Table 1.─Annual estimates and uncertainty

Figure 1.─Area of timberland and forest land by yea

Figure 2.─Area of timberland for top six forest types

by stand-size class.

Pennsylvania’s Forest Resources, 2006 Research Note NRS

This publication provides an overview of forest resource attributes for Pennsylvania based on an annual 

inventory conducted by the Forest Inventory and Analysis program at the Northern Research Station of the U.S

Forest Service (NRS-FIA). These annual estimates, along with web-posted core tables, will be updated annua

For more information regarding past inventory reports for this state, inventory program information, and 

sampling/estimation procedures, please refer to the citations at the end of this report.

1

14,000

14,500

15,000

15,500

16,000

16,500

17,000

17,500

18,000

1950 1960 1970 1980 1990 2000 20

Year

Area (1,000 acres)

Timberland

Forest Land

0.0

500.0

1,000.0

1,500.0

2,000.0

2,500.0

3,000.0

3,500.0

Small Medium Large

Stand size class

Timberland (1,000 acres)

Sugar maple/beech/yellow birch

White oak/red oak/hickory

Chestnut oak/black oak/scarlet oak

Chestnut oak

Red maple/upland

Cherry/ash/yellow-poplar
Figure 4.─Area of timberland by stand-s

class and year.

Table 2.─Volume estimates for the top 10 species based on the volume of live trees

Figure 3.─Area of forest land (1,000 acre

by broad ownership group.

2

4,779.2

11,820.4

Public Private

0

2,000

4,000

6,000

8,000

10,000

12,000

02468

Year

Area (1,000 acres)

Large Medium Small

Rank Species Sampling Sampling 

Error Error

(%) (%)

1 Red maple 6,194.7 2.7 14,785.7 3.8

2 Black cherry 3,293.5 4.4 10,440.4 5.8

3 Northern red oak 2,955.0 4.1 11,315.4 4.7

4 Sugar maple 2,403.5 5.0 6,460.2 6.2

5 Chestnut oak 2,213.8 4.3 5,709.8 5.2

6 Eastern hemlock 1,744.3 5.9 5,203.2 7.0

7 White ash 1,486.6 5.6 4,634.3 7.2

8 White oak 1,482.5 5.2 4,624.0 6.3

9 Yellow-poplar 1,369.2 8.1 5,745.0 9.1

10 Black birch 1,323.5 5.0 2,507.9 6.9

Other softwoods 1,940.3 5.7 5,665.3 6.8

Other hardwoods 28,667.9 1.9 81,815.5 2.5

All Species 31,866.5 1.2 91,597.8 1.7

Volume of live trees 

on timberland 

(Million Cubic Feet)

Volume of sawtimber trees 

on timberland (Million 

Board Feet)
Pennsylvania Issue Update – Need for Full Remeasurement

Figure 5.─Average annual net growth, removals, and mortality of growing stock on timberland 

with 67 percent (A) and 95 percent (B) confidence intervals, 2006.

The major benefit of repeated inventories is the ability to accurately estimate change in resource attributes 

over time. Of critical importance are inventory change components, or average annual net growth, removal

and mortality. These components measure the resource’s ability to expand over time and can be expressed 

in biomass units, cubic-foot volume, or board-foot volume. As such, change components are perhaps the 

most fundamental estimates of short-term resource sustainability available from the inventory. Net growth i

equal to gross growth minus mortality, or the amount of wood lost due to trees dying since the previous 

inventory. Removals includes trees that have been harvested and trees on land converted to nonforest use

Comparing net growth to removals indicates both the direction and magnitude of resource change, e.g., a 

large positive margin of net growth over removals foretells large gains.

The 2006 resource change components estimates are based on remeasurement of two inventory panels or 

40 percent of the forested samples. To date, this level of remeasurement has not provided a level of 

precision that allows meaningful analysis for all species because of the relatively low percentage of 

remeasured samples. The sample of mortality and removal trees is particularly small compared to growth.

As illustrated in Figure 5, the relationships between the three change components and their respective 

sampling errors has varying effects on the analysis of sustainability. For common species, such as soft (red

maple, there appears to be adequate precision to draw substantive conclusions; however, for less common 

species, such as ash and hickory, the results are less illustrative. The analysis also depends on the level of 

precision required. Figure 5 shows the results for both 67 and 95 percent levels of confidence. As more 

inventory panels are remeasured, the ability to assess these aspects of sustainability will improve.

3

0

50

100

150

200

Soft Maple Select Red

Oaks

Ash Hickory

Million Cubic Feet aaaa

Net Grow th

Mortality

Removals

0

50

100

150

200

Soft Maple Select Red

Oaks

Ash Hickory

Million Cubic Feet aaaa

Net Grow th

Mortality

Removals

A

B
Bechtold, W.A.; Patterson, P.L. 2005. The enhanced Forest Inventory and Analysis program: national sampling 

design and estimation procedures. Gen. Tech. Rep. SRS-80. Asheville, NC: U.S. Department of Agriculture, Forest 

Service, Southern Research Station. 85 p.

Smith, W.B. 2002. Forest inventory and analysis: a national inventory and monitoring program. Environmental 

Pollution. 116: 233-242.

USDA Forest Service. 2004. Forest Inventory and Analysis national core field guide, volume 1: field data collection 

procedures for phase 2 plots, version 4.0 [Online], available at www.fia.fs.fed.us/library/field-guides-methods-proc 

(verified 5 August 2008). 

Ferguson, Roland H. 1955. The timber resources of Pennsylvania. Upper Darby, PA: U.S. Department of Agriculture, 

Forest Service, Northeastern Forest Experiment Station. 46 p.

Ferguson, Roland H. 1968. The timber resources of Pennsylvania. Resour. Bull. NE-8. Upper Darby, PA: U.S. 

Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 145 p.

Considine, Thomas J.; Powell, Douglas S. 1980. Forest statistics for Pennsylvania--1978. Resour. Bull. NE-65. 

Broomall, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 88 p.

Alerich, Carol A. 1993. Forest statistics for Pennsylvania--1978 and 1989. Res. Bull. NE-126. Radnor, PA: U.S. 

Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 244 p.

McWilliams, William H.; Stout, Susan L.; Bowersox, Todd W.; McCormick, Larry H. 1995. Advance tree-seedling 

regeneration and herbaceous cover in Pennsylvania forests. Northern Journal of Applied Forestry. 12(4): 187-191.

McWilliams, William H.; Cassell, Seth P.; Alerich, Carol L.; et al. 2007. Pennsylvania's forest 2004. Resour. Bull. NRS20. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 86 p.

FIA Program Information

Additional Pennsylvania Inventory Information

McWilliams, William H. 20087. Pennsylvania’s forest resources, 2006. Res. Note. NRS-25. Newtown Square, PA: U.S. 

Department of Agriculture, Forest Service, Northern Research Station. 4 p.

Citation for this Publication

4

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