvania. Upper Darby, PA: U.S. Department of

Agriculture, Forest Service, Northeastern Forest

Experiment Station. 46 p.

Ferguson, Roland H. 1968. The timber resources of

Pennsylvania. Resour. Bull. NE-8. Upper Darby, PA:

U.S. Department of Agriculture, Forest Service,

Northeastern Forest Experiment Station. 145 p.

Marquis, David A., ed. 1994. Quantitative silviculture

for hardwood forests of the Alleghenies. Gen. Tech.

Rep. NE-183. Radnor, PA: U.S. Department of

Agriculture Forest Service, Northeastern Forest

Experiment Station. 143 p.

McWilliams, William H.; King, Susan L.; Scott, Charles

T. 2002. Assessing regeneration adequacy in

Pennsylvania’s forests: a pilot study. In: Reams,

Gregory A.; McRoberts, Ronald E.; Van Deusen, Paul

C., eds. Proceedings of the second annual forest

inventory and analysis symposium; 2000 October 17-

18; Salt Lake City, UT. Gen. Tech. Rep. SRS-47.

Asheville, NC: U.S. Department of Agriculture, Forest

Service, Southern Research Station: 119-122.

McWilliams, William H.; Stout, Susan L.; Bowersox,

Todd W.; McCormick, Larry H. 1995a. Advance treeseedling regeneration and herbaceous cover in

Pennsylvania forests. Northern Journal of Applied

Forestry. 12(4): 187-191.

McWilliams, William H.; Bowersox, Todd W.; Gansner,

David A.; Stout, Susan L.; McCormick, Larry H.

1995b. Landscape-level regeneration adequacy for

native hardwood forests of Pennsylvania. In:

Gottschalk, Kurt W.; Fosbroke, Sandra L. C., eds.

Proceedings, central hardwood forest conference; 1995

March 5-8; Morgantown, WV. Gen. Tech. Rep. NE197. Radnor, PA: U.S. Department of Agriculture,

Forest Service, Northeastern Forest Experiment Station:

196-203.

Smith, Brad W.; Vissage, John S.; Darr, David R.;

Sheffield, Raymond M. 2001. Forest resources of the

United States, 1997. Gen. Tech. Rep. NC-219. St.

Paul, MN: U.S. Department of Agriculture, Forest

Service, North Central Research Station. 190 p.
15

Index to Tables

Resource Tables for 2001

Table 1.

Land area by land class, Pennsylvania, 2001.

Table 2.

Area of forest land by forest type, forest-type group, and

stand-size class, Pennsylvania, 2001.

Table 2. (SE)

Area of forest land by forest type, forest-type group, and

stand-size class, Pennsylvania, 2001.

Table 3.

Area of timberland by forest type, forest-type group, and

stand-size class, Pennsylvania, 2001.

Table 3. (SE)

Area of timberland by forest type, forest-type group, and

stand-size class, Pennsylvania, 2001.

Table 4.

Area of timberland by forest-type group and stocking

class of all live trees, Pennsylvania, 2001.

Table 4. (SE)

Area of timberland by forest-type group and stocking

class of all live trees, Pennsylvania, 2001.

Table 5.

Number of live trees (1.0+ inches d.b.h.) on forest land

by species and diameter class, Pennsylvania, 2001.

Table 5. (SE)

Number of live trees (1.0+ inches d.b.h.) on forest land

by species and diameter class, Pennsylvania, 2001.

Table 6.

Number of live trees (1.0+ inches d.b.h.) on timberland

by species and diameter class, Pennsylvania, 2001.

Table 6. (SE)

Number of live trees (1.0+ inches d.b.h.) on timberland

by species and diameter class, Pennsylvania, 2001.

Table 7.

Number of trees (5.0+ inches d.b.h.) on timberland by

species and tree class, Pennsylvania, 2001.

Table 7. (SE)

Number of trees (5.0+ inches d.b.h.) on timberland by

species and tree class, Pennsylvania, 2001.

Table 8.

Number of growing-stock trees (5.0+ inches d.b.h.) on

timberland by species and diameter class, Pennsylvania,

2001.

Table 8. (SE)

Number of growing-stock trees (5.0+ inches d.b.h.) on

timberland by species and diameter class, Pennsylvania,

2001.

Table 9.

Net volume of all trees (5.0+ inches d.b.h.) on

timberland by class of timber and species group,

Pennsylvania, 2001.

Table 9. (SE)

Net volume of all trees (5.0+ inches d.b.h.) on

timberland by class of timber and species group,

Pennsylvania, 2001.

Table 10.

Sound volume of all trees (5.0+ inches d.b.h.) on forest

land by species and diameter class, Pennsylvania, 2001.

Table 10. (SE)

Sound volume of all trees (5.0+ inches d.b.h.) on forest

land by species and diameter class, Pennsylvania, 2001.

Table 11.

Net volume of growing-stock trees on timberland by

species and forest-type group, Pennsylvania, 2001.

Table 11. (SE)

Net volume of growing-stock trees on timberland by

species and forest-type group, Pennsylvania, 2001.

Table 12.

Net volume of growing-stock trees on timberland by

species and diameter class, Pennsylvania, 2001.

Table 12. (SE)

Net volume of growing-stock trees on timberland by

species and diameter class, Pennsylvania, 2001.

Table 13.

Net volume of sawtimber trees on timberland by species

and forest-type group, Pennsylvania, 2001.

Table 13. (SE)

Net volume of sawtimber trees on timberland by species

and forest-type group, Pennsylvania, 2001.

Appendix
16

Table 14.

Net volume of sawtimber trees on timberland by species

and diameter class, Pennsylvania, 2001.

Table 14. (SE)

Net volume of sawtimber trees on timberland by species

and diameter class, Pennsylvania, 2001.

Table 15.

 Sound biomass on forest land by species and

component, Pennsylvania, 2001.

Table 15. (SE)

Sound biomass on forest land by species and

component, Pennsylvania, 2001.

Resource Tables for 1989 (Revised)

Table 1.

Land area by land class, Pennsylvania, 2001.

Table 2.

Area of forest land by forest type, forest-type group, and

stand-size class, Pennsylvania, 1989.

Table 3.

 Area of timberland by forest type, forest-type group, and

stand-size class, Pennsylvania, 1989.

Table 4.

Area of timberland by forest-type group and stocking

class of live trees, Pennsylvania, 1989.

Table 5.

Number of live trees (1.0+ inches d.b.h.) on forest land

by species and diameter class, Pennsylvania, 1989.

Table 6.

Number of live trees (1.0+ inches d.b.h.) on timberland

by species and diameter class, Pennsylvania, 1989.

Table 7.

Number of trees (5.0+ inches d.b.h.) on timberland by

species and tree class, Pennsylvania, 1989.

Table 8.

Number of growing-stock trees (5.0+ inches d.b.h.) on

timberland by species and diameter class, Pennsylvania,

1989.

Table 9.

Net volume of live trees (5.0+ inches d.b.h.) on

timberland by class of timber and species group,

Pennsylvania, 1989.

Table 10.

Sound volume of live trees (5.0+ inches d.b.h.) on forest

land by species and diameter class, Pennsylvania, 1989.

Table 11.

Net volume of growing-stock trees on timberland by

species and forest-type group, Pennsylvania, 1989.

Table 12.

Net volume of growing-stock trees on timberland by

species and diameter class, Pennsylvania, 1989.

Table 13.

Net volume of sawtimber trees on timberland by species

and forest-type group, Pennsylvania, 1989.

Table 14.

Net volume of sawtimber trees on timberland by species

and diameter class, Pennsylvania, 1989.























































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McWilliams, William H.; Alerich, Carol A.; Devlin, Daniel A.; Lister, Tonya W.;

Sterner, Stephen L.; Westfall; James A. 2002. Annual inventory report for

Pennsylvania’s forests: results from the first two years. Resour. Bull. NE-156.

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

Northeastern Research Station. 71 p.

In 2000, the USDA Forest Service’s Forest Inventory and Analysis (FIA) program

implemented a new system for inventory and monitoring Pennsylvania’s forest

resources. The most salient benefit of the new inventory process will be a nearly

threefold improvement in timeliness. This report summarizes the results of the first 2

years of annual inventory measurements. The area of forest land in Pennsylvania

has remained stable since a previous inventory in 1989. The Keystone State's

forests continue to mature as larger trees and an increase in inventory volume were

recorded. A separate study of tree seedlings revealed a general lack of regeneration

in one-third to one-half of the stands in which regeneration should be adequate.

Keywords: forest composition; forest health; sustainability; timber volume; tree

regeneration
Headquarters of the Northeastern Research Station is in Newtown Square,

Pennsylvania. Field laboratories are maintained at:

Amherst, Massachusetts, in cooperation with the University of Massachusetts

Burlington, Vermont, in cooperation with the University of Vermont

Delaware, Ohio

Durham, New Hampshire, in cooperation with the University of New Hampshire

Hamden, Connecticut, in cooperation with Yale University

Morgantown, West Virginia, in cooperation with West Virginia University

Parsons, West Virginia

Princeton, West Virginia

Syracuse, New York, in cooperation with the State University of New York,

College of Environmental Sciences and Forestry at Syracuse University

Warren, Pennsylvania

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Whitten Building, 14th and Independence Avenue SW, Washington, DC 20250-9410, or call

(202)720-5964 (voice and TDD). USDA is an equal opportunity provider and employer.

“Caring for the Land and Serving People Thr ving People Through Research”