United States Department of Agriculture

Pennsylvania Forests 

2014

Forest Service Northern 

Research Station

Resource Bulletin

NRS-111

Publication Date

May 2017
Abstract

This report summarizes the third cycle of annualized inventory of Pennsylvania with field data 

collected from 2009 through 2014. Pennsylvania has 16.9 million acres of forest land dominated by 

sawtimber stands of oak/hickory and maple/beech/birch forest-type groups. Volumes continue to 

increase as the forests age with an average of 2,244 cubic feet per acre on timberland. Sawtimber 

volume has risen 24 percent in 10 years to 115 billion board feet. Net growth outpaced removals by 

a ratio of 2.4:1 on timberland. Additional information on land-use change, fragmentation, ownership, 

forest composition, structure and age distribution, carbon stocks, regeneration, invasive plants, 

insect pests, and wood products is also presented. Sets of supplemental tables are available online 

at https://doi.org/10.2737/NRS-RB-111 and contain: 1) tables that summarize quality assurance and 

2) a core set of tabular estimates for a variety of forest resources.

Acknowledgments

The authors would like to thank those who contributed to this assessment of Pennsylvania’s forest 

resources. The dedicated and vital data collection staff who took the measurements upon which 

this analysis is based are: Bill Moir, Todd Renninger, Mike Whitehill, Dave Berger, Bryan Tirrell, 

Ron Yaworsky, Richard Starr, Thomas Willard, Steve Potter, Chris Coolbaugh, Tony Olsen, Paul 

Natiella, Tom Albright, Joe Kernan, Jason Gould, Chris Tucci, and Charlie Butler. Thank you to the 

Pennsylvania Department of Conservation and Natural Resources (PA DCNR), Bureau of Forestry 

for the cooperation that makes this possible. We are also grateful to our reviewers, Amanda Parks 

(PA DCNR Bureau of Forestry), James Finley (Pennsylvania State University), Patrick Drohan 

(Pennsylvania State University), and Susan Stout (U.S. Forest Service) for their efforts to ensure we 

provide clear, useful information. Additional thanks are due to the rest of the Northern Research 

Station’s Forest Inventory and Analysis staff who prepare, process, and compile all the data.

Cover: Fall foliage as seen from High Knob overlook near Hillsgrove, Sullivan County. 

Photo by Thomas Albright, U.S. Forest Service.

Manuscript received for publication September 2016

Published by:

U.S. FOREST SERVICE

11 CAMPUS BLVD SUITE 200

NEWTOWN SQUARE PA 19073-3294

May 2017

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

Printed on recycled paper
Pennsylvania Forests 2014

Thomas A. Albright, William H. McWilliams, Richard H. Widmann, Brett J. Butler, 

Susan J. Crocker, Cassandra M. Kurtz, Shawn Lehman, Tonya W. Lister, Patrick D. Miles, 

Randall S. Morin, Rachel Riemann, and James E. Smith

Contact Author:

Thomas A. Albright

talbright@fs.fed.us

412-523-0103

About the Authors

Thomas A. Albright is a forester with the Forest 

Inventory and Analysis (FIA) program, Northern 

Research Station, Williamsport, PA.

William H. McWilliams, Tonya W. Lister, and 

Randall S. Morin are research foresters with 

the FIA program, Northern Research Station, 

Newtown Square, PA.

Richard H. Widmann is a forester with the FIA 

program, Northern Research Station, Newtown 

Square, PA.

Brett J. Butler is a research forester with the FIA 

program, Northern Research Station, Amherst, MA.

Susan J. Crocker and Patrick D. Miles are 

research foresters with the FIA program, 

Northern Research Station, St. Paul, MN.

Cassandra M. Kurtz is a natural resources 

specialist with the FIA program, Northern 

Research Station, St. Paul, MN.

Shawn Lehman is a forest program manager 

with the Pennsylvania Department of 

Conservation and Natural Resources, Bureau 

of Forestry, Resource Inventory and Monitoring 

Section, Spring Mills, PA.

Rachel Riemann is a research forester and 

geographer with the FIA program, Northern 

Research Station, Troy, NY.

James E. Smith is a research plant physiologist 

with the FIA program, Northern Research 

Station, Durham, NH.
Foreword

Pennsylvania’s 16.9 million acres of forests provide numerous ecological, economic, 

and social benefits and services. These forests are home to thousands of plant, 

mammal, bird, fish, reptile, amphibian, insect, and fungi species that are dependent 

on forest habitats. Pennsylvania forests support more than 2,100 forest product 

establishments employing approximately 58,000 residents that contribute an 

estimated $19 billion to the state’s economy. In addition, forests provide for clean 

water, soil stabilization, and opportunities for healthful recreation.

An understanding of current conditions and how they are changing over time 

is of fundamental importance for sustaining the benefits and services provided 

by Pennsylvania forests. The report summarizes the latest statewide inventory of 

Pennsylvania forests and is the result of a cooperative effort between the U.S. Forest 

Service Forest Inventory and Analysis program and the Pennsylvania Department of 

Conservation and Natural Resources, Bureau of Forestry.

This report highlights some encouraging trends for the future of Pennsylvania forests; 

it also raises concerns that require vigilant monitoring. Encouraging trends include 

a relatively stable forest land base, a slight increase in tree regeneration, and an 

increase in annual growth of tree volume. Issues of concern include a dearth of early 

successional forest habitat, shifts in species composition, an increase in invasive plant 

species, and the impacts of exotic pests such as emerald ash borer, gypsy moth, and 

hemlock woolly adelgid.

I hope that you can take some time to read and enjoy this report. Then, I hope that 

you spend some time in the forests of Pennsylvania with a greater understanding of 

the wonderful resource we call “Penn’s Woods.”

Daniel A. Devlin

Pennsylvania State Forester
Contents

Highlights � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 1

Background � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 3

Forest Features � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 11

Forest Resource Attributes � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 32

Forest Indicators of Health and Sustainability � � � � � � � � � � � � � � � � � � � � � � � 82

Forest Economics � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 118

Looking Forward � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 124

Literature Cited � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 129

Appendix � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 138

Pennsylvania Forests Summary Tables

 Online at https://doi.org/10.2737/NRS-RB-111

Additional Resources

 Online at https://doi.org/10.2737/NRS-RB-111
Quinn Run in Sullivan County. Photo by Thomas Albright, U.S. Forest Service.
 | 1

Highlights

On the Plus Side

• The forested area of Pennsylvania remains stable, totaling an estimated 16.9 million 

acres.

• Sawtimber stands continue to increase in area, representing 67 percent of all 

timberland.

• The continuing increase in volume results in a total of 2,244 cubic feet per acre on 

timberland, a 250 percent increase from 1955.

• Timberland sawtimber volume increased 24 percent since 2004 to an estimated 115 

billion board feet.

• The net growth-to-removals ratio increased to 2.4:1 overall on timberland.

• Small improvements in regeneration of commercially desirable species were 

observed.

Issues to Watch

• Development, both industrial and residential, continues to alter the character of 

Penn’s Woods because of forest conversion and fragmentation.

• The area of young, early successional forest continues to decline. Only an estimated 

1.5 million acres of timberland (9 percent) are in small diameter stands.

• Timberland continues to age. Stands over 80 years old accounted for 39 percent of 

all timberland area. Only 15 percent of timberland area is in stands 0 to 40 years 

old.

• Private landowners continue to control 70 percent of all forest land, but few owners 

have management plans or receive management advice. Less than 14 percent of the 

estimated 8.9 million acres owned by family forest owners are under management 

plans.

• Stocking levels on private timberland continued to shift toward the lower stocking 

classes. Widening disparities between stocking levels for all live trees and growingstock trees may indicate a need for more programs to assist landowners with forest 

management.
2 | 

• Regeneration remains a challenge. Nearly 20 percent of sample plots had high 

browse impacts, indicating that white-tailed deer are a factor in regeneration 

difficulties.

• Old and new insect pests threaten forest health. Gypsy moths have defoliated 

more than 3 million acres of Pennsylvania since 2000. Emerald ash borer and the 

hemlock woolly adelgid are having significant impacts on their hosts.

• Invasive plant species remain a concern, choking out native understories and 

altering habitat and food supplies for wildlife as well as inhibiting regeneration.
 | 3

Overlooking the Pine Creek Valley in Lycoming County. Photo by Thomas Albright, U.S. Forest Service.

Background
4 | BACKGROUND

An Overview of Forest Inventory

What is FIA?

The Forest Inventory and Analysis program, commonly referred to as FIA, is 

the Nation’s forest census. It was established by the U.S. Congress to “make and 

keep current a comprehensive survey and analysis of the present and prospective 

conditions of and requirements for the renewable resources of the forest and range 

lands of the United States” (Forest and Rangeland Renewable Resources Planning 

Act of 1974; 16 USC 1601 [note]). FIA has been collecting, analyzing, and reporting 

on the Nation’s forest resources for more than 80 years with the first FIA inventory 

of Pennsylvania forests completed in 1955. Information is collected on the status and 

trends of the extent, composition, structure, health, and ownership of the forests. This 

information is used by policy makers, resource managers, researchers, and the public 

to better understand forest resources and to make more informed decisions about 

their future.

What is this report?

This report is a summary of the findings from the seventh survey of the forest 

resources of Pennsylvania conducted by FIA. This report uses data from the third 

cycle of plot measurement using the annualized inventory of plots. Data for this 

survey were collected between 2009 and 2014, but throughout this report, we refer 

to 2014 as the inventory year. Previous periodic forest inventories of Pennsylvania 

were completed in 1955 (Ferguson 1958), 1965 (Ferguson 1968), 1978 (Considine and 

Powell 1980), and 1989 (Alerich 1993, Widmann 1995); full-cycle annualized reports 

were published for 2004 (McWilliams et al. 2007) and 2009 (McCaskill et al. 2013). 

The results of the survey are divided into chapters that focus on forest features, forest 

health, and forest economics. See “Statistics and Quality Assurance for the Northern 

Research Station Forest Inventory and Analysis Program, 2016” (Gormanson et 

al. 2017), available at https://doi.org/10.2737/NRS-GTR-166, for details about data 

collection, estimation procedures, and statistical reliability. Definitions for FIA terms 

commonly found in the 5-year reports are available at http://www.nrs.fs.fed.us/fia/

data-tools/state-reports/glossary/default.asp. Supplemental tables summarizing the 

reported results can be found online at https://doi.org/10.2737/NRS-RB-111.
BACKGROUND | 5

A Guide to Forest Inventory

What is a tree?

Trees are perennial woody plants with central stems and distinct crowns. FIA defines 

a tree as any perennial woody plant species that can attain a height of 15 feet at 

maturity. A complete list of the tree species measured in Pennsylvania during this 

inventory is included in the appendix. Throughout this report, the size of a tree is 

usually expressed as diameter at breast height (d.b.h.), in inches. This is the diameter, 

outside the bark, at a point 4.5 feet above the ground.

What is a forest?

A forest is a collection of trees and most people would agree on what a forest is. But in 

order for statistics to be reliable and comparable, a definition must be created to avoid 

ambiguity.

FIA defines forest land as land that is at least 10 percent stocked with trees of any 

size or land formerly having had such tree cover and not currently developed for 

nonforest use. Generally, the minimum area for classification as a forest is 1 acre in 

size and at least 120 feet in width. There are more specific criteria for defining forest 

land near streams, rights-of-way, and shelterbelt strips (U.S. Forest Service 2012). 

What is the difference between timberland, reserved forest 

land, and other forest land? 

FIA classifies the forest land into three categories:

Timberland—forest land that is producing or is capable of producing crops 

of industrial wood and is not withdrawn from timber utilization by statute or 

administrative regulation. These areas are capable of producing at least 20 cubic feet 

of industrial wood per acre (equivalent to the solid wood content of about 1⁄4 cord) 

per year. Inaccessible and inoperable areas can be included. 

Reserved forest land is all forest land withdrawn from timber utilization through 

statute without regard to productive status (e.g., state parks, natural areas, national 

parks, and Federal wilderness areas). All reserved forest land is in public ownerships.

Other forest land consists of forest land that is not capable of growing 20 cubic feet 

per acre per year and is not restricted from harvesting (e.g., some surface-mined areas 

with extremely degraded soil and some poorly drained areas where water inhibits 

tree growth). Sometimes such forest lands are referred to as being “less productive” or 

“unproductive” with respect to wood fiber production.
6 | BACKGROUND

Since 2000, the annual inventory design has allowed for reporting volumes on all forest 

land in Pennsylvania. As a result, there is now one set of remeasured plots across all 

forest land with associated estimates of growth, removals, and mortality. Before the 

2000-2004 inventory cycle (referred to as the 2004 inventory) in Pennsylvania, for 

most attributes, FIA included only data collected on timberland plots. Therefore, trend 

analyses that use data prior to 2000 are limited to timberland for many attributes.

A word of caution on suitability and availability...

FIA does not attempt to identify those lands suitable or available for timber 

harvesting, particularly since such suitability and availability is subject to changing 

laws, economic and market constraints, physical conditions, adjacency to human 

populations, and ownership objectives. The classification of land as timberland does 

not necessarily mean it is suitable or available for timber production. Forest inventory 

data alone are inadequate for determining the area of forest land available for timber 

production. Additional factors, such as those listed, need to be considered when 

estimating the timber base, and these factors may change over time.

How do we estimate a tree’s volume?

To estimate a live tree’s volume, FIA uses volume equations developed for each tree 

species group found within the northeastern United States. Individual tree volumes are 

based on species, diameter, and height. FIA reports volume in cubic feet and board feet 

(International 1⁄4-inch rule). Board-foot volume measurements are applicable only for 

sawtimber-size trees. In Pennsylvania, wood often is measured in cords (a stack of wood 

8 feet long by 4 feet wide and 4 feet high). A cord of wood consists of about 79 to 85 

cubic feet of solid wood, and the remaining 43 to 49 cubic feet are bark and air. 

How is forest biomass estimated? 

The U.S. Forest Service has developed estimates of specific gravity for many tree 

species (U.S. Forest Service 1999). These specific gravities are applied to estimates 

of tree volume to estimate the biomass of merchantable trees (weight of the bole). 

Regression models are used to estimate the biomass of stumps (Raile 1982), limbs, 

and bark (Hahn 1984), and belowground stump and coarse roots (Jenkins et al. 2004). 

Currently, FIA does not report the biomass of foliage. FIA can report biomass as green 

or oven-dry weight. Green weight is the weight of a freshly cut tree. Oven-dry weight 

is the weight of a tree with no moisture content; oven-dry weight is used to report 

biomass in this report. On average, 1.9 tons (2,000 pounds/ton) of green biomass 

equals 1 ton of oven-dry biomass.
BACKGROUND | 7

How do we estimate all the forest carbon pools?

FIA does not directly measure the carbon in standing trees; it estimates forest carbon 

pools by assuming that half the biomass in standing live and dead trees consists of 

carbon. Additional carbon pools (e.g., soil, understory vegetation, belowground 

biomass) are modeled based on stand and site characteristics (e.g., stand age and 

forest type). 

Regional analysis

Throughout this report, references are made to regions of Pennsylvania. These 

ecopolitical regions (Fig. 1) reflect the diverse landscape of the State to facilitate 

meaningful analysis on a more local scale.

Forest inventory sample design

FIA has established a set of permanent inventory plots across the United States that 

are periodically revisited. Each plot consists of four 24-foot radius subplots for a total 

area of about one-sixth of an acre. All plots (i.e., forested and nonforest) are randomly 

located within a hexagon that is about 6,000 acres in size. Therefore, each plot represents 

about 6,000 acres of land and can be used to generate unbiased estimates and associated 

sampling errors for attributes such as total forest land area. Full details of sample design 

and estimation procedures are available in Bechtold and Patterson (2005).

Northwest

North Central Northeast

South Central

Southwest

Southeast

Figure 1.—Ecopolitical regions of Pennsylvania.

Projection: Pennsylvania State Plane North, NAD83. Source: U.S. Forest Service, Forest Inventory and Analysis program, 2009. Geographic base data are 

provided by the National Atlas of the USA®. FIA Data and Tools are available online at http://www.fia.fs.fed.us/tools-data/.

Cartography: T. Albright, U.S. Forest Service, March 2016.
8 | BACKGROUND

Understanding FIA data

Before 2000, FIA inventories were completed every 10 to 20 years. With these periodic 

inventories, it took decades to identify trends. With the new annual inventory, some 

trends are easier to identify because a subset of observations (about 20 percent) 

are made every year. It is still necessary to look over long time periods because 

many trends such as forest succession can be difficult to discern in short timespans. 

Definitions, methods, location, ownership, precision, scale, and temporal trends are 

important factors to consider when analyzing FIA data. Estimates are derived from 

sample plots throughout a state. Larger geographic areas will contain more plots and 

thus produce more reliable estimates. For example, there usually are not enough plots 

within a county or single forest type from which to derive reliable estimates. It is 

also important to consider the degree to which a variable can be measured precisely. 

For instance, a stand variable, such as age, is not as precise as forest type; and a tree 

variable, such as crown dieback, is not as precise as diameter. Location and ownership 

are similarly important considerations when analyzing the status and trends of forests. 

Forest resources vary by geographic unit and owner group. 

Some definitions and procedures have changed between inventories. Because of these 

changes, some comparisons and estimates should be made with caution. A glossary of 

FIA terms commonly found in the 5-year reports is available at http://www.nrs.fs.fed.

us/fia/data-tools/state-reports/glossary/default.asp. 

As previously stated, the annual inventory measures a subset of observations (about 

20 percent) every year. After 5 years of data collection, an analysis is completed and 

a report created based on the full set, or “cycle” of plots. This creates a yearly moving 

window of 5-year cycles. The last year of each full cycle is used to identify the full 

set of plots. For example, the cycle of plots measured from 2009 through 2014 are 

collectively labeled the 2014 inventory and were used to produce this 2014 report. The 

2004 inventory was the first annual inventory to include the complete cycle of annual 

inventory plots (McWilliams et al. 2007) and the 2009 inventory was the first annual 

inventory to include a complete remeasurement of plots (McCaskill et al. 2013). This 

report for 2014 encompasses the second complete remeasurement of plots. 

In Pennsylvania, 5,010 plot locations were selected for measurement during the 2014 

inventory cycle. Of these, 3,023 contained forest land, 1,516 were nonforest, and 

471 were not sampled due to access constraints. All estimates of current forest area, 

composition, volume, and other forest statistics are based on the 4,539 sampled plots. 

Estimates of change (e.g., change in forest area, growth, mortality, and removals) are 

based on the 4,207 plots sampled during both the 2009 and 2014 cycles.
BACKGROUND | 9

To improve the consistency, efficiency, and reliability of the inventory, procedures and 

definitions have been updated over time. Major changes occurred with the annual 

inventory begun in 1999. For the sake of consistency, a new, national plot design was 

implemented by FIA units throughout the United States in 1999. See “Statistics and 

Quality Assurance for the Northern Research Station Forest Inventory and Analysis 

Program, 2016” (Gormanson et al. 2017), available at https://doi.org/10.2737/NRSGTR-166, for more information on sampling, sources of error, and determining 

statistically significant differences between estimates. Estimates for the 2014 inventory 

use the most recent updated protocols. 

What is P2+?

In 2012 Northern Research Station FIA began implementation of the Phase 2 Plus 

(P2+) protocol. This 12.5 percent subset of all plots is sampled during the leafon portion of the field season (May through September). The suite of additional 

measurements consists of an advanced tree seedling regeneration (ATSR) survey, 

vegetation profile (Veg), invasive plant species (Invasives) survey, down woody 

materials (DWM) tally, and additional tree crown variables (Crowns). Half of P2+ 

plots (6.25 percent of all plots) are selected for soils measurements during the summer 

window. In Pennsylvania, state-agency funding provides for a doubling of the sample 

for ATSR, Veg, and Invasives, maintaining historical sampling intensity and providing 

consistency with historical estimates of regeneration, vegetation, and invasive plants. 

What is the National Woodland Owner Survey?

The National Woodland Owner survey is conducted periodically by the Forest 

Service (NWOS; http://www.fia.fs.fed.us/nwos). It is aimed at increasing our 

understanding of woodland owners, who are the critical link between forests and 

society (Butler et al. 2016). The most recent survey was conducted from 2011 through 

2013. Questionnaires were mailed to individuals and private groups who own the 

woodlands where FIA has an established inventory plot. Results from Pennsylvania, 

included in this report, are based on 214 responses from family forest owners in the 

most recent survey (Butler et al. 2016).

Where can I find additional information?

Detailed information on forest inventory methods, data quality estimates, and 

important resource statistics can be found in Gormanson et al. (2017), available at 

https://doi.org/10.2737/NRS-GTR-166. Tables that summarize quality assurance, as 

well as a core set of tabular estimates for a variety of forest resources, are available in 
10 | BACKGROUND

Microsoft® Excel format at https://doi.org/10.2737/NRS-RB-111. Most data used in 

this report can be downloaded from the FIA Web site (http://www.nrs.fs.fed.us/fia) 

and are also accessible using the Web tools for Forest Inventory Data Online (FIDO) 

and EVALIDator (Miles 2015). These tools allow public access to all FIA databases. 

This enables anyone to generate tables and maps of forest statistics through a 

Web browser without having to understand the underlying data structures. These 

programs are available at http://www.fia.fs.fed.us/tools-data/. Some graphs and tables 

in the printed portion of this report show only a sample of the prominent categories 

and values available for summarizing data. More categories may be found in online 

summary tables and custom tables created with FIDO and EVALIDator. Definitions 

of tables and fields are available in the database users manual (Woudenberg et al. 

2010). Other FIA maps and tables for Pennsylvania’s forest inventories are available at 

http://www.nrs.fs.fed.us/fia. 
 | 11

Mountaintop natural gas well pad in Lycoming County. Photo by Thomas Albright, U.S. Forest Service.

Forest Features
12 | FOREST FEATURES

Area and Land Use

Background

Demand for residential and commercial development places increased pressure on 

forest ecosystems, which provide habitat for forest-dwelling species, protect water and 

soil quality, mitigate air pollution, sequester carbon, and offer a wide range of economic 

and other benefits. The northeastern United States experienced a period of rapid growth 

in the 1990s, which raised a great concern about the effects of increased urban pressures 

on forest resources. Some areas in this region experienced significant forest loss and 

forest fragmentation due to land-use change as population and urban development 

increased. Current census data, however, suggest that the southern and western regions 

of the United States are now experiencing relatively more population growth and urban 

development than the Northeast. Between 2010 and 2015, Pennsylvania’s population 

increased only an estimated 0.8 percent compared to the 4.1 percent national average. 

This modest growth may indicate there is less pressure from urban development and 

less risk of permanent forest loss due to land-use change.

Forest land area in Pennsylvania remained relatively stable between 2009 and 2014; 

however, some areas of the State experienced forest loss, while other areas saw 

increases in forest land. To better understand Pennsylvania’s forest land dynamics, it is 

important to explore underlying land-use changes. FIA characterizes the areas of the 

State using several use categories which are generalized to the following classes: forest, 

agriculture (including pasture and cropland), developed land (including residential 

and commercial areas, and rights-of-way), water, and other nonforest land. Estimates 

for land use are produced from all measured plots in an inventory cycle. Land-use 

change is analyzed by comparing the land use on current inventory plots with land 

uses recorded for the same location during the previous inventory. Understanding 

land-use change dynamics helps land managers make informed policy decisions.

What we found

An estimated 16.9 million acres of Pennsylvania was classified as forest land in 

2014 (Fig. 2). This represents about 58 percent of the total area of the State. The 

overwhelming majority of forest land (16.3 million acres) was also considered 

timberland, that is, land meeting minimum productivity standards that is not 

reserved from harvesting by statute (Table 1). The 16.9 million acre estimate 

represents a continuation of a trend observed in 2004 of about 1 percent increases 

in forest land during each 5-year period. Forest land has remained fairly stable since 

the 1960s; the estimate for forest land peaked at 17.0 million acres in 1965 (Fig. 3). 

Historical estimates of forest land area are available from FIA reports (Alerich et 
FOREST FEATURES | 13

Distribution of Forest Land

n Nonforest n Forest n Open water

Figure 2.—Distribution of forest land, Pennsylvania, 2009.

Projection: Pennsylvania State Plane North, NAD83. Sources: U.S. Forest Service, Forest Inventory and Analysis program, 2009; National Land Cover Database 

2011. Geographic base data are provided by the National Atlas of the USA®. FIA Data and Tools are available online at http://www.fia.fs.fed.us/tools-data/.

Cartography: T. Albright, U.S. Forest Service, March 2016.

Table 1.—Area of forest land (acres) by land class, Pennsylvania

Forest land class 2004 2009 2014

Timberland 15,951,811 16,122,058 16,325,199

Reserved forest land 522,102 542,788 566,987

Other forest land 99,072 74,349 23,999

Total forest land 16,572,981 16,739,199 16,916,190

16.3 

16.6 

16.9 

17.2 

1989 1994 1999 2004 2009 2014 

10 

15 

20 

25 

30 

35 

40 

1600 1650 1700 1750 1800 1850 1900 1950 2000 

Forest Land Area (million acres) 

Year 

Figure 3.—Historical estimates of forest land area, Pennsylvania. 

Error bars represent a 68 confidence interval around the 

estimated mean.
14 | FOREST FEATURES

al. 1993; Considine and Powell 1980; Ferguson 1958, 1968; McCaskill et al. 2013; 

McWilliams et al. 2007) and Illick (1923).

Relative to the total area of the State, there was little land-use change in Pennsylvania 

from the 2009 inventory to the 2014 inventory. Most of the State either remained 

forested or stayed nonforest (57 and 41 percent, respectively; Fig. 4). Pennsylvania lost 

321,000 acres of forest land and gained 399,000 acres from 2009 to 2014, resulting in a 

slight net gain in forest land area (Fig. 5). The majority (48 percent) of the gross forest 

loss is from forest land converting to developed land, specifically commercial and 

residential development (Fig. 5A).

FIA data can be used to characterize the forest land lost and gained to see if it differs 

from forest land that remained forested. Pennsylvania forests are dominated by stands 

in the large (68 percent) and medium (23 percent) diameter size classes. Only 10 

percent of forest area is in small diameter and nonstocked stands. The forest area lost 

had 52 percent of its area in small diameter and nonstocked stands and the forest land 

gained had 46 percent in small diameter and nonstocked stands. Lands moving to forest 

land classification are generally in early successional development, and these gains are 

typically attributed to changes in agricultural use representing true reversions to forest 

land. Forty-eight percent of the forest area lost was from large and medium diameter 

stands. These losses generally represent lands converted to a nonforest land use. 

However, 54 percent of the land representing forest gain was in large and medium 

diameter size classes. These “new” forest lands result from small changes in use, making 

previously unqualified areas meet FIA’s forest size requirements. Forest that was lost or 

gained was also more likely to be in private ownership.

Remained forest

57%

Remained nonforest

41%

Forest gain

1%

Forest loss

1%

Figure 4.—Change dynamics showing proportion of 

unchanged area, forest loss, and forest gain, Pennsylvania, 

2009 to 2014. 
FOREST FEATURES | 15

Figure 5.—Gross forest loss and forest gain by land-use category for the State (A) and regions (B-G), 

Pennsylvania, 2009 to 2014.

Forest loss 

0 100 200 300 400 500 

Forest gain 

Area (thousand acres) 

Statewide 

Northeast 

Forest loss 

0 30 60 90 120 150

Forest gain 

Area (thousand acres) 

North Central 

Forest loss 

Forest gain 

Area (thousand acres) 

Northwest 

Forest loss 

Forest gain 

Area (thousand acres) 

Southwest 

Forest loss 

Forest gain 

Area (thousand acres) 

South Central 

Forest loss 

Forest gain 

Area (thousand acres) 

Southeast 

Forest loss 

Forest gain 

Area (thousand acres) 

n Developed

n Agricultural

n Other nonforest 

A 

B C 

D E

F G

0 30 60 90 120 150

0 30 60 90 120 150 0 30 60 90 120 150

0 30 60 90 120 150 0 30 60 90 120 150
16 | FOREST FEATURES

Estimates of forest loss and gain varied by Pennsylvania region (Fig. 5 B-G). Gains 

in forest land were greater than losses in nearly all regions with the exception of the 

Northwest and North Central regions. Net loss of forest land was greatest in the North 

Central region, but this is also the largest and most forested region of Pennsylvania, 

so the amount of forest land lost (32,000 acres) was small relative to the total amount 

of forest land and resulted in only a 0.6 percent decrease. Most of the forest land lost 

was converted to developed uses (67 percent) (Fig. 5C), including activities associated 

with Marcellus shale development (Fig. 6).

The greatest net gain in forest land area was in the Southeast region, where there was 

a 5 percent increase in forest area (Fig. 5G). The Southwest region experienced the 

greatest fluctuation in forest area with the highest gross gains and losses of any region. 

In this region, loss of forest land area totaled more than 91,000 acres, but was offset by 

forest gains of 132,000 acres (Fig. 5B).

Persistent forest land is concentrated primarily in central Pennsylvania (Fig. 7). There 

appears to be a cluster of forest gain plots, on which 10 percent or more of the area 

has gained forest land, in the Southeast region of the State near the Philadelphia 

suburbs. This result is consistent with the net increases in forest land area observed in 

the summary for this region.

A B

Figure 6.—Land-use change due to Marcellus shale development, Lycoming County, Pennsylvania, 2006 

(A) and 2015 (B). 
FOREST FEATURES | 17

What this means

Overall, there was a small net gain in forest land in Pennsylvania from 2009 to 2014, 

which suggests continued conservation and valuation of the State’s forest resources. 

Some of these gains are likely to have come from residential and commercial open 

land allowed to return to forest and from reverting agricultural land. Gains and 

losses of forest land in Pennsylvania may also be from marginal forest land moving 

into and out of the forest land base. This movement between forest and nonforest 

classifications may result from small changes in understory disturbance, forest extent 

(i.e., minimum size requirements), or forest cover (i.e., minimum canopy cover 

requirements), which can lead to lands not meeting FIA’s definition of forest land. 

Net gain in forest land area was greatest in the Southeast region, and forest land gains 

were greater than or nearly equal to losses in almost all other regions of the State. The 

stability of the forest land base may be due in part to policies and programs, such as 

conservation easements and the Clean and Green tax program, which Pennsylvania 

has in place to promote forest conservation.

Figure 7.—Distribution of remeasurement inventory plots showing forest gains and losses, Pennsylvania, 

2009 to 2014. Plot locations are approximate.

FIA Remeasured Plots

l Forest loss l Remained forest l Forest gain l Remained nonforest
18 | FOREST FEATURES

Urbanization and Fragmentation 

Impacts on Forest Land

Background

The expansion of urban lands that accompanies human population growth often 

results in the fragmentation and urbanization of remaining natural habitat (Wilcox 

and Murphy 1985). Fragmentation, parcelization, and urbanization can be barriers to 

stewardship if forest tracts are too small or isolated for effective management (Shifley 

and Moser 2016). Forest fragmentation affects forest ecosystem processes by changing 

microclimate conditions and limiting the ability of tree species to move in response 

to climate change (Iverson and Prasad 1998). Intact functioning forests are critical 

for protecting both the quantity and quality of surface and groundwater resources 

(McMahon and Cuffney 2000, Riva-Murray et al. 2010), and can enhance the ability 

of forest systems to adapt to temperature and rainfall pattern changes and relative 

phenological shifts associated with climate change. 

Forest fragmentation and habitat loss diminish biodiversity and are a major threat 

to animal populations worldwide (Honnay et al. 2005, Rosenberg et al. 1999). This 

is particularly true for species that require interior forest conditions for all or part of 

their life cycle (Donovan and Lamberson 2001), or are wide-ranging, slow-moving, 

or slow reproducing (Charry and McCollough 2007, Forman et al. 2003). Changes 

in forest patch size, in connectivity, and in the amount of forest-nonforest edge all 

directly affect the amount and quality of interior forest. These factors also affect the 

ease with which nonnative invasive or generalist species gain a foothold and spread 

across the landscape. Landscape pattern metrics help quantify the characteristics of 

fragmentation, and the addition of spatial census data contributes information on 

types and levels of urbanization.

We adapted a spatial integrity index (SII) developed by Kapos et al. (2002) for the 

2000 Global Forest Resources Assessment (FRA2000) to create a single metric 

where 1 indicates highly fragmented area and 10 represents the highest forest spatial 

integrity. The SII integrates three fragmentation components—patch size, local forest 

density, and patch connectivity to core forest areas—that affect forest ecosystem 

functioning.

Forest ecosystem processes operate at different scales, similar to the way that 

animal species see the landscape very differently depending on the scale at which 

they operate; thus, it is important to evaluate forest integrity at varying scales. We 

calculated spatial integrity at two scales using reliable and widely available datasets: 

2006 National Land Cover Database (NLCD) at 30 m (Fry et al. 2011) and 2009 FIA 
FOREST FEATURES | 19

forest cover at 250 m (Wilson et al. 2012). Both scales fall within the 10 to 1,000 

km2 range at which linkages between patterns and processes are often of greatest 

management interest (Forman and Godron 1986). 

In the SII calculation, core forest is defined by a minimum patch size and minimum 

local forest density within a defined local neighborhood (Table 2). A forest fragment 

(unconnected area) is defined by a maximum patch size, maximum local forest 

density, and minimum distance to core forest. The spatial integrity of remaining forest 

land is scaled between fragmented and core forests (low, medium, and high integrity). 

At the 250 m scale, core forest requires a minimum forest patch size of 1,544 acres, 

and patches less than 30 acres are fragments. At the 30 m scale, the analogous 

minimum area is 22 acres, and patches less than 2.5 acres are fragments.1 These scales 

capture a relatively broad range of definitions for core forest and spatial integrity that 

are expected to bracket the appropriate scales for understanding forest fragmentation 

impacts on a wide range of wildlife species and ecosystem processes.

SII is just one piece of the fragmentation puzzle. Because it does not consider 

underlying housing density or proximity to roads, additional metrics are necessary. 

The wildland-urban interface (WUI) is the zone where human development meets 

or intermingles with undeveloped wildland vegetation (Radeloff et al. 2005). It is 

associated with a variety of human-environment conflicts. Radeloff et al. (2005) 

have defined WUI by housing density (“intermix” areas, which have a minimum 

of 16 houses per square mile), proximity to developed areas (“interface” areas), and 

percentage of vegetation coverage (minimum 50 percent). We intersected WUI 

intermix areas (U.S. Census Bureau 2011) with forest land from the 2011 NLCD 

1 Riemann, R. 2014. Adaptation of a spatial integrity index to 30 m and 250 m scales, and its application across the 

northeastern United States. Unpublished paper on file at: U.S. Forest Service, Northern Research Station, Forest 

Inventory and Analysis Program, Troy, NY.

Table 2.—Spatial Integrity Index (SII) parameters used in calculations at each scale

Scale

Definition of Core 250 m 30 m

patch size >1,544 acres >22 acres

local forest density ≥90% ≥90%

 (neighborhood radius) 0.78 mile 0.09 mile

Definition of Unconnected Fragment 250 m 30 m

patch size <30 acres < 2.5 acres

local forest density ≤10% ≤10%

 (neighborhood radius) 0.78 mile 0.09 mile

distance to core >4.2 miles >0.5 miles
20 | FOREST FEATURES

(Homer et al. 2015) to examine changes in forest land area by WUI housing density. 

In addition, the coincidence of SII core forest (based on forest canopy) and WUI 

intermix was identified.

Neither of the previous indices captures the full impact of roads on forest land. Roads 

can have a variety of effects: direct hydrological, chemical, and sediment impacts; 

anthropogenic impacts; invasive species; habitat fragmentation; and wildlife mortality. 

We identified the amount of forest land (2001 NLCD; Homer et al. 2007) within 650 

and 1,310 feet from a road (U.S. Census Bureau 2000). In general, when more than 60 

percent of a region is within 1,310 feet of a road, cumulative ecological impacts from 

roads are an important consideration (Riitters and Wickham 2003).

What we found

Considering SII at the 250 m scale, 56 percent of Pennsylvania forest land is core forest, 

24 percent has high integrity, 11 percent has medium integrity, 1 percent has low spatial 

integrity, and 8 percent of the forest is in unconnected fragments. At the 30 m scale, 69 

percent of Pennsylvania forest land is core forest, 19 percent has high spatial integrity, 6 

percent has medium or low integrity, and 6 percent of the forest is in unconnected 

fragments (Table 3). Forest connectivity at the 250 m scale is highest in the North 

Central region, and lowest in the Southeast region (Fig. 8); note how the remaining 

large areas of relatively continuous forest clearly stand out. At the 30 m scale, the lower 

threshold of 22 acres for defining core forest results in more forest patches considered 

core (Fig. 9). It is important to note that the SII is depicting tree cover only and may not 

incorporate the presence of local development associated with or underlying this tree 

cover. Addressing this requires the use of census-derived housing density. 

Table 3.—Spatial Integrity Index (SII) by region, scale, and with and without wildland-urban interface (WUI) 

intermix as core forest, Pennsylvania

30-m Scale 250-m Scale

Forest 

fragment

Low 

SII

Medium 

SII

High 

SII

Core 

forest

Core 

forest 

if WUI 

removed

Forest 

fragment

Low 

SII

Medium 

SII

High 

SII

Core 

forest

Core 

forest 

if WUI 

removed

Region - - - - - - - - - percent - - - - - - - - - - - - - - - - - - percent - - - - - - - - - 

North Central 2 0 3 15 81 68 1 1 4 17 77 66

Northeast 4 1 4 18 73 48 4 1 10 28 58 39

Northwest 7 1 8 29 55 34 16 3 28 26 28 18

South Central 5 1 3 14 76 56 6 1 5 27 60 49

Southeast 32 3 13 22 30 13 56 1 9 17 17 11

Southwest 6 1 8 28 57 33 11 3 22 30 35 25

State total 6 1 5 19 69 49 8 1 11 24 56 44

State total after 

removing WUI 

areas

6 2 6 37 49 8 3 12 33 44
FOREST FEATURES | 21

Figure 8.—Forest land by Spatial Integrity Index at the 250 m scale, Pennsylvania, 2009. Data source: 

Wilson et al. (2012).

Forested Area

n Unconnected n Low Integrity Nonforest

n Med Integrity n High Integrity

n Core Forest

A B

Forested Area

n Unconnected

n Low Integrity

n Med Integrity

n High Integrity

n Core Forest

Nonforest

Figure 9.—Forest land by Spatial Integrity Index at the 250 m scale (A) and 30 m scale (B) in west-central 

Pennsylvania, 2009 and 2006, respectively. Data source for 250 m scale: Wilson et al. (2012); for 30 m 

scale: Fry et al. (2011).
22 | FOREST FEATURES

Between 2000 and 2010, Pennsylvania’s population increased by 3.4 percent, to 12.7 

million. During that same time period housing units increased by 6.1 percent (U.S. 

Census Bureau 2011). Stated another way, between 2000 and 2010 housing units 

increased at a pace 1.8 times the rate of population increase, a trend not unique to 

Pennsylvania. In recent decades this housing growth has occurred in suburban rings 

around urban centers and in rural areas. Lepczyk et al. (2007), Theobald (2005), and 

Hammer et al. (2004) observed that among the areas currently facing rapid housing 

density increases are amenity-rich rural places around lakes and forest recreation 

areas. The 2010 Census reported a 9 percent increase in second homes from 2000, 

which partially explains housing increases (U.S. Census Bureau 2011). This can put 

additional pressure on forested areas even above the general increases in population 

density and housing density.

Forest land with sufficient underlying housing density to qualify as WUI has shown 

slow but steady increases. In 1990, 31 percent of Pennsylvania forest land was in low and 

medium density WUI. This increased to 34 percent of the forest land in 2000, and 

further to 35 percent in 2010, although there is substantial local variation. Chester, 

Delaware, and Montgomery Counties, in the Southeast region, all experienced between 

10 and 20 percent increases in WUI forest land between 2000 and 2010. Bucks, 

Cumberland, Franklin, Lancaster, and York Counties experienced increases of between 

5 and 10 percent. Thirty-three counties experienced no change or negative change, 

indicating that no increase in WUI areas occurred or previously classified WUI forest 

land was converted to nonforest. As can be expected, WUI areas are concentrated 

adjacent to population centers; the less densely populated central portion of the 

Commonwealth has relatively little WUI (Table 4, Fig. 10). By integrating SII results at 

the 250 m scale with WUI, core forest drops from 56 percent to 44 percent statewide. At 

the 30 m scale, core forest drops from 69 percent to 49 percent of forest land when WUI 

areas are accounted for (Table 3). This represents a substantial change in core forest land 

due to underlying or nearby house densities. When WUI status is incorporated into SII 

results for southeastern Pennsylvania, core forest at the 30 m scale decreases from 30 

percent to 13 percent of forest land (Fig. 11).

Roads are pervasive in the landscape, often hidden from aerial view throughout 

large areas of continuous canopy. In 2000, 73 percent of Pennsylvania forest land 

was within 1,310 feet of a road, and 46 percent was within 650 feet. In the North 

Central region, 39 percent of forest was within 650 feet of a road versus 67 percent 

for the Southeast region (Table 4, Fig. 12). Since 2000, additional road and pipeline 

infrastructure has been built, and road use has increased, due to industrial gas 

development in north-central Pennsylvania. 
FOREST FEATURES | 23

Table 4.—Distribution of forest land with respect to several urbanization and 

fragmentation factors, expressed as a percentage of the forest land in each region, 

Pennsylvania 

Region

Forest land as a 

percentage of total 

land in regiona

Percentage of forest 

land in wildlandurban intermixb

Percentage of forest 

land <650 feet 

from a roadc

North Central 77 19 39

Northeast 68 40 45

Northwest 56 42 43

South Central 62 31 42

Southeast 29 52 67

Southwest 62 49 55

State total 62 35 46

a Percent forest estimate based on NLCD 2011 (includes woody wetland). Values are generally higher than 

estimates from FIA plot data.

b Approximating the forest land potentially affected by underlying or nearby development. Data source: 

U.S. Census (2011).

c Approximating the forest land potentially affected by roads. Data source: U.S. Census (2000).

Figure 10.—Forest land by wildland-urban interface status, Pennsylvania, 2010.

Data sources: WUI data are based on the 2010 Census and NLCD 2011.

Forested Area

n Non-WUI n WUI Nonforest
24 | FOREST FEATURES

Forested Area

n Unconnected

n Low Integrity

n Med Integrity

n High Integrity

n Core Forest

Nonforest

A B

Figure 11.—Forest land by Spatial Integrity Index (SII) at the 30 m scale, with (A) and without (B) 

incorporating wildland-urban interface status into SII, in east-central Pennsylvania, 2010.

Forested Area

n <650 feet n 650-1,310 feet n >1,310 feet

Figure 12.—Forest land by distance from the nearest road with summary pie charts for each region, 

Pennsylvania, 2000 roads (restricted to 2001 NLCD forest).
FOREST FEATURES | 25

What it means

Pennsylvania has a diverse landscape, ranging from the heavily forested North Central 

region (77 percent forested) to the heavily agricultural and urban Southeast region 

(29 percent forested) (Jin et al. 2013). Urbanization affects all regions by increasing 

population density, development, and other anthropogenic pressures on natural 

habitats. Both urbanization and forest fragmentation change forest land use, frequently 

decreasing the likelihood that forest land will produce forest products and potentially 

increasing its use for outdoor recreation; frequently, however, urbanization increases 

“posting” of forested land, which decreases outdoor recreation opportunities and alters 

local cultural use of forest land (Butler 2008, Kline et al. 2004, Wear et al. 1999).

Using SII at either scale, 56 to 69 percent of Pennsylvania forest land is core forest and 

7 to 9 percent is in unconnected fragments or has low spatial integrity. Statewide, core 

forest drops 12 to 20 percentage points by including WUI areas. Roads further reduce 

spatial integrity in some areas.

Fragmentation and urbanization continue to change how Pennsylvania’s forests 

function, affecting forest health and sustainability, and their ability to supply forest 

products and ecosystem services. As housing development continues to sprawl into 

rural areas, fragmentation is a growing concern to land managers because forest 

stewardship becomes increasingly difficult on smaller ownerships. Conservation and 

planning activities that focus on preserving or creating connections between forest 

patches can maintain the benefits of high integrity and core forests. Road layout and 

design practices can help to enhance forest resilience. Effectively managing these 

concerns is crucial to the future sustainability of forests and forest-dwelling species.

Ownership

Background

As the major share of Pennsylvania forest land, private forests are essential to the 

character of the Commonwealth. The values they provide in terms of habitat, water 

quality, wood products, and recreation benefit not only the landowner, but society at 

large. Because landowners are the primary decisionmakers in land management, the 

availability and quality of forest resources are, to a large extent, determined by those 

owners. By understanding the priorities of forest landowners, the forest conservation 

community can better help them meet their needs, and in so doing, work to conserve 

the Commonwealth’s forests for future generations. The National Woodland Owner 

Survey (NWOS; www.fia.fs.fed.us/nwos), conducted by FIA, studies private forest 

landowners’ attitudes, management objectives, and concerns. It focuses on the diverse 
26 | FOREST FEATURES

and dynamic group of owners that is least understood—families, individuals, trusts, 

estates, and family partnerships, collectively referred to as “family forest owners.” The 

NWOS results reported here are based on responses from 214 of Pennsylvania’s family 

forest owners who participated from 2011 and 2013 (Butler et al. 2016).

What we found

Family forest owners hold an estimated 8.9 million acres (52 percent) of forest land in 

Pennsylvania (Fig. 13). That total, combined with an estimated 2.3 million acres (13 

percent) owned by corporations and an estimated 800,000 acres (5 percent) owned by 

other private owners (including conservation organizations and hunting clubs), places 

70 percent of Pennsylvania forest land in private hands. 

Public owners control 5.0 million acres of Pennsylvania’s forest land, mostly in the 

North Central region (Fig. 14). The Federal government manages an estimated 600,000 

acres of forest land, primarily on the Allegheny National Forest in the North Central 

region. State forests, parks, and gamelands make up 3.9 million acres of forest land. 

Municipal and county government agencies control an estimated 500,000 acres. 

Management of these lands is guided by more policies and procedures than the 

management of privately owned forest. Publicly owned timberland is professionally 

managed for a broad range of goods and services to allow for the sustainable use of 

natural resources. 

According to the NWOS, there are an estimated 166,000 family forest owners across 

Pennsylvania who own 10 acres or more of forest land. This amounts to 7.6 million 

acres, with an average forest holding of 45 acres. About three-quarters of these family 

forest owners have less than 50 acres of forest land (Fig. 15). However, as a proportion 

of total family forest land, nearly two-thirds is in holdings of 50 acres or more. An 

estimated 393,000 family forest owners have between 1 and 9 acres of forest land, 

collectively holding the remaining 1.3 million acres.

The primary reasons reported for owning forest land include aesthetics, wildlife, 

nature, and privacy (Fig. 16). The most common activities on family forest land are 

personal recreation, such as hunting and hiking, and cutting trees for personal use, 

such as firewood (Fig. 17). A high percentage (39 percent) of family forest owners 

report having participated in a preferential property tax program, but few have 

participated in any other traditional forestry management and assistance programs 

in the past 5 years (Fig. 18). The most common “other” activity was receiving forest 

management advice, which was reported by fewer than 15 percent of the owners. 

Only an estimated 10 percent of owners have management plans. The average age of 

family forest owners in Pennsylvania was 61 years; 47 percent of the family forest land 

was owned by people who are 65 years of age or older (Fig. 19).
FOREST FEATURES | 27

0 10 20 30 40 50 60 

Local 

State 

Federal 

Other private 

Corporate 

Family 

Percent 

Owner Group 

Figure 13.—Percentage of forest land by owner group, Pennsylvania, 2013. 

Error bars represent a 68 percent confidence interval around the estimated 

mean.

n Private n Public n Nonforest n Open water

Figure 14.—Public and private ownership of forest land, Pennsylvania, 2012.

Projection: Pennsylvania State Plane North, NAD83. Source: U.S. Forest Service, Forest Inventory and Analysis program, 2009. Geographic base data are 

provided by the National Atlas of the USA®. FIA Data and Tools are available online at http://www.fia.fs.fed.us/tools-data/.

Cartography: T. Albright, U.S. Forest Service, March 2016.
28 | FOREST FEATURES

0 10 20 30 40 50 

10-19 

20-49 

50-99 

100-199 

200-499 

500-999 

1000+ 

Percent 

Size of Forest Holdings (acres) 

n Acres

n Ownerships 

Figure 15.—Percentage of family forest owners and acres of 

forest land by size of forest landholdings, Pennsylvania, 2013. 

Error bars represent a 68 percent confidence interval around the 

estimated mean.

0 20 40 60 80 100 

NTFPs 

Cabin 

Firewood 

Timber 

Farm 

Investment 

Recreation 

Family 

Hunting 

Home 

Water 

Legacy 

Privacy 

Nature 

Wildlife 

Beauty 

Percent 

Reason for Owning 

n Acres

n Ownerships 

Figure 16.—Percentage of family forest owners and acres of forest 

land by reasons given for owning forest land ranked as very important 

or important, Pennsylvania, 2013. Categories are not exclusive. 

NTFPs indicates nontimber forest products. Error bars represent a 68 

percent confidence interval around the estimated mean.
FOREST FEATURES | 29

0 20 40 60 80 100 

Controlled burn 

Eliminated insects 

Reduced fire hazard 

NTFPs 

Roads 

Grazing 

Controlling invasives 

Trails 

Cut trees-sale 

Wildlife habitat 

Cut trees-personal 

Recreation 

Percent 

Activity 

n Acres

n Ownerships 

Figure 17.—Percentage of family forest owners and acres of forest land by 

activities in the past 5 years, Pennsylvania, 2013. Categories are not exclusive. 

NTFPs indicates nontimber forest products. Error bars represent a 68 percent 

confidence interval around the estimated mean.

0 10 20 30 40 50 60 

Easement 

Cost share 

Certification 

Management plan 

Advice 

Tax program 

Percent 

Forest Management Program 

n Acres

n Ownerships 

Figure 18.—Percentage of family forest owners and acres of forest land by 

participation in forest management programs, Pennsylvania, 2013. Categories 

are not exclusive. Error bars represent a 68 percent confidence interval 

around the estimated mean.
30 | FOREST FEATURES

What this means

The future of the forests lies primarily in the hands of those who own and control 

the land as the primary decisionmakers. Additionally, foresters, educators, loggers, 

researchers, and others all have an interest in, and therefore responsibility for, 

implementing and promoting sound forest management practices. It is therefore 

critical to understand the different types of forest owners, their attitudes, and 

behaviors, and to identify the policies and programs that can help them conserve the 

forests for current and future generations. Generally, having both private and public 

ownerships enhances the benefits and ecological services provided by Pennsylvania’s 

forests. These diverse ownerships create private market opportunities while protecting 

critical areas and providing for public recreation. Family forest owners are the least 

understood owner group and the future of their forest is arguably the most uncertain. 

They own their land primarily for amenity reasons, but many are actively doing things 

with their land. The vast majority does not have management plans and most have 

not participated in any other traditional forest management planning or assistance 

programs. There are significant opportunities to assist these owners with management 

and stewardship of their forests. Programs such as Tools for Engaging Landowners 

Effectively (http://www.engaginglandowners.org) can help the conservation 

community develop and implement programs more effectively and efficiently. Penn 

State Extension’s Center for Private Forests also conducts applied research on private 

forests and provides education and outreach to landowners and industry. Another 

important factor to watch is the aging of the family forest owners. The relatively 

advanced age of many of the owners portends the transfer of land passing to the 

0 5 10 15 20 25 30 35 40 

<45 

45-54 

55-64 

65-74 

75+ 

Percent 

Age of Primary Owner (years)

n Acres

n Ownerships 

Figure 19.—Percentage of family forest owners and acres of forest land 

by age of primary owner, Pennsylvania, 2013. Error bars represent a 68 

percent confidence interval around the estimated mean.
FOREST FEATURES | 31

next generation in the not-too-distant future. To help owners meet their bequest 

goals, programs are available, such as Your Land Your Legacy (http://masswoods.

net/monthly-update/your-land-your-legacy-deciding-future-your-land), Ties to the 

Land (http://tiestotheland.org), and the Pennsylvania Department of Conservation 

and Natural Resources’ Bureau of Forestry Private Woodland Legacy Planning 

Partnership. But it is uncertain who the future forest owners will be and what they 

will do with their land.
32 | FOREST RESOURCE ATTRIBUTES

Young oak forest 8 years after harvest in Lycoming County. Photo by Thomas Albright, U.S. Forest Service.

Forest Resource Attributes
FOREST RESOURCE ATTRIBUTES | 33

Forest Composition

Background

Forest tree species composition is the result of the long-term interaction of climate, 

soils, disturbance, competition among plants, and other factors. Causes of forest 

disturbances in Pennsylvania include timber harvesting, insects and diseases, ice 

storms, wind, droughts, wildfires, and land clearing followed by abandonment. As 

forests recover from disturbance and mature, changes in growing conditions favor 

the growth of shade-tolerant species over shade-intolerant species in the understory 

unless forest management practices intervene to work toward the perpetuation of 

shade-intolerant species. White-tailed deer (Odocoileus virginianus) can affect species 

composition by heavily browsing some species while avoiding others. In many parts 

of the State, the prolonged abundance of deer continues to have a profound effect 

on forest community species composition. In addition, increases in competing 

vegetation, invasive species, past management practices, acid deposition, and climate 

change may also be contributing drivers of composition.

Forest attributes recorded by FIA that describe forest composition include forest type 

and numbers of trees by species and size. Forest types describe groups of species that 

frequently grow in association with one another and dominate the stand. Similar 

forest types are combined into forest-type groups. Changes in area by forest type 

are driven by changes in the species composition of large diameter trees, and while 

these large trees represent today’s forest, the composition of the smaller diameter 

classes represents the future forest. Generally, trees in the larger diameter classes are 

those that currently dominate the overstory and those in the smaller diameter classes 

represent trees available for recruitment into the overstory as large trees either die or 

are removed by harvesting. Comparisons of species composition by size can provide 

insights into future changes in overstory species. In this discussion, “seedling size” 

refers to trees at least 1 foot tall but less than 1 inch in diameter. “Sapling size” refers 

to trees at least 1 inch but less than 5 inches in diameter at breast height. See Figure 1 

for a map of Pennsylvania regions.

What we found

The 2014 inventory identified 101 tree species (appendix), and 58 forest types in 

Pennsylvania. These forest types are combined into 16 forest-type groups. Ninetyseven percent of the forest land in the State (16.3 million acres) is occupied by stands 

dominated by hardwood species, and 3 percent (586,000 acres) is predominantly 

occupied by softwood species. The largest hardwood forest-type groups are the oak/

hickory group, which covers 9.1 million acres (54 percent), and the maple/beech/
34 | FOREST RESOURCE ATTRIBUTES

birch group, which covers 5.5 million acres (33 percent). Nearly all of the stands in 

softwood groups are in the white pine/red pine/hemlock group, which covers 382,000 

acres. The oak/hickory forest-type group is the dominant group in all but the North 

Central region of the State (Fig. 20), where nearly half the area is in the maple/beech/

birch group (Fig. 21).

Many species are common to several forest-type groups, but there are generally 

substantial differences in composition between groups. For example, species such as 

red maple, ash, sweet birch, and northern red oak are common in both the oak/

hickory and maple/beech/birch forest-type groups, but clear differences can be seen 

in the proportion of oak species by biomass between the two groups (Fig. 22A, B). In 

the oak/hickory forest-type group, oaks account for 47 percent of the biomass, 

whereas in the maple/beech/birch forest-type group oaks make up only 6 percent. 

These are two of the six forest-type groups that describe the current composition of 

overstory trees, and they have undergone little change in extent since 2004 (Fig. 23).

n Softwood n Maple/beech/birch n Nonforest

n Oak/hickory n Other hardwoods n Open water

n Oak/pine

Forest-type Group

Figure 20.—Major forest-type groups, Pennsylvania, 2009.

Projection: Pennsylvania State Plane North, NAD83. Source: U.S. Forest Service, Forest Inventory and Analysis program, 2009. Geographic base data are 

provided by the National Atlas of the USA®. FIA Data and Tools are available online at http://www.fia.fs.fed.us/tools-data/.

Cartography: T. Albright, U.S. Forest Service, March 2016.
FOREST RESOURCE ATTRIBUTES | 35

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

 Northwest 

 North Central 

Northeast 

 Southeast 

South Central 

Southwest 

State 

Forest-type Group as a Percentage

of Forest Area by Region 

Region/State 

n Oak/hickory

n Maple/beech/birch

n Elm/ash/cottonwood

n Aspen/birch

n White pine/red pine/hemlock

n Oak/pine

n Other

Figure 21.—Most abundant forest-type groups on forest land by region, Pennsylvania, 2014. 

21% 

20% 

18% 

8% 

7% 

6% 

5% 

4% 

2% 

9% 

B

n Red maple 

n Ash

n Northern red oak

n Other 

n Sugar maple 

n American beech 

n Sweet birch

n Black cherry 

n Hemlock 

n Yellow birch 

17% 

14% 

8% 

5% 

16% 

5% 

5% 

5% 

5% 

3% 

17% 

A

n Northern red oak

n Black oak 

n Black cherry

n Ash 

n Chestnut oak

n Red maple 

n Hickory

n Other

n White oak 

n Yellow-poplar

n Sweet birch 

Figure 22.—Species composition within the oak/hickory forest-type group (A) and the maple/beech/birch 

forest-type group (B), by percentage of total biomass in the forest type, on forest land, Pennsylvania, 2014. 
36 | FOREST RESOURCE ATTRIBUTES

American beech is the most numerous seedling size tree, followed by red maple, sweet 

birch, and ash (Fig. 24). Although these species are fairly common throughout the 

State, their distribution is uneven. In the North Central and Northeast regions beech 

accounts for 22 and 17 percent of seedlings (including root sprouts), respectively, 

whereas in other regions beech is much less prominent (Fig. 25). Ash has the largest 

percentage of seedlings in the Northwest and Southeast regions, 14 and 12 percent, 

respectively. Sweet birch has the largest percentage of seedlings in the South Central 

region at 15 percent, and is among the five most numerous species for seedlings in 

four other regions. Although red maple is not the leading seedling species in any of 

the regions, it is among the top three species in every region and is more numerous 

statewide than all the oaks combined.

The total number of sapling size trees in Pennsylvania decreased by 5 percent since 

2004 (Fig. 26). Notable decreases in sapling numbers were recorded for red maple 

(-12 percent), black cherry (-28 percent), ash (-18 percent), and northern red oak (-23 

percent). Increases were found for sweet birch (+11 percent), American beech (+28 

percent), yellow-poplar (+42 percent), and white oak (+26 percent). Since 2004, two 

noncommercial species that typically grow in the understory, eastern hophornbeam 

and American hornbeam, had large increases, 35 and 44 percent, respectively.

Oak, red maple, black cherry, sugar maple, and hemlock currently dominate the 

larger diameter classes within the Commonwealth (Fig. 27). Oaks make up at least 25 

0 

2 

4 

6 

8 

10 

Oak/hickory 

Maple/beech/birch 

Other hardwoods 

White pine/red pine/hemlock 

Elm/ash/cottonwood 

Aspen/birch 

Forest Land Area (million acres) 

Forest-type Group 

n 2004 

n 2009 

n 2014

Figure 23.—Area of forest land by forest-type group and inventory year. Error 

bars represent a 68 percent confidence interval around the estimated mean.
FOREST RESOURCE ATTRIBUTES | 37

0 1 2 3 4 5 

Elm (0.6) 

Yellow birch (0.8) 

White pine (0.8) 

Black oak (1.0) 

Blackgum (1.2) 

E. hemlock (1.3) 

Yellow-poplar (1.3) 

Hickory (1.6) 

A. hornbeam (2.2) 

Chestnut oak (2.3) 

Hawthorn spp. (2.4) 

N. red oak (2.7) 

E. hophornbeam (2.7) 

Sugar maple (3.2) 

White oak (3.3) 

Sassafras (3.7) 

Striped maple (4.4) 

Serviceberry spp. (5.4) 

Black cherry (7.1) 

Ash (7.5) 

Sweet birch (10.4) 

Red maple (13.1) 

American beech (14.0) 

Number of Stems (billions) 

Species

Figure 24.—Number of seedlings by species on timberland, Pennsylvania, 

2014. Percentage of total seedlings is shown in parentheses. Error bars 

represent a 68 percent confidence interval around the estimated mean.

0 5 10 15 20 25 

Beech 

Sweet birch 

Red maple 

Ash 

Black cherry 

Striped maple 

Chestnut oak 

Sassafras 

Red maple 

Sweet birch 

Chestnut oak 

Sweet birch 

Red maple 

Black cherry 

Ash 

Black cherry 

Sweet birch 

Ash 

Red maple 

Beech 

Black cherry 

Serviceberry 

Sweet birch 

Red maple 

Beech 

Amer. hornbeam 

Beech 

Red maple 

Black cherry 

Ash 

Southwest South Central Southeast Northeast North Central Northwest 

Percentage of Total Seedlings in Region 

Region, Species 

Figure 25.—Five seedling species with the most seedlings, by region, 

and by percentage of total seedlings in the region, Pennsylvania, 2014. 
38 | FOREST RESOURCE ATTRIBUTES

0 500 1,000 

Black locust (-2) 

Elm (-27) 

White oak (26) 

Aspen (-26) 

Yellow-poplar (42) 

Chestnut oak (-11) 

Pin cherry (-7) 

Hickory (1) 

Serviceberry spp. (11) 

N. red oak (-23) 

White pine (-5) 

Hawthorn spp. (-23) 

Hemlock (-9) 

Amer. hornbeam (44) 

Ash (-18) 

E. hophornbeam (35) 

Blackgum (-18) 

Striped maple (-3) 

Sugar maple (-3) 

Black cherry (-28) 

American beech (28) 

Number of Saplings (millions) 

Species (Percent Change, 2004 to 2014) 

n 2004 

n 2009 

n 2014

Sweet birch (11) 

Red maple (-12) 

Figure 26.—Number of saplings by species on timberland, 

Pennsylvania, 2004, 2009, and 2014. Species are ranked by 

numbers of stems, 2014. Error bars represent a 68 percent 

confidence interval around the estimated mean.

Northern red oak 

Chestnut oak 

Other oaks 

Red maple 

Black cherry 

Sugar maple 

Sweet birch

Hemlock 

Ash 

American

beech 

All other growing-stock species 

Noncommercial hardwoods 

0 

20 

40 

60 

80 

100 

Seedling 

2 4 6 8 

10 

12 

14 16 18 20 22 24 

25+ 

Species as a Percentage of Total Trees in Class 

Diameter Class (inches) 

Figure 27.—Species composition by diameter class on 

timberland, Pennsylvania, 2014.
FOREST RESOURCE ATTRIBUTES | 39

percent of trees in diameter classes 14 inches and larger, but are poorly represented 

in the sapling size classes. Less than 6 percent of trees in the 2- and 4-inch classes are 

oak species. Hemlock is similar to the oaks with small percentages in seedling size (1 

percent of all stems) and 2-inch class (2 percent of trees), whereas 6 percent of trees 

in diameter classes 8 inches and larger are hemlock. Red maple is the most numerous 

species in all diameter classes 2 inches and larger. The largest proportion of red maple 

trees are in the 6-, 8-, and 10-inch classes, where they compose nearly a quarter 

of the trees in each of these classes. Red maple represents 22 percent of all trees in 

Pennsylvania that are greater than 5 inches diameter at breast height. Red maple, 

American beech, and sweet birch have the largest numbers of seedlings and saplings 

in the State. Beech and sweet birch are poorly represented in large-size trees.

What this means

The large numbers of tree species, forest types, and forest-type groups in the 

Commonwealth demonstrate the great diversity in Pennsylvania forests. This rich 

diversity enhances the forest’s ability to provide a variety of goods and services, and 

fosters resilience to disturbances, such as insects and diseases. The stability of the oak/

hickory and other major forest-type groups since 2004 does not depict the underlying 

shifts in species composition that are likely to occur, as species now in the understory 

grow into the canopy and replace large trees that currently dominate the overstory. 

These shifts will occur slowly as large trees are harvested or succumb to natural 

mortality, potentially changing the future species composition of Pennsylvania’s forests. 

The overall decrease in numbers of saplings since 2004 is likely the result of stand 

dynamics and the maturing of Pennsylvania’s forests. The vast majority of saplings 

grow in the understory and many have poor live crown ratios; as a result, expected 

mortality of sapling size trees is high. Decreases in saplings can also be due to few 

seedlings growing into the sapling size class. Although many of the data for numbers 

of seedlings and saplings have high sampling errors, some general trends emerge 

from the sapling data. Less preferred white-tailed deer browse species fare better 

than favored species; shade-tolerant species are reproducing better than shadeintolerant species; and species that can take advantage of small canopy gaps created 

by disturbance, such as partial harvesting, are increasing in number. Sweet birch 

and American beech are not preferred browse for white-tailed deer, are tolerant of 

shaded conditions, and can respond well to gaps created by partial harvests and other 

disturbances. These species have large numbers of seedlings in the understory.

Throughout the State, a lack of oaks in the smaller diameter classes means that as 

large oaks are harvested or die, they are likely to be replaced by species such as red 

maple, sweet birch, and others that now represent large portions of sapling and 
40 | FOREST RESOURCE ATTRIBUTES

seedling size trees. Red maple is ubiquitous, occurring prominently in all diameter 

classes across the State. Large numbers of red maple, sweet birch, and beech saplings 

and seedlings mean that these species are readily available to fill canopy gaps. Red 

maple is among the top three species ranked by sapling and seedling numbers in 

every region of the State, and sweet birch and beech are among the few species that 

showed increases in numbers of saplings. 

Decreases in the oak portion of the resource have been attributed to inadequate 

oak regeneration, the subsequent lack of oaks growing into the larger diameter 

classes, and selective harvesting of oak over other species. Generally, current forest 

management practices do not promote the regeneration of oaks, and silvicultural 

tools (fencing to exclude deer, controlled fires to inhibit competing species, and 

seed tree retention) to promote oak regeneration are seldom used on private land. 

Contributing factors to poor oak regeneration are lack of fire, understory growing 

conditions that favor more shade-tolerant hardwoods, white-tailed deer preferentially 

browsing oak seedlings, acorn consumption by animals and insects, and the low 

intensity harvesting practices that leave only small gaps in the canopy. 

Eastern hemlock is among the leading large canopy trees across the northern 

three regions of the State. This species is poorly represented in the sapling and 

seedling size classes and is likely to be replaced by other species because of a 

lack of regeneration. Hemlock is the most shade tolerant of all tree species in 

North America and can withstand suppression from overstory trees for as long 

as 400 years (Godman and Lancaster 1990). In a maturing forest resource such 

as Pennsylvania’s, it would be expected that a very shade tolerant species such as 

hemlock would increase. But hemlock is readily browsed by white-tailed deer, 

affecting the numbers of hemlock seedlings and saplings. Hemlock woolly adelgid, 

a nonnative insect pest, may also be a contributing factor because it reduces the 

vigor and causes mortality of large hemlocks, thereby reducing seed production (see 

Hemlock Woolly Adelgid starting on p. 108). 

Despite high numbers of small ash and beech trees, notably ash in the Northwest, 

Southeast, and Southwest regions and beech in the North Central region, the 

outlook for these species is difficult to assess given the impacts of insect and disease 

outbreaks. Emerald ash borer (EAB; see Emerald Ash Borer starting on p. 106) is a 

relatively new insect pest and to date, ash trees have exhibited little or no resistance 

to it, so the future of ash is bleak. It is expected that many of the beech trees now in 

the understory will succumb to beech bark disease as they mature (see Beech Bark 

Disease starting on p. 115), although beech is likely to persist in the understory 

because infected trees produce large numbers of root sprouts (i.e., beech brush). 

The future value of ash and beech for producing timber products and hard mast for 
FOREST RESOURCE ATTRIBUTES | 41

wildlife will most likely decrease as beech bark disease and EAB continue to spread. 

Land managers may need to work to promote regeneration of other species to fill 

the ecological niche these species occupy. Practices to improve species composition 

in recently harvested stands could include enhancing deer management techniques, 

establishing tree regeneration prior to overstory removal, and treatments. Currently 

a large portion of seedlings and saplings comprises beech, ash, and noncommercial 

species such as eastern hophornbeam, hornbeam, and striped maple. These species 

thrive in the canopy gaps created by partial harvesting, a harvesting practice that is 

common in Pennsylvania. As beech and many noncommercial species can interfere 

with the regeneration of more valuable species, removing these species before or after 

harvests will allow more diverse species recruitment. 

Long-term changes in forest composition can alter wildlife habitats and affect the 

value of the forest for timber products. The lack of an oak seedling and sapling base 

from which recruitment into the larger diameter classes can occur is changing the 

composition of the timber resource away from oaks toward more red maple, sweet 

birch, blackgum, and other non-oak species. To remain sustainable, the composition 

of the timber harvest in the State will need to shift to reflect changes in the resource.

Projected changes in species composition due to climate change suggest that by 

2100 growing conditions in the northeastern United Sates will become more suitable 

for oaks and less suitable for maples (Iverson and Prasad 1998, Rustad et al. 2012, 

Vose et. al. 2012). Current trends in Pennsylvania do not reflect these projected 

changes indicating that to date, other factors, such as browse by white-tailed deer, 

successional stage, cutting practices, fire suppression, competing vegetation, invasive 

species, localized topographic and watershed features, soil conditions, and insects and 

diseases are driving changes in forest composition. Current trends may also suggest 

that Pennsylvania’s forests are becoming less resilient to predicted changes in climate. 

To maintain forest productivity and ensure a sustainable supply of ecosystem goods 

and services, natural resource managers will need new management strategies and 

practices that promote adaptation to climate variability and change. 

Forest Succession

Background

The amount and character of forest land in various stages of succession determine 

the values and services available for the public good. A balanced distribution of forest 

land by age, or stage of successional development, ensures long-term diversity and 

sustainability of resources. Healthy young forest provides unique wildlife habitat for 
42 | FOREST RESOURCE ATTRIBUTES

early successional obligate and facultative wildlife species that are declining due to 

habitat loss (Goodrich et al. 2002). Mid- and late successional forests dominate the 

landscape and the resources and benefits available as they account for 95 percent 

of the State’s timberland. Although very rare, old-growth remnant forests offer 

understanding and knowledge of forest conditions prior to European settlement, as 

well as a unique suite of ecosystem services. 

The current distribution of forest land is the result of land-use changes that occurred 

about a century ago (Nowacki and Abrams 2014). From about 1880 to 1920, forests 

were cleared for agriculture and for supplying much needed wood resources. On the 

more productive sites in the southern portions of the Commonwealth, forests were 

cleared for agricultural production. On less productive mountainous sites, forest 

resources were used to build cities, provide heat, and meet other needs. Most of the 

timber harvesting occurred over a 20-year period from 1900 to 1920. This resulted in 

an agricultural land base and an extensive block of young forest of a similar age that 

stands today as a legacy of the clearing and timbering era. 

The conversion of old forest to new forest was so extensive that by 1922, Joseph 

Illick, then Director of the Bureau of Forestry, concluded that only about 25,000 

acres could be classified as “original forest” (1923). The new forest originated without 

active regeneration management and was composed of species that had ecological 

advantages, such as prolific stump sprouting, intolerance of shade, and habitat 

generalization. Oaks, black cherry, and red maple achieved canopy status quickly and 

remain as dominant species in the present forest. Species that were more prevalent in 

the original forest, such as American beech, white pine, and eastern hemlock, remain, 

but are of lesser status today. 

This section discusses the distribution of timberland by stand-size and stand-age class, or 

successional stage. Timberland is used because it is an estimate that excludes forest land 

designated as wilderness, and so is not available for management. A dearth of young and 

old growth timberland mixed with mid- and late successional forest is described. The 

emphasis is on the imbalanced distribution of timberland by successional stage to better 

inform forest management and policy on this important forest sustainability topic.

What we found

Contemporary forest issues are rooted in the history of land use and forest growth since 

the end of the 19th century. The estimated area of forest land during the presettlement 

period is 28.6 million acres (Fig. 3). By 1860, just before the building of the timber 

economy, forest land had decreased by about one-third (to 18.8 million acres), primarily 

reflecting a diversion of land for agricultural use. As timber harvesting expanded, the 
FOREST RESOURCE ATTRIBUTES | 43

area of forest further declined to a low of 12.0 million acres in 1900, or 42 percent of 

the original forest. As marginal agricultural land reverted to forest, the acreage had 

increased to 17.1 million acres by 1965. The forest land base has remained stable since 

then, reflecting a depletion of most of the agricultural land available for reversion.

Stand-size and stand-age class are two variables that describe forest succession, or the 

division of the forest into successional stages. Stand-size class is a broad measure of 

succession based on the plurality of relative stocking of sample trees (Stout and Nyland 

1986) grouped into three classes: small, medium, and large (Arner et al. 2001). The 

advantage of stand size for describing forest succession is that it is available in digitized 

publications as far back as the first Pennsylvania FIA report for 1955 (Ferguson 1958). 

The availability of FIA results as early as 1955 and the Illick report (1923) provide the 

opportunity to track the decline in the area of small-size stands since the beginning of 

the 20th century (Fig. 28). In 1900, small-size stands accounted for 93 percent of 

timberland due to the extensive removal of merchantable wood. This percentage 

decreased to about 20 percent in 1960 and fell to 9 percent by 2014. 

The FIA stand-age estimates are based on increment cores of trees that represent 

the predominant canopy of the forest condition. Two or three trees are cored and a 

weighted average is computed by using the percentage of the canopy that each sample 

tree represents and the tree age measurement. To illustrate, if a white ash (72 years) 

93 

40 

23 

19 18 

15 

11 11 9 

0 

20 

40 

60 

80 

100 

1900 

1922 

1955 

1965 

1978 

1989 

2004 

2009 

2014 

Percent 

Inventory Year 

Figure 28.—Percentage of timberland classified as the small stand-size class 

(sapling-seedling), by year, Pennsylvania. Estimates for 1900 and 1922 are 

approximated from findings of Illick (1923).
44 | FOREST RESOURCE ATTRIBUTES

and red oak (86 years) are cored and those species represent 30 and 70 percent of the 

stand, respectively, then the age assigned is 82 years [(72 × 0.30) + (86 × 0.70)].

The relationship between stand-size and stand-age classes shows how the two 

classifications interact (Fig. 29). For example, small saplings and seedlings may be 

sampled with larger trees that are given more weight in the classification based on 

diameter. If a few medium or large trees are included in a sample of seedlings and 

saplings, the classification may be a medium or large stand-size class rather than a 

small size class. This means that some young stands are assigned to the medium and 

large classes, as shown for the 0- to 20-year class.

The stand-age profile expressed both as a percentage of total timberland and as acres 

provides an interpretation of current age structure (Fig. 30). The maturing forest in the 

41- to 120-year range makes up 84 percent of Pennsylvania’s timberland. Young forests 

from 0 to 20 years are only 6 percent of timberland. Using a broad definition for 

old-growth forest of 141 years and older captures timberland with trees from the time 

prior to wide-scale timbering, but this component may still have been disturbed 

(Pennsylvania Department of Conservation and Natural Resources, Bureau of Forestry 

2015). Using this definition, only 0.2 percent of the timberland would be old growth, or 

only 33,100 acres (subject to a sampling error of plus or minus 17,000 acres).

The stand-age profile for public and private owners reveals that 57 percent of public 

timberland is older than 80 years, compared to 33 percent of private holdings (Fig. 31). In 

terms of acres, private owners have the most acreage in mid- and late stages of succession 

that could be available to fill the gap in overall young forest acreage following stand0

1

2

3

4

0-20 21-40 41-60

Timberland Area (million acres)

Stand-age Class (years) 

Stand-size Class

n Small

n Medium

n Lage

61-80 81-100 100+

Figure 29.—Area of timberland by stand-age class and stand-size class, 

Pennsylvania, 2014.
FOREST RESOURCE ATTRIBUTES | 45

6 

9 

17 

29 28 

10 

1 0.20 0.01 

0 

10 

20 

30 

40 

0-20 

21-40 

41-60 

61-80 

81-100 

101-120 

121-140 

141-160 

161+ 

Timberland Area (percent) 

Stand-age Class (years) 

Timberland Area (million acres) 

0

1

2

3

4

5

0-20 

21-40 

41-60 

61-80 

81-100 

101-120 

121-140 

141-160 

161+ 

Stand-age Class (years) 

A

B

Figure 30.—Percentage of timberland (A) and area of timberland (B) by 

stand-age class, Pennsylvania, 2014.
46 | FOREST RESOURCE ATTRIBUTES 5 7 

7 

24 

38 

17 

2 

0.37 

0.00 

6 

9 

21 

30 

24 

7 

1 

0.14 

0.02 

0 

10 

20 

30 

40 

0-20 

21-40 

41-60 

61-80 

81-100 

101-120 

121-140 

141-160 

161+ 

Timberland Area (percent) 

Stand-age Class (years) 

0 

1 

2 

3 

4 

0-20 

21-40 

41-60 

61-80 

81-100 

101-120 

121-140 

141-160 

161+ 

Timberland Area (million acres) 

Stand-age Class (years) 

Owner Group

n Public

n Private 

A

B

Owner Group

n Public

n Private 

Figure 31.—Percentage of timberland (A) and area of timberland (B) by 

stand-age class and ownership, Pennsylvania, 2014.
FOREST RESOURCE ATTRIBUTES | 47

initiation disturbance. The proportions of public and private timberland in the 0- to 20-

year age class are 5 and 6 percent, respectively; however, more than three times the acreage 

of early-successional timberland is in private hands than in public ownership.

What this means

Extensive harvesting about a century ago created a widespread even-aged forest and 

nearly extirpated old-growth forest. The comparative lack of acreage in the youngest 

and oldest stand-age classes makes it timely to review approaches to achieving a better 

long-term balance of stand-age classes. Management of new young forests is needed 

to support the values and benefits of all stages of forest succession. The challenge for 

forest managers is to create young forests under conditions that are very different 

from those during the initiation of contemporary forests. They must now consider 

several interrelated factors that challenge prescriptive decisions for reestablishing 

forest ecosystems during stand initiation:

• Herbivory: white-tailed deer

• Lack of fire in oak management

• Competing native vegetation: mountain laurel (Kalmia latifolia), eastern hayscented 

fern (Dennstaedtia punctilobula), and New York fern (Thelypteris noveboracensis)

• Competing nonnative vegetation: bush honeysuckles (Lonicera spp.), multiflora 

rose (Rosa multiflora), and other species

• Gypsy moth and other nonnative pests/pathogens (see also Tree Pests and Diseases 

of Special Concern section starting on p. 106)

• Poor cutting practices and lack of planning on private timberland

• High cost of regeneration management (shelterwood, herbicide, fence)

• Fragmentation, parcelization, and urban influence

• Pollutant deposition 

• Changing climate

• Interaction of all of the above impacts.

The findings for both public and private forests show a dearth of young timberland to 

replace older timberland. This has created a deficit in faunal diversity and abundance 

for early-successional species compared to conditions common 100 years ago. The 

character and abundance of native tree species are also threatened due to the challenges 

of regeneration management and particularly the interactions between species.
48 | FOREST RESOURCE ATTRIBUTES

The lack of old-growth forest in Pennsylvania constitutes another acute forest health 

issue. The opportunity for today’s late-successional forest to evolve as tomorrow’s 

old growth is enormous but problematic. Forest management activities directed 

at fostering and stewarding future old growth are hampered by the same set of 

interrelated stress factors mentioned earlier.

Comparing management approaches of public and private owners elucidates 

key differences that will have an impact on future forests. Pennsylvania’s primary 

public owners are the Allegheny National Forest, Bureau of Forestry, and the Game 

Commission, all of which have overarching forest management plans that consider the 

amount of old forest, special ecosystems, and rare habitat (Pennsylvania Department 

of Conservation and Natural Resources, Bureau of Forestry 2015, U.S. Forest 

Service 2007)2. Professionally managed stands have science-based plans that address 

regeneration management when stand replacement is called for. Private timberland 

owners are a diverse group with a wide range of reasons for owning forests, but most 

do not have a management plan or participate in planning or assistance programs. 

Furthermore, the cost of implementing silvicultural prescriptions to achieve successful 

regeneration is often a difficult obstacle to overcome. Hence, many private owners 

are unprepared when a regeneration harvest is warranted. Unfortunately, this lack of 

planning can result in the use of harvesting practices (e.g., “select” cutting or highgrading) that remove only the best trees and leave behind a degraded stand. 

It is important to recognize that a long history of forest management research has 

produced methods for regenerating forests under stress, such as herbivory and 

undesired plant invasion. Managers need to consider existing methods and keep 

abreast of new research to make fully informed decisions. Most of the lessons learned 

for managing forests under stress are not new, but in Pennsylvania, the full suite 

of stressors and their complex interactions must be considered. Some prominent 

examples of management solutions are discussed next.

• Prescriptions that establish, recruit, and retain desirable seedlings from the mature 

stand prior to harvest through the stem exclusion phase after harvest will need to 

pay particular attention to contemporary drivers and stressors, such as invasive 

plants and climate change (Dey 2014). 

• Herbivory by white-tailed deer needs to be considered before harvest in stands 

scheduled for stand initiation in medium- and high-pressure subregions. 

2 Also: Pennsylvania Department of Conservation and Natural Resources, Bureau of Forestry. 2015. 2015 State 

forest resource management plan (Draft). On file at: Harrisburg, PA: Department of Conservation and Natural 

Resources, Bureau of Forestry. 193 p.
FOREST RESOURCE ATTRIBUTES | 49

• The shelterwood system and related management prescriptions described by Brose 

et al. (2008) for oak/hickory and Marquis (1994) for maple/beech/birch can be 

highly successful at regenerating stands.

• Controlling composition and structure of understory vegetation in stands with 

entrenched competing vegetation typically require expensive treatments (Jackson 

and Finley 2011).

• Fencing is often needed to reduce deer impacts and facilitate application of 

herbicides and other controls (Jackson and Finley 2011).

• Fire is a useful and well-understood practice in Pennsylvania and restores a natural 

process (Brose et al. 2014).

• Developing adequate stocking of desired species requires vigilant stewardship 

through the sapling stage in many cases.

• Information available so far indicates a slow restorative process for understories 

with sparse regeneration and entrenched competing vegetation that requires longterm commitment (Latham et al. 2005).

Although the challenges of regenerating Pennsylvania’s maturing forests are 

troublesome, they can be overcome by diligent planning and rigorous forest 

management activity. This is important because trends indicate less agricultural land 

will be reverting to forest and management of existing timberland will be the primary 

option for new stand development. Unlike other stages of succession, young forests 

are ephemeral and quickly grow to medium size. Establishment and maintenance of 

healthy young forests is likely to be one of the paramount issues facing Pennsylvania’s 

environmental community in the 21st century.

Forest Structure

Background

Stand-size class and relative stocking are important descriptors of any forest. FIA 

categorizes the stand size based on the size of trees occupying a majority of the area 

within a condition and reports them as one of three classes: large diameter (minimum 

11.0 inch d.b.h. for hardwoods and 9.0 inch d.b.h. for softwoods), medium diameter 

(5.0 inch to 10.9 inch d.b.h. for hardwoods and 5.0 to 8.9 inch d.b.h. for softwoods), 

and small diameter (less than 5.0 inch d.b.h.). These classes can be referred to as 

sawtimber, poletimber, and seedling/sapling, respectively and are also indicative of 

the forest developmental stage.
50 | FOREST RESOURCE ATTRIBUTES

Relative stocking is a measure of the area occupancy of trees in a forested stand. 

Understanding stocking is critical to gaining a perspective on stand dynamics, 

especially competition between individuals, individual tree growth rates, and 

light distribution. FIA classifies stocking into five categories: overstocked (>100 

percent), full (60-100 percent), moderate (35-59 percent), poor (10-34 percent), 

and nonstocked (0-9 percent). Overstocked stands are exceedingly dense, resulting 

in crowded trees fighting for limited resources at the expense of health and growth. 

Increased mortality and lack of regeneration, especially of shade-intolerant species, 

are characteristic of overstocked stands. Stands considered fully stocked are of 

sufficient density to effectively utilize the site resources, and moderately stocked 

stands have ample room for ingrowth with canopy gaps allowing light to reach 

the forest floor. Poorly stocked stands have sparse canopy cover and are open to 

colonization by invasive and undesirable species. Nonstocked stands are typically 

found after a severe disturbance, but have not been converted to a nonforest land use.

FIA evaluates stocking in two ways: using growing-stock trees only and using all live trees. 

Growing-stock trees are commercial species with less than two-thirds rough and rotten 

cull. Live-tree stocking includes trees of noncommercial species and cull trees. These trees 

do add value to a forest as food and habitat sources for wildlife and provide the diversity 

necessary for a healthy forest, but also occupy space that could grow trees of higher 

commercial value. Comparisons of growing-stock stocking and live-tree stocking provide 

some insight into the relative proportions of merchantable tree species and cull trees.

What we found

Pennsylvania’s forests continue to grow in size class. In 2014, 11 million (67 percent) of 

the 16.3 million acres of timberland were classified as large diameter stands, up from 9.3 

million acres (58 percent) in 2004 (Fig. 32). Conversely, over the same time period, the 

poletimber class decreased by 1.1 million acres to an estimated 3.7 million acres (23 

percent). The small diameter class also decreased by roughly 300,000 acres resulting in a 

2014 estimate of 1.5 million acres (9 percent). Eighty-three percent of all large diameter 

stands were in the fully stocked or moderately stocked classes (Fig. 33). Publicly owned 

timberland had a higher percentage of large diameter stands than privately owned 

timberland, 71 and 66 percent, respectively.

Eighty-five percent of Pennsylvania’s timberland in 2014 was classified as fully (48 

percent) or moderately (37 percent) stocked with all live trees. Nine percent was 

poorly stocked, 5 percent was overstocked, and about 1 percent of timberland was 

nonstocked. Removing noncommercial species and cull trees from consideration 

finds 3 percent overstocked, 38 percent fully stocked, 39 percent moderately stocked, 

18 percent poorly stocked, and 3 percent nonstocked.
FOREST RESOURCE ATTRIBUTES | 51

1 3 6

14

29 23

41

40

25

42

28

33

2 1

12

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

Large Medium Small 

Timberland Area (percent) 

Stand-size Class 

n Nonstocked 

n Poorly stocked 

n Moderately stocked

n Fully stocked 

n Overstocked

Figure 33.—Percentage of timberland area by stocking class and stand-size class, 

Pennsylvania, 2014.

0 

2 

4 

6 

8 

10 

12 

Large Medium Small 

Timberland Area (million acres) 

Stand-size Class 

n 2004

n 2009 

n 2014

Figure 32.—Acres of timberland by stand-size class, Pennsylvania. 

Error bars represent a 68 percent confidence interval around the 

estimated mean.
52 | FOREST RESOURCE ATTRIBUTES

Statewide, timberland area shifted to lower live-tree stocking classes with both upper 

classes losing acreage. The area of overstocked and fully stocked stands decreased 8 

and 3 percent, respectively, between 2004 and 2014. The moderate and poor stocking 

classes both increased in area by 9 percent over the same time. When considering 

only growing stock, changes in area by stocking class were more pronounced. For 

growing stock, overstocked acreage decreased by 14 percent and fully stocked areas 

decreased by 10 percent. Stands moderately stocked with growing stock increased in 

area by 4 percent, and stands poorly stocked with growing-stock trees increased in 

area by 31 percent from 2004 to 2014.

On privately owned timberland, stocking of growing-stock trees differed substantially 

from all live trees (Fig. 34). Since 2004 the disparity in area poorly stocked with growing 

stock and poorly stocked with all live trees has grown substantially. The 2014 estimate of 

private timberland poorly stocked with growing stock was 2.4 million acres, double the 

estimated acreage poorly stocked with all live trees. In 2004, there was only 71 percent 

more area poorly stocked with growing stock compared to poorly stocked with all 

live trees. The proportion of private timberland classified as either fully or moderately 

stocked with growing-stock trees dropped from 79 percent in 2004 to 74 percent in 

2014. Twenty-three percent of privately held timberland was classified as poorly stocked 

or nonstocked with growing stock trees, up from 18 percent in 2004. The widening 

disparity between growing stock and all live stocking indicates an increasing amount of 

timberland dominated by trees of little commercial value.

Publicly owned timberland showed similar trends from 2004 to 2014, but to a lesser 

extent (Fig. 35). Areas overstocked and fully stocked with commercial trees decreased 9 

and 6 percent, respectively, while moderate and poorly stocked areas increased 12 and 

30 percent, respectively. Eighty-three percent of the 4.5 million acres of public 

timberland in 2014 was either fully or moderately stocked with growing-stock trees and 

14 percent was classified as poorly stocked or nonstocked, up from 11 percent in 2004.

What this means

A healthy mature forest has a diversity of species and tree forms and should have 

a greater stocking level for all live trees than just growing stock (because growing 

stock is a subset of all live trees). However, the increasing proportion of timberland 

moderately stocked to overstocked with live trees that is poorly stocked with 

growing stock suggests that some forces are at work selectively removing the 

growing stock from Pennsylvania’s forests. Sustainable forest management becomes 

increasingly difficult and costly on land with poor growing-stock stocking. Although 

noncommercial species and cull trees have value, thinning them from fully stocked 

stands can increase resources available for the remaining growing-stock trees as 
FOREST RESOURCE ATTRIBUTES | 53

0 

1 

2 

3 

4 

5 

6 

7 

Overstocked Fully Moderate Poorly Nonstocked 

Area of Private Timberland (million acres) 

Stocking Class 

n 2004 All Live

n 2004 Growing Stock

n 2014 All Live

n 2014 Growing Stock 

Figure 34.—Area of private timberland by stocking class, 

Pennsylvania, 2004 and 2014. Errors bars represent a 68 

percent confidence interval around the estimated mean.

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

Overstocked Fully Moderate Poorly Nonstocked 

Area of Public Timberland (million acres) 

Stocking Class 

n 2004 All Live

n 2004 Growing Stock

n 2014 All Live

n 2014 Growing Stock 

Figure 35.—Area of public timberland by stocking class, 

Pennsylvania, 2004 and 2014.
54 | FOREST RESOURCE ATTRIBUTES

well as create canopy gaps for regeneration of less shade-tolerant species. The 

increasing amount of timberland acreage classified as poorly stocked with growingstock trees may represent a legacy of poor management. Stands managed primarily 

for short-term economic gain disproportionately contain trees with poor form and 

low commercial value. This devalues the residual stand by removing the seed source 

for desirable species, allows the expansion of noncommercial tree species, and may 

provide opportunities for invasive plants to dominate the site. Private timberland with 

increased area of stands poorly stocked with commercially valuable trees is indicative 

of challenges facing individual landowners. Programs and education emphasizing the 

importance of sustainable forest management will be invaluable going forward to slow 

the proliferation of stands with high proportions of cull trees and noncommercial 

species. The National Woodland Owner Survey has found that less than 13 percent 

of family forest owners, with a total of 2.2 million acres, have received management 

advice for their timberland. Proper forest management techniques that balance the 

economic value of timber with the health of the residual stand are crucial for the 

long-term sustainability of the State’s forest resources.

The continuing shift of acreage from small and medium diameter stands into large 

diameters indicates a lack of harvesting and disturbance sufficient to convert stands 

back to early successional stages. A diversity of forest successional stages supports a 

greater diversity of the wildlife species that depend on those forests to provide both 

food and cover. Additionally, forests that contain stands of multiple sizes may be 

more resilient to insect and disease outbreaks and other disturbances. Because the 

bulk of large diameter stands are either fully or moderately stocked, opportunities for 

management abound with stand improvement activities funded by the removal of a 

portion of the sawtimber. These opportunities are more available on timberland with 

high growing-stock stocking. Monitoring forest structure and identifying trends in 

the resource is crucial for Pennsylvania’s forest sustainability.

Volume on Timberland

Background

Volume estimates provide the opportunity to evaluate trends in the wood resource, 

potential uses of that wood, and its economic value. FIA reports tree volume as 

sound and net volume of live trees and growing-stock trees (cubic feet), sawtimber 

trees (board feet, International 1⁄4-inch rule), and biomass (dry tons). Each of these 

measures characterizes the wood resource in a different way and provides insight 

into its use and management. Cubic foot and board foot estimates quantify the 

volume of wood on timberland available for potential utilization. Biomass estimates 
FOREST RESOURCE ATTRIBUTES | 55

help quantify carbon storage. Because of changes in procedures, comparisons to 

inventories prior to 2000 are less consistent for some measures.

FIA calculates a cubic foot volume for all trees 5 inches in diameter and larger. The 

sound volume of live trees makes deductions only for rotten and missing wood. Net 

sound-wood volume, also referred to as net volume, is sound volume with additional 

deductions for tree form, including sweep, crooks, and forks. It includes qualifying 

sections of cull trees (trees with more than two-thirds cull due to rot and form or those 

of a noncommercial species). Growing-stock trees must be of commercial species and 

contain less than two-thirds cull. The requirements to qualify as growing stock make it 

the most restrictive and subjective of the volume measures. Sawtimber is the volume in 

the saw-log portion of growing-stock trees. The minimum diameter at breast height for 

sawtimber trees is 11 inches for hardwood species and 9 inches for softwood species.

What we found

There is an estimated 41.7 billion cubic feet of sound wood volume on Pennsylvania 

timberland (Fig. 36). Eighty percent of this volume, 33.3 billion cubic feet, is contributed 

by growing-stock volume in growing-stock trees. Also contained within the boles of 

growing-stock trees is an additional 4.1 billion cubic feet of sound wood that is too 

defective to qualify as growing-stock volume. Trees not meeting growing-stock 

standards either because they have large amounts of defect or are noncommercial 

species are classified as rough or rotten “cull” trees. Rough and rotten cull trees account 

for a combined 4.2 billion cubic feet, or 10 percent of sound volume on timberland. In 

addition to the volume of trees growing on timberland, an estimated 1.8 billion cubic 

feet of sound volume is growing on reserved and other forest land, a 21.5 percent 

increase since 2004. Though the volume on reserved land is not available for harvesting, 

it provides habitat for wildlife and many ecosystem services, including carbon storage.

Sound cull in growing-stock trees

(4.1 billion cubic feet) 10%

Rough cull trees

(3.6 billion cubic feet) 9% 

Rotten cull trees

(0.6 billion cubic feet) 1% 

Growing stock 

(33.4 billion cubic feet) 80% 

Figure 36.—Components of live sound wood volume on timberland, 

Pennsylvania, 2014.
56 | FOREST RESOURCE ATTRIBUTES

Recent volume increases are a continuation of a 60-year trend. Since 2004, increases 

have been observed in sound wood volume (14.1 percent), net sound volume (12.9 

percent), growing-stock volume (9.0 percent), and sawtimber volume (23.5 percent) 

on Pennsylvania timberland (Fig. 37). Net volume averages 2,244 cubic feet per acre 

of timberland across the State, two and a half times the volume estimated in 1955 

(Fig. 38). Volume per acre is higher on public timberland than on private ownerships 

and greatest on the Allegheny National Forest; county and municipal ownerships had 

the largest percentage increase since 2004 (Fig. 39). Per-acre volumes are highest in 

the Southeast region and are lowest in the South Central region. (Fig. 40) These 

regions experienced the largest and smallest increases in per-acre volume since 2004, 

20.3 percent in the Southeast region and 5.8 percent in the South Central region.

0 30 60 90 120 

Sawtimber

(+23.5%)

Growing-stock

(+9.0%)

Net Volume

(+12.9%)

Sound Volume

(+14.1%)

Measure of Volume

(Percent Change, 2004 to 2014)

n 1989

n 2004

n 2009

n 2014

Figure 37.—Four measures of volume on timberland by inventory year, 

Pennsylvania. Volumes are expressed in billion cubic feet, except for 

sawtimber, which is in billion board feet (International 1⁄4-inch rule). Note: 

1989 sound volume not available due to procedural changes. Error bars 

represent a 68 percent confidence interval around the estimated mean.

0 

500 

1,000 

1,500 

2,000 

2,500 

1950 1960 1970 1980 1990 2000 2010 2020 

Average Net Volume per Acre

(cubic feet) 

Year 

Figure 38.—Average net volume per acre on timberland, by 

inventory year, Pennsylvania. 
FOREST RESOURCE ATTRIBUTES | 57

0 500 1,000 1,500 2,000 2,500 3,000 

Southwest

(+13.1)

South Central

(+5.8)

Southeast

(+20.3)

Northeast

(+8.9)

North Central

(+10.1)

Northwest

(+10.1)

State average

(+10.3)

Volume per Acre (cubic feet)

State/Region (Percent Change, 2004 to 2014)

n 1989

n 2004

n 2009

n 2014

Figure 40.—Average net volume per acre of timberland, by region and 

inventory year, Pennsylvania. 

0 1,000 2,000 3,000 

National

forest

(+9.0)

State

(+9.4)

County and

municipal

(+14.4)

Private

(+10.4)

Average of all

ownerships

(+10.3)

Average Volume per Acre (cubic feet) 

Ownership (Percent Change, 2004 to 2014) 

n 1989

n 2004

n 2009

n 2014

Figure 39.—Average net volume per acre of timberland, by major 

ownership and inventory year, Pennsylvania. Error bars represent 

a 68 percent confidence interval around the estimated mean. 
58 | FOREST RESOURCE ATTRIBUTES

Volumes have shifted toward the larger tree diameter classes, which is an indication 

of the aging forest age class distribution of Pennsylvania’s forests. Between 2004 and 

2014, net volume decreased by 6.7 percent in diameter classes less than 12 inches, 

while volume in classes 12 inches and larger increased by 21.9 percent (Fig. 41). All of 

the volume gains were in trees large enough to produce saw logs. 

Red maple continues to be the most voluminous species followed by black cherry, 

northern red oak, sugar maple, and chestnut oak (Figs. 42, 43), but volume changes 

were inconsistent across species. Although most major species exhibited increases in 

volume, net volume decreases were observed for American beech, aspen, black locust, 

sassafras, and elm. Large percentage increases in volume were found in yellow-poplar, 

sweet birch, and white pine (Fig. 42).

Since 2004, sawtimber volume on timberland has increased by 23.5 percent and now 

totals 115.4 billion board feet. Ninety percent (104 billion board feet) of this volume 

is in hardwood species, making Pennsylvania the leading state in the Nation for 

growing hardwood sawtimber. Red maple is the leading sawtimber species by volume, 

followed by northern red oak, black cherry, sugar maple, and yellow-poplar (Fig. 44). 

Since 2004, all major species increased in board foot volume, although the increase 

for beech was significantly lower than for other species.

Across all ownerships, the distribution of hardwood sawtimber by tree grade 

changed very little between the 2004 and 2014 inventories. A little over 50 percent 

of hardwood sawtimber volume was contained in trees graded 1 and 2 (Fig. 45). In 

absolute terms, the volume in grades 1 and 2 increased by 26 percent to 54 billion 

board feet, while volume in the lowest grade (tie/local use) increased by 16 percent 

to 21 billion board feet. The distribution of grade by ownership shows that publicly 

owned lands have a higher proportion of sawtimber volume in the higher quality 

grades than privately held timberland. Public timberland has nearly 60 percent of its 

sawtimber volume classified as grade 1 or 2 (20.1 billion board feet) whereas private 

timberland has only 48 percent of its volume in the same grades (33.6 billion board 

feet; Fig. 46). Furthermore, most of the sawtimber volume gain on public timberland 

was in tree grade 1, whereas the bulk of the increase in private sawtimber volume was 

in both grade 1 and the lower quality grade 3. 

Of the major species in the State, northern red oak and yellow-poplar have the largest 

percentage of their volume in grades 1 and 2, each with nearly 70 percent of their 

volume in these valuable grades (Fig. 47). Red maple is the leading species in board 

foot volume as well as other volume measures and generally grades more poorly than 

other major species. Beech has the lowest portion of volume in grades 1 and 2 (11 

percent) and the highest portion in the low tie/local use grade (64 percent).
FOREST RESOURCE ATTRIBUTES | 59

-20 

0 

20 

40 

60 

80 

100 

6 8 10 12 14 16 18 20 22 24 26 28 30+ 

Volume Change (percent) 

Diameter Class (inches) 

Figure 41.—Percent change in net volume, by diameter class on 

timberland, Pennsylvania, 2004 to 2014.

0 1 2 3 4 5 6 7 

Elm (-25)

Sassafras (-0.2)

Black locust (-22)

Black walnut (+54)

Blackgum (+22)

Yellow birch (+13)

Amer. basswood (+11)

Aspen (-3)

Hickory (+20)

White pine (+33)

Amer. beech (-4)

Black/scarlet oak (+12)

Sweet birch (+20)

White oak (+4)

Yellow-poplar (+28)

Ash (+9)

Hemlock (+14)

Chestnut oak (+7)

Sugar maple (+11)

Northern red oak (+19)

Black cherry (+15)

Red maple (+13)

Volume (billion cubic feet)

Species/Species Group (Percent Change, 2004 to 2014)

n 1989

n 2004

n 2009

n 2014

Figure 42.—Net volume for the 22 most voluminous species or species groups 

on timberland, by inventory year, Pennsylvania. Error bars represent a 68 

percent confidence interval around the estimated mean and are not available 

for species groups.
60 | FOREST RESOURCE ATTRIBUTES

0 2 4 6 

Elm (-31.4)

Black locust (-35.9)

Black walnut (+44.1)

Blackgum (+8.9)

Yellow birch (+8.2)

Amer. basswood (+13.9)

Aspen (-4.0)

Amer. beech (-8.2)

Hickory (+18.1)

White pine (+28.6)

Black/scarlet oak (+11.5)

Sweet birch (+14.2)

Ash (+3.5)

White oak (+3.8)

Yellow-poplar (+28.4)

Hemlock (+14.0)

Chestnut oak (+2.7)

Sugar maple (+9.6)

Northern red oak (+17.1)

Black cherry (+7.7)

Red maple (+7.4)

Volume (billion cubic feet)

Species/Species Group (Percent Change, 2004 to 2014)

n 1989

n 2004

n 2009

n 2014

Figure 43.—Growing-stock volume by species or species group and 

inventory year, on timberland, Pennsylvania. Error bars represent a 68 percent 

confidence interval around the estimated mean and are not available for 

species groups.
FOREST RESOURCE ATTRIBUTES | 61

0 5 10 15 20 

Red pine (+16)

Blackgum (+39)

Yellow birch (+33)

Black walnut (+95)

Aspen (+23)

Amer. basswood (+23)

Amer. beech (+4)

Sweet birch (+27)

Hickory (+30)

White pine (+40)

Black/scarlet oak (+24)

Ash (+15)

Hemlock (+21)

White oak (+14)

Chestnut oak (+19)

Yellow-poplar (+39)

Sugar maple (+23)

Black cherry (+21)

Northern red oak (+27)

Red maple (+25)

Volume (billion board feet, International 1⁄4-inch rule)

Species/Species Group (Percent Change, 2004 to 2014)

Total BF volume increased by

+23.5 percent 2004 to 2014

n 1989

n 2004

n 2009

n 2014

Figure 44.—Sawtimber volume on timberland by species or species group and inventory 

year, Pennsylvania. Error bars represent a 68 percent confidence interval around the 

estimated mean and are not available for species groups.
62 | FOREST RESOURCE ATTRIBUTES

0 5 10 15 20 25 

2004 

2009 

2014 

2004 

2009 

2014 

Hardwood Sawtimber Volume (billion board feet) 

Owner Group and Inventory Year 

n Grade 1

n Grade 2

n Grade 3

n Tie/local use 

Private Owners Public Owners

Figure 46.—Hardwood sawtimber volume by tree grade, 

ownership, and inventory year, Pennsylvania.

10

26 30 31 20

24

24 21

39

28

28

28

30

21

18

20

0 

20 

40 

60 

80 

100 

120 

1989 2004 2009 2014 

Hardwood Volume (billion board feet) 

Inventory Year 

n Grade 1

n Grade 2

n Grade 3

n Tie/local use 

Figure 45.—Hardwood sawtimber volume by tree grade and inventory year 

with percentage of total volume by grade, Pennsylvania. 
FOREST RESOURCE ATTRIBUTES | 63

Among the regions, the species with the greatest net volume differ, but across all 

regions, the 10 most voluminous species represent about 80 percent of the total net 

volume in each region (Table 5). Red maple reaches its greatest proportion of net 

volume across the northern half of the State, where it represents at least one-fifth of the 

total volume in the Northwest (27 percent), North Central (23 percent), and Northeast 

(20 percent) regions. In the South Central region, oaks reach their highest proportion 

of total volume; chestnut oak, northern red oak, white oak, and black oak combined 

account for 42 percent of the total volume in the region. Across the State, species of ash 

represent between 3 (South Central region) and 10 (Southeast region) percent of total 

volume. Ash volume increased by 14.5 and 21.3 percent in the Northeast and Southeast 

regions, respectively, whereas changes in ash volume in other regions ranged from +6.2 

percent in the North Central region to -2.5 percent in the South Central region. Yellowpoplar is the dominant species in the Southeast unit, where it increased in volume by 

52.8 percent since 2004 and composes 22 percent of total net volume.

4 

8 

10 

18 

17 

18 

19 

23 

33 

34 

33 

46 

38 

53 

50 

7 

20 

19 

17 

24 

23 

24 

29 

20 

24 

27 

17 

27 

15 

19 

25 

43 

45 

38 

30 

35 

37 

38 

25 

23 

30 

23 

20 

17 

18 

64 

28 

27 

27 

29 

24 

19 

10 

22 

18 

10 

14 

14 

15 

12 

0 20 40 60 80 100 

Beech 

Aspen 

Sweet birch 

Scarlet oak 

Hickory 

Red maple 

Sugar maple 

Chestnut oak 

Black cherry 

Basswood 

White oak 

Ash 

Black oak 

Yellow-poplar 

N. red oak 

Volume (percent) 

Species 

n Grade 1

n Grade 2

n Grade 3

n Tie/local use 

Figure 47.—Percentage of saw-log volume by tree grade for major species, Pennsylvania, 2014. 
64 | FOREST RESOURCE ATTRIBUTES

Table 5.—Ten most voluminous species by region, ranked by 2014 volume, and net volume by species, 

percentage of regional volume, and percent change in volume between 2004 and 2014, on timberland, 

Pennsylvania

Region

Volume in region, 

2014 (million ft3)

Volume as a 

percentage of 

unit volume

Volume percent 

change, 

2004 to 2014

Northwest Red maple 605 27 16.4

Black cherry 287 13 -2.2

Northern red oak 168 8 20.9

Sugar maple 155 7 -0.4

Ash 113 5 0.7

Hickory 106 5 13.8

Hemlock 106 5 47.1

American beech 84 4 -11.8

Yellow-poplar 77 3 2.3

White oak 77 3 -24.2

Regional total 2,223 100 5.9

North Central Red maple 2,796 23 10.7

Black cherry 1,630 13 11.9

Sugar maple 1,277 10 7.7

Northern red oak 1,065 9 14.7

Hemlock 925 8 19.0

Sweet birch 597 5 19.3

Chestnut oak 550 4 16.1

Ash 531 4 6.2

American beech 486 4 -15.1

White oak 467 4 6.0

Regional total 12,256 100 10.7

Northeast Red maple 1,443 20 11.8

Chestnut oak 632 9 1.0

Hemlock 631 9 14.2

Northern red oak 536 8 13.1

Sugar maple 532 8 7.0

Ash 409 6 14.5

Black cherry 397 6 19.0

White oak 381 5 1.4

Sweet birch 338 5 21.8

American beech 269 4 6.3

Regional total 7,097 100 11.2

(continued)
FOREST RESOURCE ATTRIBUTES | 65

Table 5.—(Continued) Ten most voluminous species by region, ranked by 2014 volume, and net volume 

by species, percentage of regional volume, and percent change in volume between 2004 and 2014, on 

timberland, Pennsylvania

Region

Volume in region, 

2014 (million ft3)

Volume as a 

percentage of 

unit volume

Volume percent 

change, 

2004 to 2014

Southeast Yellow-poplar 552 22 52.8

Ash 261 10 21.3

Northern red oak 233 9 32.0

Chestnut oak 204 8 36.8

Red maple 179 7 14.6

Black oak 174 7 10.4

Hickory 153 6 30.8

Black walnut 87 3 68.1

Sweet birch 86 3 19.1

Black cherry 83 3 24.0

Regional total 2,545 100 32.8

South Central Chestnut oak 960 15 -0.6

Northern red oak 948 15 15.5

Red maple 705 11 15.5

White oak 396 6 1.2

Sweet birch 382 6 18.3

Black oak 293 5 9.8

Black cherry 282 5 33.0

Yellow-poplar 273 4 5.5

Hickory 251 4 17.5

Sugar maple 246 4 3.6

Regional total 6,217 100 8.3

Southwest Black cherry 1,244 20 16.8

Red maple 1,051 17 15.8

Northern red oak 564 9 33.5

Yellow-poplar 556 9 39.4

Sugar maple 481 8 34.0

Ash 233 4 5.7

White oak 230 4 22.5

Hickory 170 3 36.9

Black oak 150 2 33.7

Chestnut oak 148 2 24.6

Regional total 6,304 100 20.0
66 | FOREST RESOURCE ATTRIBUTES

What this means

Pennsylvania is the heart of the Nation’s hardwood resource. All measures of volume 

for the State’s timber resources have continued to increase to levels unseen since 

the wide-scale harvesting of the early 20th century. Most of the inventory volume 

is in trees that meet minimum requirements to qualify as growing-stock trees. The 

concentration of volume increases in sawtimber-size trees explains why increases 

in board-foot volume (+23.5 percent) were higher than increases in growing-stock 

cubic-foot volume (+9.0 percent). As trees grow into sawtimber size, their economic 

value can increase markedly because they can yield higher value timber products. 

Despite the substantial increase in sawtimber volume, trends in tree quality and 

species composition raise concern for the sustainability of some high-value species. 

Furthermore, the shift of volume out of the poletimber size class into sawtimber is 

one more indication that Pennsylvania’s smaller diameter trees are not being replaced.

Since 2004, sound wood volume increased by 14.9 percent, or 57 percent more

than the increase of growing-stock volume, even though these two measures refer

to bole volume between a 1-foot stump and a 4-inch top diameter. The difference is

that measurements of sound wood exclude only rotten and missing wood, whereas

measures of growing-stock volume also take deductions for rough cull (i.e., sweep, 

crook, and forks) and exclude trees classified as cull or noncommercial species. 

These measures indicate that low-value wood is increasing faster than the higher

quality timber.

Overall forest quality is affected by changes in species composition, though other 

factors are also involved. Since 2004, yellow-poplar and northern red oak, which 

typically grade higher than other species, had large increases in board-foot volume. 

The low numbers of red oak seedlings and saplings indicate a lack of regeneration that 

will affect the abundance of this species in the future. The numbers of yellow-poplar 

seedlings and saplings appear adequate to sustain this species. Red maple continues 

to be the leading species by growing-stock and sawtimber volume and has had a 

large increase in volume since 2004. It makes up a large portion of both seedlings and 

saplings, suggesting that large amounts of red maple volume will continue to grow 

to sawtimber size. Because tree grades for red maple are typically poorer than other 

major species, the yield of clear high-value lumber from red maple logs is less than 

that of other species such as yellow-poplar and red and white oak. Currently, however, 

there is high demand for high-quality red maple lumber.

There is a large amount of sound volume in the cull sections of growing-stock trees 

and trees classified as rough and rotten cull. This wood could present opportunities 

for increased utilization of low-value wood, much of which is now left in the woods 

during harvest operations either in standing live trees or as logging residue. Although 
FOREST RESOURCE ATTRIBUTES | 67

cull trees have low value for wood products, they are often of high value for wildlife 

habitat. Many of the same features that decrease the value for wood products increase 

these species' value for wildlife, such as bole cavities, large amounts of rot, and broken 

tops. Cull trees and portions of growing-stock trees left in the woods as logging 

residues provide habitat for wildlife and provide for nutrient recycling. 

In Pennsylvania, 60 percent of sawtimber-size hardwood trees are less than 15.0 inches

in diameter. These trees are too small for grade 1 and are given a lower grade solely on

d.b.h. Forest landowners can receive better financial returns by practicing sustainable

forestry and thinning around trees with potential to grow into quality grade 1 and 2

trees. By using silvicultural tools that promote high-value species and increase tree

quality, landowners can improve the financial return from their harvest and improve

residual forest health. Having markets for small trees and lower grade wood products,

such as pallets, pulpwood, wood pellets, and biomass energy gives landowners

opportunities to apply best management practices and improve overall stand quality.

Without markets for low-value wood, landowners have little incentive to remove lowvalue trees during harvesting operations and many are left in the residual stand.

The diversity of tree species ensures that no single species represents more than about 

one-quarter of the total volume in any region. There are few areas in Pennsylvania 

where any species dominates by volume. This diverse mix reduces the impact of 

insects and diseases that affect a single species; however, this diversity may be in 

jeopardy. Statewide, red maple is the most numerous species, representing 22 percent 

of all trees over 5 inches. Because it has the second most seedlings—more seedlings 

than all oaks combined—red maple is likely to increase in dominance.

Changes in ash volume by region indicate that mortality and slowed growth caused 

by the emerald ash borer (EAB) has most likely affected ash in the four regions that 

represent the western two-thirds of the State. The impact of EAB has not yet shown 

up in the data for the two eastern regions. Currently ash species represent between 3 

(South Central region) and 10 percent (Southeast region) of total volume. The impact 

of EAB will be proportional to the ash volume, so future impacts are likely to be 

greatest in the Southeast region as it continues to move east, although EAB is likely to 

cause decreases in ash volume throughout the State. 

The high volumes are further evidence that Pennsylvania’s forests are maturing and trees

continue to increase in size. The lack of management to replace some portion of this

older forest with younger stands that will grow the sawtimber of the future is a concern.

This maturing is occurring over the broad landscape. Larger and older trees may be

more susceptible than younger trees to windstorms, ice storms, drought, and exotic

insects and diseases, all of which may increase. Furthermore, because the majority of

growth is now occurring on large trees, there are fewer trees growing into the sawtimber
68 | FOREST RESOURCE ATTRIBUTES

size class. Declining ingrowth into the sawtimber size class places increasing importance 

on practicing good forest management to maintain a high-quality resource. Because 

of the large portion of Pennsylvania’s wood resource contained in large sawtimbersize trees of desirable species, the production of high-quality lumber is the likely use 

for the bulk of its hardwood resource and the main goal of most forest management. 

Pulpwood, biomass, and wood for low-value uses such as pallet lumber are typically byproducts of managing for high-quality timber in the State.

Components of Annual Volume Change: 

Growth, Removals, and Mortality

Background

Well-tended forests supply a continuous flow of products and services without 

impairing long-term productivity or the ecological integrity of the forest. One way 

to judge the sustainability of a forest is to examine components of annual change 

in inventory volume from the perspectives of growth, removals, and mortality. Net 

growth includes growth (accretion) on trees measured previously, ingrowth3

 of trees 

reaching the 5-inch threshold for volume measurement, deductions for mortality 

due to natural causes, and tree volume on land reverting to forest. Removals include 

trees harvested and trees removed from the inventory because the forest land was 

converted to a nonforest use. On timberland, removals also include trees on land 

reclassified as reserved or other forest land. Analysis of these individual components 

can help us better understand causes for net change in volume.

What we found

Tree growth in Pennsylvania has greatly outpaced mortality and removals during the 

past 50 years. The most recent inventory revealed that since 2009, gross growth in 

the net volume of live trees on timberland is more than 1.1 billion cubic feet annually 

(Fig. 48). Annual mortality averages 322 million cubic feet, resulting in a net growth 

of 807 million cubic feet per year. Annual removals averaged 340 million cubic feet 

and result from harvest (87 percent), land-use change to nonforest (12 percent), and 

land-use change to other forest land (1 percent), leaving an annual net increase of 

467 million cubic feet on Pennsylvania’s timberland (Fig. 48). As a percentage of the 

current inventory, gross growth was 3.1 percent, mortality was 0.9 percent, net growth 

3 Ingrowth on timberland refers to the estimated net volume of trees that became 5.0 inches d.b.h. or larger during 

the period between inventories as well as the estimated net volume of trees 5.0 inches d.b.h. and larger growing on 

land that was reclassified from nonforest to timberland. 
FOREST RESOURCE ATTRIBUTES | 69

was 2.2 percent, and removals were 0.9 percent. These result in an average annual net 

increase in total volume of 1.3 percent (Table 6).

On land classified as timberland in both 2009 and 2014, 77 percent of net growth 

was on trees previously in the 6-inch diameter class and larger (accretion) and the 

remaining 23 percent was from trees that were less than the 5-inch threshold in 2009 

and are now 5 inches in diameter or larger (ingrowth). Fifty-eight percent of the 

accretion was on trees that previously were in diameter classes 12 inches and larger 

(sawtimber size) (Fig. 49).

Statewide, 87 percent of the removals were attributable to harvesting on land that 

remained in timberland, 12 percent was on timberland diverted to a nonforest land 

use, and 1 percent was from timberland reclassified to other forest land. The regions 

with the highest percentage of removals due to land-use change were the Northeast 

(27 percent) and the Southwest (17 percent). On land classified as timberland in both 

2009 and 2014, removals were concentrated on trees in the 14- to 18-inch diameter 

classes in the 2009 inventory (Fig. 50). These classes account for 45 percent of these 

harvest removals by volume.

Harvests were primarily from highly stocked stands. Sixty-one percent of harvest 

removals came from stands that previously had a live-tree basal area greater than 120 

square feet per acre and 30 percent from stands with previous basal areas of 81 to 

120 square feet per acre. The 2014 inventory found evidence of harvest on 1.2 million 

-400 

-200 

0 

200 

400 

600 

800 

1000 

1200 

Gross Growth Mortality Net Growth Removals Net Change 

Volume (million cubic feet) 

Components of Change 

Figure 48.—Average annual components of change in net volume 

on timberland, Pennsylvania, 2014. Error bars represent a 68 percent 

confidence interval around the estimated mean. 
70 | FOREST RESOURCE ATTRIBUTES

Table 6.—Average annual components of change in net volume as a percentage of current volume on 

timberland, by region, Pennsylvania, 2014

Pennsylvania region Gross growth Mortality Net growth Removals Net change

 - - - - - - - - - - - - - - - - - - - - - percent - - - - - - - - - - - - - - - - - - - - -

Northwest 3.7 0.8 2.9 1.4 1.6

North Central 2.4 0.7 1.8 1.0 0.8

Northeast 3.1 1.0 2.1 1.0 1.1

Southeast 4.0 0.9 3.1 0.8 2.3

South Central 3.2 1.3 1.9 0.9 1.0

Southwest 3.7 0.8 2.8 0.7 2.2

State 3.1 0.9 2.2 0.9 1.3

-20 

0 

20 

40 

60 

80 

100 

120 

6 8 10 12 14 16 18 20 22 24 26 28+ 

Growth Volume (million cubic feet) 

Previous Diameter Class (inches) 

Figure 49.—Average annual net growth (volume) on live trees (i.e., 

accretion) by 2009 diameter class on timberland, Pennsylvania, 2014. 

Error bars represent a 68 percent confidence interval around the 

estimated mean.
FOREST RESOURCE ATTRIBUTES | 71

acres during the 5 years between plot measurements. A fairly high density of trees 

was retained on most of these harvested acres. Thirty-one percent of the harvested 

area currently has a basal area per acre between 81 and 120 square feet per acre, and 

22 percent currently has a basal area of at least 120 square feet. Only 16 percent of the 

harvested area currently has a basal area of less than 40 square feet. On timberland 

with evidence of harvesting over the 5-year remeasurement period, volume currently 

averages 1,837 cubic feet of sound wood per acre. This is equivalent to 81 percent of 

the average volume on timberland with no evidence of harvesting over the same time 

period. Trees previously classified as growing stock had a higher rate of removal, 0.9 

percent per year, than trees that were classified as cull, 0.4 percent per year. 

On timberland, the ratio of total net growth to removals (G/R) averaged 2.4:1 over the 

5-year period between plot measurements. This compares to an average G/R ratio of 

2.0:1 during the 2009 inventory. Most of the increase in the G/R ratio is due to a 21 

percent decrease in removals since the 2009 inventory. If growth and removals due to 

land-use change are excluded, the current G/R ratio is 2.3:1. The G/R ratio was lowest 

in the North Central region (1.8:1), where removals were 37 percent of the statewide 

removals and growth accounted for 27 percent of the State’s net growth. The G/R ratio 

was highest in the Southwest and Southeast regions, where growth outpaced removals 

0 

10 

20 

30 

40 

50 

60 

6 8 10 12 14 16 18 20 22 24 26 28+ 

Removals Volume (million cubic feet) 

Previous Diameter Class (inches) 

Figure 50.—Average annual removals (volume) by 2009 diameter class 

on timberland, Pennsylvania, 2014. Data exclude removals due to forest 

land being diverted to nonforest uses. Error bars represent a 68 percent 

confidence interval around the estimated mean.
72 | FOREST RESOURCE ATTRIBUTES

by ratios of 4.3:1 and 3.9:1, respectively (Fig. 51). Growth-to-removals ratios were 

2.3:1 on privately owned timberland and 2.9:1 on publicly owned timberland.

In terms of growth and removals by species, red maple had the largest volume of both 

growth and removals, accounting for 18 percent of total growth and 16 percent of 

removals; and together oak species account for 19 percent of growth and 21 percent of 

removals (Fig. 52). Growth-to-removals ratios varied considerably among major 

species in the State, with various reasons for individual species having high and low 

ratios. Blackgum and sweet birch have relatively high G/R ratios, 5.8:1 and 3.9:1, 

respectively, because of large numbers of small trees crossing the 5-inch threshold for 

measurement (ingrowth) and low removals. Additionally, blackgum has very low 

mortality. Conversely, yellow-poplar has a high G/R ratio of 4.2:1 because of growth 

on large trees (accretion) with low recruitment into the 6-inch class and low mortality. 

Despite large amounts of ingrowth for American beech, this species had low net 

growth because of high mortality. Generally net growth for the oaks when compared 

to other species was lower because only small amounts of growth were attributed to 

ingrowth and large amounts of removals occurred in large trees. In contrast, the 

growth observed in red maple and black cherry was balanced across diameter classes. 

Statewide net growth exceeded removals for all major species, with the exceptions of 

American beech and aspen (quaking and bigtooth aspen combined), where removals 

outpace growth by ratios of 0.9:1 and 0.7:1, respectively. 

What this means

Today’s well-stocked forests are a product of growth consistently outpacing removals 

during the last 60 years and the surplus of timber accumulating in the forest. Since 2009, 

net growth has occurred at more than twice the rate of removals, with the net change 

amounting to an annual increase of 1.3 percent in inventory volume. This implies that the 

current level of removals is sustainable and that increases in volume will continue at the 

State level and in all regions. Where harvesting took place, the cuts were light and retained 

a relatively high volume of residual trees. These light harvests influence the future growth 

and species composition of Pennsylvania’s forests. Future growth will tend to occur on 

residual trees rather than ingrowth in response to gaps in the canopy. The reproduction 

that does occur will favor more shade-tolerant species at the expense of shade-intolerant 

species. The growth occurring on trees previously measured and especially on trees 11 

inches in diameter and larger means there are few new trees growing into the sawtimber 

size classes and in many cases stands are composed of residual trees left after harvest. This 

puts increased importance on practicing good forest management, where high-quality 

crop trees are retained and tended toward future harvests. 
FOREST RESOURCE ATTRIBUTES | 73

0 50 100 150 200 250 

Southwest (4.3)

South Central (2.2)

Southeast (3.9)

Northeast (2.1)

North Central (1.8)

Northwest (2.2)

Volume (million cubic feet)

n Growth

n Removals 

Region (Growth-to-Removals Ratio) 

Figure 51.—Average annual growth and removals of net volume on 

timberland by region, Pennsylvania, 2014. Error bars represent a 68 percent 

confidence interval around the estimated mean.

0 50 100 150 

Cucumbertree (2.5)

Yellow birch (3.4)

Black walnut (5.6)

Blackgum (5.8)

Aspen (0.7)

Scarlet oak (2.1)

Beech (0.9)

Black oak (1.6)

White oak (1.5)

Hickory (4.7)

Hemlock (1.9)

Chestnut oak (2.5)

White pine (4.1)

Sweet birch (3.9)

Ash (1.1)

Sugar maple (2.2)

Yellow-poplar (4.2)

Northern red oak (2.5)

Black cherry (3.4)

Red maple (2.8)

Net Volume (million cubic feet)

Region (Growth-to-Removals Ratio) 

n Growth

n Removals 

Figure 52.—Average annual growth and removals of net volume on 

timberland by species, Pennsylvania, 2014. Error bars represent a 68 

percent confidence interval around the estimated mean.
74 | FOREST RESOURCE ATTRIBUTES

Over half the removals in the State occurred in the North Central and Northeast 

regions. These regions contributed a disproportionate share of the Commonwealth’s 

total removals, although they experienced lower growth rates than other regions of 

Pennsylvania. The Southwest and Southeast regions had the highest growth rates and 

low harvest rates; as a result, these regions had the highest annual volume increase. 

The concentration of large urban areas and fragmented, small ownerships most likely 

impedes harvesting in these regions. 

Comparing the G/R ratios of individual species to the average ratio for all species 

(2.4:1) reveals which species are increasing in importance and which are decreasing. 

The high G/R ratios for red maple, hickory, sweet birch, and blackgum indicate these 

species will increase in importance in Pennsylvania’s forests. Yellow-poplar also has 

a high G/R ratio, but because much of its growth is on large diameter trees with 

little ingrowth, the ratio is likely to decrease. Similarly, for oak species, most growth 

is attributed to accretion on large trees; because of low ingrowth into the 5-inch 

diameter class, the rate of future growth in oaks is likely to decrease. The G/R ratio 

for ash indicates a positive annual change in volume. However, future growth is being 

threatened by the exotic insect pest emerald ash borer (EAB). Currently, ash species 

account for 5 percent of net growth in Pennsylvania. This is unlikely to continue as 

the EAB spreads across the State, slowing ash growth and increasing mortality. 

Tree Mortality

Background

The volume of trees that die from natural causes, such as insects, diseases, fire, wind, 

and competition from other trees, is reported as mortality; harvested trees are not 

included in mortality estimates. Tree mortality is a natural process that occurs in a 

functioning ecosystem. Dramatic increases in mortality can indicate forest health 

problems, such as invasions by exotic insects and diseases.

What we found

In Pennsylvania, the average annual rate of mortality for live trees on timberland was 

0.9 percent over the 5-year remeasurement period. This is the same rate found in the 

2009 inventory. If only growing-stock trees are considered, the mortality rate for this 

period is 0.7 percent, again the same as the 2009 inventory. The mortality rate of live 

trees in Pennsylvania was lower than in the neighboring states of Ohio (1.2 percent), 

New York (1.1 percent), New Jersey (1.1 percent), Maryland (1.0), and West Virginia 

(1.0). Rates were highest in the South Central region (1.3 percent), and lowest in the 

North Central region (0.7 percent) (Fig. 53).
FOREST RESOURCE ATTRIBUTES | 75

Mortality rates were generally higher for smaller diameter trees than for larger ones, 

although rates were highest for trees in the 30-inch diameter class and larger (Fig. 54). 

The mortality rate in the 6-inch class was 1.6 percent per year, nearly double the average 

rate across all diameter classes. The 20-inch diameter class had the lowest mortality rate at 

0.5 percent. Trees less than 11.0 inches in diameter accounted for 37 percent of the total 

mortality by volume even though they represent only 26 percent of total tree volume.

Red maple, the leading species by volume in the State, had an annual mortality rate of 

0.5 percent—nearly 50 percent less than the State average for all species. Other species 

with low mortality were blackgum, yellow-poplar, and white pine: 0.2, 0.3, and 0.4 

percent, respectively. Species with highest annual mortality rates were elm (8.3 percent), 

black locust (4.9 percent), aspen (2.6 percent) and sassafras (1.9 percent) (Fig. 55). 

0.9 

0.8 

1.3 

0.9 

1.0 

0.7 

0.8 

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 

State

Southwest

South Central

Southeast

Northeast

North Central

Northwest

Mortality Rate (percentage of volume) 

Region 

Figure 53.—Average annual mortality as a percentage of current live tree 

volume on timberland by region, Pennsylvania, 2014.
76 | FOREST RESOURCE ATTRIBUTES

0.0 2.0 4.0 6.0 8.0 10.0 

Elm (8.3)

Black locust (4.9)

Aspen (2.6)

Pitch and Virginia pine (2.5)

Sassafras (1.9)

Scarlet oak (1.6)

American beech (1.4)

Ash (1.2)

Chestnut oak (1.1)

Hemlock (1.1)

Yellow birch (1.1)

Basswood 1.0)

White oak (0.9)

Northern red oak (0.8)

Black oak 0.7)

Cucumbertree 0.7)

Black cherry 0.7)

Sugar maple(0.7)

Sweet birch (0.7)

Black walnut (0.6)

Hickory (0.5)

Red maple (0.5)

White pine (0.4)

Yellow-poplar (0.3)

Blackgum (0.2)

Mortality Rate (percentage of volume)

Species/Species Group 

State average for all species 0.9 

Figure 55.—Average annual mortality as a percentage of current live tree 

volume for major species on timberland, Pennsylvania, 2014. Error bars 

represent a 68 percent confidence interval around the estimated mean.

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

6 8 10 12 14 16 18 20 22 24 26 28 30+ 

Mortality Rate (percentage of volume) 

Diameter Class (inches) 

Figure 54.—Average annual mortality as a percentage of current live tree 

volume on timberland by previous diameter class, Pennsylvania, 2014. Error 

bars represent a 68 percent confidence interval around the estimated mean.
FOREST RESOURCE ATTRIBUTES | 77

What this means

Mortality rates in Pennsylvania are lower than surrounding states. Pennsylvania’s 

lower rates, although difficult to explain, could be the result of a currently greater 

impact of insects and diseases, such as beech bark disease, Dutch elm disease, elm 

yellows, and emerald ash borer in surrounding states (see also Tree Pests and Diseases 

of Special Concern section starting on p. 106). Further, a greater portion of stands 

in other states may be in the stem exclusion stage of development, where small tree 

mortality is expectedly high. Much of the mortality in Pennsylvania is attributable to 

insects and diseases that target specific species, or stand dynamics. Currently beech, 

elm, hemlock, and ash species are under attack by exotic insects and diseases and 

have mortality rates higher than the State average for all species. 

Stocking and age-class data for Pennsylvania describe a maturing forest and crowded 

conditions. As trees compete for light and growing space, some fall behind their 

neighbors, lose vigor, and succumb to insects, diseases, and their inability to compete 

for resources. This is evident in the higher mortality rates in small diameter classes, 

where trees are in the understory and have live crown ratios of 20 percent or less. 

Species classified as early successional and intolerant of shaded conditions, such as 

aspen, black locust, pitch and Virginia pine, and sassafras, all have high mortality 

rates and should be expected to decline in importance as stands age. 

Mortality rates vary between species, with many species deviating substantially 

from the State average. Having a large diversity of species contributes to the overall 

resilience of Pennsylvania’s forests, as the impacts of insects and diseases that attack 

individual species is confined to a smaller portion of the resource.

Forest Carbon

Background

Forests sequester carbon from the atmosphere, thus playing a critical role in global 

climate change. Because the dry biomass of trees is about 50 percent carbon, forests 

contain the largest reserves of sequestered carbon among terrestrial ecosystems. 

Regional and national greenhouse gas reporting forums include forest carbon stocks 

because increases in these carbon stocks represent quantifiable partial offsets to 

other greenhouse gas emissions. For example, carbon sequestered by U.S. forests 

represented an offset of more than 11 percent of total U.S. greenhouse gas emissions 

in 2013 (U.S. Environmental Protection Agency [EPA] 2015). The continuing increase 

in Pennsylvania forest carbon stocks contributes to this offset.
78 | FOREST RESOURCE ATTRIBUTES

Carbon accumulates in growing trees via the photosynthetic process and is stored as 

wood. Over time, this stored carbon also accumulates in dead trees, woody debris, 

litter, and forest soils. Roots are the belowground portion of trees and are reported as 

part of live biomass, not in the soils estimates. For most forests, understory grasses, 

forbs, and non-vascular plants represent minor pools of carbon stocks. Carbon loss 

from a forest stand includes mechanisms such as respiration (including live trees and 

decomposers), combustion from wildland fires, runoff or leaching of dissolved or 

particulate organic particles, or direct removal such as the harvest and use of wood. 

Regarding greenhouse gas reporting, it is important to note that not all losses result in 

release of carbon dioxide to the atmosphere; many wood products not used as a fuel 

source represent continued long-term carbon sequestration.

The carbon pools discussed or depicted here are:

• Living plant biomass (live trees ≥1 inch d.b.h. and understory vegetation)

• Dead wood (standing dead trees, down dead wood, and forest floor litter)

• Soil organic matter exclusive of coarse roots and estimated to a depth of 1 meter (3.3 feet).

Carbon estimates for ecosystem pools are based on sampling and modeling. Because 

of the variability in information available for each pool, greater interpretive results 

can be derived for certain carbon estimates than for others. For example, due to the 

level of sampling and availability of allometric relationships applied to the tree data, 

the greatest confidence is in the estimate of live tree carbon. Limited data and high 

variability mean lower confidence in the soil organic carbon estimates and hence, 

limited interpretation. Additional information on current approaches for determining 

forest carbon stocks are described in U.S. EPA (2015), U.S. Forest Service, Forest 

Inventory and Analysis (2014), and O’Connell et al. (2014). The carbon estimates 

provided here are consistent with the methods used to develop the forest carbon 

reported in the U.S. EPA’s Inventory of U.S. Greenhouse Gas Emissions and Sinks: 

1990–2013 (published April 2015); however, this 2014 inventory summary includes 

some newer data relative to the Pennsylvania forest contribution (U.S. EPA 2015).

What we found

Total forest ecosystem carbon stocks in Pennsylvania are estimated to be 1,298 million 

tons of carbon, a 4 percent increase from 5 years ago. Live trees and soil organic carbon 

are the largest pools and account for 87 percent of forest carbon stocks (Fig. 56). Thirtyone percent of carbon is in the wood and bark of boles of trees at least 5 inches d.b.h.

Average aboveground carbon per acre (Fig. 57) and net accumulation increase with stand 

age; as such, total carbon stocks are the product of carbon per acre and total acres of forest 
FOREST RESOURCE ATTRIBUTES | 79

36 

31 

8 

3 

3 

8 

1 

2 

1 

8 

51

n Soil organic carbon

n Forest floor/litter

n Down dead wood

n Standing dead trees

n Understory

n Live trees 

n Live trees, bole

n Live trees, saplings

n Live trees, top/branches

n Live trees, stump

n Live trees, coarse roots

Percentage of Forest Carbon

Stocks in All Pools

Percentage of Forest Carbon,

Live Trees

Figure 56.—Percentage of total forest carbon stocks by detailed pool, Pennsylvania, 

2014. Percentages may not sum to totals due to rounding. 

0 

5 

10 

15 

20 

25 

30 

35 

40 

45 

50 

0-20 21-40 41-60 61-80 81-100 101+ 

Carbon Stocks (short tons per acre) 

Age Class (years) 

n Aboveground live biomass 

n Aboveground dead wood and litter 

Figure 57.—Aboveground carbon stocks per acre for live and dead 

components on forest land by stand-age class, Pennsylvania, 2014.
80 | FOREST RESOURCE ATTRIBUTES

within each age class. The majority of carbon stocks are in the mid- to older-age classes. 

Sixty-three percent of total aboveground carbon stocks are in the two age classes from 

61 to 100 years old (57 percent of forest land); in contrast, the two youngest age classes 

together account for only 7 percent of forest carbon stocks (14 percent of forest land).

Species composition also affects the amount of carbon sequestered. Note that the 

variability in average carbon per acre (shorts tons) for the major forest-type groups 

identified in Pennsylvania (Fig. 58) is most closely associated with variability in livetree biomass. Statewide, 87 percent of total carbon was in the two forest-type groups 

that make up 86 percent of forest land area: oak/hickory (52 percent) and maple/

beech/birch (34 percent). 

The current carbon estimation methods and data were also applied to the 2004 and 

2009 Pennsylvania forest inventories (Fig. 59) to produce summaries consistent with 

those provided here for the 2014 inventory. Overall forest carbon per acre increased 

by 3 percent relative to 5 years ago, and live tree carbon per acre values increased by 5 

percent. Total estimated forest land increased by 1 percent over the same period; total 

carbon stocks in 2014 are therefore 4 percent greater than the equivalent values 

calculated for 2009, surpassing the 3 percent increase between 2004 and 2009.

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

White/red/jack pine 

Other softwoods 

Oak/hickory 

Elm/ash/cottonwood 

Maple/beech/birch 

Other hardwoods 

Carbon Stocks (short tons per acre) 

n Live vegetation 

n Soil organic 

n Litter 

n Dead wood 

Figure 58.—Average carbon stocks per acre on forest land by forest-type 

group and carbon pool, Pennsylvania, 2014.
FOREST RESOURCE ATTRIBUTES | 81

What this means

In general, forest carbon stocks and changes broadly reflect other measures of forest 

resources such as stand age, volume, or stocking. Carbon summaries are useful 

to compare Pennsylvania’s carbon trends to those of other states, regions, and the 

Nation. In brief, the carbon summaries show: 

• Just over half of total carbon is in live trees

• The majority of carbon is in stands of 61 to 100 years 

• Specific stand-level carbon varies

• Overall forest carbon in Pennsylvania has increased over the past 5 years.

For any stand, carbon stocks depend on site history, management, stand age, and tree 

composition and size, much of which can be heavily influenced by forest management 

practices. Removal of wood products used in construction and furniture manufacturing 

results in long-term carbon storage and makes room for new, younger stands to capture 

and store new carbon. Although older forests store more carbon, younger age classes 

show greater rates of increase in carbon sequestration. Stands show the greatest rate 

of carbon accumulation moving from the 0-20 year class to the 21-40 year class and 

41-60 year class. This storage is equivalent to an additional 10 tons of carbon per acre 

for each increase of one age class. Subsequently, more-mature stands gain only 3 to 4 

tons of carbon per acre with each increase in age class (from 61-80 years to 81-100 years 

old and then to the 101+ age class). Thus, managing forests for a more balanced ageclass distribution could result in greater rates of increase in carbon stocks in the future. 

Continued monitoring of forest carbon is prudent as we look for ways to mitigate the 

effects of increasing atmospheric carbon dioxide levels.

n Live trees

n Down and dead wood 

0 

200 

400 

600 

800 

1,000 

1,200 

1,400 

2004 2009 2014 

Carbon Stocks (million tons) 

n Standing dead

n Forest floor/litter

n Understory 

n Soil organic 

Figure 59.—Total carbon stocks on forest land by carbon pool and 

inventory year, Pennsylvania.
82 | 

Hayscented fern bed in sugar maple forest in Potter County. Photo by Thomas Albright, U.S. Forest Service.

Forest Indicators of Health and 

Sustainability
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 83

Regeneration Status

Background

Pennsylvania’s forest ecosystems face numerous regeneration stressors (e.g., 

herbivory, competing understory vegetation, invasive plants, insects, diseases, and 

climate change). As stands that make up these systems mature and undergo stand 

replacement disturbances, it is imperative to know the condition of the regeneration. 

Abundance and composition of tree seedlings drive the sustainability of forest 

ecosystems in the early years of stand development and set the stage for future 

composition and structure. The vitality of timber and invaluable ecosystem services, 

such as soil conservation, watershed protection, scenic beauty, and opportunities for 

personal enjoyment are other important reasons that forest regeneration bears careful 

monitoring.

To fill the need for more detailed information on regeneration in Pennsylvania, the 

Northern Research Station (NRS), Forest Inventory and Analysis (FIA) program 

added regeneration indicator protocols to a subset of NRS-FIA sample plots measured 

in the growing season during the periodic inventory in 1989 (McWilliams et al. 

1995). This marked the beginning of the Pennsylvania Regeneration Study (PRS). 

The PRS protocols continued with the annual inventory system that was initiated in 

2000. The procedures measure all established trees seedlings (less than 1-inch d.b.h.) 

at least 2 inches tall by height class and include an herbivory impact assessment for 

the area surrounding the sample location. In addition to core results used in standard 

reports, the data were analyzed for regeneration adequacy using metrics developed 

for the PRS (McWilliams et al. 2015). The PRS was implemented to provide empirical 

results on the quality and quantity of advance regeneration because of concern that 

herbivory and other factors were impeding regeneration success across the State. The 

PRS approach compares the number of seedlings and saplings encountered on NRSFIA samples to accepted regeneration management guidelines to classify each sample 

as having adequate regeneration or not. Only samples from plots 40- to 75-percent 

stocked with live trees are used so that findings are limited to samples with adequate 

light for establishing advance regeneration. The metrics are adjusted using the browse 

impact code because forests under higher herbivory pressure require more seedlings 

for adequate regeneration than those under less pressure. 

The regeneration indicator findings are used by forest managers and policy makers 

making decisions to improve landscape-scale regeneration. This section delivers an 

update of regeneration status since the previous report.
84 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

What we found

As Pennsylvania’s forest stands continue to age, young forest has become rare as 

older, more mature stands dominate the forested landscape. Statewide, the area of 

small (sapling-seedling) stands decreased from 15 to 9 percent of the forest land, a 

loss of about 1 million acres. The oak/hickory and maple/beech/birch forest-type 

groups dominate Pennsylvania’s woods with nearly 9 out of 10 acres of the forest land. 

In terms of age, only 4 percent of this forest land in these two groups is in the 0- to 

20-year-old age class. This compares to 72 percent of the acreage in these groups that 

is 60 years and older.

Results of the browse impact assessment show that about 83 percent had medium or 

high levels of browse impact on understory plants (Fig. 60). Only 17 percent of the 

samples had low browse levels. 

19 

64 

17 

0 20 40 60 

High or very high 

Moderate 

Very low or low 

Percentage of Plots 

Browse Impact 

Figure 60.—Distribution of forested P2+ samples on forest land by browse 

impact, Pennsylvania, 2014. Error bars represent a 68 percent confidence 

interval around the estimated mean.
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 85

The total number of seedlings was estimated at 135.9 billion, or a statewide average of 

7,115 seedlings per acre. Sixty-five percent of the seedlings were less than 1 foot tall, 29 

percent were 1.0 to 4.9 feet, and 6 percent were 5.0 feet and taller (Fig. 61). No apparent 

pattern was found in the distribution of the number of seedlings per acre other than a 

greater frequency of samples in the highest class (more than 10,000 seedlings per acre, 

occurring on 56 percent of plots statewide) across the northern tier (Fig. 62).

Fifty-two species/species groups were encountered by the regeneration indicator 

samples. Maple was the most common genus with roughly half of the seedlings 

(Fig. 63). Ash ranked second with 10 percent. All the other genera had less than 

10 percent of the population. The five species with the largest number of seedlings 

were red maple (31 percent of the seedlings), white ash (9 percent), black cherry 

(7 percent), sugar maple (6 percent), and American beech (6 percent). There was 

also an abundance of species that are not capable of achieving high canopy, such as 

serviceberry and hawthorn species.

Comparing species abundance by using the percentage of the total number of trees 

by size class highlights potential pathways for future canopy dominants (Fig. 64). 

Prospective “gainers” are those species with relatively high percentages of stems 

in the regeneration pool of seedlings and saplings compared to larger trees. Red 

maple, birch species, American beech, and the “other” group are the most apparent 

gainers. The situation for ash species appears favorable; however, expectations for the 

ashes should be tempered with information on the prospective demise of ash due to 

impacts of the emerald ash borer. Most species in the “other” group occupy low- to 

mid-canopy position, such as striped maple and sassafras. Prospective “losers” in the 

process of developing future canopy dominants are species with lower percentages in 

the regeneration pool than the adult pool. The list of potential losers includes sugar 

maple, black cherry, red oak, white oak, hickory/walnut, yellow-poplar, and eastern 

hemlock. The distribution of stem abundance by size class is out of balance for these 

species with seedlings, saplings, and young adults rare compared to older adults. 

Many of the species in the overstory of Pennsylvania’s forests (e.g., the oaks and 

yellow-poplar) are either intolerant or intermediate in shade tolerance and typically 

require significant disturbance for a successful regeneration process.
86 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

Figure 61.—Total and average number of seedlings per acre on forest land by 

height class, Pennsylvania, 2014. Error bars represent a 68 percent confidence 

interval around the estimated mean.

0 20,000 40,000 60,000 80,000 100,000 

Total Number of Seedlings 

Seedling Length 

0 1,000 2,000 3,000 4,000 5,000 

2.0-11.9 inches 

1.0-4.9 feet 

5.0 feet and longer 

Number of Seedlings per Acre 

2.0-11.9 inches 

1.0-4.9 feet 

5.0 feet and longer Seedling Length 

A

B
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 87

Figure 62.—Percentage of forested P2+ samples on forest land by class 

of number of seedlings per acre (A) and distribution of seedling classes (B), 

Pennsylvania, 2014. Error bars represent a 68 percent confidence interval 

around the estimated mean. Depicted plot locations are approximate.

0 10 20 30 40 50 60 

>10,000 

5,001-10,000 

0-5,000 

Percentage of Plots 

Number of Seedlings per Acre 

Seedlings per Acre

l 1-5,000 l 5,001-10,000 l >10,000

A

B
88 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

0 5 10 15 20 25 30 35 40 45 50 

Red maple 

Total Number of Seedlings (billions) 

0 500 1,000 1,500 2,000 2,500 3,000 

Red maple 

Average Number of Seedlings 

per Acre of Forest Land 

0 5 10 

Chokecherry 

Black oak 

Pignut hickory 

American elm 

Eastern white pine 

Scrub oak 

American hornbeam 

White oak 

Eastern hophornbeam 

Yellow-poplar 

Hawthorn spp. 

Blackgum 

Chestnut oak 

Northern red oak 

Sassafras 

Striped maple 

Sweet birch 

Serviceberry spp. 

American beech 

Sugar maple 

Black cherry 

White ash 

Total Number of Seedlings (billions) 

Species 

0 200 400 600 800 

Chokecherry 

Black oak 

Pignut hickory 

American elm 

Eastern white pine 

Scrub oak 

American hornbeam 

White oak 

Eastern hophornbeam 

Yellow-poplar 

Hawthorn spp. 

Blackgum 

Chestnut oak 

Northern red oak 

Sassafras 

Striped maple 

Sweet birch 

Serviceberry spp. 

American beech 

Sugar maple 

Black cherry 

White ash 

Average Number of Seedlings 

per Acre of Forest Land 

Species 

A B

C D

Figure 63.—Number of seedlings (A and C) and average number of seedlings per acre (B and D) on forest 

land by species for species with at least 1 percent of the total number of seedlings, Pennsylvania, 2014. 

Error bars represent a 68 percent confidence interval around the estimated mean.
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 89

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

2.0 to 11.9 inches 

1.0 to 4.9 feet 

5 feet 

1.0-2.9 3.0-4.9 5.0-6.9 7.0-8.9 

9.0-10.9 

11.0-12.9 

13.0-14.9 15.0-16.9 17.0-18.9 19.0-20.9 21.0-28.9 

29.0+ 

Percent 

Seedling Length or Diameter Class 

n Other

n Eastern hemlock

n American beech

n Yellow-poplar

n Hickory/walnut

n Birch

n Ash

n White oak

n Red oak

n Black cherry

n Sugar maple

n Red maple

Figure 64.—Percentage of total number of seedlings, live saplings, 

and dominant and codominant growing-stock trees (adults; larger 

than 5.0 inches in diameter) on forest land for select species 

by seedling height or diameter class, Pennsylvania, 2012–2014 

(seedlings) and 2010–2014 (adults). Species were selected based 

on total aboveground biomass. Size classes are height classes for 

seedlings, and 2-inch diameter classes for saplings and adults. 
90 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

The PRS has provided an array of metrics designed to address objectives that range 

from replacing timber species to replacing any tree species at all. The metrics vary 

depending on the list of species used for evaluating existing tree seedlings and 

saplings found in the samples. Five species groups were used:

• Commercially desirable species preferred for timber management

• All commercial species

• High-canopy dominant species that make up at least 1 percent of the State’s tree biomass

• All high-canopy species

• All tree species including undesirable and low-canopy species.

The findings are expressed as a population estimate of the percentage of samples 

deemed to have adequate stocking of tree seedling and sapling regeneration.

Findings of the first PRS analysis conducted using the 1989 periodic inventory data 

are not directly comparable to these results because the impact of herbivory was not 

included in the assessment in the same manner (McWilliams et al. 1995). However, 

the analysis did examine a range of findings from low to high deer impact to offer a 

range for consideration by decisionmakers. The most conservative estimates based on 

low herbivory impact showed that only 21, 28, and 41 percent were adequately stocked 

with desirable, commercial, or any tree species, respectively. These findings provide a 

benchmark for comparison to the more recent results of the annual inventory.

The results for the two commercial species groups follow a similar pattern of slight 

decreases from 2004 to 2009 and then an increase in 2014 with the highest percentages 

reported so far. Currently, the percentage of samples in the desirable and commercial 

groups was 41 and 59 percent, respectively (Fig. 65). The difference between these two 

groups was that the commercial group included American beech and birch; the 

desirable group did not. The results for the all-tree species group have shown 

improvement throughout the study period. For the two canopy replacement groups, the 

trends were similar to the commercial groups, but the percentages with adequate 

regeneration were slightly higher (Fig. 66). For three of the six regions (the Southwest, 

South Central, and Northwest), the percentage of samples in the desirable species group 

exceeded the statewide percentage in 2014 (Fig. 67). All regions except the South 

Central and Southeast equaled or exceeded the 2014 statewide average for percentage of 

plots adequately stocked with regeneration for high canopy dominant species (Fig. 68). 

The statewide average for percentage of plots adequately stocked with regeneration for 

all high-canopy species in 2014 was exceeded only in the Northeast, Southwest, and 

South Central regions. See the appendix for a list of tree species recorded in 

Pennsylvania with commercial and canopy status groups.
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 91

40 37 41 

53 51 

59 58 59 

68 

0 

10 

20 

30 

40 

50 

60 

70 

80 

2004 2009 2014 

Percent 

Inventory Year 

n Desirable 

n Commercial 

n All species 

Figure 65.—Percentage of regeneration samples adequately stocked with 

advance regeneration for stands from 40- to 75-percent stocked with live trees 

for the commercial and all-species groups, Pennsylvania.

49 49 53 54 52 

59 58 58 

68 

0 

10 

20 

30 

40 

50 

60 

70 

80 

2004 2009 2014 

Percent 

Inventory Year 

n High canopy dominants 

n All high canopy 

n All species 

Figure 66.—Percentage of regeneration samples adequately stocked with 

advance regeneration for stands from 40- to 75-percent stocked with live trees 

for the high-canopy and all-species groups, by inventory year, Pennsylvania.
92 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

Northwest 

36 34 

46 45 45 

57 

31 29 33 

49 48 56 

North Central 

Northeast 

Southwest 

50 45 

57 53 54 62 

45 45 48 

58 55 61 

South Central 

41 38 37 

56 55 63 

36 31 24 

41 42 

30 

Southeast 

0 

20 

40 

60 

80 

2004 2009 2014 

Percent 

Inventory Year 

n Desirable

n All commercial 

0 

20 

40 

60 

80 

2004 2009 2014 

Percent 

Inventory Year 

0 

20 

40 

60 

80 

2004 2009 2014 

Percent 

Inventory Year 

0 

20 

40 

60 

80 

2004 2009 2014 

Percent 

Inventory Year 

0 

20 

40 

60 

80 

2004 2009 2014 

Percent 

Inventory Year 

0 

20 

40 

60 

80 

2004 2009 2014 

Percent 

Inventory Year 

n Desirable

n All commercial 

n Desirable

n All commercial 

n Desirable

n All commercial 

n Desirable

n All commercial 

n Desirable

n All commercial 

Figure 67.—Percentage of regeneration samples adequately stocked with advance regeneration for stands 

from 40- to 75-percent stocked with live trees for the commercial species groups by eco-political region 

and inventory year, Pennsylvania.
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 93

53 48 

57 57 53 62 

50 49 51 58 56 61 

Northwest 

47 46 54 49 48 56 

42 40 

55 46 45 

57 

38 38 

21 

42 43 

30 

52 52 60 56 55 

64 

North Central 

Northeast 

Southwest South Central 

Southeast 

0 

20 

40 

60 

80 

2004 2009 2014 

Percent 

Inventory Year 

0 

20 

40 

60 

80 

2004 2009 2014 

Percent 

Inventory Year 

0 

20 

40 

60 

80 

2004 2009 2014 

Percent 

Inventory Year 

0 

20 

40 

60 

80 

2004 2009 2014 

Percent 

Inventory Year 

n High canopy dominants

n All high canopy 

0 

20 

40 

60 

80 

2004 2009 2014 

Percent 

Inventory Year 

0 

20 

40 

60 

80 

2004 2009 2014 

Percent 

Inventory Year 

n High canopy dominants

n All high canopy 

n High canopy dominants

n All high canopy 

n High canopy dominants

n All high canopy 

n High canopy dominants

n All high canopy 

n High canopy dominants

n All high canopy 

Figure 68.—Percentage of regeneration samples adequately stocked with advance regeneration for stands 

from 40- to 75-percent stocked with live trees for the high-canopy species groups by ecopolitical region 

and inventory year, Pennsylvania.
94 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

What this means

Pennsylvania’s forest ecosystems adapted following large-scale forest clearing of the 

late 19th and early 20th centuries (Nowacki and Abrams 2014). This process resulted 

in a largely even-aged forest. After a century of growth and wildfire suppression, the 

forests continue to age and have withstood many catastrophic stressors such as the 

chestnut blight (Cryphonectria parasitica) and gypsy moth (see Gypsy Moth starting 

on p. 111). A lack of management and fire means that the mix of species that make up 

the future forest will be different from today as red maple and other mesophytic and 

shade-tolerant species expand their distribution (Fei and Steiner 2007, Nowacki and 

Abrams 2008). 

The Commonwealth’s forests face a variety of contemporary health risks. Some 

prominent examples are herbivory, invasive plants, insects and diseases, and forest 

fragmentation and parcelization. Regeneration is an integral process in ameliorating 

risks and managing composition and structure during the early phases of forest 

development following a stand initiation disturbance. 

Deer browsing is a major factor affecting regeneration in the eastern United 

States (Russell et al. 2001, White 2012). The finding that nearly 9 out of 10 of 

the regeneration indicator samples had at least medium browse is an indication 

that browsing is having an impact. In general, forest managers need to consider 

regeneration management methods that limit the effects of deer browsing during the 

stand initiation phase when browse impact is medium or high. Lacking intervention, 

areas with high deer populations will have limited reproduction of desirable seedlings. 

Impacts of deer browsing are especially problematic in combination with habitat 

fragmentation, which occurs more commonly in heavily populated areas of the State 

(Augustine and Decalesta 2003). 

The results suggest a continuing shift toward red maple and other mesophytic and 

shade-tolerant species (i.e., birches, and American beech). The most noteworthy issue 

is a proliferation of red maple seedlings and saplings. Red maple is mesophytic and 

shade-tolerant, which has given it an advantage during the regeneration phase in stands 

with low light on a wide variety of sites, from very wet to very dry. This has created an 

imbalance in the distribution of trees by size class with red maple seedlings dominating 

the seedling, sapling, and young adult size classes at the expense of other species that are 

intermediate or shade-intolerant, and more site-specific (e.g., oaks and hickories). 

Regenerating oak/hickory forests is often difficult in the eastern United States 

and management challenges, such as lack of fire and overbrowsing, are recurrent 

across the forested landscape (Holt and Fischer 1979). The size-class imbalance 

just described is especially problematic for oak/hickory forests, which are the most 

common forest-type group in the State, occupying more than half of the forest land. 
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 95

This means that forest policy makers and managers need to consider these trends 

when planning for the future of oak/hickory. The long-term future of oak-dominated 

forests will depend on management strategies that establish oak seedlings and foster 

development of saplings and adults along with associate species (hickories and 

yellow-poplar); these strategies require stand-tending prescriptions that forestall 

development of shade-tolerant species (Abrams 1992, Dey 2014).

Maple/beech/birch is the second most important forest-type group in Pennsylvania, 

with about one-third of the forest land. The future of this forest-type group appears to 

be positive because of the large population of red maple, birch, and American beech 

seedlings and saplings that could lead to eventual canopy dominance. It should be 

noted that many of the American beech seedlings in the samples are suppressed root 

sprouts commonly referred to as “beech brush,” which do not develop into mature 

canopy trees. Beech brush represents an obstacle to establishing preferred species and 

often needs to be weeded out by using mechanical or herbicide prescriptions.

Regeneration has improved over the last 25 years as indicated by both the commercial 

and high-canopy metrics in the PRS analysis. The metric for all tree species 

highlighted improvements that were about 10 percent higher than the other metrics. 

This difference is due to the inclusion of undesirable and low-canopy species, which 

means managers need to consider this issue in making management prescriptions in 

stands where such species compete with preferred species.

In 1989, regeneration was described as “impoverished” across all ownerships, foresttype groups, and regions of the Commonwealth. The results presented here represent 

very important trends in the history of Pennsylvania’s forests. It is well known 

that deer browsing is the major driver that has limited regeneration quality and 

abundance. Ongoing deer management policies and programs implemented by the 

Pennsylvania Game Commission have resulted in monumental improvements in the 

delicate balance between healthy forest and wildlife habitat (Rosenberry et al. 2009).

There is still considerable room for improving regeneration as stands are prepared 

for harvest, particularly in the case of providing a better mix of preferred species. 

Weed species and other competing vegetation need to be controlled to ensure that the 

composition, structure, and function of the future forests meet managers’ goals and 

objectives. Managers need to consider strategies that take into account prospective 

conversion of critical forest types, such as oak/hickory forests, where advance 

regeneration is dominated by red maple and shade-intolerant species. The dearth 

of young forest habitat means there are tremendous opportunities for creating new 

young forests by actively managing stands prior to harvest. An increase in the area 

of young stands would also expand food sources in areas with low availability, thus 

reducing browsing pressure.
96 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

Eventually, most forest stands will undergo either anthropogenic or natural stand 

replacement events, such as harvest or mortality, and will require regeneration to 

establish new young forest. Successful establishment of healthy young forests depends on 

forest regeneration. The oak/hickory and maple/beech/birch forest-type groups require 

advance regeneration to secure a component of desirable species. Management options 

for establishing regeneration of preferred species will also be driven by the amount of 

browse present. The key to successful regeneration will be diligent stewardship and 

continued monitoring to ensure a bright future for Pennsylvania’s forest ecosystems.

Tree Crown Health and Damage

Background

The crown condition of trees is influenced by various biotic and abiotic stressors. 

Biotic stressors include native or introduced insects, diseases, invasive plant species, 

and animals. Abiotic stressors include drought, flooding, cold temperatures or freeze 

injury, nutrient deficiencies, the physical properties of soils that affect moisture and 

aeration, and toxic pollutants. 

Invasions by exotic diseases and insects are one of the most important threats to the 

productivity and stability of forest ecosystems around the world (Liebhold et al. 1995, 

Pimentel et al. 2000, Vitousek et al. 1996). Over the last century, Pennsylvania’s forests 

have suffered the effects of well-known exotic and invasive agents such as chestnut 

blight, Dutch elm disease, gypsy moth, hemlock woolly adelgid, and the beech bark 

disease complex. More-recent invaders include the emerald ash borer and thousand 

cankers disease (a complex involving the beetle Pityophthorus juglandis and the 

fungus Geosmithia morbida).

Tree-crown dieback has been shown to be the best crown variable to use for 

predicting tree survival (Morin et al. 2015). Crown dieback was collected on 294 P2+ 

plots (a subset of FIA Phase 2 plots, on which additional measurements are taken) 

and is defined as recent mortality of branches with fine twigs, reflecting the severity 

of recent stresses on a tree. A crown was labeled as “poor” if crown dieback was 

greater than 20 percent. This threshold is based on findings by Steinman (2000) that 

associated crown ratings with tree mortality. 

Tree damage is assessed on trees at least 5.0 inches d.b.h. on all plots. Up to three of 

the following types of damage can be recorded: insect damage, cankers, decay, fire, 

animal damage, weather, and logging damage. If more than three types of damage are 

observed, decisions about which three to record are based on the relative impact on 

tree health (U.S. Forest Service 2012).
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 97

What we found

The incidence of poor crown condition is rare in Pennsylvania. Very few plots had 

greater than 20 percent of tree basal area with poor crowns (Fig. 69). The species with 

the highest proportion of live basal area containing poor crowns is white ash (10 

percent; Table 7), but plots with higher relative proportion of white ash with poor 

crowns have a random spatial pattern across the State. Conversely, all other species 

had a very low occurrence of poor crowns. The proportion of eastern hemlock basal 

area with poor crowns dropped substantially since 2009, from 5 to 2 percent.

Average crown dieback ranged from less than 1 percent for sweet birch and yellowpoplar to 3 percent for white ash (Table 8). An analysis of trees from the 2009 

inventory remeasured in the 2014 inventory confirmed that the proportion of trees 

that die increases with increasing crown dieback (Fig. 70). Nearly 50 percent of trees 

with crown dieback above 20 percent in the 2009 inventory were dead when visited in 

the 2014 inventory.

Damage was recorded on about 27 percent of the Pennsylvania trees, but there was 

considerable variation between species. The most frequent damage on all species was 

decay (19 percent of trees), but this ranged from 4 percent of eastern hemlock to 30 

percent of sugar maple. Notably, insect damage was present on 10 percent of eastern 

hemlock trees and 8 percent of sugar maple trees. The occurrence of all other injury 

types was very low (Fig. 71).

Percent of Live Basal Area with Poor Crowns

l 0.0 l 0.1-5.0 l 5.1-20 l >20 n Nonforest n Forest

Figure 69.—Percentage of live basal area with poor crowns, Pennsylvania, 2014. Depicted plot locations 

are approximate. 

Projection: Pennsylvania State Plane North, NAD83. Sources: U.S. Forest Service, Forest Inventory and Analysis program, 2009, 2014. Geographic base data are 

provided by the National Atlas of the USA®. FIA Data and Tools are available online at http://www.fia.fs.fed.us/tools-data/.

Cartography: R.S. Morin, U.S. Forest Service, October 2015.
98 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

Table 7.—Percentage of live-tree basal area with poor 

crowns, Pennsylvania, by inventory year 

Species

Percentage of basal area 

with poor crowns

2009 2014

White ash 6.1 10.3

Eastern hemlock 4.9 1.7

Red maple 2.2 1.7

Chestnut oak 0.6 1.6

Sugar maple 1.3 1.3

Black cherry 4.1 1.3

Sweet birch 0.4 0.8

Yellow-poplar 0.0 0.0

White oak 0.1 0.0

Northern red oak 1.3 0.0

Table 8.—Mean crown dieback expressed as a percentage and other statistics for live 

trees (>5 inches d.b.h.) on forest land by species, Pennsylvania, 2014

Trees 

Species sampled Mean SE Minimum Median Maximum

- - - - - - - - - - - - - - - percent - - - - - - - - - - - - - - -

White ash 222 3.1 0.80 0 0 99

Black cherry 613 2.2 0.27 0 0 99

Red maple 1,310 2.0 0.20 0 0 99

Chestnut oak 351 1.7 0.34 0 0 80

Sugar maple 410 1.6 0.35 0 0 99

Eastern hemlock 444 1.4 0.30 0 0 80

White oak 129 1.2 0.23 0 0 15

Northern red oak 278 1.0 0.14 0 0 15

Sweet birch 449 0.9 0.25 0 0 99

Yellow-poplar 145 0.3 0.09 0 0 5
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 99

0

10

20

30

40

50

60

70

80

90

100

0 1-10 11-20 >20 

Frequency (percent) 

Crown Dieback (percent) 

n Cut

n Mortality

n Survivor

Figure 70.—Crown dieback distribution by tree survivorship for 

remeasured trees, Pennsylvania, 2009 to 2014.

50 70 90 110 

All 

Black cherry 

Chestnut oak 

Eastern hemlock 

Northern red oak 

Red maple 

Sugar maple 

Sweet birch 

White ash 

White oak 

Yellow-poplar 

Percentage of Trees 

Species 

n None 

n Animal 

n Cankers 

n Decay 

n Insect damage 

n Logging/human 

n Other 

n Weather 

Figure 71.—Percentage of trees with damage, Pennsylvania, 2014. Note that bars do not 

sum to 100 because multiple damages can be recorded on trees.
100 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

What this means

The majority of tree species in Pennsylvania were generally in good health. As in most 

eastern U.S. forests, decay was the most commonly observed damage. This is not 

unusual because nearly 70 percent of Pennsylvania’s forests are large diameter stands 

composed of mature trees. The high occurrence of insect damage for sugar maple is 

most likely due to the sugar maple borer (Glycobius speciosus), which can cause lumber 

defects, but rarely causes mortality (Hoffard and Marshall 1978, Morin et al. 2016). The 

high occurrence of insect damage for eastern hemlock is due to hemlock woolly adelgid. 

The health of tree crowns in American beech, eastern hemlock, and ash species should 

be monitored closely because of the expected impacts of beech bark disease, hemlock 

woolly adelgid, and emerald ash borer, respectively (see Tree Pests and Diseases of 

Special Concern section starting on p. 106).

Invasive Plants

Background

Invasive plant species (IPS) are both native and nonnative and have negative ecological 

impacts. Several characteristics contribute to their success, such as prolific seed 

production, rapid growth, vegetative propagation, and endurance of harsh conditions. IPS 

can quickly invade forests, changing the availability of light, water, and nutrients (Kuebbing 

et al. 2014). IPS can form dense understories that inhibit regeneration and reduce wildlife 

diversity and abundance by altering forest structure and forage availability (Pimentel et 

al. 2005). Invasive species monitored in forest ecosystems also affect agricultural systems 

(Kurtz 2013). An example is common barberry, an alternate host for wheat stem rust 

(Puccinia graminis), which can cause the complete loss of grain fields. Common buckthorn 

is another troublesome IPS as it is an alternate host for the soybean aphid (Aphis glycines). 

Although there are some beneficial uses for these invaders (e.g., culinary and medicinal 

use, and soil contaminant extraction) (Kurtz 2013), the negative effects outweigh these 

benefits. Two examples of past uses overshadowed by current problems are: multiflora 

rose, once promoted for planting as a living pasture fence, and autumn-olive, widely 

planted to restore degraded land by fixing soil nitrogen and as wildlife habitat with its 

abundant fruit production. Now, each year, inspection, management, and mitigation of 

IPS cost billions of dollars (Kurtz 2013, Pimentel et al. 2005).

To monitor IPS, FIA assessed the presence of 40 IPS (39 species and one 

undifferentiated genus4

; Table 9) on 688 forested P2+ plots during the 2014 inventory. 

To maintain regional consistency, the species list is not customized for Pennsylvania, 

4 Hereafter these 39 species and one undifferentiated genus (nonnative bush honeysuckles, Lonicera spp.) are 

referred to as “invasive species,” “invasive plants,” or “IPS.”
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 101

Table 9.—Common and scientific names of invasive plants monitored 

and recorded on Phase 2 invasive plots, Pennsylvania, 2014

Tree Species

*Ailanthus Ailanthus altissima

*Black locust Robinia pseudoacacia 

Chinaberry Melia azedarach

Chinese tallow Triadica sebifera

*Norway maple Acer platanoides

*Paulownia Paulownia tomentosa

Punktree Melaleuca quinquenervia

*Russian-olive Elaeagnus angustifolia

Saltcedar Tamarix ramosissima

Siberian elm Ulmus pumila

Silktree Albizia julibrissin

Shrub Species

*Autumn-olive Elaeagnus umbellata

*Common barberry Berberis vulgaris

*Common buckthorn Rhamnus cathartica

European cranberrybush Viburnum opulus

*European privet Ligustrum vulgare

*Glossy buckthorn Frangula alnus

*Japanese barberry Berberis thunbergii

*Japanese meadowsweet Spiraea japonica

*Multiflora rose Rosa multiflora

*Nonnative bush honeysuckle Lonicera spp.

Vine Species

*English ivy Hedera helix

*Japanese honeysuckle Lonicera japonica

*Oriental bittersweet Celastrus orbiculatus

Herbaceous Species

Bohemian knotweed Polygonum xbohemicum 

*Bull thistle Cirsium vulgare

*Canada thistle Cirsium arvense

*Creeping jenny Lysimachia nummularia

*Dames rocket Hesperis matronalis

European swallow-wort Cynanchum rossicum

*Garlic mustard Alliaria petiolata

*Giant knotweed Polygonum sachalinense

*Japanese knotweed Polygonum cuspidatum

*Leafy spurge Euphorbia esula 

Louise's swallow-wort Cynanchum louiseae 

*Purple loosestrife Lythrum salicaria

*Spotted knapweed Centaurea stoebe ssp. micranthos

Grass Species

*Common reed Phragmites australis

*Nepalese browntop Microstegium vimineum

*Reed canarygrass Phalaris arundinacea

*Found on P2 invasive plots, Pennsylvania, 2014.
102 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

but represents native and nonnative species of regional concern. When reviewing 

these data, remember that the inventory takes place only on forested land so areas 

with less forest have fewer plots.

What we found

Of the 40 invasive plants monitored, 30 were observed (Table 10). Multiflora rose 

(Fig. 72) was the most commonly observed species (326 plots; 47 percent) and was 

found throughout the State. Nonnative bush honeysuckles were the second most 

common IPS; they occurred on 25 percent of the plots and were also found throughout 

Pennsylvania. Garlic mustard and Japanese barberry were found on 23 and 20 percent 

of plots, respectively. One or more of the monitored invasive species were present on 

421 plots, with the number of invasive species per plot ranging from 0 to 11 (Fig. 73). 

Plots in the southern half of the State had the greatest number of IPS per plot (Fig. 74). 

Comparing the 2014 inventory to the 2009 inventory, there was a similar percentage 

of multiflora rose, garlic mustard, and Japanese barberry, but it is important to note 

that there were only about half as many plots measured in the 2009 inventory (337 

forested plots sampled; McCaskill et al. 2013). Regionally, Pennsylvania’s forests 

have a higher percentage of plots invaded (61 percent) than neighboring New York 

(51 percent; Widmann et al. 2015) but a lower percentage than Ohio (93 percent; 

Widmann et al. 2014). The number of IPS observed was similar across these states 

with 29 species in New York and 28 in Ohio. 
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 103

Table 10.—Invasive plants recorded on Phase 2 invasive plots, Pennsylvania, 

2014

Species Number of plots Percentage of plots

Multiflora rose 326 47.4

Nonnative bush honeysuckles 173 25.1

Garlic mustard 161 23.4

Japanese barberry 140 20.3

Nepalese browntop 120 17.4

Black locust 90 13.1

Autumn-olive 76 11

Oriental bittersweet 71 10.3

Japanese honeysuckle 59 8.6

European privet 51 7.4

Ailanthus 40 5.8

Norway maple 21 3.1

Creeping jenny 14 2

Dames rocket 14 2

Canada thistle 11 1.6

Glossy buckthorn 11 1.6

Common barberry 7 1

Common buckthorn 7 1

Bull thistle 6 0.9

Japanese knotweed 5 0.7

Reed canarygrass 4 0.6

Giant knotweed 3 0.4

Spotted knapweed 3 0.4

English ivy 2 0.3

Japanese meadowsweet 2 0.3

Paulownia 2 0.3

Russian-olive 2 0.3

Common reed 1 0.1

Leafy spurge 1 0.1

Purple loosestrife 1 0.1
104 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

Figure 72.—Distribution of multiflora rose on forest land, Pennsylvania, 2014. Depicted plot locations are 

approximate. 

Projection: Pennsylvania State Plane North, NAD83. Data source: U.S. Forest Service, Forest Inventory and Analysis program, 2010–2014 Phase 2 invasive 

data. Source for state and county layers: ESRI Data and Maps 10.1. Source for forest/nonforest: NLCD 2006.

Cartography: C.M. Kurtz, U.S. Forest Service, December 2015.

0 

50 

100 

150 

200 

250 

300 

0 1 2 3 4 5 6 7 8 9 10 11 

Number of P2 Invasive Plots 

Number of invasive Plant Species per Plot 

Figure 73.—Number of P2 invasive plots, by number of invasive plant 

species reported, Pennsylvania, 2014. 
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 105

What this means

Invasive species are a concern throughout the Commonwealth because many IPS are 

effective competitors and can change forested ecosystems by inhibiting tree regeneration, 

displacing native species, and altering forage. Furthermore, IPS can cause negative 

economic impacts by reducing timber yield and aesthetic beauty as well as making it 

more difficult to regenerate stands without implementing measures to control invasive 

species. Although some invasive plants become established with little to no disturbance, 

development (residential and industrial) of adjacent areas contributes to forest invasion 

as does preferential browsing of non-invasive species by white-tailed deer. Additional 

investigation may reveal correlations between IPS and influential site and regional features 

as well as IPS factors associated with forest dynamics. Continual monitoring and reporting 

of IPS is necessary to inform managers and the public of their occurrence and spread.

Number of Invasive Plant Species per Plot

l 0 l 1-2 l 3-4 l 5-7 l 8-11

Figure 74.—Distribution and abundance of invasive plant species on forest land, Pennsylvania, 2014. 

Depicted plot locations are approximate.

Projection: Pennsylvania State Plane North, NAD83. Data source: U.S. Forest Service, Forest Inventory and Analysis program, 2010–2014 Phase 2 invasive 

data. Source for state and county layers: ESRI Data and Maps 10.1. Source for forest/nonforest: NLCD 2006.

Cartography: C.M. Kurtz, U.S. Forest Service, December 2015.
106 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

Tree Pests and Diseases of Special Concern

EMERALD ASH BORER

Background

A wood-boring beetle native to Asia, emerald ash borer (EAB; Agrilus planipennis) is 

a pest of all North American ash (Fraxinus spp.) and has recently been found to attack 

white fringetree (Chionanthus virginicus), an understory shrub native to southern 

Pennsylvania but not tallied by FIA (Cipollini 2015, Herms and McCullough 2014, 

Natural Resources Conservation Service 2015). Although EAB shows some preference 

for stressed trees, all trees greater than 1 inch in diameter are susceptible regardless 

of vigor (Herms and McCullough 2014). Since its 2002 discovery in southeastern 

Michigan, EAB has been identified in 25 states (as of December 2015). EAB has been 

present in Pennsylvania since 2007 and was confirmed in 62 counties as of September 

2016 (Pennsylvania State University 2016b). 

What we found

Pennsylvania forest land contains an estimated 270.9 million ash trees (≥1-inch d.b.h.), 

about 3 percent of total species composition, which represents a 12 percent decrease 

since 2004. White ash is the most numerous ash species in the State, making up 94 

percent of total ash abundance; green ash and black ash make up 4 and 2 percent, 

respectively. Ash is distributed across Pennsylvania; however, the majority of ash is 

concentrated in the northern half of the State (Fig. 75). Ash mortality has increased 

substantially since 1989, more than doubling from 6.3 million cubic feet to 14.4 million 

cubic feet. The mortality rate for ash statewide was 1.16 percent of net volume per year, 

higher than all species (0.9 percent). In counties containing EAB, the rate of ash 

mortality increases with increasing length of infestation (Fig. 76); however, as a group, 

counties where EAB has not been detected had the highest rate of ash mortality. Ash 

volume continued to increase, reaching an estimated net live tree volume of 1.8 billion 

cubic feet on forest land, 9 percent higher than the 2004 estimate.

What this means

Even though ash is a relatively small component of overall forest land, its prominence 

in rural, riparian, and urban forests makes EAB a significant threat to the health and 

composition of Pennsylvania’s forests. The loss of ash in forested ecosystems will 

affect species composition and alter community dynamics while urban areas face 

significant costs for hazard mitigation, tree removal, and replacement. The increase in 
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 107

1,773

None detected

Figure 75.—Ash volume (trees at least 5 inches d.b.h.) on forest land, with year of first EAB detection, by 

county, Pennsylvania, 2014.

Projection: Pennsylvania State Plane North, NAD83. Sources: U.S. Forest Service, Forest Inventory and Analysis program, 2009; Pennsylvania Department of 

Conservation and Natural Resources, 2016. Geographic base data are provided by the National Atlas of the USA®. FIA Data and Tools are available online at 

http://www.fia.fs.fed.us/tools-data/.

Cartography: T. Albright, U.S. Forest Service, March 2016.

0 0.5 1 1.5 2 2.5 3 

Ash statewide 

All species statewide 

None as of 2015 

2007-2009 

2010-2012 

2013-2015 

Mortality Rate (percentage of volume) 

Year EAB First Confirmed 

Figure 76.—Ash mortality rates by year EAB detected, ash mortality rate 

statewide, and mortality rate for all tree species, Pennsylvania, 2014. Error 

bars represent a 68 percent confidence interval around the estimated mean.
108 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

the ash mortality rate since first detection suggests that the northern tier counties will 

experience more ash mortality in the coming years. Furthermore, EAB can exist at 

low densities before detection (Herms and McCullough 2014) and this may partially 

explain the elevated mortality rate in areas with no confirmed EAB infestation. Ash 

also faces more challenges; for example, ash yellows, a disease that causes decline 

of ash species, is known to exist in Pennsylvania but data on its extent are lacking. 

Continued monitoring of ash resources will help identify long-term impacts of EAB 

in forested settings as well as the extent of other causes of elevated mortality.

HEMLOCK WOOLLY ADELGID

Background

Eastern hemlock is the Pennsylvania state tree and a major component of the State’s

forests. It ranks as the sixth most important species in terms of cubic-foot volume, but its

value goes far beyond timber. The wildlife habitat and food it provides, and the unique

niche it fills in riparian areas by shading streams and lowering water temperatures, make it

ecologically very important. Forests with the highest proportion of hemlock volume are

generally located throughout the northern tier, specifically in the North Central and

Northeast regions (Fig. 77). Hemlock woolly adelgid (HWA; Adelges tsugae) is an insect

pest native to East Asia and was first found in the eastern United States in the 1950s (Ward

et al. 2004). Since then, it has slowly expanded its range, often reaching high densities and

causing widespread defoliation and eventually mortality (McClure et al. 2001, Orwig et al.

2002). Mortality generally begins to increase dramatically after about 15 years of

infestation (Morin and Liebhold 2015).

What we found

HWA was first discovered in southeastern Pennsylvania in 1979 and it has since spread

to 59 of the 67 counties (Fig. 77). Over 94 percent of the estimated 1.96 billion cubic feet

of hemlock in the State was in counties that had an HWA population as of 2014. Thirtyone percent of hemlock volume was in areas infested for 15 years or more. An additional

23 percent of the State’s hemlock volume was in counties infested for 10 to 15 years.

Hemlock volume continued to increase, though at varying levels as the length of 

infestation correlates to slower rates of increase. Areas infested with HWA for 5 years 

or less saw a 25 percent increase in hemlock volume from 2004 to 2014 (Fig. 78). 

Similarly, areas infested between 5 and 10 years increased hemlock volume by 28 

percent over the same period. Infestations 10 to 15 years old held volume increases 

to 12 percent, while areas infested for 15 years or more had a minimal increase in 

volume of 1 percent from 2004 to 2014.
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 109

Counties infested with HWA show substantial increases in the hemlock mortality rate 

around 15 years after HWA appears. Hemlock in counties infested with HWA in 2000 

had an average mortality rate of 2.1 percent of net volume per year in 2014 (Fig. 79). 

The mortality rate in counties infested for 10 to 15 years was 0.7 percent and the rate 

in counties infested for 10 years or less was 0.6 percent.

1,538

0

Figure 77.—Eastern hemlock volume (trees at least 5 inches d.b.h.) on forest land, with counties infested 

by HWA, by number of years of infestation, Pennsylvania, 2014.

Projection: Pennsylvania State Plane North, NAD83. Sources: U.S. Forest Service, Forest Inventory and Analysis program, 2009, and Forest Health Protection, 

2016. Geographic base data are provided by the National Atlas of the USA®. FIA Data and Tools are available online at http://www.fia.fs.fed.us/tools-data/.

Cartography: T. Albright, U.S. Forest Service, March 2016.
110 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

1.06 

2.08 

0.71 

0.55 

0.55 

0 0.5 1 1.5 2 2.5 

Statewide

average

>15 

11-15 

6-10 

1-5 

Hemlock Mortality Rate (percent of volume per year) 

Number of Years of H

WA Infestation 

Figure 79.—Average annual mortality of eastern hemlock expressed as 

a percentage of hemlock volume by number of years of HWA infestation, 

and the statewide average, Pennsylvania, 2014.

0 

100 

200 

300 

400 

500 

600 

700 

800 

1-5 (25%) 6-10 (28%) 11-15 (12%) >15 (1%) 

Volume (million cubic feet) 

Years of HWA Infestation 

n 2004

n 2009

n 2014 

Figure 78.—Eastern hemlock volume (trees at least 5 inches d.b.h.) on 

forest land, by inventory year and years of HWA infestation as of 2014, 

Pennsylvania. The percent volume increase between 2004 and 2014 

is shown in parentheses. Error bars represent a 68 percent confidence 

interval around the estimated mean.
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 111

What this means

HWA has already spread across most of Pennsylvania. In areas where it has been present 

for 15 years or more, hemlock mortality has increased substantially and volume growth 

has leveled off. Some of the areas with the highest densities of hemlock have not been 

infested long enough to have suffered major impacts, but hemlock mortality is likely to 

increase in the near future as an additional 450 million cubic feet of hemlock will move 

into the 15 year infestation category by 2019. If current trends continue, that will mean 

the majority of hemlock volume will have minimal increases in volume and mortality 

rates in excess of 2 percent of volume per year.

In an effort to forestall these effects, the Bureau of Forestry has developed the Eastern 

Hemlock Conservation Plan and has been treating high-value hemlocks in state parks 

and state forests since 2004. Predatory beetle releases have been conducted since 1999. 

The purpose of treating high-value hemlocks with insecticides is to keep hemlock 

habitat and trees protected until predatory beetles become established and contribute 

to hemlock woolly adelgid control.

The importance of hemlock in the forest ecosystem is hard to overstate. It is a late 

successional, highly shade tolerant species that is very long-lived and would be 

expected to be on the rise as forests age. The loss of hemlock as a result of HWA 

invasion has impacts on ecosystem properties such as stream temperatures and 

soil chemistry (Orwig et al. 2008, Stadler et al. 2005) so the status of this important 

species needs continued monitoring. With no effective landscape-level controls yet 

available, hemlock woolly adelgid will have a very significant lasting impact on the 

character of Penn’s Woods. 

GYPSY MOTH

Background

Gypsy moth (Lymantria dispar) first caused damage in Pennsylvania in the 1920s, but 

extensive damage began in about 1970. Since then, periodic outbreaks have occurred, 

making it the most destructive forest pest in the State. The largest outbreaks took 

place during the 1980s and early 1990s. Aerial surveys in 2006–2008 determined 

that gypsy moth populations were again on the rise; more than 2 million acres of 

defoliation were detected over that 3-year period. 

Quantifying gypsy moth defoliation can help land managers plan for suppression 

activities. Tree species were split into preferred and nonpreferred suitability classes 

based on previously published field and laboratory tests (Liebhold et al. 1995). Species 

from suitability class 1 were considered preferred and all others were considered 
112 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

nonpreferred. Annual mortality rates were calculated for preferred and nonpreferred 

species. Mortality was computed by using remeasured plots (originally surveyed 

2004–2008 and remeasured 2009–2013) as proportions of live volume at the time of the 

initial survey (i.e., annual mortality volume divided by live volume at time 1). Plots were 

assigned years of defoliation based on the 10 years before measurement; for example, a 

plot that was measured in 2010 was assigned the number of defoliations that occurred 

between 2000 and 2009. Historical defoliation records were recorded by U.S. Forest 

Service, Northeastern Area State and Private Forestry and assembled at the Northern 

Research Station, Morgantown, WV, and are available online (http://www.fs.fed.us/

ne/morgantown/4557/gmoth/atlas/#defoliation). These data were not based upon 

systematic surveys and therefore slight inconsistencies may exist among years and states 

in how gypsy moth defoliation was surveyed and recorded.

What we found

About 31 percent of the live tree volume in Pennsylvania’s forests is preferred by gypsy 

moth. Oaks and aspens are the most abundant preferred species in Pennsylvania. The 

density of preferred gypsy moth host species is highest in the mountainous region of 

central and northeastern Pennsylvania (Fig. 80). The largest gypsy moth defoliation 

events were concentrated in the Allegheny and Pocono Mountain regions of the State 

(Fig. 81). According to aerial surveys reported by U.S. Forest Service Forest Health 

Protection, between 2000 and 2014 nearly 3.3 million acres were defoliated at least 

one time (Fig. 82). More than 610,000 of those acres had two defoliations and nearly 

120,000 acres were defoliated three or more times. Most of the defoliated area 

occurred in forest land classified as the oak/hickory forest-type group. The annual 

mortality rate in species preferred by gypsy moth is more than double in areas 

defoliated two or more times in the 10-year period prior to plot remeasurement 

compared to areas with no defoliations over the same period (Fig. 83).
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 113

Percentage of Live Basal Area Preferred by Gypsy Moth

n 0-5 n 6-25 n 26-50 n 51-75 n >75 n Nonforest

Figure 80.—Percentage of live basal area in host tree species that are preferred by gypsy moth, 

Pennsylvania, 2009.

Projection: Pennsylvania State Plane North, NAD83. Sources: U.S. Forest Service, Forest Inventory and Analysis program, 2009. Geographic base data are 

provided by the National Atlas of the USA®. FIA Data and Tools are available online at http://www.fia.fs.fed.us/tools-data/.

Cartography: R.S. Morin, U.S. Forest Service, November 2015.

Years of Gypsy Moth Defoliation 2000-2014

n 0 n 1 n 2 n >2 n Nonforest

Figure 81.—Number of gypsy moth defoliations, Pennsylvania, 2000 to 2014. 

Projection: Pennsylvania State Plane North, NAD83. Sources: U.S. Forest Service, Forest Inventory and Analysis program, 2009; U.S. Forest Service, Forest 

Health Protection and its partners, 2016. Geographic base data are provided by the National Atlas of the USA®. FIA Data and Tools are available online at http://

www.fia.fs.fed.us/tools-data/.

Cartography: T. Albright, U.S. Forest Service, March 2016.
114 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

1 2 3 or more 

Acres Defoliated (thousands) 

Number of Defoliations

Figure 82.—Acres of gypsy moth defoliation by number of 

defoliations, Pennsylvania, 2000 through 2014.

0 

0.5 

1 

1.5 

2 

2.5 

3 

3.5 

0 1 2 

Annual Mortality Rate

(percentage of live volume) 

Years of Defoliation 

n Nonpreferred

n Preferred

Figure 83.—Annual mortality rate by gypsy moth host 

preference, Pennsylvania, 2011. Error bars represent a 68 

percent confidence interval around the estimated mean. Years of 

defoliation is based on the number of defoliations that occurred 

on a plot within the 10 years prior to measurement.
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 115

What this means

Gypsy moth has been affecting the forests of Pennsylvania for more than 40 years. 

During that time defoliation has been cyclical with peaks every 5 to 10 years (Fig. 84). 

Although defoliation does have an impact on the health and survival of host tree 

species, the Pennsylvania Department of Conservation and Natural Resources has a 

comprehensive suppression program to reduce the impacts of gypsy moth which 

includes aerial spray treatments when gypsy moth population cycles peak.

BEECH BARK DISEASE

Background

American beech is a major component of the maple/beech/birch forest-type group,

which covers 33 percent of the forested area in Pennsylvania (Fig. 20). American beech

is an important pulpwood and firewood species and is also an important wildlife mast

producer. Beech bark disease (BBD) is an insect-fungus complex involving the beech 

scale insect (Cryptococcus fagisuga Lind.) and the exotic canker fungus Neonectria 

coccinea (Pers.:Fr.) var. faginata Lohm. or the native Neonectria galligena Bres. This 

complex kills or injures American beech. Three phases of BBD are generally recognized:

1) the “advancing front,” which corresponds to areas recently invaded by scale

populations; 2) the “killing front,” which represents areas where fungal invasion has

occurred and tree mortality begins (typically 3 to 5 years after the scale insects appear,

but sometimes as long as 20 years); and 3) the “aftermath forest,” which are areas where

the disease is endemic (Houston 1994, Shigo 1972). BBD was inadvertently introduced

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

4,000 

4,500 

5,000 

1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 

Acres of Defoliation (thousands) 

Year 

Figure 84.—Acres defoliated by gypsy moth, Pennsylvania, 1970 

through 2013.

Source: U.S. Forest Service, State and Private Forestry, 2015 Gypsy Moth Digest – defoliation data.
116 | FOREST INDICATORS OF HEALTH AND SUSTAINABILITY

via ornamental beech trees into North America at Halifax, Nova Scotia, in 1890 and 

then began spreading to the south and west. By 1975 beech bark disease had been 

discovered in much of northeastern Pennsylvania and it has since spread across most of 

the State, including where beech densities are highest (Fig. 85).

What we found

Currently, the annual mortality rate for American beech by live volume per year is 1.4 

percent, 50 percent higher than the average rate of 0.9 percent for all tree species (see 

Tree Mortality section starting on p. 74). Consequently, the impacts of BBD mortality 

have resulted in reductions of large diameter beech along with corresponding increases 

in small diameter beech since 1989 (Fig. 86). The number of beech seedlings (including 

root sprouts) increased by 9 percent between 2009 and 2014 while the number of 

sawtimber size trees (11 inches and larger) decreased 3 percent over the same period.

What this means

Most of Pennsylvania’s forest infested by BBD is in the aftermath phase. Aftermath 

forests are often characterized by a dearth of large beech trees due to BBD-induced 

mortality and increasing numbers of beech seedlings and saplings. This condition, 

often referred to as “beech brush,” can interfere with regeneration of other hardwood 

species such as sugar maple (Hane 2003). The condition consists of trees with low 

vigor and slow growth that often succumb to the disease before making it into the 

overstory. These trees are also unlikely to reach sawtimber size or produce mast. 

Efforts to mitigate the effects of beech brush on regeneration can incur significant 

costs for mechanical or chemical controls.
FOREST INDICATORS OF HEALTH AND SUSTAINABILITY | 117

American Beech Volume (ft3/acre)

n 0-50 n 51-200 n 201-350 n 351-700 n >700

n Nonforest n Infested counties

Figure 85.—American beech volume (trees at least 5 inches d.b.h.) on forest land, Pennsylvania, 2009, with 

beech bark disease-infested counties displayed.

Projection: Pennsylvania State Plane North, NAD83. Source: U.S. Forest Service, Forest Inventory and Analysis program, 2009. Geographic base data are 

provided by the National Atlas of the USA®. FIA Data and Tools are available online at http://www.fia.fs.fed.us/tools-data/.

Cartography: R.S. Morin, U.S. Forest Service, November 2015.

0 

2 

4 

6 

8 

10 

12 

14 

16 

Seedling 

2 4 6 8 

10 12 

14 16 

18 

20 

21.0-28.9 

Percentage of All Trees that are American Beech 

Diameter Class 

n 2004

n 2009

n 2014 

Figure 86.—Proportion of all trees that are American beech, by 

diameter class and inventory year on timberland, Pennsylvania.
118 | 

Logging operation in Berks County. Photo by Richard Widmann, U.S. Forest Service.

Forest Economics
FOREST ECONOMICS | 119

Timber Products

Background

Pennsylvania’s forest industry provides jobs and income from harvesting timber and 

producing products, such as lumber and pulp. In 2012, the industry had more than 

$11 billion in sales and contributed $19 billion to the overall economy (Pennsylvania 

Department of Conservation and Natural Resources 2015). At that time, it was 

estimated there were more than 2,100 forest products processors supporting about 

58,000 jobs. The industry has a presence in all counties, particularly in the rural 

counties, where forests and timber processors are concentrated. It is important 

to track species used and products manufactured to better manage and sustain 

the Commonwealth’s forest resources, support rural economies, and fill a critical 

information need for policy makers and others. 

This section combines information on harvest removal estimates on FIA plots and 

the results of a timber products output survey conducted for 2012 (Pennsylvania 

Department of Conservation and Natural Resources 2015). The FIA harvest estimates 

represent the volume of stumpage removed from the State’s public and private forest 

land. These estimates provide contextual information on Pennsylvania’s harvest 

relative to other eastern States and trends in FIA. The timber products output survey 

contacted 430 primary processing facilities in Pennsylvania with a response rate of 

73 percent, or 312 facilities. Product output statistics are estimates of the volume of 

stumpage converted to products and hence do not match FIA’s removals. Estimates of 

the amount of wood processed are based on 253 mills that reported product volume 

and 192 that reported residue volume. The information includes product output by 

region, product type, and species.

A previous report published for 2009 was devoted to understanding the impact of the 

nationwide recession that decreased production starting around 2007 (McCaskill et al. 

2013, Smith and Guldin 2012). In 2010, the Pennsylvania Hardwoods Development 

Council reported the industry was in “terrible trouble” and the recession resulted in 

the closing of many small and medium-size mills and decreased production by large 

mills (Pennsylvania Hardwoods Development Council 2010). This section focuses on 

Pennsylvania’s harvest and production trends since then.

What we found

Pennsylvania has long been a leader in the harvest of hardwood sawtimber. Despite 

the economic downturn just before the last forest inventory, the State now ranks 

fourth nationally for hardwood sawtimber removals based on the FIA estimates, with 
120 | FOREST ECONOMICS

0.9 billion board feet (Fig. 87). Tennessee ranks first in hardwood sawtimber removal 

with 1.2 billion board feet, followed by North Carolina and Mississippi, each with 

about 1.0 billion board feet. Although Pennsylvania’s hardwood harvest estimate 

ranks below these States, the estimates for North Carolina, Mississippi, and 

Pennsylvania are not statistically different at the 68 percent confidence level.

Examination of total harvest removals highlights the importance of hardwoods, 

which account for about 90 percent of total harvest volume for both sawtimber and 

growing stock (Fig. 88). Estimates from the 1978 and 1989 periodic inventories are 

not directly comparable to the results of the annual inventory because they include 

removals attributed to land-use change and are limited to removals from timberland 

(Alerich 1993, Considine and Powell 1980). Removal estimates are not available for 

2004 due to the inconsistencies with the 1989 periodic inventory. Despite these 

limitations, the removals reported for 2009 represent a peak in FIA removals 

estimates for Pennsylvania. 

Information from the annual inventory shows that harvest of hardwood growing 

stock and sawtimber decreased by 22 and 27 percent, respectively, since 2009. 

Although a relatively minor component of total removals, harvest removals of 

softwood growing stock and sawtimber increased by 27 and 23 percent, respectively. 

The survey of timber products industries revealed that the total volume processed in 

2012 was 184.7 million cubic feet based on 253 respondents, which is equivalent to 

about 1.2 billion board feet (Pennsylvania Department of Conservation and Natural 

Resources 2015). The North Central and South Central regions accounted for 59 

percent of total production (Fig. 89). 

The mixed hardwood species group made up most of the product volume with 20 

percent of the total (Table 11). The remaining 12 percent of volume processed was 

composed of ash, hemlock, chestnut oak, hickory, black oak, and other species. 

Logs processed into lumber and other sawn products accounted for 637.9 million 

board feet, equivalent to 100.8 million cubic feet (Fig. 90). Using supplemental 

information, the Pennsylvania Department of Conservation and Natural Resources’ 

mill study estimated that non-respondents represented about 25 percent of statewide 

saw-log production, which means that actual saw-log production could be as high 

as 850 million board feet. Pulp and chips totaled 2.5 million green tons, produced 

primarily for the paper industry. Exported log production was 14.9 million board 

feet. In addition, 66.3 million cubic feet of residues were produced as by-products of 

primary roundwood processing (Fig. 91). Most of this material (96 percent) was bark, 

coarse residues, and sawdust.
FOREST ECONOMICS | 121

0 500 1,000 1,500 

Virginia 

Pennsylvania 

Mississippi 

North Carolina 

Tennessee 

Harvest Removals

(million board feet, International 1/4-inch rule) 

Figure 87.—Average annual hardwood sawtimber harvest 

removals for the five leading states in hardwood sawtimber 

removals, 2014. Error bars represent a 68 percent confidence 

interval around the estimated mean.

0 

500 

1,000 

1,500 

1978 1989 2009 2014 

Harvest Removals

(million board feet, International 1/4-inch rule) 

Year 

0 

100 

200 

300 

400 

1978 1989 2009 2014 

Harvest Removals

(million cubic feet) 

Year 

A

B

n Hardwoods

n Softwoods

n Hardwoods

n Softwoods

Figure 88.—Average annual harvest removals for sawtimber (A) and growing-stock trees (B) on forest land 

by inventory year, Pennsylvania.

47�8 MMCF

(35%) 18�4 MMCF

(13%)

Unspecified 12�6 MMCF (9%)

13�5 MMCF

(10%)

7�4 MMCF

(5%)

32�7 MMCF

(24%)

5�5 MMCF

(4%)

Figure 89.—Total volume (million cubic feet) and percentage of primary timber 

product production by region, Pennsylvania, 2012 (Pennsylvania Department of 

Conservation and Natural Resources 2015). [Note: based on 242 mill responses.]
122 | FOREST ECONOMICS

100.8 

81.5 

0 

20 

40 

60 

80 

100 

120 

140 

160 

180 

200 

Production Volume (million cubic feet) 

n Lumber 

n Pulp/chips

n Log exports 

2 

67 

24 

7 

Lumber n Lumber 

n Cants 

n Veneer

n Other 

2 90 

3 

5 

Pulp/Chips n Pulp/chips 

n Composite chips 

n Energy chips 

n Other 

Figure 90.—Total volume of production by product and percentage of production for lumber and pulp/

chips by product type, Pennsylvania, 2012 (Pennsylvania Department of Conservation and Natural 

Resources 2015). [Note: based on 253 mill responses.]

Table 11.—Volume (million cubic feet) and percentage of total timber 

products processed by the nine species/species groups contributing at 

least 5 percent of total product volume, Pennsylvania, 2012

Species/Species group

Volume

(million cubic feet) Percent

Mixed hardwoods 36.7 20

Red oak 24.2 13

Miscellaneous softwood 22.9 13

Other species 15.8 9

Red (soft) maple 15.0 8

Black cherry 12.6 7

Yellow-poplar 12.5 7

White oak 11.1 6

Sugar (hard) maple 9.0 5
FOREST ECONOMICS | 123

What this means

Perhaps the most important issue to address with the harvest and timber products 

information is how the timber industry of Pennsylvania has fared since the economic 

recession of a decade ago. The results indicate that harvest has not recovered to 2009 

levels for both growing-stock and sawtimber trees. The decrease was most apparent 

for sawtimber; however, Pennsylvania still ranks among the leading states for 

hardwood sawtimber removals. This means that the recession has affected hardwood 

sawtimber harvest across many states, and Pennsylvania’s situation mirrors others. 

One important factor is how timber prices have trended over the past decade. Timber 

market reports compiled by Penn State’s Cooperative Extension Service (Pennsylvania 

State University 2016a) show mixed trends by species and region. In general, prices 

for black cherry and sugar maple have both trended downward. Red maple prices 

have remained level, while prices for oak have increased slightly in some markets. 

Having markets for wood is essential to forest management. Despite the loss of some 

milling capacity, Pennsylvania’s mills continue to provide landowners markets for 

their timber. The income landowners receive from selling timber is an incentive to 

keep land in forest. Income from harvests can help pay property taxes and fund forest 

management activities such as wildlife habitat improvements and invasive species 

control. Careful monitoring of timber products output is needed to formulate policies 

and programs that support the State’s wood economy.

27.5 (41% )

20.9 (32%) 

15.5 (23%) 

2.1 (3% ) 0.4 (1%) 

n Bark 

n Coarse 

n Sawdust

n Shavings 

n Log/Sections 

Figure 91.—Total volume (million cubic feet) and percentage 

of residue by-products by residue type, Pennsylvania, 2012 

(Pennsylvania Department of Conservation and Natural Resources 

2015). [Note: based on 192 mill responses.]
124 | 

Rock walls lining an abandoned road in Bradford County. Photo by Thomas Albright, U.S. Forest Service.

Looking Forward
LOOKING FORWARD | 125

Future Forests of Pennsylvania

Background

This section focuses on anticipated changes to the forests of Pennsylvania between 

2010 and 2060. The analysis is derived entirely from the Northern Forest Futures 

study (Shifley and Moser 2016). A large component of future forest change will be the 

result of normal forest growth, aging, natural regeneration, and species succession. In 

addition, the following external forces will drive forest change: 

• Population increases will cause conversion of roughly 1.6 million acres of forest 

land to urban land (Nowak and Walton 2005)

• Economic conditions will affect forest products consumption, production, and 

harvest rates

• Invasive species will spread and affect forest change

• Changes in population, the economy, energy consumption, and energy production 

will affect future climate change

• Climate change will affect patterns of forest growth and species succession.

The Northern Forest Futures study used several alternative scenarios that cover a range 

of assumptions about the economy, population, climate, and other driving forces. The 

assumptions were incorporated into analytical models that estimated how northern 

forests are likely to change under each alternative scenario. The seven scenarios (A1B-C, 

A1B-BIO, A2-C, A2-BIO, A2-EAB, B2-C, and B2-BIO) are based on a storyline and 

storyline variation. They are identified by their storyline identifier (A1B, A2, or B2) 

followed by a hyphen and then their storyline variation (C, BIO, or EAB).

The three storylines are:

1) A1B—Rapid economic globalization. International mobility of people, ideas, and 

technology. Strong commitment to market-based solutions. Strong commitment to 

education. High rates of investment and innovation in education, technology, and 

institutions at the national and international levels. A balanced energy portfolio 

including fossil fuel-intensive and renewable energy sources. Utilizes the CGCM3.1 

climate model (Canadian Centre for Climate Modelling and Analysis 2014).

2) A2—Consolidation into economic regions. Self-reliance in terms of resources 

and less emphasis on economic, social, and cultural interactions between regions. 

Technology diffuses more slowly than in the other scenarios. International disparities 

in productivity, and hence income per capita, are largely maintained or increased in 

absolute terms. Utilizes the CGCM3.1 climate model.
126 | LOOKING FORWARD

3) B2—A trend toward local self-reliance and stronger communities. Communitybased solutions to social problems. Energy systems differ from region to region, 

depending on the availability of natural resources. The need to use energy and other 

resources more efficiently spurs the development of less carbon-intensive technology 

in some regions. Utilizes the CGCM2 climate model (Canadian Centre for Climate 

Modelling and Analysis 2014).

The three storyline variations are as follows:

• C—Continuation of the observed recent rates of forest removals due to timber 

harvesting and land use conversion from forest to another land use.

• BIO—Increased harvest and utilization of woody biomass for energy variation, 

available for all three storylines (A1B, A2, and B2).

• EAB—Potential impact of continued spread of the emerald ash borer with 

associated mortality of all ash trees in the affected areas – available for only one 

scenario (A2).

What we found

Anticipated declines in forest land in Pennsylvania from 2010 to 2060 break the 

recent observed stability in forest land area since the 1989 inventory (Fig. 92). 

Specifically, over the next 50 years forest land area is projected to decline from an 

estimated 16.7 million acres in 2010 to 15.0 million acres (a loss of 10 percent) in 

2060 under scenario A1B-C; to 15.3 million acres (a loss of 8 percent) under scenario 

A2-C; and to 15.9 million acres (a loss of 5 percent) under scenario B2-C. Only three 

scenarios are represented in Figure 92 as the climate model and variations on the 

storylines do not affect projections of forest land area under this model. Only the 

storylines developed around differing demographics and levels of economic activity 

alter the modeled area of forest land. Scenarios with increasing population and 

economic activity project less forest land over the time period.

Emerald ash borer, initially detected in Pennsylvania in June 2007, has been detected 

in 62 of Pennsylvania’s 67 counties (Pennsylvania State University 2016b). Ash species 

make up 4.7 percent of the current total live tree volume on forest land. Under the 

A2-EAB scenario live ash volume is projected to go to zero by 2025. The impact on 

total live tree volume from the loss of the ash component is short-lived as other 

species are expected to fill the void. The difference in total live tree volume between 

scenario A2-C and A2-EAB by 2060 is negligible (0.3 percent less under scenario 

A2-EAB) (Fig. 93).
LOOKING FORWARD | 127

13.0 

13.5 

14.0 

14.5 

15.0 

15.5 

16.0 

16.5 

17.0 

17.5 

18.0 

1930 1950 1970 1990 2010 2030 2050 2070 

Forest Land Area (million acres) 

Year 

Historical

A1B-C

A2-C 

B2-C 

Figure 92.—Projected forest land area for Pennsylvania by scenario, 

2010–2060.

25 

27 

29 

31 

33 

35 

37 

39 

2000 2010 2020 2030 2040 2050 2060 2070 

Live Tree Volume (billion cubic feet) 

Year 

A1B-C

A1B-BIO 

A2-C

A2-BIO

B2-C

B2-BIO

A2-EAB 

Figure 93.—Live tree volume on forest land in Pennsylvania by scenario, 

2010–2060.
128 | LITERATURE CITED

Impacts of high biomass utilization on total live tree volume are much more 

pronounced than the impacts of EAB. As a result of these high levels of removals, live 

tree volume on forest land is projected to decrease under all three high biomass 

utilization scenarios (Fig. 94): A1B-BIO (a decline of 22 percent), B2-BIO (a decline 

of 12 percent), and A2-BIO (a decline of 5 percent). 

What this means

The area of forest land is expected to decrease under each of the three storylines in 

response to increases in population and economic activity. Scenarios assuming greater 

increases in population and economic activity are projected to have greater losses of 

forest land. 

The projected loss of forest land is substantial. The loss of between 5 and 10 percent 

of forest land, depending on scenario, is somewhat offset by increases in volume 

per acre under scenarios A1-C, A2-C, B2-C, and A2-EAB. Harvest rates under the 

high biomass utilization scenarios (Fig. 94) have a large impact on volumes for those 

scenarios after 2050, resulting in declining volumes per acre.

It is important to note that predictions are future possibilities, not future truths. 

Forest and development planning, energy policy, and control of invasive plants and 

pests can all have a significant mitigating impact on future forest loss.

0 

200 

400 

600 

800 

1,000 

1,200 

1,400 

2000 2010 2020 2030 2040 2050 2060 2070 

Year 

Average Annual Growing-Stock Removals

(million cubic feet)

A1B-C

A1B-BIO 

A2-C

A2-BIO

B2-C

B2-BIO

A2-EAB 

Figure 94.—Average annual growing-stock removals on timberland in 

Pennsylvania by scenario, 2010–2060.
LITERATURE CITED | 129

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Appendix

Tree species, greater than or equal to 1 inch in diameter, found on FIA inventory plots by regeneration 

species groups, Pennsylvania, 2014

Common name Genus Species

Timber 

speciesa

Timber 

code

Canopy 

speciesb

Canopy 

code

white fir Abies concolor l 3 2

Fraser fir Abies fraseri l 3 l 3

eastern redcedar Juniperus virginiana l 3 l 3

tamarack (native) Larix laricina t 1 n 2

larch spp. Larix spp. t 1 n 2

Norway spruce Picea abies l 3 n 2

white spruce Picea glauca l 3 n 2

blue spruce Picea pungens l 3 n 2

red spruce Picea rubens l 3 n 2

jack pine Pinus banksiana w 2 n 2

Austrian pine Pinus nigra w 2 n 2

table mountain pine Pinus pungens t 1 n 2

red pine Pinus resinosa t 1 n 2

pitch pine Pinus rigida t 1 n 2

eastern white pine Pinus strobus t 1 s 1

Scotch pine Pinus sylvestris t 1 n 2

Virginia pine Pinus virginiana t 1 n 2

Douglas-fir Pseudotsuga menziesii l 3 l 3

eastern hemlock Tsuga canadensis t 1 s 1

boxelder Acer negundo l 3 l 3

black maple Acer nigrum l 3 n 2

striped maple Acer pensylvanicum l 3 l 3

Norway maple Acer platanoides l 3 n 2

red maple Acer rubrum t 1 s 1

silver maple Acer saccharinum l 3 n 2

sugar maple Acer saccharum t 1 s 1

mountain maple Acer spicatum l 3 l 3

buckeye, horsechestnut spp. Aesculus spp. l 3 n 2

ailanthus (tree of heaven) Ailanthus altissima l 3 l 3

European alder Alnus glutinosa l 3 l 3

common serviceberry Amelanchier arborea l 3 l 3

pawpaw Asimina triloba l 3 l 3

yellow birch Betula alleghaniensis w 2 n 2

sweet (black) birch Betula lenta w 2 s 1

a t = Desirable w = Commercial l = Other 

b s = High canopy dominant n = High other l = Other. High-canopy dominants are species that account

for at least 2 percent of total live-tree biomass within the State and typically form high canopy. (continued)

n
APPENDIX | 139

(Continued) Tree species, greater than or equal to 1 inch in diameter, found on FIA inventory plots by 

regeneration species groups, Pennsylvania, 2014

Common name Genus Species

Timber 

speciesa

Timber 

code

Canopy 

speciesb

Canopy 

code

river birch Betula nigra w 2 n 2

paper birch Betula papyrifera w 2 n 2

gray birch Betula populifolia l 3 l 3

American hornbeam 

(musclewood)

Carpinus caroliniana l 3 l 3

mockernut hickory Carya alba t 1 s 1

bitternut hickory Carya cordiformis t 1 s 1

pignut hickory Carya glabra t 1 s 1

shagbark hickory Carya ovata t 1 s 1

American chestnut Castanea dentata l 3 l 3

catalpa spp. Catalpa spp. l 3 n 2

hackberry Celtis occidentalis w 2 n 2

eastern redbud Cercis canadensis l 3 l 3

flowering dogwood Cornus florida l 3 l 3

hawthorn spp. Crataegus spp. l 3 l 3

American beech Fagus grandifolia w 2 s 1

white ash Fraxinus americana t 1 s 1

black ash Fraxinus nigra t 1 n 2

green ash Fraxinus pennsylvanica t 1 s 1

ginkgo, maidenhair tree Ginkgo biloba l 3 n 2

honeylocust Gleditsia triacanthos l 3 n 2

Kentucky coffeetree Gymnocladus dioicus w 2 n 2

American holly Ilex opaca l 3 l 3

butternut Juglans cinerea t 1 n 2

black walnut Juglans nigra t 1 n 2

sweetgum Liquidambar styraciflua w 2 n 2

yellow-poplar Liriodendron tulipifera t 1 s 1

Osage-orange Maclura pomifera l 3 l 3

cucumbertree Magnolia acuminata t 1 n 2

umbrella magnolia Magnolia tripetala l 3 l 3

sweet crab apple Malus coronaria l 3 l 3

apple spp. Malus spp. l 3 l 3

white mulberry Morus alba l 3 l 3

red mulberry Morus rubra l 3 l 3

mulberry spp. Morus spp. l 3 l 3

blackgum Nyssa sylvatica w 2 n 2

eastern hophornbeam Ostrya virginiana l 3 l 3

paulownia, princesstree Paulownia tomentosa l 3 l 3

a t = Desirable w = Commercial l = Other 

b s = High canopy dominant n = High other l = Other. High-canopy dominants are species that account

for at least 2 percent of total live-tree biomass within the State and typically form high canopy. (continued)
140 | APPENDIX

(Continued) Tree species, greater than or equal to 1 inch in diameter, found on FIA inventory plots by 

regeneration species groups, Pennsylvania, 2014

Common name Genus Species

Timber 

speciesa

Timber 

code

Canopy 

speciesb

Canopy 

code

American sycamore Platanus occidentalis l 3 n 2

balsam poplar Populus balsamifera w 2 n 2

eastern cottonwood Populus deltoides w 2 n 2

bigtooth aspen Populus grandidentata w 2 n 2

quaking aspen Populus tremuloides w 2 n 2

sweet cherry, domesticated Prunus avium l 3 l 3

pin cherry Prunus pensylvanica l 3 l 3

black cherry Prunus serotina t 1 s 1

cherry and plum spp. Prunus spp. l 3 l 3

chokecherry Prunus virginiana l 3 l 3

white oak Quercus alba t 1 s 1

swamp white oak Quercus bicolor t 1 n 2

scarlet oak Quercus coccinea t 1 s 1

northern pin oak Quercus ellipsoidalis t 1 n 2

scrub oak Quercus ilicifolia l 3 l 3

shingle oak Quercus imbricaria t 1 n 2

bur oak Quercus macrocarpa t 1 s 1

swamp chestnut oak Quercus michauxii t 1 n 2

pin oak Quercus palustris t 1 s 1

dwarf chinkapin oak Quercus prinoides l 3 l 3

chestnut oak Quercus prinus t 1 s 1

northern red oak Quercus rubra t 1 s 1

black oak Quercus velutina t 1 s 1

black locust Robinia pseudoacacia w 2 n 2

black willow Salix nigra w 2 n 2

sassafras Sassafras albidum l 3 l 3

American basswood Tilia americana t 1 n 2

white basswood Tilia heterophylla l 3 n 2

American elm Ulmus americana w 2 n 2

slippery elm Ulmus rubra w 2 n 2

a t = Desirable w = Commercial l = Other 

b s = High canopy dominant n = High other l = Other. High-canopy dominants are species that account

 for at least 2 percent of total live-tree biomass within the State and typically form high canopy.)
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7442; or (3) email: program.intake@usda.gov.

Albright, Thomas A.; McWilliams, William H.; Widmann, Richard H.; Butler, Brett J.; 

Crocker, Susan J.; Kurtz, Cassandra M.; Lehman, Shawn; Lister, Tonya W.; 

Miles, Patrick D.; Morin, Randall S.; Riemann, Rachel; Smith, James E. 2017. 

Pennsylvania forests 2014. Resour. Bull. NRS-111. Newtown Square, PA: U.S. 

Department of Agriculture, Forest Service, Northern Research Station. 140 p. 

This report summarizes the third cycle of annualized inventory of Pennsylvania with field 

data collected from 2009 through 2014. Pennsylvania has 16.9 million acres of forest 

land dominated by sawtimber stands of oak/hickory and maple/beech/birch foresttype groups. Volumes continue to increase as the forests age with an average of 2,244 

cubic feet per acre on timberland. Sawtimber volume has risen 24 percent in 10 years to 

115 billion board feet. Net growth outpaced removals by a ratio of 2.4:1 on timberland. 

Additional information on land-use change, fragmentation, ownership, forest composition, 

structure and age distribution, carbon stocks, regeneration, invasive plants, insect pests, 

and wood products is also presented. Sets of supplemental tables are available online 

at https://doi.org/10.2737/NRS-RB-111 and contain: 1) tables that summarize quality 

assurance and 2) a core set of tabular estimates for a variety of forest resources.

KEY WORDS: inventory, land use, fragmentation, forest statistics, forest land, timberland, 

forest ownership, forest regeneration, volume, carbon, growth, removals, mortality, forest 

health, timber products, forest pests, invasive plants, Pennsylvania
Northern Research Station

www.nrs.fs.fed.us