Vermont’s Forests 

2007

Resource Bulletin

NRS-51

United States 

Department of Agriculture

Forest 

Service

Northern 

Research Station
 Abstract

The fi rst full annual inventory of Vermont’s forests reports more than 4.5 million acres of forest land with 

an average volume of more than 2,200 cubic feet per acre. Forest land is dominated by the maple/beech/

birch forest-type group, which occupies 70 percent of total forest land area. Sixty-three percent of 

forest land consists of large-diameter trees, 27 percent contains medium-diameter trees, and 9 percent 

contains small-diameter trees. The volume of growing stock on timberland has been rising since the 

1980s and currently totals nearly 9 billion cubic feet. The average annual net growth of growing stock 

on timberland from 1997 to 2007 is approximately 180 million cubic feet per year. Additional information 

is presented on forest attributes, land use change, carbon, timber products, and forest health. Detailed 

information on forest inventory methods and data quality estimates is included in a DVD at the back of 

the report. Tables of population estimates and a glossary are also included.

Acknowledgments

The authors would like to thank Vermont’s inventory crew members over the 2003-2007 inventory cycle: 

Aaron Clark, Robert Gregory, John Higham, Paul Kelley, Katherine Locke, Jason Morrison, Joyce Quinn, 

Ann Quinion, Keith Raymond, Jennifer Thompson, Bryan Tirrell, and Ashley Zickefoose. Thanks also 

to Virginia G. Anderson, Barbara Burns, Charles Canham, Paul Frederick, Chris Matera, and George 

McCaskill for serving as reviewers and providing insightful, constructive comments.

Published by: For additional copies:

U.S. FOREST SERVICE U.S. Forest Service

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July 2011

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

Cover: Vermont sugar maples. Photo by Ronald Kelley.

Manuscript received for publication February 2011

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Room 326-W, Whitten Building, 14th and Independence Avenue, SW, Washington, DC 20250-9410, or call (202) 

720-5964 (voice or TDD). USDA is an equal opportunity provider and employer.
Randall S. Morin, Chuck J. Barnett, Gary J. Brand, Brett J. Butler, Robert De Geus, 

Mark H. Hansen, Mark A. Hatfi eld, Cassandra M. Kurtz, W. Keith Moser, Charles H. Perry, 

Ron Piva, Rachel Riemann, Richard Widmann, Sandy Wilmot, and Chris W. Woodall

Contact Author: 

Randall S. Morin, rsmorin@fs.fed.us 

610-557-4054

About the Authors

 Randall S. Morin is a research 

forester with the Forest Inventory 

and Analysis (FIA) program, 

Northern Research Station, 

Newtown Square, PA.

Chuck J. Barnett and Richard 

Widmann are foresters with the 

FIA program, Northern Research 

Station, Newtown Square, PA.

Gary J. Brand, Mark H. Hansen, 

W. Keith Moser, Charles H. 

Perry, and Chris W. Woodall are 

research foresters with the FIA 

program, Northern Research 

Station, St. Paul, MN.

Brett J. Butler is a research 

forester with the FIA program, 

Northern Research Station, 

Amherst, MA.

Robert De Geus is a wood 

utilization forester with the 

Vermont Department of 

Forests, Parks and Recreation, 

Waterbury, VT.

Mark A. Hatfi eld, Cassandra M. 

Kurtz, and Ron Piva are foresters 

with the FIA program, Northern 

Research Station, St. Paul, MN.

Rachel Riemann is a research 

forester with the FIA program, 

Northern Research Station, 

Troy, NY.

Sandy Wilmot is a forest health 

specialist with the Vermont 

Department of Forests, Parks and 

Recreation, Waterbury, VT.

Vermont’s Forests 2007
Foreword

Forests dominate Vermont’s landscape, covering over 75 percent of the state. Our forested 

ecosystem provides the basis for biological diversity, natural communities, scenic landscapes, and 

recreational opportunities. As a natural resource, forests provide an important economic base 

supporting a diverse forest products industry, as well as a myriad of ecosystem services such as 

clean water, clean air, and carbon storage. 

In Vermont, we recognize that sustainable forests begin with healthy forests. And we recognize 

that managing forests sustainably involves the recognition of connections among ecological, 

social, and economic systems to maintain forest health while preserving options for future 

generations and meeting the needs for the present.

To make informed decisions about forest resources, it is important to have accurate and timely 

forest resource information. The Department of Forests, Parks and Recreation is pleased to 

partner with the U.S. Forest Service in the Forest Inventory and Analysis (FIA) of Vermont. The 

more we know and understand of the wonderful resources of Vermont’s forests, the better we 

can sustain our forests. Decisions and actions we make today will infl uence our forests for years 

to come. Livable communities, functioning natural systems, and our quality of life depend 

on healthy, sustainable forests. We must accept and embrace responsibility as stewards of this 

valuable resource.

Steven Sinclair, Vermont State Forester
Contents

Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Forest Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Forest Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Forest Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Literature Cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Statistics and Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DVD
vi

Vermont fall color. Photo by Randall Morin, U.S. Forest Service.
1

On the Plus Side

Vermont’s forest land base has remained stable since 1997 

at 75 percent of total land area, making it the fourth most 

forested state in the United States.

Timberland makes up 98 percent of Vermont’s forest land.

Ninety-seven percent of Vermont’s forest land is in 

patches larger than 100 acres, a size preferred by many 

wildlife species.

Only 3 percent of forest land in Vermont is near 

population centers that exceed 150 people per square 

mile, the density at which the probability of commercial 

forestry drops to zero.

Most of Vermont’s forest land is well stocked with trees 

of commercial importance. Changes in stand stocking 

indicate that forest management practices over the past 

three decades may have improved the general stocking 

condition across the State. 

The quality of saw logs in Vermont has remained stable since 

the last inventory, but the value of sawtimber has increased 

based upon the increase in available board-foot volume.

Most of the wood-processing facilities in Vermont are 

sawmills processing primarily State-grown saw logs. These 

mills provide woodland owners with an outlet to sell 

timber and provide jobs in some of the rural areas.

Lichen species richness scores fell into the medium and 

high categories across Vermont; this is likely to be related 

to levels of sulfate deposition.

In Vermont and New Hampshire, the presence of invasive 

plant species is relatively low compared to neighboring 

New England states.

Decreases in foliar injury from ozone have occurred as 

ozone exposure rates have also decreased.

Areas of Concern

People at least 65 years old make up 24 percent of 

Vermont’s family forest owners and own 36 percent of 

family forest acreage. Because of the large change in 

ownership that is likely to occur in the next two decades, 

it will be important to watch how the new owners 

manage their lands.

Due to the continuing increases in volume, Vermont’s 

timber resource is at record levels. However, this increase 

has leveled off and may continue to do so as the forest 

continues to mature, reducing future growth rates.

The mortality rate (0.9 percent) for 1997 to 2007 is the 

highest ever reported in an FIA inventory of Vermont, 

but this rate is comparable to those in surrounding states.

Twenty percent of the American beech basal area had 

poor crowns; this condition is likely to be related to the 

impacts of beech bark disease.

Issues to Watch

Reversion of farmland to forest land continues to 

outpace the loss of forest land to development. Vermont’s 

forest base has remained stable since 1997.

The small parcels held by many landowners complicate 

the economics of forest management and the delivery of 

government programs. The trend toward more landowners 

with smaller parcels will only increase this problem.

Cumulative ecological impacts on forest land from roads 

should be a very real consideration.

A statistically signifi cant decrease in area of smalldiameter stands and a statistically signifi cant increase in 

area of large-diameter stands have both occurred over 

the past three decades. There needs to be continued 

monitoring as the forest matures and less area contains 

stands of small-diameter trees.

Highlights
2

The 1997 to 2007 period is the fi rst time that the 

growth-to-removal ratio dropped below 2.0:1.0 since 

the 1960s. Even with the slower growth rate, the current 

level of removals appears to be sustainable barring any 

increases in mortality.

Vermont’s forests are continuing to accumulate biomass 

as the forests mature. Because most of the biomass is in 

the boles of growing-stock trees, and most of the gains 

in biomass stocks are found in the high value sawtimbersize trees, only a fraction of the accumulated material is 

available for use as fuel.

Changes in species composition point toward potential 

reductions in tree quality for sawtimber into the future. 

Two of the species with a high proportion of low grade 

volume, American beech and red maple, are the same 

species that are showing large increases in saplings.

An important consideration for landowners actively 

managing their land is the ability of the primary woodproducts industry to retain pulp mills, sawmills, and 

veneer mills. The number of wood-processing mills has 

been steadily declining across the region.

The scarcity of large coarse woody debris resources may 

indicate lower quality habitat for some wildlife species.

Invasive insect pests that may impact abundant tree 

species in Vermont in the future include the emerald ash 

borer and Asian longhorned beetle.

The presence of invasive plants may have caused a 

reduction in seedling cover based upon data collected in 

Vermont and New Hampshire.
3

Background

Photo by Randall Morin, U.S. Forest Service.
4

 BACKGROUND

Data Sources and Techniques

The forests of Vermont are one of the State’s most 

valuable assets due to their importance to Vermont’s 

economy and the quality of life for its residents. Accurate 

and statistically defensible information is critical for 

understanding the current conditions, interpreting trends 

over time, and projecting future scenarios. In this report 

we highlight the current status and trends observed in 

Vermont’s forests.

This inventory was a cooperative effort of the Northern 

Research Station, the Vermont Department of Forests, 

Parks and Recreation, and landowners of Vermont, and 

is the culmination of the fi rst complete inventory of 

Vermont’s forests using FIA’s annualized forest inventory 

system. Previous forest inventories, completed in 1948 

(McGuire and Wray 1952), 1965 (Kingsley and Barnard 

1968), 1973 (Kingsley 1977, Frieswyk and Malley 

1985), 1983 (Frieswyk and Malley 1985, Frieswyk and 

Widmann 2000), and 1997 (Frieswyk and Widmann 

2000), were collected under a different inventory 

system in which states were inventoried periodically 

with no measurements made between inventories. The 

annualized system was implemented to provide updated 

forest inventory information every year based on a 5-

year cycle. The FIA program is the only source of data 

collected from a permanent network of ground plots 

from across the Nation that allows for comparisons 

among states and regions.

The FIA sampling design is based on a tessellation of the 

United States into hexagons approximately 6,000 acres in 

size with at least one permanent plot established in each 

hexagon. In Phase 1 (P1), of FIA’s multi-phase inventory, 

the population of interest is stratifi ed and plots are 

assigned to strata to increase the precision of estimates. 

In Phase 2 (P2), tree and site attributes are measured for 

forested plots established in each hexagon. Phase 2 plots 

consist of four 24-foot fi xed-radius subplots on which 

standing trees are inventoried. During Phase 3 (P3), 

forest health indicators are measured on a 1/16th subset 

of the entire FIA ground plot network so that each plot 

represents approximately 96,000 acres. The forest health 

indicators are tree crown condition, lichen communities, 

forest soils, vegetation diversity, down woody material, 

and ozone injury.

A Beginners Guide to the 

Forest Inventory

What is a tree?

The FIA program of the U.S. Forest Service defi nes a 

tree as a perennial woody plant species that can attain a 

height of at least 15 feet at maturity.

What is a forest?

A forest can come in many forms depending on climate, 

quality of soils, and the available gene pool for the 

dispersion of plant species. Forest stands range from 

very tall, heavily dense, and multi-structured, to short, 

sparsely populated, and single layered. FIA defi nes forest 

land as land that is at least 10 percent stocked by trees 

of any size or formerly having been stocked and not 

currently developed for nonforest use. The area with 

trees must be at least 1 acre in size and 120 feet wide.

What is the difference between 

timberland, reserved forest land, and 

other forest land?

From an FIA perspective, there are three types of forest 

land: timberland, reserved forest land, and other forest 

land. In Vermont, almost all (98 percent) of forest land 

is classifi ed as unreserved and productive timberland, 

1.5 percent is reserved and productive forest land, and 

the remaining 0.5 percent is unproductive reserved or 

unreserved forest land.
5

 BACKGROUND

• Timberland is unreserved forest land that meets the 

minimum productivity requirement of 20 cubic feet 

per acre/year.

• Reserved forest land is land withdrawn from timber 

utilization through legislation or administrative 

regulation.

• Other forest land is commonly found on low-lying 

sites or high craggy areas with poor soils where the 

forest is incapable of producing 20 cubic feet per 

acre. In earlier inventories, FIA measured trees only 

on timberland plots and did not report volumes on 

all forest land. Since the implementation of the new 

annual inventory in Vermont in 2003, FIA has been 

reporting volume on all forest land. 

• The second remeasurement of Vermont is in its 

fourth fi eld season, and by 2012, FIA will be able to 

compare two sets of growth, mortality, and removal 

data. Much of the trend reporting in this publication 

is focused on timberland, because comparing current 

data to data from older periodic inventories requires 

timberland estimates.

How many trees are in Vermont?

Vermont’s forest land contains about 835 million live 

trees that are at least 5 inches in diameter at breast 

height (d.b.h., diameter of the tree at 4.5 feet above the 

ground). We do not know the exact number of trees 

because the estimate is based upon only a sample of the 

total population. The frequency estimates are calculated 

from fi eld measurement of 802 forested plots classifi ed 

by ownership. For information on sampling errors, see 

the Statistics and Quality Assurance DVD at the back of 

this report.

How do we estimate a tree’s volume?

The volume for a specifi c tree species is usually 

determined by the use of volume equations developed 

specifi cally for a given species. Sample trees are felled and 

measured for length, diameter, and taper. Several volume 

equations have been developed at the Northern Research 

Station for each tree species found in the region. Models 

have been developed from regression analysis to predict 

volumes within a species group. We produce individual 

tree volumes based upon species, diameter, and 

merchantable height. Tree volumes are reported in cubicfoot and International 1⁄4-inch rule board-foot scale.

How much does a tree weigh?

Specifi c gravity values for each tree species or group 

of species were developed at the U.S. Forest Service’s 

Forest Products Laboratory and applied to FIA tree 

volume estimates for developing merchantable tree 

biomass (weight of tree bole). To calculate total live-tree 

biomass, we have to add the biomass for stumps (Raile 

1982), limbs and tops (Hahn 1984), and belowground 

stump and coarse roots (Jenkins et al. 2004). We do not 

currently report live biomass for foliage. FIA inventories 

report biomass weights as oven-dry short tons. Oven-dry 

weight of a tree is the green weight minus the moisture 

content. Generally, 1 ton of oven-dry biomass is equal to 

1.9 tons of green biomass.

How do we compare data from 

different inventories?

Comparing new inventories with older datasets is 

commonly conducted to analyze trends or changes 

in forest growth, mortality, removals, and ownership 

acreage over time (Powell 1985). A pitfall occurs when 

the comparison involves data collected under different 

schemes or processed using different algorithms. 

Recently, signifi cant changes were made to the methods 

for estimating tree-level volume and biomass (dry 

weight) for northeastern states, and the calculation 

of change components (net growth, removals, and 

mortality) was modifi ed for national consistency. These 

changes have focused on improving the ability to report 

consistent estimates across time and space—a primary 

objective for FIA. Regression models were developed for 

tree height and percent cull to reduce random variability 

across datasets.
6

 BACKGROUND

Before the Component Ratio Method (CRM) was 

implemented, volume and biomass were estimated using 

separate sets of equations (Heath et al. 2009). With 

the CRM, determining the biomass of individual trees 

and forests has become simply an extension of our FIA 

volume estimates. This allows us to obtain biomass 

estimates for growth, mortality, and removals of trees 

from our forest lands, not only for live trees, but also for 

their belowground coarse roots, standing deadwood, and 

down woody debris.

Another new method, termed the “midpoint method,” 

has introduced some differences in methodology for 

determining growth, mortality, and removals to a 

specifi ed sample of trees (Westfall et al. 2009). The 

new approach involves calculating tree size attributes 

at the midpoint of the inventory cycle (2.5 years for a 

5-year cycle) to obtain a better estimate for ingrowth, 

mortality, and removals. Although the overall net change 

component is equivalent under the previous and new 

evaluations, estimates for individual components will 

be different. For ingrowth, the midpoint method can 

produce a smaller estimate because the volumes are 

calculated at the 5.0-inch threshold instead of using 

the actual diameter at time of measurement. The actual 

diameter could be larger than the 5.0-inch threshold. 

The estimate for accretion is higher because growth on 

ingrowth, mortality, and removal trees are included. As 

such, the removals and mortality estimates will also be 

higher than before (Bechtold and Patterson 2005).

A word of caution on suitability and 

availability

FIA does not attempt to identify which lands are suitable 

or available for timber harvesting especially because 

suitability and availability are subject to changing 

laws and ownership objectives. Simply because land is 

classifi ed as timberland does not 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 harvesting because laws and 

regulations, voluntary guidelines, physical constraints, 

economics, proximity to people, and ownership 

objectives may prevent timberland from being available 

for production.
7

 Forest Features

Vermont fall color. Photo by Sandy Wilmot, Vermont Department of Forests, Parks & Recreation
8

FEATURES

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

4,000 

1950 1960 1970 1980 1990 2000 

Area (thousand acres) 

Year 

Figure 3.—Area of farmland (includes farm woodlots), Vermont, 1940-2008. 

(source: National Agriculture Statistics Service)

Dynamics of the Forest Land 

and Timberland Base

Background

Vermont hosts the transition of the maple/beech/birch 

forests of the northeastern United States to the spruce/fi r 

forests of northern New England. Because forests are so 

important for wood products, tourism, clean water, wildlife 

habitat, and biomass energy, evaluating change in the status 

and condition of those forests is important. The amounts of 

forest land and timberland are vital measures for assessing 

forest resources and making informed decisions about their 

management and future. Gains or losses in forest area are 

an indication of forest sustainability, ecosystem health, 

and land use practices, and they have a direct effect on the 

ability of forests to provide goods and services. Additionally, 

these measures are the basis for FIA’s estimates of numbers 

of trees, and amounts of wood volume and biomass.

What we found

Forests are the dominant land cover across most of 

Vermont. The percentage of forest cover generally 

increases from west to east (Fig. 1), mostly due to the 

belt of agricultural land in the Champlain Valley in 

northwestern Vermont. When FIA completed its fi rst 

inventory (1948) within Vermont, only 63 percent of the 

State’s area was forested. Subsequent inventories showed 

a steady increase in forest cover as lands were re-forested 

due to the abandonment of farmland. Vermont’s forested 

land base increased rapidly between the 1940s and 1970s 

and continued to increase at a decreasing rate until the 

1990s (Fig. 2). By contrast, the amount of farmland 

decreased by nearly 1.6 million acres over that period (Fig. 

3). Much of the nearly 1 million acre increase in forest 

land is due to farmland reverting back into forest through 

natural regeneration, although a substantial portion of lost 

farmland was also developed to meet the needs of a growing 

population. These reverted forests have increased the total 

forest land area in Vermont and nearly offset losses of forest 

land to development. Since 1997 the amount of forest 

cover has remained relatively stable (Figs. 2, 4). Currently, 

Vermont is about 75 percent forested.

Figure 1.—Distribution of forest land in Vermont, 2006.

Projection: Vermont State Plane, NAD83.

Sources: NLCD2006. Geographic base data are 

provided by the National Atlas of the USA. FIA 

data and Tools are available online at 

http://www.fi a.fs.fed.us/tools-data/

Cartography: R.S. Morin. March 2011

Water

Nonforest

Forest

3,600 

3,800 

4,000 

4,200 

4,400 

4,600 

4,800 

1948 1958 1968 1978 1988 1998 2008 

Area (thousand acres) 

Year 

Timberland 

Forest land 

Figure 2.—Area of forest land and timberland, Vermont, 1948, 1966, 1973, 1983, 

1997, and 2007. Error bars represent 68% confi dence interval around estimate.

N
9

FEATURES

1948

Figure 4.—Distribution of relative area of forest land by county and inventory 

year, Vermont, 1948, 1966, 1973, 1983, 1997, and 2007. (Grand Isle County 

not reported in 1966 or 1973 inventories and combined with Franklin County in 

1983 and 1997 inventories.)

Projection: Vermont State Plane, NAD83.

Sources: U.S. Forest Service, Forest Inventory and Analysis Program, 1948, 1966, 1973, 1983, 1997, and 

2007 data. Geographic base data are provided by the National Atlas of the USA. FIA data and Tools are 

available online at http://www.fi a.fs.fed.us/tools-data/

Cartography: R.S. Morin. May 2011

What this means

At 75 percent, Vermont is the fourth most forested state 

in the United States. The current statewide estimate 

of forest land remains statistically unchanged since 

1997 (Fig. 1). Future changes in Vermont’s forest land 

base will depend on the pace of land development, 

particularly in the northwestern and southern parts of 

the State, and the economics of farming.

Availability and Productivity 

of Forest Land 

Background

FIA’s three categories of forest land—timberland, 

reserved forest land, and other forest land—help clarify 

the availability of forest resources for forest management 

planning. Two criteria are used to determine the 

category: reserved status (unreserved or reserved) and site 

productivity (productive or unproductive). Forest land 

that is capable of growing trees at a rate of at least 20 

cubic feet per year and that is not legally restricted from 

being harvested is classifi ed as timberland. If harvesting 

is restricted on forest land by statute or administrative 

decision, then it is designated as reserved regardless of its 

productivity class. The harvesting intentions of private 

forest land owners are not used to determine the reserved 

status. The other forest land category is made up of 

forest land that is unreserved and low in productivity.

What we found

Ninety-eight percent of Vermont’s forest land meets 

the defi nition of timberland (Figs. 2, 5). The current 

statewide estimate of timberland has remained statistically 

unchanged since 1997. Most of the land in the reserved 

class is designated natural areas on the Green Mountain 

National Forest. Other forest land (i.e., unreserved and 

unproductive) is rare in Vermont and only accounts for 

less than 1 percent of total land area (Fig. 5).

1 2 3

4

5

8

11

1966

14

6

9

7

10

12

13

1 2 3

4

5

8

11

14

6

9

7

10

12

13

1 2 3

4

5

8

11

14

6

9

7

10

12

13

1 2 3

4

5

8

11

6

9

7

10

12

13

1 2 3

4

5

8

11

14

6

9

7

10

12

13

1 2 3

4

5

8

11

6

9

7

10

12

13

1973 1983

1997 2007

14

14

Relative Area 

of Forest Land 

(percent of county 

land area)

 Less than 26

 26-50

 50-75

 More than 75

 1. Grand Isle

 2. Franklin

 3. Orleans

 4. Lamoille

 5. Chittenden

 6. Caledonia

 7. Washington

 8. Addison

 9. Orange

 10. Rutland

 11. Windsor

 12. Bennington

 13. Windham

 14. Essex
10

FEATURES

What this means

Because the vast majority of Vermont’s forest land is 

classifi ed as timberland, it is potentially available for 

harvesting timber or other forest products. It also means 

that trends observed on timberland are likely to apply to 

forest land as well. The demand for forest products will 

increase as the number of industries that utilize them 

expands. Therefore, the balance of supply and demand 

for these forest products needs to be closely monitored. 

Later sections in this report provide more details on 

the amount of forest land actively managed for forest 

products and a more accurate estimate of the amount of 

timberland truly available for harvesting.

Ownership of Forest Land

Background

Forest land owners are a primary factor in determining 

how the distribution, composition, structure, and 

health of forest ecosystems will change into the future. 

Different types of owners (e.g., private, public) have 

varying objectives, opportunities, and constraints 

that govern their decisions about forest management 

practices. FIA conducts the National Woodland Owner 

Survey (NWOS) to further our understanding of who 

owns forest land, why they own it, and what they intend 

to do with it. The NWOS collects data on forest holding 

characteristics, ownership histories, ownership objectives, 

forest uses, forest management practices, preferred 

methods for receiving information, concerns, future 

intentions, and demographics (see Butler 2008).

What we found

A relatively small proportion of Vermont’s forest land is 

owned by the public (20 percent; Fig. 6). The Federal 

Government holds 489,000 acres (11 percent) of forest 

land, most of which is administered by the Green 

Mountain National Forest (424,900 acres of forest land). 

The State of Vermont holds 382,600 acres of forest 

land (8 percent) in various state agencies including state 

parks and forests, and local governments hold another 

42,700 acres of forest land (1 percent; Fig. 7). Public land 

increased by about 160,000 acres between 1997 and 2007 

after remaining stable between 1983 and 1997 (Fig. 8).

Vermont’s forest land is primarily held by private 

landowners (80 percent). Approximately 3 million acres, 

64 percent, of forest land is owned by 87,000 families 

and individuals (Butler 2008). Other kinds of private 

owners (e.g., corporations, nonfamily partnerships, 

nongovernmental organizations, clubs, and other 

nonfamily private groups) hold another 723,600 acres 

of forest land (16 percent; Fig. 7).

The number of family or individual forest owners in 

Vermont increased by 40 percent over the past two 

decades, from 62,000 to 87,000 (Butler 2008, Widmann 

and Birch 1988), during which the average forest 

landholding size decreased from 65 acres (Widmann and 

Birch 1988) to 37 acres (Butler 2008). The majority of 

family forest owners (53 percent) hold less than 10 acres 

of forest land, but represent only 6 percent of the total 

family forest land base in Vermont (Fig. 9). Family forest 

owners have a wide variety of reasons for holding forest 

land and objectives for land management. The most 

widely cited reason for forest land ownership in Vermont 

is that the forest land is part of residential property. 

Other common reasons are related to aesthetics, 

recreation, and family legacy (Fig. 10). Although only 

8 percent of individual or family forest owners listed 

timber production as an important reason for owning 

(4,493,300)

74%

(74,700)

1%

(20,600)

<1%

(1,511,000)

25% Timberland

Reserved forest land 

Other forest land 

Nonforest 

Figure 5.—Land area (acres) by major use, Vermont, 2007.
11

FEATURES

0 

10 

20 

30 

40 

50 

60 

1-9 

10-19 20-49 

50-99 

100-199 200-499 

500-999 

1,000+ 

Family Forest Owners (%) 

Size of Forest Holdings (acres) 

Area

Owners

Figure 9.—Area of family or individual owned forests and number of family or 

individual forest owners by size of forest landholdings, Vermont, 2006.

0 20 40 60 80 100

Timber production 

Part of farm 

Land investment 

Firewood production 

Family legacy 

Recreation (incl. hunting) 

Aesthetics/biodiversity 

Home/privacy 

Reason for Ownership 

Area

Owners

(%)

Figure 10.—Percentage of area and owners of family forests by reason for 

owning forest land, Vermont, 2006. (Numbers include landowners who ranked 

each objective as very important (1) or important (2) on a seven-point Likert 

scale. Categories are not mutually exclusive.)

(2,950,700)

64%

(723,600)

16%

(489,000)

11%

(382,600)

8%

(42,700)

1%

Family and individual

Other private

Federal

State

Local

Figure 7.—Forest land area (acres) by major ownership category, Vermont, 2007.

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

4,000 

4,500 

1983 1997 2007 

Area of Forest Land (thousand acres) 

Inventory Year 

Public

Private

Figure 8.—Forest land area by major ownership category, Vermont, 1983, 

1997, and 2007. Error bars represent 68% confi dence interval around estimate.

Figure 6.—Distribution of forest land by owner group, Vermont, 2007.

Forest Land Ownership

Water

 Nonforest

 Private

 Public

Projection: Vermont State Plane, NAD83. 

Sources: PAD v4.6, 2007. NLCD 2001. Geographic 

base data are provided by the National Atlas of the 

USA. FIA data and Tools are available online at 

http://www.fi a.fs.fed.us/tools-data/

Cartography: R.S. Morin. Apr. 2011

forest land, 53 percent of family forest owners (holding 

81 percent of family forest area) had harvested trees from 

their properties and 32 percent (holding 67 percent of 

family forest area) had harvested saw logs (Fig. 11).

Only 15 percent of family forest owners have a written 

management plan, but 50 percent of the family owned 

forest land is governed by one (Fig. 12). However, 26 

percent of the owners holding 54 percent of the family 

forest acreage have sought management advice. Private 

consultants and the Vermont Department of Forests, 

Parks and Recreation were most often contacted for 

advice. Additionally, about 30 percent of eligible privately 
12

FEATURES

owned forest land is currently enrolled in Vermont’s Use 

Value Appraisal (UVA) program (VFPR 2010). The UVA 

program, also called “Current Use” or “Land Use,” enables 

landowners who practice long-term forest management 

to have their enrolled land appraised for property taxes 

based on its value for forestry, rather than its fair market 

(development) value.

Nearly one-quarter of Vermont’s family forest owners are 

at least 65 years old. This group of owners also controls 

more than 35 percent of the family forest acreage (more 

than 2 million acres) in the State (Fig. 13). The 25 percent 

of family forest owners who have owned their forest for 

less than 10 years presumably refl ects the increase in the 

number of owners over the past decade. On the other 

hand, the tenure of family forest ownership is generally 

much longer. More than 40 percent of the family forest 

acreage has been under the same ownership for more than 

25 years (Fig. 14). The majority of family forest owners 

(51 percent) have minimal activity planned for their forest 

land over the next 5 years. The most common activity 

planned is harvesting fi rewood (Fig. 15).

Have written 

management plan 

Sought advice 

Private consultant 

State forestry agency 

Logger 

Another landowner

Extension

Federal agency 

Other 

Other state agency 

Forest industry 

10 0 20 40 30 60 50 

Family Owned Forests (%) 

Source of Advice 

Area

Owners

Figure 12.—Percentage of area and owners of family forests who have 

a written management plan, who have sought advice, and advice source, 

Vermont, 2006. (Categories are not mutually exclusive.)

0 

10 

20 

30 

40 

50 

<35 35-44 45-54 55-64 65-74 75+ No answer 

Family Owned Forests (%) 

Age Class (years) 

Area

Owners

Figure 13.—Percentage of area and owners of family forests by age of 

primary decisionmaker, Vermont, 2006.

 5 

 10 

 15 

 20 

 25 

 30 

 35 

 40 

<10 10-24 25-49 50+ No answer 

Family Owned Forests (%) 

Years of Ownership 

Area

Owners

Figure 14.—Percentage of area and owners of family forests by ownership 

tenure, Vermont, 2006.

 20 

 40 

 60 

 80 

 100 

Trees 

harvested

Saw 

logs

Veneer 

logs

Pulpwood Firewood

Family Owned Forests (%) 

Products Harvested 

Area

Owners

Figure 11.—Percentage of area and owners of family forests by harvesting 

experience and products harvested, Vermont, 2006. (Categories are not 

mutually exclusive.)
13

FEATURES

0 10 20 30 40 50 60 

Minimal activity 

No activity 

Harvest firewood 

No current plans 

Collect nontimber 

forest products 

Harvest saw logs 

or pulpwood 

Transfer some or all 

of forest land to heirs 

Unknown 

Sell some or all 

of forest land 

Buy more forest land 

Other 

No answer 

Land use conversion 

(forest to other) 

Land use conversion 

(other to forest) 

Subdivide some or 

all of forest land 

Family Owned Forests (%) 

Future Plans for Next Five Years 

Area

Owners

Figure 15.—Percentage of area and owners of family forests by plans for next 

5 years, Vermont, 2006.

What this means

Public ownership of forest land has increased in Vermont 

over the past 25 years. This increase refl ects increases in 

forest land ownership on the Green Mountain National 

Forest and within State and local governments. The 

number of forest land acres in public ownership is likely to 

increase in the coming years as more lands are conserved.

Because the majority of Vermont’s forest land is held 

by private landowners, future forest conditions will be 

greatly infl uenced by the decisions these owners make. 

The small parcels held by many landowners complicate 

the economics of forest management and the delivery of 

government programs. The trend of greater numbers of 

landowners controlling smaller parcels will only increase 

this problem into the future. If this trend continues, 

access to Vermont’s timber resources by the forest industry 

could decrease. Furthermore, landowners of smaller tracts 

of forest are less likely to allow access to their lands for 

recreation, which could lead to a decrease in forest-related 

recreation opportunities for people in Vermont.

Although the vast majority of landowners did not give 

a high priority to timber production, most appear to be 

willing to harvest when conditions are right. Because most 

owners do not have a written management plan, many 

harvests are unlikely to be a part of long-term planning.

The large number of landowners who are 65 years or 

older are likely to represent a large turnover of forest 

land ownership in the future. When forest land changes 

owners, parcelization and unsustainable harvesting 

practices are more likely to occur. In addition, increasing 

numbers of new landowners may make it more diffi cult 

for government agencies to provide advice, education, 

and services to family forest owners.

Urbanization and 

Fragmentation of Forest Land

Background

Forest fragmentation and habitat loss diminish 

biodiversity (Honnay et al. 2005). Fragmentation of 

forests is also recognized as a major threat to animal 

populations worldwide (Rosenberg et al. 1999a), 

particularly for bird species that are sensitive to habitat 

fragmentation (Donovan and Lamberson 2001) and for 

species that are wide ranging, slow moving, and/or slow 

reproducing (Forman et al. 2003, Maine Audubon 2007). 

The expansion of urban lands that accompanies human 

population growth often results in the fragmentation 

of natural habitat (Wilcox and Murphy 1985). Honnay 

et al. (2005) point out that spatial/physical fragmentation 

of habitats is only one of the human-induced processes 

affecting natural habitats and their biodiversity. 

Urbanization, increasing the proximity of people, 

development, and other anthropogenic pressures to natural 
14

FEATURES

habitats, and changing the ways in which humans use those 

natural habitats, can also lead to overexploitation of species, 

environmental/habitat deterioration, and introduction 

of exotic species. In addition to the negative effects on 

forested ecosystems, the fragmentation and urbanization 

of forest land may have direct economic and social effects. 

For example, smaller patches of forest or those in more 

populated areas are less likely to be managed for forest 

products (e.g., Kline et al. 2004, Wear et al. 1999) and are 

more likely to be “posted” (i.e., not open for public use) 

(Butler et al. 2004), potentially affecting forest industries as 

well as outdoor recreation opportunities and local culture. 

Forest land is also a signifi cant factor in the protection 

of surface and groundwater, and fragmentation and 

urbanization of that forest land have been observed to affect 

both water quality and quantity (e.g., Hunsaker et al. 1992, 

McMachon and Cuffney 2000, Riva-Murray et al. 2010).

The metrics presented here relate to some aspect of 

urbanization or fragmentation that is or has been 

documented to have or suspected of having an effect on 

the forest, its management, or on its ability to provide 

ecosystem services and products (Riemann et al. 2008). 

These measures are forest edge versus interior, proximity 

to roads, patch size, local human population density, and 

intermixed house densities.

What we found

In Vermont, 73 percent of the forest land is more than 

300 feet from an agriculture use or developed edge. This 

ranges from 39 percent in more fragmented Grand Isle 

County to 92 percent in Essex County (Table 1).

Figures 16 and 17 show where and to what extent forest land 

is affected by roads. As both Forman (2000) and Riitters and 

Table 1.—The distribution of forest land with respect to several urbanization and fragmentation factors, expressed as a percent of the forest land in each county, 

Vermont, 2007

Addison 56 25 71 58 92 3

Bennington 86 21 81 59 98 3

Caledonia 80 21 70 43 98 2

Chittenden 64 53 66 47 93 14

Essex 93 6 92 61 99 1

Franklin 62 24 64 54 95 4

Grand Isle 38 87 39 41 77 6

Lamoille 84 30 77 56 98 3

Orange 81 27 68 38 98 2

Orleans 75 19 69 51 97 2

Rutland 78 28 73 54 97 4

Washington 83 41 73 45 98 5

Windham 87 43 72 42 98 3

Windsor 83 38 69 39 97 3

State Total 78 29 73 49 97 3

a

 Percent forest estimate based on NLCD 2001. Values are generally higher than estimates from FIA plot data. 

b

 Approximating the forest land potentially affected by underlying development. 

c

 Approximating the forest land undisturbed by edge conditions. 

d

 Approximating the forest land outside the effects of roads. 

e

 Approximating the forest land with potentially enough core area for sustainable interior species populations. 

f

 Approximating the forest land not available for commercial forestry. 

 Forest land

 Forest land with Forest land Forest land located in a block

 house density > 295 feet Forest land located in with population

 % forest land > 15.5 per from an ag or > 980 feet patches > 100 densities > 

County in countya

 square mileb developed edgec from a roadd acres in sizee 150/square milef

 

 
15

FEATURES

Figure 16.—Distribution of forest land in distance to the nearest road classes 

(includes all roads), Vermont, 2000 and 2001.

Forest – Distance to Road 

 On road 

 < 325 feet 

 325 - 1,640 feet

 1,640 - 3,280 feet

 > 3,280 feet 

Nonforest Land Cover

 Urban development

 Barren

 Agriculture

 Water

Projection: Vermont State Plane, NAD83.

Sources: National Land Cover Dataset 2001, 

TIGER/Dynamap 2000 Geographic base 

data are provided by the National Atlas of 

the USA. FIA data and Tools are available 

online at http://www.fi a.fs.fed.us/tools-data/

Cartography: R. Riemann. Jan. 2011

0 

5 

10 

15 

20 

25 

on road 

< 200 

200-330 330-650 650-980 

980-1,310 

1,310-1,640 

1,640-1,970 1,970-2,300 

2,300-2,620

2,620-2,950 2,950-3,280 

3,280 

Forest Land (%) 

Distance to Road (feet) 

Figure 17.—Distribution of forest land in distance to road classes (includes all 

roads), Vermont, 2000 and 2001.

Figure 18.—Percent of forest cover in patches less than 100 acres, by 

62.1-square mile grid cell, Vermont, 2000.

Percentage of Forest in Patches 

Less Than 100 Acres

 > 30

 20 - 30

 10 - 20

 < 10

Projection: Vermont State Plane, NAD83.

Sources: National Land Cover Dataset 2001

Geographic base data are provided by the

National Atlas of the USA. FIA data and

Tools are available online at

http://www.fi a.fs.fed.us/tools-data/

Cartography: R. Riemann. Jan. 2011

0 10 20 30 40 50 60 70 80 90 100

Addison 

Bennington 

Caledonia 

Chittenden 

Essex 

Franklin 

Grand Isle 

Lamoille 

Orange 

Orleans 

Rutland 

Washington 

Windham 

Windsor 

Forest Land 

County 

(acres) 

>50K

10K-50K

5K-10K 

1K-5K 

500-1K

100-500

50-100

< 50

Figure 19.—Distribution of forest land by patch size by county, Vermont, 2000.

et al. 2000). Forested areas containing higher proportions 

of small patches (<100 acres) occur along the river valleys in 

northwestern Vermont (Fig. 18). Most counties have a very 

low proportion of forest land in small patches (Fig. 19).

Wickham (2003) reported, this effect can be quite extensive, 

even in areas that appear to be continuous forest land from 

the air. In Vermont, for example, 22 percent of the forest 

land is within 330 feet of a road of some sort and 48 percent 

is within 980 feet.

Forest land in Vermont occurs primarily as a relatively 

contiguous forest matrix within which urban development, 

agriculture, roads, and other nonforest areas occur (Riitters 
16

FEATURES

The Wildland-Urban Interface (WUI) is commonly 

defi ned as the zone of transition between unoccupied 

land and human development; here we use a house 

density of above 15.5 houses per square mile as the 

threshold for WUI. Figures 20 and 21 illustrate how 

much forest land is affected by house densities greater 

than 15.5 houses per square mile. Counties range from 6 

percent (Essex) to 53 percent (Chittenden) of the forest 

intermixed with house densities of >15.5 per square mile, 

except for Grand Isle County at 87 percent (Fig. 21). 

Almost 25 percent of the live-tree basal area in Vermont 

is within the WUI, but this proportion is higher for 

eastern white pine (Pinus strobus) and eastern hemlock 

(Tsuga canadensis) (Fig. 22).

Table 1 brings many of these factors together and 

presents the extent to which the current forest land base 

is being infl uenced by one or more of the factors. For 

example, in Essex County, which is 93 percent forested, 

6 percent of the forest land is potentially affected by 

house densities greater than 15.5 per square mile, and 92 

percent of the forest land is far enough from an edge to 

be considered interior forest. Nearly all of the forest land 

is in large patches (>100 acres), but only 61 percent is 

more than 980 feet from a road. In Windham County, 

which is 87 percent forested, 43 percent of the forest 

land is potentially affected by house densities greater 

than 15.5 per square mile, and 72 percent of the forest 

land is far enough from an edge to be considered interior 

forest. Nearly all of that forest land is in large patches 

(>100 acres), but only 42 percent is more than 980 feet 

from a road. On the other end of the spectrum are the 

forests in Grand Isle County, which occupy 38 percent 

of the land area and occur largely mixed with housing 

densities above 15 per square mile (87 percent of the 

forest land). The forests tend to occur in smaller patches 

(77 percent of the forest is in patches >100 acres), and 

the county has correspondingly much less interior forest 

land than other areas (39 percent). 

Figure 20.—Distribution of forest land by house density classes, Vermont, 

2000 and 2001.

Forest by House Density 

(Census 2000 – block level data) 

houses / sq. mile

 0

 < 15.5

 15.5 - 127

 127 - 1,920

 > 1,920 

 Nonforest

 Water

Projection: Vermont State Plane, NAD83. 

Sources: National Land Cover Dataset 2001. 

Geographic base data are provided by the National 

Atlas of the USA. FIA data and Tools are available 

online at http://www.fi a.fs.fed.us/tools-data/

Cartography: R. Riemann. Jan. 2011

0 10 20 30 40 50 60 70 80 90 100

County 

Forest Land (%) 

(houses per square mile) 

0

< 15.5

15.5-127 

127-1,920 

> 1,920 

Windsor 

Windham 

Washington 

Rutland 

Orleans 

Orange 

Lamoille 

Grand Isle 

Franklin 

Essex 

Chittenden 

Caledonia 

Bennington 

Addison 

Figure 21.—Distribution of forest land by county and house density class, 

Vermont, 2000 and 2001.
17

FEATURES

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

All Sugar

maple

Red

maple

Eastern 

white pine

Eastern 

hemlock

Live Basal Area (%) 

Species 

Non-WUI WUI

Figure 22.—Proportion of basal area in the Wildland-Urban Interface (WUI) by 

species, Vermont, 2007.

What this means

Edge effects vary somewhat with distance from forest 

edge, depending on the type of effect and species of 

vegetation or wildlife, (e.g., Chen et al. 2002, Flaspohler 

et al. 2001, Rosenberg et al. 1999a), but 100 to 300 feet 

is frequently used as a general range for the “vanishing 

distance” or the distance into a patch where the edge 

effect disappears and interior forest conditions begin.

Figures 16 and 17 depict the pervasiveness of roads in 

the landscape, even in Vermont. Road effects diminish 

when distance from road to forest reaches about 330 

feet for secondary roads (a rough estimate of a highly 

variable zone), 1,000 feet for primary roads in forest 

(assuming 10,000 vehicles per day), and 2,650 feet from 

roads in urban areas (50,000 vehicles per day) (Forman 

2000). Roads have a variety of effects, including 

hydrologic changes, chemical changes (salt, lead, 

nutrients), sediment load changes, noise level changes, 

introduction of invasive species, habitat fragmentation, 

increases in human access, impacts on forest ecosystem 

processes, wildlife movement and mortality, and 

human use of the surrounding area. Vermont and the 

northern New York-New England forest region are 

some of the few areas in the eastern United States with 

less than 60 percent of their land area within 1,250 

feet of the nearest road (Riitters and Wickham 2003). 

With 62 percent of Vermont’s forest land within 1,310 

feet of a road statewide, cumulative ecological impacts 

from roads should be a very real consideration. Actual 

ecological impacts of roads will vary by the width of 

the road and its maintained right-of-way, number of 

cars, level of maintenance (salting, etc.), number of 

wildlife-friendly crossings, hydrologic changes made, 

perviousness of road surfaces, location with respect to 

important habitat, and other factors. These variables 

also suggest some of the changes that can be made to 

moderate the impact of roads (Forman 2000, Forman 

et al. 2003, Maine Audubon 2007).

Habitat requirements for wildlife vary by species, but 

for reporting purposes it is often helpful to summarize 

forest patch data using general guidelines. Many wildlife 

species prefer contiguous forest patches that are at least 

100 acres. This patch area is often used as the minimum 

size that still contains enough interior forest to be 

a source rather than a sink for populations of some 

wildlife species. Excluding the impact of roads that do 

not break the tree canopy, the majority of Vermont’s 

forest land is in patches larger than 100 acres. 

Human population is generally recognized as having 

a negative effect on the viability and practice of 

commercial forestry (Barlow et al. 1998, Kline et al. 

2004, Munn et al. 2002, Wear et al. 1999). Working 

in Virginia, Wear et al. (1999) identifi ed a threshold of 

150 people per square mile as the population density 

at which the probability of commercial forestry drops 

to practically zero. Only 3 percent of forest land 

in Vermont is near population centers that exceed 

the threshold of 150 people per square mile, but 

this proportion is higher in northwest Vermont in 

Chittenden (14 percent) and Grand Isle (6 percent) 

counties (Table 1).

Forest intermixed with houses represents areas of forest 

cover most likely to be in nonforest land use and more 

likely to be experiencing pressures from recreation, 

invasive plant species, and other local human effects. 

This intermix area also represents a challenge to 

managing forest fi res. A threshold of 15.5 houses per 

square mile represents the approximate density at which 

fi refi ghting switches from “wildland” to “structure” 
18

FEATURES

techniques and costs (Radeloff et al. 2005). Although 

the other pressures from high housing densities are likely 

to be more of an issue than forest fi res in Vermont, 

thresholds for those issues are less developed at this 

point. Therefore, Figure 20 should be interpreted as 

identifying where areas of increased pressure from 

intermixed residential development are likely to occur. 

Nationwide, increases in lower density, “exurban” 

development have been forecast by both Theobald 

(2005) and Hammer et al. (2004), particularly at the 

urban fringe and in amenity rich rural areas.

Forest health, sustainability, management opportunities, 

and the ability of forest land to provide needed products 

and ecosystem services are affected to varying degrees, 

and in different ways, by changes in the fragmentation 

of forests and urbanization. 

Stand Size and Structure – 

A Growing, Maturing Forest

Background

Tree diameter measurements are used by FIA to assign 

one of three stand-size classes to sampled stands, which 

give a general indication of stand development. The 

categories are determined by the class that accounts for 

the most stocking of live trees per acre. Small-diameter 

stands are dominated by trees less than 5 inches d.b.h. 

Medium-diameter stands have a majority of trees at least 

5 inches d.b.h. but fewer than in the large-diameter 

stands. Large-diameter stands consist of a preponderance 

of trees at least 9 inches in d.b.h. for softwoods and 11 

inches d.b.h. for hardwoods.

Stocking is a measure of the relationship between the 

growth potential of a site and the occupancy of the land 

by trees. The relative density (or stocking) of a forest is 

important for understanding growth, mortality, and yield. 

Five classes of stocking are reported by FIA: nonstocked 

(0 to 9 percent), poor (10 to 34 percent), moderate (35 

to 59 percent), full (60 to 100 percent), and overstocked 

(>100 percent). Stocking levels in Vermont are examined 

using all live trees and growing-stock trees only to identify 

the amount of growing space being used to grow trees 

of commercial value as opposed to the amount occupied 

by trees of little to no commercial value. For a tree to 

qualify as growing stock, it cannot be a noncommercial 

species (e.g., striped maple (Acer pensylvanicum), eastern 

hophornbeam (Ostrya virginiana), and pin cherry (Prunus 

pensylvanica)) or contain large amounts of cull (rough 

and rotten wood). The growth potential of a stand is 

considered to be reached when it is fully stocked. As 

stands become overstocked, trees become crowded, growth 

rates decline, and mortality rates increase. Poorly stocked 

stands can result from poor harvesting practices or forest 

growth on abandoned agricultural land; in contrast to 

moderately stocked stands, poorly stocked stands are not 

expected to grow into a fully stocked condition within a 

practical amount of time for timber production. 

What we found

The distribution of forest land by size class has changed 

substantially since 1983 (Fig. 23). A statistically 

signifi cant decrease in area of small-diameter stands and 

a statistically signifi cant increase in area of large-diameter 

stands have both occurred. Area of medium-diameter 

stands has remained unchanged. The trend is even more 

evident when the current estimates are compared with 

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

Small Medium Large 

Area of Forest Land (thousand acres) 

Stand-size Class 

1983

1997

2007

Figure 23.—Area of forest land by stand-size class, Vermont, 1983, 1997, and 

2007. Error bars represent 68% confi dence interval around estimate.
19

FEATURES

those from the 1948 inventory (McGuire and Wray 1952; 

Fig. 24). Timberland area in medium-diameter stands 

decreased from 40 percent in 1948 to only 27 percent 

in 2007, and timberland area in large-diameter stands 

increased from 51 percent in 1948 to 64 percent in 2007.

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

Small Medium Large 

Area of Timberland (thousand acres) 

Stand-size Class 

51%

64% 

9% 9% 

40% 

27% 

1948

2007

Figure 24.—Area of timberland by stand-size class, Vermont, 1948 and 2007.

1983

1997

2007

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

Area of Forest Land (thousand acres) 

Stocking Class 

Nonstocked Poorly Moderately Fully Overstocked 

Figure 25.—Area of forest land by stocking class of all live trees, Vermont, 1983, 

1997, and 2007. Error bars represent 68% confi dence interval around estimate.

1983

1997

2007

0 

500 

1,000 

1,500 

2,000 

2,500 

Nonstocked Poorly Moderately Fully Overstocked 

Area of Forest Land (thousand acres) 

Stocking Class 

Figure 26.—Area of forest land by stocking class of growing-stock trees, 

Vermont, 1983, 1997, and 2007. Error bars represent 68% confi dence interval 

around estimate.

0 

100 

200 

300 

400 

500 

600 

700 

800 

900 

1,000 

0-20 21-40 41-60 61-80 81-100 100+ 

Area of Forest Land (thousand acres) 

Age Class of Overstory Trees (years) 

Nonstocked

Poorly stocked

Moderately stocked

Fully stocked

Overstocked

Figure 27.—Area of forest land by stocking class of growing-stock trees and 

stand-age class, Vermont, 2007.

Since 1983, forest land area in the moderately and fully 

stocked classes for all live trees and growing-stock trees 

has increased by 1.5 million acres for all trees and by 

400,000 acres for growing-stock trees; at the same time 

overstocked area has decreased by 1.4 million acres for all 

trees and by 500,000 acres for growing-stock trees. Only 

about 30 percent of stands are less than fully stocked as 

of 2007. A comparison of nonstocked or poorly stocked 

stands for all live trees and growing-stock trees in 2007 

reveals that the area is 2.5 times greater for growing-stock 

trees (489,000 to 198,000 acres) (Figs. 25, 26). Out 

of the nearly one-half million acres that are poorly or 

nonstocked with growing-stock trees, nearly 33 percent 

are less than 40 years old and 80 percent are less than 80 

years old (Fig. 27).

What this means

The trend of increasing forest land area in large-diameter 

stands demonstrates clearly the continuing maturation 

of Vermont’s forests to stands of larger, older trees. An 

important component of forest biodiversity is complex 

structural features. Although the area of forest in smaller 

diameter stands is decreasing, mature stands do provide 
20

FEATURES

diverse structures because of gap dynamics and the 

presence of shade-tolerant species in the understory. The 

diversity of tree ages and sizes present in mature forests 

provides a broad range of habitats for wildlife and other 

organisms and makes forests more dynamic and better 

able to recover from disturbance. 

The shifts in forest area out of nonstocked, poorly 

stocked, and overstocked stands into moderately and fully 

stocked stands indicate that forest management practices 

over the past three decades have improved the general 

stocking condition across the State. The majority of 

Vermont’s forest land is well stocked with tree species of 

commercial importance. From a commercial perspective, 

continued management of these stands should keep them 

growing optimally by preventing them from becoming 

overstocked. From an ecological perspective, Vermont has 

a very low percentage of older forests, so consideration 

may be given to allowing some areas to continue growing 

beyond commercial benchmarks, which would allow the 

development of some ecologically mature forests that 

support certain wildlife species and ecological processes. 

Although the nearly one-half million acres of forest land 

that is poorly or nonstocked with commercially important 

species represents a loss of potential growth, these forests 

do contribute to biodiversity. However, the higher light 

levels and open growing conditions in these poorly 

stocked or nonstocked stands may make them more 

susceptible to invasion by nonnative plant species (e.g., 

common barberry (Berberis vulgaris), multifl ora rose (Rosa 

multifl ora)).

Numbers of Trees

Background

A basic component of forest inventory is the number of 

trees; these estimates are simple, reliable, and comparable 

with estimates from past inventories. When combined 

with species and size, estimates of numbers of trees are 

valuable for showing the structure of forests and changes 

that are occurring over time. Young forests generally have 

many more trees per acre than older forests, but the latter 

usually have much more wood volume (or biomass) than 

younger forests. 

What we found

Between 1983 and 1997, numbers of trees increased across 

all diameter classes with the greatest increases occurring in 

the smaller d.b.h. classes. Since 1997, the number of trees 

in the 12-inch and smaller d.b.h. classes has decreased while 

the number of trees in the larger classes has continued to 

increase. The curves of numbers of trees by diameter class 

have shifted to the right (Fig. 28). In general, the percentage 

increase in the number of trees by diameter class increased 

with increasing diameter class (Fig. 29).

0 

50 

100 

150 

200 

250 

300 

6 8 10 12 14 16 18 20 22 24+ 

Number of Trees (million trees) 

Diameter Class (inches) 

1983 

1997 

2007 

Figure 28.—Number of growing-stock trees on timberland by diameter class, 

Vermont, 1983, 1997, and 2007.

-15 

-10 

-5 

0 

5 

10 

15 

20 

25 

30 

35 

6 8 10 12 14 16 18 20 22-29 29+ 

Change (%) 

Diameter Class (inches at breast height) 

Figure 29.—Percent change in the numbers of growing-stock trees by 

diameter class, Vermont, 1997-2007.
21

FEATURES

When we look at growing-stock trees 5 inches and larger 

d.b.h., sugar maple (Acer saccharum) continues to be the most 

numerous tree species in Vermont even though it decreased 

in number between 1997 and 2007. Most other abundant 

species in Vermont also decreased in number during that 

period—eastern hemlock, balsam fi r (Abies balsamea), red 

spruce (Picea rubens), yellow birch (Betula alleghaniensis), 

eastern white pine, and paper birch (Betula papyrifera). 

Red maple (Acer rubrum) numbers remained stable while 

American beech (Fagus grandifolia) and white ash (Fraxinus 

americana) actually increased in numbers (Fig. 30).

0 25 50 75 100 125 150 

White ash 

Paper birch 

Eastern white pine 

Yellow birch 

Red spruce 

American beech 

Balsam fir 

Eastern hemlock 

Red maple 

Sugar maple 

Number of Growing-stock Trees (million trees) 

Species 

-2% 

No change 

-5% 

-22% 

+9% 

-12% 

-2% 

-10% 

-20% 

+11% 

1983

1997

2007

Figure 30.—Number of growing-stock trees on timberland by species, 

Vermont, 1983, 1997, and 2007, and percent change, Vermont, 1997-2007.

0 200 400 600 

Paper birch 

Eastern hemlock 

White ash 

Yellow birch 

Red spruce 

Red maple 

Balsam fir 

Sugar maple 

American beech 

Noncommercial species 

Number of Saplings (million trees) 

Species 

+12

+45%

-4%

+7%

+5%

+18%

+17%

+32%

+11%

+41%

1997

2007

Figure 31.—Number of saplings (1 to 4.9 inches in d.b.h.) on timberland by 

species, Vermont, 1997 and 2007, and percent change, Vermont, 1997-2007. 

(Noncommerical species includes striped maple, eastern hophornbean, pin 

cherry, and other species with poor form).

decreasing, indicating that as trees grow into larger size 

classes they are not being replaced by smaller trees growing 

into the medium-diameter classes, but the number of trees 

in the medium-diameter category should increase when 

ingrowth from the small-diameter classes occurs (Fig. 32).

Saplings in today’s forest are a prime indicator of the 

composition of the future forest. Saplings eventually 

replace large trees that are harvested or killed by insects, 

diseases, or weather events. The increasing dominance of 

American beech in the understory will have an impact on 

the future species composition of Vermont’s forests. The 

lack of eastern white pine saplings may indicate a future 

By contrast, most tree species increased in numbers of problem with regeneration of white pine stands.

sapling-size trees (1 to 4.9 inches d.b.h.). Due to a large 

increase between 1997 and 2007, American beech saplings 

have surpassed sugar maple to become the most numerous 

of any species in Vermont. Other abundant tree species 

showing large increases in number of saplings during this 

period are white ash and paper birch. The only major 

species to show a decrease in number of saplings is sugar 

maple (Fig. 31).

What this means

Since 1983, the number of large-diameter trees has been 

increasing steadily in Vermont. More recently, the number 

of trees in the 6- through 12-inch d.b.h. classes has been 

1983

1997

2007

0 

500 

1,000 

1,500 

2,000 

2,500 

Large Medium Small 

Number of Growing-stock Trees 

(million trees) 

Diameter Size Class 

Figure 32.—Number of growing-stock trees by size class, Vermont, 1997 and 2007.
22

FEATURES

Biomass

Background

Due to the important role of trees in the carbon cycle, 

forests act as a major sink for carbon by removing 

carbon dioxide from the atmosphere and storing it in 

wood tissue. About half of a trees biomass is comprised 

of carbon. The increasing interest in carbon dynamics 

for questions related to carbon sequestration, emission 

reduction targets, production of biofuels, and forest 

fi re fuel loadings makes estimates of biomass a critical 

component of the FIA program. Biomass is defi ned by 

FIA as the aboveground weight of live trees composed 

of the boles, aboveground portion of stumps, tops, and 

limbs (but excluding foliage). Due to increases in tree 

volume, Vermont’s forests contribute signifi cantly to 

carbon sequestration (uptake and storage). Vermont has 

also been a leader in biomass heat and power for the 

past two decades and continues to increase use of energy 

derived from sustainably harvested biomass.

What we found

The forest land of Vermont has an estimated 273.3 

million dry tons of aboveground tree biomass (an average 

of 59.6 tons per acre). The distribution of biomass per 

acre on forest land is displayed in Figure 33. Biomass per 

acre is highest in southern Vermont and along the Green 

Mountains in north-central Vermont.

The largest portion of the biomass is in the boles of 

growing-stock trees (63 percent), but this is also the part 

of the tree that can be converted into valuable wood 

products. The other 37 percent of the biomass is in tops, 

limbs, stumps, cull trees, or trees of noncommercial 

species (Fig. 34).

Total live dry biomass on timberland has increased by 44 

percent since 1983 (189.4 to 268.9 million dry tons). 

This increase is primarily due to the increasing size of 

sawtimber trees in Vermont. Biomass also increased slightly 

in the sapling size class. By contrast, biomass decreased in 

poletimber-sized trees during this period (Fig. 35).

Figure 33.—Live-tree biomass per acre of trees at least 1 inch d.b.h. (dry 

tons), Vermont, 2006.

Biomass of Live Trees on 

Forest Land (tons per acre)

 0 - 10

 10 - 20

 20 - 40

 40 - 60

 60 - 175

 Water

 Nonforest

Projection: Vermont State Plane, NAD83.

Sources: FIA and NLCD 1992.

Geographic base data are provided by the National 

Atlas of the USA. FIA data and Tools are available 

online at http://www.fi a.fs.fed.us/tools-data/

Cartography: R.S. Morin. Dec. 2010

63%

19%

8%

8% 2%

Growing-stock bole 

( 5 inches d.b.h.) 

Growing-stock tops/

limbs/stumps

( 5 inches d.b.h.) 

Saplings 

(<5 inches d.b.h.) 

Non-growing-stock bole 

( 5 inches d.b.h.)

Non-growing-stock tops/

limbs/stumps

( 5 inches d.b.h.)

Figure 34.—Percentage of live-tree biomass (trees 1 inch d.b.h. and larger) on 

forest land by aboveground component, Vermont, 2007.

Figure 35.—Distribution of live-tree biomass (trees at least 1 inch d.b.h.) on 

timberland by species group and 2-inch diameter class, Vermont, 1983 and 2007.

0 

5,000 

10,000 

15,000 

20,000 

25,000 

30,000 

35,000 

2 6 10 14 18 22 26 30 34 38 42+ 

Biomass (thousand dry tons) 

Diameter Class (inches) 

Hardwoods-1983

Hardwoods-2007

Softwoods-1983

Softwoods-2007
23

FEATURES

What this means

Vermont’s forests are continuing to accumulate biomass 

as the forests mature. Because most of the biomass is 

contained in the boles of growing-stock trees, and most 

of the gains in biomass stocks are found in the high value 

sawtimber-size trees, only a fraction of the accumulated 

material is available for use as fuel. If the demand for 

biomass increases with increases in heating, power 

production, and (potentially) the production of liquid 

fuels, the market would become more competitive as the 

wood products industry looks for more material. This 

creates an opportunity for enhancing forest management 

practices to benefi t both traditional forest products 

supplies and those for bioenergy. The Biomass Energy 

Resource Center produced a detailed report on supply 

and sustainability of woody biomass (Sherman 2007).

Private forest landowners are the holders of the majority 

of Vermont’s biomass (78 percent). Thus they play an 

important role in sustaining this resource. Currently, 

forest landowners are not fi nancially compensated for the 

carbon sequestration service that is provided by the trees 

on their land. Markets for forest carbon sequestration 

are growing so this scenario could change in the future. 

If carbon trading and biomass production become more 

common, reliable estimates of biomass and carbon in 

forests, both in the aboveground biomass and in soils, 

will become more important. The future of this scenario 

depends on political decisions and crude oil prices.

Volume of Growing-stock 

Trees

Background

To assess the amount of wood available for commercial 

products, the FIA program computes growing-stock 

volumes for trees meeting requirements for size, 

straightness, soundness, and species that are growing 

on timberland and available for harvest. Growing-stock 

volume includes only trees at least 5 inches d.b.h. and 

excludes rough, rotten, and dead trees in addition to 

noncommercial tree species. The forest products industry 

relies on this estimate of growing-stock volume as its 

resource base. Current volumes and changes in volume over 

time can characterize forests and reveal important resource 

trends, which is especially important because many past FIA 

inventories have only growing-stock estimates available.

What we found

The total growing-stock volume of the State has increased 

steadily since the 1960s as many cleared areas have begun 

to grow into forests again. The 2007 estimate of 9 billion 

cubic feet has not changed statistically since the 1997 

inventory. The increase in growing-stock volume of about 

0.3 percent annually is a reduction compared with the 

2- to 5-percent annual increases in previous decades (Fig. 

36). Distributions of growing-stock volumes by diameter 

class from the current and two previous inventories reveal a 

steady shift in timber volume toward larger diameter trees 

(Fig. 37). During the most recent inventory period (2003-

2007), volume increased in all d.b.h. classes larger than 10 

inches, but decreased in the 6-, 8-, and 10-inch diameter 

classes (Fig. 38). 

Softwoods

Hardwoods

0 

1,000 

2,000 

3,000 

4,000 

5,000 

6,000 

7,000 

1948 1966 1973 1983 1997 2007 

Growing-stock Volume (million ft3) 

Inventory Year 

Figure 36.—Growing-stock volume on timberland by species group and 

inventory year, Vermont, 1948, 1966, 1973, 1983, 1997, and 2007. Error bars 

represent 68% confi dence interval around estimate.

The level of growing-stock volume on timberland in 

Vermont averages almost 2,000 cubic feet per acre. Of 

this volume, 68 percent is in hardwood species and 32 

percent is in softwood species. Sugar maple (25 percent), 
24

FEATURES

American beech (23 percent), red maple (15 percent), 

and yellow birch (10 percent) make up nearly 75 percent 

of the hardwood growing-stock volume. Balsam fi r (42 

percent), red spruce (24 percent), eastern hemlock (18 

percent), and eastern white pine (18 percent) account for 

nearly 93 percent of softwood growing-stock volume.

Sugar maple continues to make up the largest amount 

of growing-stock volume, followed by red maple, 

eastern hemlock, and eastern white pine. These species 

make up 56 percent of the total growing-stock volume 

in Vermont. The only species that showed signifi cant 

increases in growing-stock volume were yellow birch 

and white ash, while the only species to have signifi cant 

decreases were paper birch and balsam fi r (Fig. 39).

-30 

-20 

-10 

0 

10 

20 

30 

40 

50 

60 

70 

80 

6 8 10 12 14 16 18 20 

Change (%) 

Diameter Class (inches) 

1983-1997

1997-2007

Figure 38.—Percent change in growing-stock volume by diameter class on 

timberland, Vermont, 1983-1997 and 1997-2007.

0 500 1,000 1,500 2,000 2,500 

Northern white-cedar 

Black cherry 

Sweet birch 

Quaking aspen 

Northern red oak 

Balsam fir 

Paper birch 

Red spruce 

White ash 

American beech 

Yellow birch 

Eastern white pine 

Eastern hemlock 

Red maple 

Sugar maple 

Growing-stock Volume (million ft3) 

Species 

1997

2007

Figure 39.—Growing-stock volume on timberland by species, Vermont, 1997 

and 2007. Error bars represent 68% confi dence interval around estimate.

0 

200 

400 

600 

800 

1,000 

1,200 

1,400 

1,600 

1,800 

6 8 10 12 14 16 18 20 

Growing-stock Volume (million ft3) 

Diameter Class (inches) 

1983 

1997 

2007 

Figure 37.—Growing-stock volume on timberland by diameter class and 

inventory year, Vermont, 1983, 1997, and 2007. Error bars represent 68% 

confi dence interval around estimate.

When we estimate board-foot volume, the order of the 

top four species by volume is slightly different from 

that of growing-stock volume. The increase in total 

board-foot volume is statistically signifi cant (from 23.1 

billion board feet in 1997 to 27.2 in 2007). Sugar maple 

remains the leading species by a large margin, but eastern 

white pine replaces red maple as the second highest and 

red maple drops below both eastern white pine and 

eastern hemlock. These four species make up 60 percent 

of the total sawtimber volume in Vermont (Fig. 40). 

Sugar maple, eastern white pine, and red maple increased 

signifi cantly in sawtimber volume between the 1997 and 

2007 inventories. Sawtimber volume of yellow birch, 

white ash, and northern red oak (Quercus rubra) also 

increased signifi cantly; no major species decreased.

The distribution of total growing-stock volume and 

growing-stock volume for the top four species is shown 

in Figure 41. Total volume is evenly distributed with 

slightly higher volumes in the southern portion of the 

State and along the Green Mountains to the north. 

Volume per acre varies spatially by species. Sugar 

maple is distributed throughout most of Vermont with 

higher volumes at higher elevations along ridges. Red 

maple is also distributed throughout the State; the 
25

FEATURES

Species 

1997

2007

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 

Sweet birch 

Black cherry 

Quaking aspen 

Balsam fir 

Paper birch 

American beech 

Red spruce 

Northern red oak 

White ash 

Yellow birch 

Red maple 

Eastern hemlock 

Eastern white pine 

Sugar maple 

Billion Board Feet 

Figure 40.—Board-foot volume on timberland by species, Vermont, 1997 and 

2007. Error bars represent 68% confi dence interval around estimate.

Figure 41.—Growing-stock volume per acre (trees at least 5 inches d.b.h.) on 

forest land, Vermont, 2006.

Projection: Vermont State Plane, NAD83.

Sources: FIA and NLCD 1992. 

Geographic base data are provided by the 

National Atlas of the USA. FIA data and Tools 

are available online at 

http://www.fi a.fs.fed.us/tools-data/ 

Cartography: R.S. Morin. Dec. 2010

Growing-stock 

Volume on 

Timberland (ft3)

 < 400

 400 - 1,000

 1,000 - 1,600

 1,600 - 2,400

 > 2,400

 Water 

 Nonforest

Eastern Hemlock

Eastern White Pine

Growing-stock 

Volume on 

Timberland (ft3)

 < 100

 100 - 250

 250 - 500

 500 - 1,000

 > 1,000

 Water

 Nonforest

Growing-stock 

Volume on 

Timberland (ft3)

 < 75

 75 - 200

 200 - 400

 400 - 600

 > 600

 Water

 Nonforest

Growing-stock 

Volume on 

Timberland (ft3)

 < 75

 75 - 150

 150 - 400

 400 - 600

 > 600

 Water 

 Nonforest

Growing-stock 

Volume on 

Timberland (ft3)

 < 75

 75 - 200

 200 - 400

 400 - 800

 > 800

 Water 

 Nonforest

Total Sugar Maple

Red Maple

highest volumes are generally in the south. Most of the 

eastern hemlock and eastern white pine volume is in 

the southern half of Vermont in the Connecticut River 

Valley along the border with New Hampshire.

What this means

Because of the continuing increases in volume, Vermont’s 

timber resources are at record levels since FIA began 

doing inventories in 1948. Although growing-stock 

volumes continue to increase, this increase has slowed 

and may continue to do so because of the aging forest 

and reduced growth rates. By contrast, signifi cant 

increases are concentrated in sawtimber-size trees, as 

illustrated by the signifi cant increase in sawtimber 

volume (17 percent). Even though the rate of increase 

is leveling off, the forests of Vermont are adding value 

at an increasing rate due to growth that is occurring 

on the higher valued trees. Landowners and the forest 

products industry can benefi t from the increase in value, 

but care in management and harvesting practices will be 

important to ensure a steady supply into the future as the 

poletimber-size trees replace the sawtimber-size trees.
26

FEATURES

0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

20 

1997 2007 

Volume (billion board feet)

Inventory Year 

13% 

27% 

19% 

17% 

23% 

36% 

41% 

24% 

Grade 1 

Grade 2 

Grade 3 

Tie/local use 

Figure 42.—Hardwood board-foot volume by tree grade, Vermont, 1997 and 2007.

maple and American beech have less than 25 percent 

of their sawtimber volume in grades 1 and 2 (Fig. 43). 

Many beech trees contain large amounts of rotten wood 

because of beech bark disease. Red maple typically has 

more defects than other species.

1 

7 

11 

18 

4 

19 

10 

15 

34 

42 

10 

18 

15 

10 

24 

17 

26 

25 

22 

35 

38 

44 

41 

42 

56 

53 

42 

38 

32 

14 

51 

31 

32 

30 

16 

11 

22 

22 

12 

9 

0 20 40 60 80 100 

American beech 

Red maple 

Quaking aspen 

Black cherry 

Paper birch 

Sweet birch 

Yellow birch 

Sugar maple 

White ash 

Northern red oak 

Saw Log Volume (%) 

Species 

Grade 1

Grade 2

Grade 3

Grade 4

Figure 43.—Percentage of saw log volume on timberland by species and tree 

grade, Vermont, 2007.

What this means

The quality of saw logs in Vermont has remained stable 

since the last inventory, but the value of sawtimber has 

increased based on the increase in available board-foot 

volume. For example, northern red oak board-foot 

volume increased signifi cantly between 1997 and 2007 

Changes in volumes by species indicate the changes 

in species composition that are occurring. Only paper 

birch and balsam fi r have shown signifi cant declines in 

growing-stock volume since 1997. For both species, this 

is refl ected in loss in growing-stock volume (Fig. 39) 

and number of growing-stock trees (Fig. 30). These two 

species may rebound in the future as numbers of saplingsize trees increase (Fig. 31).

Hardwood Sawtimber Quality

Background

Species, size, and quality of a tree determine its value in the 

forest products market. The highest quality timber, used in 

the manufacture of cabinets, furniture, fl ooring, or other 

millwork, is the most valuable. Lower quality trees are 

used as pallets, pulpwood, and fuelwood. The quality of an 

individual tree varies by species as well as diameter, growth 

rate, and management practice. Hardwood trees must be at 

least 11 inches d.b.h. to qualify as sawtimber. FIA assigns 

tree grades to sawtimber-size trees as a measure of quality. 

Tree grade is based on tree diameter and the presence or 

absence of defects such as knots, decay, and curvature of 

the bole. The grades decrease in quality from grade 1 (high 

grade lumber) to tie/local use material.

What we found

The proportion of sawtimber volume in tree grades 1 

and 2 has remained stable at 40 percent since 1997; 

however, in absolute terms, the volume in grades 1 and 2 

has increased from 5.8 to 7.1 billion board feet. Volume 

in the lowest grade (tie/local use) increased from 2.8 to 

4.3 billion board feet and increased as a proportion of 

the total from 19 to 24 percent (Fig. 42).

In Vermont, northern red oak and white ash are the only 

species with more than 50 percent of their sawtimber 

volume in tree grades 1 and 2. Sugar maple, yellow 

birch, and sweet birch have at least 35 percent of their 

sawtimber volume in grades 1 and 2. By contrast, red 
27

FEATURES

(Fig. 40) and the highest proportion of that volume is in 

grade 2 or better trees (77 percent). Changes in species 

composition point toward potential reductions in tree 

quality into the future. Some of the species with a high 

proportion of low grade volume, American beech and 

red maple (Fig. 43), are the same ones that are showing 

large increases in saplings (Fig. 31).

Average Annual Net Growth 

and Removals

Background

Forests provide a renewable resource if they are well 

managed to provide a constant supply of useful products 

without impacting long-term productivity. The rate of 

growth is an indicator of the overall condition of a stand 

as well as forest health, successional stage, and tree vigor. 

Average annual net growth (gross growth minus mortality) 

is calculated by measuring trees at two points in time and 

by determining the average annual change over the time 

period. Net growth is negative when mortality exceeds gross 

growth. A useful measure to assess growth is the percentage 

of annual net growth to current inventory volume. Average 

annual net growth estimates are based on change in volume 

of growing stock on timberland between the 1997 and 

2007 inventories.

What we found

Since 1965, average annual net growth has been steadily 

increasing (Fig. 44). Net growth averaged 180 million 

cubic feet annually between 1997 and 2007, about 2 

percent of growing-stock volume on timberland. In 

comparison to previous inventories, this proportion is one 

of the lowest ever reported (Fig. 45). About 66 percent of 

net annual growth was in hardwoods and 79 percent was 

on privately owned land.

The top nine species by growing-stock volume accounted 

for 91 percent of the average annual net growth of 

0 

50 

100 

150 

200 

1948 1965 1973 1983 1997 2007 

Growing-stock Volume (million ft3 ) 

Inventory Year 

1.4 : 1 

2.2 : 1 

3.2 : 1 

2.3 : 1 1.7 : 1 Net growth 

Removals 

Mortality 

Figure 44.—Net growth, removals, mortality, and growth-to-removal ratio 

of growing stock on timberland, Vermont, 1948, 1965, 1973, 1983, 1997, and 

2007. Error bars represent 68% confi dence interval around estimate.

Figure 45.—Net growth of growing stock on timberland as a percent of growingstock volume on timberland, Vermont, 1948, 1965, 1973, 1983, 1997, and 2007.

0 

0.5 

1 

1.5 

2 

2.5 

3 

3.5 

4 

1948 1965 1973 1983 1997 2007 

Net Growth to Growing-stock Volume (%) 

Inventory Year 

Hardwoods 

Softwoods 

Total 

growing stock on timberland from 1997 to 2007. The 

ratio of growth to removals averaged 1.7:1.0 for 1997 to 

2007, but variation between species was considerable. 

Net growth exceeded removals for all major species. 

Sugar maple had the highest amount of removals, but its 

growth still exceeded removals by 1.8:1.0. Eastern white 

pine and balsam fi r ranked second and third in removals, 

respectively. While eastern white pine growth exceeded 

removals by 1.5:1.0, balsam fi r growth was nearly even 

with removals at 1.1:1.0. Eastern hemlock, red maple, and 

northern red oak had the highest growth-to-removals ratios 

at 3.2:1.0, 2.8:1.0, and 2.8:1.0, respectively (Fig. 46).
28

FEATURES

What this means

The well-stocked stands in the current forests of Vermont 

developed as a result of the growth-to-removal ratios being 

well above 1.0:1.0 for the last half century, but Vermont’s 

forests have matured and the rate of growth has slowed. In 

fact, the 1997 to 2007 period is the fi rst time the growthto-removal ratio has dropped below 2.0:1.0 since the 1960s 

(Fig. 44). Even with the slower growth rate, the current 

level of removals appears to be sustainable for the near term 

barring more increases in mortality. Nunery and Keeton 

(2010) concluded that unmanaged stands will sequester 

more carbon than those that are actively managed. 

Therefore, even with slowing net growth rates, as long as 

removals are less than net growth, the forests of Vermont 

should continue to sequester more carbon than they emit. 

Fortunately, more than 90 percent of the removals are due 

to harvesting and not land use change. Trees will regenerate 

because the land remains in timberland.

A comparison of the growth-to-removals ratios of 

individual species to the average for all species indicates 

which species may be decreasing or increasing in 

abundance. Red maple has a higher growth-to-removals 

ratio than sugar maple, which suggests that it may increase 

in relative volume. This increase may be due to sugar maple 

being preferred over red maple as a timber species. The low 

growth-to-removals ratios of eastern white pine (1.5:1.0) 

and balsam fi r (1.1:1.0) suggest that both of those species 

may be decreasing in abundance (Fig. 46). This could 

be true especially for eastern white pine given the lack of 

eastern white pine saplings present in the State (not in the 

top 10 species for numbers of saplings – Fig. 31).

Average Annual Mortality

Background

Mortality is a natural part of stand development in 

healthy forest ecosystems. Many factors contribute to 

mortality including competition, succession, insects, 

disease, fi re, human activity, drought, and many others. 

Mortality is often initiated by one causal agent (inciting 

factor), then followed by contributing stress factors 

making the underlying cause diffi cult to identify. 

Although mortality is a natural event in a functional 

forest ecosystem, dramatic increases in mortality indicate 

forest health problems. Average annual growing-stock 

mortality estimates represent the average cubic-foot 

volume of sound wood that died each year between 

the 1997 and 2007 inventories. During this interval, 

Vermont has experienced a range of disturbances that 

have stressed forests, either as inciting factors or as 

contributors to the mortality.

What we found

The estimated average annual mortality rate for growingstock trees in Vermont for 2007 was 85 million cubic 

feet, which is approximately 0.9 percent of growingstock volume. This is the highest mortality rate ever 

reported in an FIA inventory of Vermont. Estimates 

from earlier inventories ranged from 0.6 to 0.7 percent. 

From 1997 to 2007, softwoods had a higher mortality 

rate than hardwoods (Fig. 47). Despite the increase, 

Vermont’s mortality rate is similar to many other states 

in the region. For example, New Hampshire’s rate is 1 

percent, Maine’s is 1.2 percent, and New York’s is 0.9 

percent. The rate of mortality is similar across diameter 

classes, increasing between 1997 and 2007 for nearly all 

diameter classes. The highest mortality rates are generally 

found in the smaller diameter trees (Fig. 48).

0 20 40 60 

American beech (1.5 :1)

Yellow birch (1.6 :1)

Northern red oak (2.8 :1)

Balsam fir (1.1 :1)

White ash (2.5 :1)

Eastern hemlock (3.2 :1)

Eastern white pine (1.5 :1)

Red maple (2.8:1)

Sugar maple (1.8 :1)

Growing-stock Volume (million ft3) 

Species 

 

 

 

 

 

 

 

Net Growth

Removals

Figure 46.—Average annual net growth, removals, and growth-to-removals 

(G/R) ratio for major species, Vermont, 2007. Error bars represent 68% 

confi dence interval around estimate; G/R for all species = 1.7:1. 
29

FEATURES

Mortality also increased across nearly all species between 

1997 and 2007. Red spruce had the largest increase in 

mortality rate, but paper birch, balsam fi r, red maple, 

and quaking aspen (Populus tremuloides) also increased 

signifi cantly. The only species for which the mortality 

rate actually decreased are white ash and northern red 

oak (Fig. 49). Although mortality rates have generally 

increased over time, most of the abundant species in 

Vermont have relatively low mortality rates. The annual 

average mortality rates of sugar maple, eastern white 

pine, eastern hemlock, red maple, yellow birch, sweet 

birch, white ash, and northern red oak are all below the 

0.9 percent annual average for tree species combined 

(Fig. 50). By contrast, quaking aspen, balsam fi r, paper 

birch, red spruce, and American beech all have mortality 

rates that are nearly double the statewide average.

What this means

Tree mortality rates in Vermont have increased over the 

rates reported in previous inventories, but these rates 

are comparable to those in surrounding states. Vermont 

tree health surveys have shown similar trends. Some of 

Hardwoods 

Softwoods 

Total 

0.0 

0.2 

0.4 

0.6 

0.8 

1.0 

1.2 

1965 1973 1983 1997 2007 

Mortality to Growing-stock Volume (%) 

Inventory Year 

Figure 47.—Mortality of growing stock on timberland as a percent of growingstock volume on timberland, Vermont, 1965, 1973, 1983, 1997, and 2007.

0 

0.2 

0.4 

0.6 

0.8 

1 

1.2 

6 8 10 12 14 16 18 20 22+ 

Annual Mortality Rate (%) 

Diameter Class (inches) 

1997

2007

Figure 48.—Average annual mortality rate (in percent) of growing-stock 

volume on timberland by diameter class, Vermont, 1997 and 2007.

0 2 4 6 8 10 12 14 16 

Northern red oak 

Sweet birch 

Northern white-cedar 

White ash 

Black cherry 

Eastern hemlock 

Yellow birch 

Eastern white pine 

Quaking aspen 

Red maple 

American beech 

Balsam fir 

Paper birch 

Red spruce 

Sugar maple 

Average Annual Mortality (million ft3) 

Species 

1997

2007

Figure 49.—Average annual mortality of growing stock on timberland for 

major species, Vermont, 1997 and 2007. Error bars represent 68% confi dence 

interval around estimate.

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 

Northern red oak 

White ash 

Eastern hemlock 

Eastern white pine 

Sugar maple 

Sweet birch 

Yellow birch 

Red maple 

Black cherry 

Northern white-cedar 

American beech 

Red spruce 

Paper birch 

Balsam fir 

Quaking aspen 

Species

Average Annual Mortality Rate (%) 

0.1

0.2

0.4

0.5

0.5

0.6

0.7

0.7

0.9

1.2

1.7

2.5

2.5

2.6

3.5

Average for all species = 0.9%

Figure 50.—Average annual mortality rate for major species, Vermont, 2007. 

Average for all species = 0.9%.
30

FEATURES

the mortality can be explained by stand dynamics (e.g., 

competition and succession) and the impacts of insects 

and diseases that affect specifi c species (e.g., beech bark 

disease on American beech). In the normal maturation 

process, some trees lose vigor and eventually die from 

being outcompeted or they succumb to insect and 

disease during their weakened state; this is especially 

apparent in trees 12 inches and smaller d.b.h. (Fig. 48).

Most species in Vermont have low mortality rates, but 

some have elevated rates. Species such as quaking aspen, 

balsam fi r, paper birch, red spruce, and American beech 

have increased the overall statewide mortality rate. 

Quaking aspen and paper birch are both early successional, 

short-lived species that are intolerant to shade, so as 

these forests age, high mortality rates are not surprising. 

American beech has been heavily impacted by beech bark 

disease for many decades. Weather-related events that 

signifi cantly affected tree health during this time period 

include the aftereffects of the 1998 ice storm and droughts 

during 1999 and 2001. Recovery from the ice storm was 

particularly poor for beech and paper birch trees. Drought 

effects were especially signifi cant for species with shallow 

root systems such as birch and beech or for species likely 

growing on sites with shallow soils such as balsam fi r and 

red spruce. Additional health problems were observed 

from forest tent caterpillar defoliation, beech bark disease, 

spruce winter injury, and balsam woolly adelgid. Recovery 

following stress events is often dependent on soil fertility; 

trees growing on calcium rich sites are more likely to 

recover (Schaberg et al. 1996, Shortle and Smith 1988).

Species Composition

Background

The species composition of a forest is the result of the 

interaction of climate, soils, disturbance, competition 

among trees species, and other factors over time. Causes 

of forest disturbance in Vermont include ice storms, 

logging, droughts, insects and diseases, and land clearing 

followed by abandonment. The species composition 

of the growing-stock volume and large-diameter trees 

represents today’s forest, while the species composition 

of the smaller diameter classes represents the potential 

future forest. Comparisons of species composition by 

diameter class can provide insights into potential changes 

in overstory species composition.

What we found

In Vermont, beech is the most numerous sapling (1 

to 4.9 inches d.b.h.), accounting for 15 percent of all 

saplings followed by sugar maple at 13 percent (Fig. 51). 

Noncommercial tree species (combined) also represent 

a large portion of saplings, at 19 percent. Striped maple 

is the most numerous of these noncommercial species 

followed by eastern hophornbeam and pin cherry. Sugar 

maple is the dominant species in all diameter classes 5 

inches d.b.h. and larger. Eastern white pine is poorly 

represented in the sapling classes (less than 1 percent), 

0 

20 

40 

60 

80 

100 

2 6 10 14 18 21.0-28.9 

Individual Species as a Percentage of Total Number 

of Trees in Class 

Diameter Class (inches) 

Noncommercial hardwoods 

All other commercial species 

Yellow birch 

Red spruce 

Eastern white pine Balsam fir 

Eastern hemlock American beech

Paper birch Red maple 

Ash Sugar maple 

Figure 51.—Species composition by diameter class on forest land, Vermont, 2007. 

(Noncommerical species includes striped maple, eastern hophornbean, pin cherry, 

and other species with poor form).
31

FEATURES

0 

2 4 6 8 10 12 14 16 18 2021.0-28.9

29.0+

5 

10 

15 

20 

25 

30 

Total Trees in Class (%) 

Diameter Class (inches) 

Figure 52.—White pine as a percentage of the total number of trees by 

diameter class on forest land, Vermont, 2007.

although it makes up a large portion of trees larger than 

20 inches d.b.h (Fig. 52). Other species, which have 

lower representation in the sapling classes compared to 

the larger diameter classes, include eastern hemlock, red 

maple, and sugar maple. In addition to American beech, 

balsam fi r and red spruce make up a higher portion of 

total saplings relative to their share of larger trees. Since 

the 1966 inventory, sugar maple, red maple, eastern 

hemlock, eastern white pine, and ash have increased 

in the proportion of total growing-stock volume they 

represent (Fig 53). Species that have decreased as a 

percentage of the total volume include spruce, yellow 

birch, beech, paper birch, and balsam fi r (Fig. 54).

0 

5 

10 

15 

20 

25 

30 

1966 1973 1983 1997 2007 

Total Volume (%) 

Inventory Year 

Sugar maple 

Hemlock 

Red maple 

Ash 

White pine 

Figure 53.—Species that have increased as a percentage of total growingstock volume on timberland, Vermont, 1966-2007.

0 

2 

4 

6 

8 

10 

12 

14 

1966 1973 1983 1997 2007

Total Volume (%) 

Inventory Year 

Spruce 

Yellow birch

Balsam fir

Beech

Paper birch

Figure 54.—Species that have decreased as a percentage of total growingstock volume on timberland, Vermont, 1966-2007.

What this means

Conditions in the understory favor reproduction 

of shade-tolerant species, as shown by the higher 

proportion of beech, sugar maple, balsam fi r, and red 

spruce in the sapling diameter classes compared to the 

larger diameter classes. Besides being shade tolerant, 

large numbers of sapling-size beech are likely the result 

of root sprouts following beech bark disease. Many of 

these young beech trees will eventually succumb to the 

disease before they have the opportunity to grow into 

the overstory, while occupying valuable growing space 

and inhibiting the growth of other more valuable species 

while alive. In contrast, eastern hemlock, another shadetolerant species, makes up a lower percentage of tree 

numbers in the sapling diameter classes when compared 

to the larger diameter trees. This indicates that hemlock 

is not regenerating as well as expected in the maturing 

forest of Vermont. Noncommercial species provide 

habitat diversity in the understory, although they can 

interfere with the reproduction of commercial species if 

they become too numerous. Striped maple now makes 

up 12 percent of trees in the 2-inch diameter class. Land 

managers should be aware of the potential of this species 

to cause problems in forest regeneration. 

Eastern white pine is well represented in the large 

diameter classes, and it ranks second statewide in 

sawtimber volume (Fig. 40). But because it is poorly 

represented in the small-diameter classes (less than 1 

percent of saplings), it will probably be replaced by other 
32

FEATURES

species as the larger eastern white pine trees die or are 

harvested. Sugar maple represents the largest portion of 

trees in every diameter class 5 inches and larger, which 

attests to the longevity and size it attains within the 

forests of Vermont. It will likely be the dominant tree 

in Vermont’s forest for the foreseeable future. Trends 

in volume show that, since 1966, eastern white pine, 

eastern hemlock, and red maple have increased in the 

portion of total volume they represent. Trends in these 

species will likely slow and reverse because these species 

are not as well represented in the sapling-size class as 

they are in larger trees. If the current species composition 

remains constant as saplings mature, these data foretell 

a future forest overstory with more spruce and fi r trees 

and fewer white pine and hemlock trees than today. 

Long-term changes in Vermont’s forest composition 

will alter wildlife habitats and affect the value of the 

forest for timber products. Close examination of species 

composition changes in the future will be necessary due 

to the potential impacts of climate change on species.
33

Forest Products

Vermont sugar maples. Photo by Ronald Kelley.
34

FOREST PRODUCTS

Timber Products

Background

The harvesting and processing of timber products creates 

a stream of income shared by timber owners, land 

managers, marketers, loggers, truckers, and processors. 

The wood products and paper manufacturing industries 

in Vermont employed more than 3,000 people, with an 

average annual payroll of more than $118 million and a 

total value of shipments of $641 million (U.S. Census 

Bureau 2007). To better manage the State’s forests, it 

is important to know the tree species, amounts, and 

locations of timber being harvested.

What we found

Surveys of Vermont’s wood-processing mills are 

conducted periodically to estimate the amount of wood 

volume that is processed into products. These surveys are 

supplemented with the most recent surveys conducted in 

surrounding states that processed wood harvested from 

Vermont. In 2005, 70 primary wood-processing mills 

were surveyed to determine what species were processed 

and where the wood material came from. These mills 

processed more than 183 million board feet.

A total of 43 million cubic feet of industrial roundwood 

was harvested from Vermont during 2005. Saw 

logs accounted for 65 percent of the total industrial 

roundwood harvested, followed by pulpwood at 24 

percent and veneer logs at 11 percent (Fig. 55). All of 

the timber harvested for pulpwood was shipped to mills 

in other states. An additional 18 million cubic feet of 

wood was harvested for fuelwood in Vermont during 

2005. Hard maple, at 17 percent, and white pine, at 

16 percent, were the two most harvested species groups 

(Fig. 56). Other important species groups harvested were 

spruce, hemlock, soft maples, red oaks, and ash.

During the process of harvesting industrial roundwood, 

23 million cubic feet of harvest residues were left on 

the ground (Fig. 57). Approximately 80 percent of the 

0 

5 

10 

15 

Growing stock Non-growing stock 

Logging Residue (million ft3) 

Tree Class 

Softwoods

Hardwoods

Figure 57.—Logging residue by tree class and species group, Vermont, 2005.

0 

5 

10 

15 

20 

Saw logs Veneer logs Pulpwood Fuelwood 

Industrial Roundwood and Fuelwood 

Harvested (million ft ) 3

Product 

Softwoods

Hardwoods

Figure 55.—Roundwood harvested by product, Vermont, 2005.

0 

5 

10 

15 

20 

White pine

Spruce

Hemlock

Other softwoods

Hard maple

Soft maple

Red oaks

Ash

Yellow birch

Other hardwoods

Industrial Roundwood Harvested

 (million ft3) 

Species Group 

Figure 56.—Roundwood harvested by major species group, Vermont, 2005.
35

FOREST PRODUCTS

logging residue came from non-growing-stock sources 

such as crooked or rotten trees, tops and limbs, and 

noncommercial species. The remaining 20 percent was 

growing-stock volume left on site. The processing of 

industrial roundwood in the State’s primary wood-using 

mills generated another 7 million cubic feet of wood and 

bark residues. Fifty-seven percent of the mill residues 

were used for pulpwood products and 43 percent were 

used for industrial and residential fuelwood.

What this means

Most of the wood-processing facilities in Vermont are 

sawmills processing logs primarily grown in the State. 

These mills give woodland owners an outlet to sell 

timber and provide jobs in some of the more rural areas. 

The demand for wood products is likely to increase, 

placing a greater demand on the resource. An important 

consideration for the future of the primary wood-products 

industry is its ability to retain industrial roundwood 

processing facilities. The number of wood-processing mills 

has been steadily declining. The loss of processing facilities 

makes it harder for landowners to fi nd markets for the 

timber harvested from their forest land.

Another important issue is the volume of harvest residues 

generated in Vermont that go unused. Almost 20 percent 

of the harvest residue is from growing-stock sources that 

could be used for products. Improved pulpwood markets 

should lead to better utilization of merchantable trees. 

The use of logging slash and mill residues for industrial 

fuelwood at cogeneration facilities and pellet mills should 

also result in better utilization of the forest resource.
36

FOREST PRODUCTS
37

Forest Indicators

Coarse woody debris. Photo by Sandy Wilmot, Vermont Department of Forests, Parks & Recreation.
38

FOREST INDICATORS

Tree Crown Conditions

Background

The crown condition of trees is infl uenced by various 

biotic and abiotic stressors. Abiotic stressors include 

drought, fl ooding, cold temperatures or freeze injury, 

nutrient defi ciencies, soil physical properties affecting 

soil moisture and aeration, and toxic pollutants. Biotic 

stressors include native or introduced insects, diseases, 

invasive plant species, and animals.

Seasonal or prolonged drought periods have long been a 

signifi cant and historical stressor in Vermont. Since the 

1997 FIA inventory, droughts occurred in some regions 

during 1999 and 2001; alternatively, some of the wettest 

years on record were 2006 and 2008 (Fig. 58; NCDC 

2010). These extreme precipitation events can produce 

conditions that facilitate insect and/or disease outbreaks 

and can be even more devastating to trees stressed by pest 

damage or other agents.

agents such as Dutch elm disease (Ophiostoma ulmi), 

chestnut blight (Cryphonectria parasitica), European 

gypsy moth (Lymantria dispar), and the beech bark 

disease complex. A more recent invader in Vermont is 

hemlock woolly adelgid (Adelges tsugae), and potential 

future invaders include emerald ash borer (Agrilus 

planipennis) and Asian longhorned beetle (Anoplophora 

glabripennis).

Tree-level crown measurements are collected on FIA 

P3 plots, including vigor class, crown ratio, light 

exposure, crown position, crown density, crown dieback, 

and foliage transparency. Three factors were used to 

determine the condition of tree crowns: crown dieback, 

crown density, and foliage transparency. Crown dieback 

is defi ned as recent mortality of branches with fi ne 

twigs and refl ects the severity of recent stresses on a 

tree. Secondly, crown density is defi ned as the percent 

of crown branches, foliage, and reproductive structures 

that block light visibility through the crown and can 

serve as an indicator of expected growth in the near 

future. Finally, foliage transparency is the amount of 

skylight visible through the live, normally foliated 

portion of the crown. Changes in foliage transparency 

can also occur because of defoliation or reduced foliage 

resulting from stresses during preceding years. A crown 

was labeled as “poor” if crown dieback was greater than 

20 percent, crown density was less than 35 percent, or 

foliage transparency was greater than 35 percent. These 

three thresholds were based on preliminary fi ndings by 

Steinman (2000) that associated crown ratings with 

tree mortality.

What we found

The incidence of poor crown condition is evenly 

distributed across Vermont (Fig. 59). The species with 

the highest proportion of live basal area containing poor 

crowns is eastern hemlock at nearly 33 percent. For 

white ash and American beech, 25 and 20 percent of the 

basal area, respectively, had poor crowns. Conversely, the 

occurrence of poor crowns in yellow birch, red maple, 

and eastern white pine was very low (Table 2).

-6 

-4 

-2 

0 

2 

4 

6 

8 

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 

PDSI 3-month Average (Jun-Aug) 

Year 

Figure 58.—Palmer Drought Severity Index 3-month average (June-August), 

Vermont, 1895-2010.

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, Vermont’s forests have suffered the 

effects of native insect pests such as forest tent caterpillar 

(Malacosoma disstria) and well-known exotic and invasive 
39

FOREST INDICATORS

The highest proportion of eastern hemlock and 

American beech basal area containing poor crowns was 

found in the northern half of Vermont. By contrast, 

poor crowns were more prevalent in white ash in the 

southern part of the State (Fig. 60).

Table 2.—Percent of live basal area with poor crowns, Vermont, 2007

Eastern hemlock 33

White ash 25

American beech 20

Red spruce 13

Balsam fi r 11

Paper birch 10

Sugar maple 10

Eastern white pine 7

Red maple 6

Yellow birch 2

 Percent of Basal Area

Species with Poor Crowns

Figure 59.—Percent of live basal area with poor crowns, Vermont, 2007.

Percent of Live Basal 

Area with Poor Crowns

 < 5

 5 - 10

 10 - 20

 20 - 50

 Water

 Nonforest

 Forest

Projection: Vermont State Plane, NAD83.

Sources: NLCD 1992, FIA 2007.

Geographic base data are provided by the National 

Atlas of the USA. FIA data and Tools are available 

online at http://www.fi a.fs.fed.us/tools-data/

Cartography: R.S. Morin. Dec. 2010

Figure 60.—Percent of live basal area with poor crowns by species, Vermont, 

2007.

Projection: Vermont State Plane, NAD83.

Sources: NLCD 1992, FIA 2007.

Geographic base data are provided by the 

National Atlas of the USA. 

FIA data and Tools are available online at 

http://www.fi a.fs.fed.us/tools-data/

Cartography: R.S. Morin. Dec. 2010

Percent of Live 

Basal Area with 

Poor Crowns

 < 5

 5 - 25

 25 - 50

 > 50

 Water

 Nonforest

 Forest

Eastern Hemlock

American Beech 

White Ash

Percent of Live 

Basal Area with

Poor Crowns

< 5

 5 - 25

 > 25

 Water

 Nonforest

 Forest

Percent of Live 

Basal Area with 

Poor Crowns

< 5

 5 - 25

 25 - 40

 > 40

 Water

 Nonforest

 Forest

What this means

Some of the highest levels of eastern hemlock density 

across its range are located in the eastern portions of 

Vermont. Eastern hemlock is an important species in 

Vermont due to its high value as timber and wildlife 

habitat, the unique niche it fi lls in riparian areas, and its 

value as an ornamental tree. Levels of eastern hemlock 

mortality have increased since the 1997 inventory (Fig. 

49). Many eastern hemlocks were classifi ed as having 

poor crowns due to high foliage transparency ratings, but 

they typically have higher foliage transparency ratings 

than many other species given their unique needle 

morphology. Hemlock woolly adelgid (HWA) can cause 
40

FOREST INDICATORS

called blue-green algae. Some enterprising fungi associate 

with both at once (Brodo et al. 2001).

Lichen community monitoring is included in the FIA 

P3 inventory to address key assessment issues such as 

the impact of air pollution on forest resources or spatial 

and temporal trends in biodiversity. This long-term 

lichen monitoring program in the U.S. dates back to 

1994. The objectives of the lichen indicator are to 

address key assessment issues such as the impact of 

air pollution on forest resources, spatial and temporal 

trends in biodiversity, and the sustainability of timber 

harvesting. Lichens occur on many different substrates 

(e.g., rocks), but FIA sampling is restricted to standing 

trees or branches/twigs that have recently fallen to the 

ground. Samples are sent to lichen experts for species 

identifi cation.

A close relationship exists between lichen communities 

and air pollution, especially acidifying or fertilizing 

nitrogen- and sulfur-based pollutants. A major reason 

lichens are so sensitive to air quality is their total reliance 

on atmospheric sources of nutrition. By contrast, it is 

diffi cult to separate tree-growth responses specifi c to air 

pollution (McCune 2000).

What we found

A total of 73 lichen species (gamma diversity) were 

sampled on the lichen plots in Vermont (Table 3). The 

most common lichen genera, Phaeophyscia, were present 

on 12 percent of the plots (Table 4). The genus with the 

highest number of species sampled was Cladonia

(7 species).

The easiest way to measure species diversity is to count 

the number of species at a site; this measure is termed 

species richness. However, species richness does not 

provide a complete picture of diversity in an ecosystem 

because abundance is excluded. Richness values fell into 

the medium and high categories across Vermont (Table 

3). The spatial distribution of lichen species richness 

scores is shown in Figure 61. In general, species richness 

scores increased with increasing latitude. The lichen 

thinning foliage, widespread defoliation, and sometimes 

mortality of eastern hemlock (McClure et al. 2001, 

Orwig et al. 2002). Although HWA was discovered 

in Vermont, in Windham County, in 2008, the poor 

crown condition of many hemlock trees is unlikely to be 

associated with it because HWA has not been discovered 

in the areas where poor crowns were sampled.

American beech is also a major component of the 

forests in Vermont. It is an important forest tree that 

is a source of wood products including pulpwood, 

fi rewood, and chips as well as a vital source of mast for 

wildlife. The poor crown condition in beech is likely to 

be related to the impacts of beech bark disease (BBD). 

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. that 

kills or injures American beech. Three phases of BBD 

infestations are generally recognized: (1) the “advancing 

front,” areas recently invaded by scale populations; 

(2) the “killing front,” areas where fungal invasion has 

occurred (typically 3 to 5 years after the scale insects 

appear, but sometimes as long as 20 years) and tree 

mortality begins; (3) the “aftermath forest,” areas where 

the disease is endemic (Houston 1994, Shigo 1972). The 

BBD killing front moved through Vermont decades ago 

and, therefore, the State is now aftermath forest.

Lichen Communities

Background

Lichens are symbiotic, composite organisms made up of 

members from as many as three kingdoms. The dominant 

partner is a fungus. Fungi are incapable of producing 

their own food, so they typically feed as parasites or 

decomposers. The lichen fungi (kingdom Fungi) cultivate 

partners that manufacture food by photosynthesis. 

Sometimes the partners are algae (kingdom Protista), 

other times cyanobacteria (kingdom Monera), formerly 
41

FOREST INDICATORS

species richness and diversity scores reported here will 

serve as baseline estimates for future monitoring at the 

state and regional level.

What this means

Due to the sensitivity of many lichen species to airborne 

pollution, it is useful to look at acid deposition levels. 

Showman and Long (1992) reported that mean lichen 

species richness was signifi cantly lower in areas of high 

sulfate deposition than in low deposition areas. Sulfate 

deposition levels have been relatively homogeneous 

across Vermont and are relatively low compared to other 

areas in the northeastern United States (Fig. 62). A 

general pattern of lower lichen species richness scores is 

evident in high deposition areas and vice versa (Fig. 63). 

But other factors may affect the distribution of lichen 

species including intrinsic forest characteristics and longterm changes in climate.

Table 3.—Lichen communities summary table, Vermont, 1994-2003

Number of plots surveyed 24

Number of plots by species richness category 

0-6 species (low) 0

7-15 species (medium) 19

16-25 species (high) 5

Median 12.5

Range of species richness score per plot (low-high) 7-22

Average species richness score per plot (alpha diversity) 12.6

Standard deviation of species richness score per plot 3.9

Species turnover rate (beta diversity)1

 5.8

Total number of species per area (gamma diversity) 73

1

Beta diversity is calculated as gamma diversity divided by alpha diversity.

 Vermont, 

Parameter 1994-2003

Phaeophyscia 11.6 5

Melanelia 8.3 5

Physcia 8.1 4

Parmelia 7.6 3

Flavoparmelia 7.2 2

Cladonia 6.0 7

Punctelia 5.7 3

Hypogymnia 5.3 2

Usnea 5.0 5

Evernia 4.8 1

Candelaria 4.7 1

Physconia 4.7 3

Cetraria 4.5 6

Myelochroa 3.3 2

Bryoria 1.2 1

Platismatia 0.9 2

Cetrelia 0.7 1

Lobaria 0.7 2

Parmeliopsis 0.7 3

Ramalina 0.5 2

Anaptychia 0.3 1

Flavopunctelia 0.3 1

Imshaugia 0.3 1

Peltigera 0.3 2

Pseudevernia 0.3 2

Pyxine 0.3 1

Leptogium 0.2 1

Menegazzia 0.2 1

Parmotrema 0.2 1

Physciella 0.2 1

Xanthoria 0.2 1

 Total 100 73

 All All 

 Genus Specimens Species

Table 4.—Percentage of specimens and number of species for lichen genera 

sampled, Vermont, 1994-2003
42

FOREST INDICATORS

Figure 63.—Estimated lichen species richness, Northeastern U.S., 2000-2003.

Projection: Albers, NAD83.

Sources: NLCD 1992, FIA 2003. Geographic base data are provided by 

the National Atlas of the USA. FIA data and Tools are available online at 

http://www.fi a.fs.fed.us/tools-data/

Cartography: R.S. Morin. Dec. 2010

Lichen Species 

Richness Score

Low

 Medium-low

 Medium-high

 High

 Water

 Nonforest

Figure 61.—Estimated lichen species richness, Vermont, 2000-2003.

Lichen Species 

Richness Score

 < 10

 10 - 12

 12 - 14

 > 14

 Water

 Nonforest

Projection: Vermont State Plane, NAD83.

Sources: NLCD 2006, FIA 2003.

Geographic base data are provided by the National 

Atlas of the USA. FIA data and Tools are available 

online at http://www.fi a.fs.fed.us/tools-data/

Cartography: R.S. Morin. Dec. 2010

Figure 62.—Mean sulfate wet deposition, Northeastern U.S., 1994-2002. 

Data source: National Atmospheric Deposition Program.

Projection: Albers, NAD83.

Sources: NLCD 1992, NADP 2002. Geographic base data are provided by the 

National Atlas of the USA. FIA data and Tools are available online at http://www.

fi a.fs.fed.us/tools-data/

Cartography: R.S. Morin. Dec. 2010

Sulfate as SO4

-2

(mg/ha)

 8 - 13

 13 - 17

 17 - 22

 22 - 26

 26 - 30

 Water

 Nonforest

Forest Soils

Background

The soils that sustain forests are infl uenced by several 

factors including climate; the trees, shrubs, herbs, and 

animals living there; landscape position; elevation; and 

the passage of time.

Forest carbon sequestration is a topic of public concern. 

Carbon stocks in soils are important long-term stores of 

carbon accumulated from woody biomass and foliage. 

The accumulation and subsequent decay of leaf litter 

adds carbon to forest soils. Tree roots—and translocation 

from the forest fl oor—add carbon to the mineral soil. 

Measurements of current carbon stocks help managers 

understand the importance of different forest types and 

landscapes in the carbon cycle. 

Atmospheric pollution is one signifi cant way that 

humans infl uence the character and quality of the soil 

and indirectly affect the forest. For example, industrial 
43

FOREST INDICATORS

In contrast, carbon in the mineral soil under Vermont’s 

forests is strongly correlated to forest-type group in 

combination with the latitudinal and longitudinal 

location (Fig. 64). Maximum soil carbon under maple/

beech/birch forests is found in the southern part of the 

State while conifer soil carbon peaks in the northeast. 

Mineral soil carbon under other types of hardwood 

forests grade from low to high, moving in a westerly 

direction. Of the three forest-type groups, conifers 

tend to store the most mineral soil carbon. We can use 

this information to build spatial predictions of carbon 

content in the top 20 cm of mineral soil. 

By focusing on tree species data, it is possible to evaluate 

tree:soil interactions with some statistical rigor. For 

example, the aluminum:calcium ratio in the soil is an 

important predictor of several measures of crown vigor in 

Vermont, and the effect varies across tree species. 

Table 5.—Predicted forest fl oor carbon (Mg ha-1) in Vermont

Conifer 2.66 2.12 3.2

Other Hardwoods 3.44 1.17 1.96

Maple/beech/basswood 3.47 3.54 4.01

 Ecological Section

Forest type M211B M211C Other

emissions of sulfur and nitrogen oxides lead to “acid 

rain.” The deposition of acids strips the soil of important 

nutrients, notably calcium and magnesium. The loss 

of calcium and magnesium results in a shifting balance 

of soil elements toward aluminum, which is toxic to 

plants in high concentrations. We can use the ratio of 

aluminum to calcium as a measure of the impact of 

acid deposition on forest soils; high ratios suggest a shift 

toward more aluminum.

What we found

Forest fl oor carbon in Vermont’s forests is strongly 

infl uenced by two factors: forest-type group and ecological 

section – a type of semi-homogeneous landscape unit 

(Table 5). Maple/beech/basswood forests tend to store the 

largest amounts of carbon in their forest fl oor. 

The uncompacted live crown ratio is determined by 

dividing the live crown length by the actual tree length. 

Larger values are associated with healthier trees; low 

values can be related to self pruning and shading from 

other tree crowns, but other reasons include defoliation 

due to dieback, and loss of branches due to breakage or 

mortality. The aluminum:calcium ratio is a signifi cant 

predictor of the uncompacted live crown ratio (Fig. 65). 

The lowest crown ratios are associated with low levels of 

aluminum, but this effect varies across tree species. The 

live crown ratios of black cherry and red maple steadily 

decline with increases in aluminum values (increasing 

aluminum:calcium ratio) (Fig. 66). This observation is 

consistent with intensive site studies conducted in New 

England (Schaberg et al. 1996, Shortle and Smith 1988).

Figure 64.—Total carbon content in the mineral soil (0-20 cm) by forest type 

and location. Note the varying range of values within each forest type.

Other Hardwoods 

Carbon Content

 115 Mg/ha

 0

 Soil sampling

 locations

Plot locations are approximate.

Data sources: U.S. Forest Service,

Forest Inventory and Analysis

program; geospatial base data

provided by the National Atlas 

of the United States.

Cartography: C.H. Perry. Dec. 2010

Maple/Beech/

Birch Carbon 

Content

100 Mg/ha

 70

 Soil sampling 

 locations

Conifers Carbon 

Content

 225 Mg/ha

 0

 Soil sampling 

locations
44

FOREST INDICATORS

What this means

Tree species occupy different niches in the landscape, 

which provides a competitive advantage for colonization, 

growth, and reproduction. Atmospheric deposition of 

different compounds changes the soil substrate through 

additions and removals of nutrients and pollutants. 

These changes in the soil chemistry infl uence the ability 

of existing trees to thrive and reproduce in their current 

locations, as well as the ability of other trees to colonize 

new landscapes. It is important to document and 

understand natural and anthropogenic processes in the soil 

because they profoundly infl uence the current health of 

forests and the success of future forest management plans.

Down Woody Materials

Background

Down woody materials, in the form of fallen trees and 

branches, fi ll a critical ecological niche in Vermont’s 

forests. Down woody materials both provide valuable 

wildlife habitat in the form of coarse woody debris and 

contribute toward forest fi re hazards via surface woody 

fuels. Pieces of wood are selected in the coarse woody 

debris sample if they are at least 3 inches in diameter 

and intersect one of three transects emanating from the 

center of each FIA plot (Woodall and Monleon 2008).

What we found

The fuel loadings of down woody materials (time-lag 

fuel classes) are not very high in Vermont (Fig. 67). 

When compared to the neighboring states of New 

Hampshire and Maine, Vermont’s fuel loadings of all 

time-lag fuel classes are not substantially different (for 

time-lag defi nitions, see Woodall and Monleon 2008). 

The size-class distribution of coarse woody debris appears 

to be heavily skewed (77 percent) toward pieces less 

than 8 inches in diameter (Fig. 68A). In the decay class 

distribution of coarse woody debris, there appears to be 

a fairly uniform distribution of stages of coarse woody 

40 50 60 70 80

White Pine

45 50 55 60

Red Maple

52 56 60 64

Sugar Maple

45 50 55 60

Paper Birch

65 75 85 95

American Beech

Al:Ca Molar Ratio

Low Med High

30 40 50 60 70

Black Cherry

Al:Ca Molar Ratio

Low Med High

Al:Ca Molar Ratio

Low Med High

Al:Ca Molar Ratio

Low Med High

Al:Ca Molar Ratio

Low Med High

Al:Ca Molar Ratio

Low Med High

Uncompacted Live Crown Ratio

Figure 66.—Uncompacted live crown ratio by aluminum to calcium ratio in 

the soil by species. Error bars represent one sampling error (68%). 50 52 54 56 58 60 62

Al:Ca Molar Ratio

Uncompacted Live Crown Ratio

Low Med High

Figure 65.—Uncompacted live crown ratio by aluminum to calcium ratio in the 

soil. Error bars represent one sampling error (68%).
45

FOREST INDICATORS

decay across the State, except for decay class three and 

four logs (75 percent) (Fig. 68B). Coarse woody debris 

in decay class three and four are typifi ed by moderate to 

heavily decayed logs that are sometimes structurally sound 

but missing most/all of their bark with extensive sapwood 

decay. There is no strong trend in coarse woody debris 

volumes/acre among classes of live-tree density (basal area/

New Hampshire

Vermont

Maine

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

1-hr 10-hr 100-hr 1000+-hr 

Fuel Loadings (tons/acre) 

Fuel-hour Classes 

Figure 67.—Means and associated standard errors of fuel loadings (tons/

acre, time-lag fuel classes) on forest land in Vermont and neighboring states, 

2004-2008. Error bars represent 68% confi dence interval around estimate.

77%

17%

5% 1%

41%

34%

9% 4%

12%

3.0-7.9 

8.0-12.9 

13.0-17.9 

18.0+ 

1

2

3

4

5

A 

B 

Figure 68.—Mean proportions of coarse woody debris total pieces per acre by 

transect diameter (inches; A) and decay classes (B) on forest land in Vermont, 

2004-2008.

0 

200 

400 

600 

800 

1,000 

1,200 

0.0-30.0 30.1-60.0 60.1-90.0 90.1-120.0 120.1+ 

Coarse Woody Debris (ft3/acre) 

Basal Area (ft2/acre) 

Figure 69.—Means and associated standard errors of coarse woody debris 

volumes (cubic feet/acre) on forest land in Vermont, 2004-2008. Error bars 

represent 68% confi dence interval around estimate.

acre). Stands with the highest volumes of coarse woody 

debris were found more often in stands with moderate 

amounts of standing live-tree density (Fig. 69).

What this means

The down woody fuel loadings in Vermont’s forests 

are not very different from those found in neighboring 

states. Therefore, only in times of extreme drought 

would these low amounts of fuels pose a hazard across 

the State. Of all down woody components, coarse 

woody debris (i.e., 1,000+-hr fuels) made up the largest 

amounts, but coarse woody debris volumes were still 

relatively low and were represented by small, moderately 

decayed pieces. The scarcity of large coarse woody debris 

resources may also indicate lower quality habitat for 

some wildlife species. Overall, because fuel loadings are 

not very high across Vermont, associated fi re dangers are 

outweighed by the benefi ts of down woody material for 

producing wildlife habitat and carbon sinks.
46

FOREST INDICATORS

Vegetation Diversity and 

Invasives

Background

Ground fl ora play many important roles in the forests 

of northern New England. Vegetation helps curtail 

erosion and runoff, regulate soil temperature, sequester 

carbon, and provide food and cover for forest animals. 

In addition, plants have the ability to fi lter pollutants 

and infl uence nutrient availability. Data on species 

composition help resource managers determine 

site quality, which serves as a guide for developing 

management goals. In New Hampshire and Vermont, 

plant species data were collected on the P2 Invasive plots 

and P3 plots. Due to the small number of plots, the data 

from the two states were analyzed together. For 2007-

2008, there were 125 P2 Invasive plots (63 in Vermont 

and 62 in New Hampshire) and 36 P3 plots (17 in 

Vermont and 19 in New Hampshire). 

What we found

All species

On the P3 plots, 343 species were found; the greatest 

quantity of classifi ed species (140) occurred in the 

forb/herb category based on classifi cation by the USDA 

Natural Resources Conservation Service’s PLANTS 

Database (Table 6). Forty-four plants were classifi ed as 

graminoids (grass or grass-like plants). Beyond these 

categories, there were 62 trees, 48 shrubs, and 10 

vines. For the P3 plots, 274 (80 percent) of the 343 

plant species were native to the U.S. and 25 species (7 

percent) were introduced (Table 7). Canada mayfl ower 

(Maianthemum canadense), the most commonly observed 

understory species, occurred on 92 percent (33 plots) of 

all P3 plots in New Hampshire and Vermont (Table 8). 

The most commonly observed tree species was American 

beech, which was found on 29 plots or 81 percent of all 

P3 plots. Of the 20 most commonly observed species, 12 

were of woody growth form.

Table 6.—Number of species on New Hampshire and Vermont P3 plots by 

growth habit (per PLANTS Database, USDA Natural Resources Conservation 

Service), 2007-2008

Forb/herb 140

Graminoid 44

Shrub 25

Shrub, subshrub, vine 2

Subshrub, forb/herb 2

Subshrub, shrub 13

Subshrub, shrub, forb/herb 6

Tree 33

Tree, shrub 27

Tree, shrub, subshrub 2

Vine 3

Vine, forb/herb 3

Vine, shrub 1

Vine, subshrub 1

Vine, subshrub, forb/herb 2

Unclassifi ed 39

Total 343

 Number of species or 

Growth habit undifferentiated genuses

Introduced to the U.S. 25 7.3

Native and introduced to the U.S. 5 1.4

Native to the U.S. 274 79.9

Unclassifi ed 39 11.4

Total 343 100

 Number of species 

 or undifferentiated 

Origin genuses Percentage

Table 7.—Number of species on New Hampshire and Vermont P3 plots by 

domestic or foreign origin (per PLANTS Database, USDA Natural Resources 

Conservation Service), 2007-2008

Nonnative invasive species

None of the 43 invasive plant species FIA monitors on P2 

Invasive plots (Table 9) were among the top 20 species on 

P3 plots. On the P3 plots, broadleaf helleborine (Epipactis 

helleborine) was the most commonly observed nonnative 

plant species (8 plots; 22 percent of P3 plots); common 

dandelion (Taraxacum offi cinale) was the second most 

common nonnative plant species (6 plots; Table 10). 
47

FOREST INDICATORS

Canada mayfl ower (33) 705 2,483

American beech (29) 622 2,453

Sugar maple (28) 714 2,775

Red maple (26) 659 1,949

Eastern hayscented fern (25) 741 2,400

Sedge (25) 616 2,579

Striped maple (25) 685 2,848

Wild sarsaparilla (25) 688 2,644

Starfl ower (23) 748 2,760

Eastern white pine (20) 632 2,260

Sensitive fern (20) 772 3,069

Yellow birch (20) 658 2,732

American red raspberry (18) 483 2,977

Paper birch (17) 813 2,515

Common ladyfern (16) 595 2,600

Eastern hemlock (16) 555 2,222

Northern red oak (16) 481 2,014

Red spruce (16) 597 2,883

Sessileleaf bellwort (16) 618 2,563

White ash (16) 661 3,130

 Tree saplings Tree seedlings 

Species per acre per acre

Table 8.—The top 20 plant species or undifferentiated genera or categories 

on New Hampshire and Vermont P3 plots, the number of plots on which the 

species were found (in parentheses), and the mean number of tree saplings and 

seedlings per acre on the plots, 2007-2008 Tree Species

Acer platanoides (Norway maple)

Ailanthus altissima (tree of heaven)

Albizia julibrissin (silktree)

Elaeagnus angustifolia (Russian olive)

Melaleuca quinquenervia (punktree)

Melia azedarach (Chinaberry)

Paulownia tomentosa (princesstree)

Robinia pseudoacacia (black locust)

Tamarix ramosissima (saltcedar)

Triadica sebifera (tallow tree)

Ulmus pumila (Siberian elm)

 Woody Species

Berberis thunbergii (Japanese barberry)

Berberis vulgaris (common barberry)

Elaeagnus umbellata (autumn olive)

Frangula alnus (glossy buckthorn)

Ligustrum vulgare (European privet)

Lonicera x. bella (showy fl y honeysuckle)

Lonicera maackii (Amur honeysuckle)

Lonicera morrowii (Morrow’s honeysuckle)

Lonicera tatarica (Tatarian bush honeysuckle)

Rhamnus cathartica (common buckthorn)

Rosa multifl ora (multifl ora rose)

Spiraea japonica (Japanese meadowsweet)

Viburnum opulus (European cranberrybush)

 Vine Species

Celastrus orbiculatus (Oriental bittersweet)

Hedera helix (English ivy)

Lonicera japonica (Japanese honeysuckle)

 Herbaceous Species

Alliaria petiolata (garlic mustard)

Centaurea biebersteinii (spotted knapweed)

Cirsium arvense (Canada thistle)

Cirsium vulgare (bull thistle)

Cynanchum louiseae (black swallow-wort)

Cynanchum rossicum (European swallow-wort)

Euphorbia esula (leafy spurge)

Hesperis matronalis (dames rocket)

Lysimachia nummularia (creeping jenny)

Lythrum salicaria (purple loosestrife)

Polygonum cuspidatum (Japanese knotweed)

Polygonum x. bohemicum (P. cuspidatum/P. sachalinense hybrid)

Polygonum sachalinense (giant knotweed)

 Grass Species

Microstegium vimineum (Japanese stiltgrass)

Phalaris arundinaceae (reed canarygrass)

Phragmites australis (common reed)

Table 9.—Invasive plant species target list for Northern Research Station FIA 

P2 Invasive plots, 2007 to present

On the P2 Invasive plots, common barberry was the most 

frequently occurring invasive plant species (4 plots; Table 

11), followed by glossy buckthorn (Rhamnus frangula), 

common buckthorn (Rhamnus cathartica), and multifl ora 

rose (3 plots). All of the invasive species found on New 

Hampshire and Vermont P2 Invasive plots were woody 

species, except for bull thistle (1 plot). The high number 

of woody plants observed refl ects the high number selected 

for monitoring on the P2 Invasive plots.

Invasive plants were widely distributed throughout 

New Hampshire and Vermont. Common barberry was 

found on plots only in Vermont (Fig. 70) even though, 

according to the NRCS PLANTS database, it is known 

to occur in New Hampshire. Another trend observed was 

that common buckthorn was found only in the southern 
48

FOREST INDICATORS

Figure 70.—Distribution of the four most frequently occurring invasive species 

(common barberry, common buckthorn, glossy buckthorn, and multifl ora rose) 

observed on 2007-2008 FIA P2 Invasive and P3 plots in New Hampshire and 

Vermont; approximate plot locations depicted. Note that common and glossy 

buckthorn each appeared on three plots; however, these species co-occurred on 

plots with multifl ora rose so their presence is not indicated on those plots.

0 5 25 0 Miles

Common Barberry

Common Buckthorn

Glossy Buckthorn

Multifl ora Rose

Projection NAD83, UTM Zone 18

Data Source: USDA Forest Service 

Forest Inventory and Analysis 

Program 2007-2008 Phase 2 

Invasive and Phase 3 data. State 

and County layers source: ESRI 

Data and Maps 2005. Depicted plot 

locations are approximate. 

Cartography: C. Kurtz. Nov. 2010

Table 10.—Nonnative plant species found on New Hampshire and Vermont P3 

plots, the number of plots (in parentheses), and the mean number of tree saplings 

and seedlings per acre on the plots. Some plots may have multiple non-native 

plant species and thus may be counted more than once in the table

Broadleaf helleborine (8) 562 2,141

Common dandelion (6) 587 2,479

Claspleaf twistedstalk (4) 600 3,017

Common yarrow (4) 600 1,151

Bird vetch (3) 526 2,158

Common buckthorn (2) 114 2,187

Common St. Johnswort (2) 487 2,699

Meadow hawkweed (2) 225 2,661

Broadleaf Solomon’s seal (1) 1,199 1,649

Bull thistle (1) 225 3,598

Climbing nightshade (1) 750 1,799

Coltsfoot (1) 225 3,598

Common barberry (1) 1,199 375

Common mallow (1) 1,574 5,098

Common mullein (1) 300 6,597

Dovefoot geranium (1) 1,199 375

European black currant (1) 750 1,799

European columbine (1) 77 3,324

European cranberrybush (1) 77 3,324

Glossy buckthorn (1) 750 1,349

Hedge false bindweed (1) 260 1,822

Japanese barberry (1) 450 1,499

Multifl ora rose (1) 750 1,349

Narrowleaf cattail (1) 675 150

Orange hawkweed (1) 1,199 375

Oxeye daisy (1) 225 3,598

Redtop (1) 1,349 1,424

Scots pine (1) 675 3,224

Smooth crabgrass (1) 750 1,349

Threadstalk speedwell (1) 1,574 1,499

 Tree saplings Tree seedlings 

Species per acre per acre

Common barberry (4) 918 656

Glossy buckthorn (3) 500 4,798

Common buckthorn (3) 126 4,332

Multifl ora rose (3) 423 4,436

Japanese barberry (2) 1,050 1,649

European cranberrybush (1) 77 3,324

Autumn olive (1) 371 3,338

Oriental bittersweet (1) 150 1,874

Bull thistle (1) 225 3,598

Black locust (1) 750 1,799

 Tree saplings Tree seedlings 

Species per acre per acre

Table 11.—Invasive plant species found on New Hampshire and Vermont P2 

Invasive plots, the number of plots (in parentheses), and the mean number of tree 

saplings and seedlings per acre on the plots, 2007-2008

part of New Hampshire and Vermont (the southernmost 

plot in Vermont, which shows multifl ora rose present, 

also had common buckthorn present), and glossy 

buckthorn and multifl ora rose were observed on plots 

only in the central portion of each of these states.
49

FOREST INDICATORS

What this means

The forests of New Hampshire and Vermont support a 

variety of species distributed across fi ve growth habits 

(forb/herb, graminoid, shrub, tree, and vine). The 

presence of nonnative invasive plants in these states 

poses risk to the forests because these plants can inhibit 

regeneration of native species and change the overall forest 

structure. Additionally, these species can change resource 

availability and the habitat quality for fl ora and fauna. 

In New Hampshire and Vermont, the presence of the 

43 monitored invasive plant species is relatively low 

(13 percent) compared to neighboring New England 

states, Maine (14 percent) (McCaskill et al. 2011.) and 

Massachusetts (45 percent) (Butler et al. in press). Even 

though the occurrence of invasive plant species is low, the 

presence of these particular species causes concern because 

vigorous individuals have the potential to rapidly increase 

in cover and extent and impact co-occurring native 

species. Currently, in New Hampshire and Vermont, the 

data suggest the presence of invasive plants may cause a 

reduction in seedling cover. This conclusion is supported 

by comparing Table 8, which shows the top 20 plant 

species found on P3 plots (none of which are invasives) 

with Figure 71, which shows the nonnative species 

found on P3 plots. Table 8 shows only one species (red 

maple) with an average number of tree seedlings fewer 

than 2,000 per acre, while Figure 71 shows 15 of the 30 

species have covers of fewer than 2,000 tree seedlings 

per acre.1

 Furthermore, plotting the percent cover of 

invasive plant species against the number of seedlings 

and saplings per acre (Fig. 72) suggests that, as invasive 

cover increases, the number of seedlings decreases. 

Although the sample size is small and only 2 percent of 

the 161 plots have invasive cover of 6 percent or more, 

this analysis raises concerns because it suggests those sites 

that do have invasives might fail to regenerate, eventually 

reducing future forest density. 

The measurement of additional P2 Invasive and P3 

plots will provide a better understanding of invasive 

plant distribution and facilitate analyses of the impact 

and spread of these species. Such knowledge can help 

forest managers understand where invasive species 

might be successful in establishing themselves and allow 

managers to craft strategies of treatment and mitigation, 

where necessary.

Tree seedlings per acre

Tree saplings per acre

0 2,000 4,000 6,000 8,000 

Broadleaf helleborine (8) 

Common dandelion (6) 

Claspleaf twistedstalk (4) 

Common yarrow (4) 

Bird vetch (3) 

Common buckthorn (2) 

Common St. Johnswort (2) 

Meadow hawkweed (2) 

Broadleaf Solomon’s seal (1) 

Bull thistle (1) 

Climbing nightshade (1) 

Coltsfoot (1) 

Common barberry (1) 

Common mallow (1) 

Common mullein (1) 

Dovefoot geranium (1) 

European black currant (1) 

European columbine (1) 

European cranberrybush (1) 

Glossy buckthorn (1) 

Hedge false bindweed (1) 

Japanese barberry (1) 

Multiflora rose (1) 

Narrowleaf cattail (1) 

Orange hawkweed (1) 

Oxeye daisy (1) 

Redtop (1) 

Scots pine (1) 

Smooth crabgrass (1) 

Threadstalk speedwell (1) 

Seedlings and Saplings Per Acre 

Nonnative Plant Species 

(number of P3 plots) 

Figure 71.—Nonnative species on New Hampshire and Vermont P3 plots, the 

number of plots (in parentheses), and the mean number of tree seedlings and 

saplings per acre on the plots, 2007-2008.

1

 Caution must be used when analyzing these data due to the low overall 

number of plots.
50

FOREST INDICATORS

Ozone Bioindicator Plants

Background

Ozone, a byproduct of industrial development, is found 

in the lower atmosphere. Ozone forms when nitrogen 

oxides and volatile organic compounds go through 

chemical transformation in the presence of sunlight 

(Brace et al. 1999). Ground-level ozone is known to have 

detrimental effects upon forest ecosystems. Certain plant 

species exhibit visible, easily diagnosed foliar symptoms 

to ozone exposure. Ozone stress in a forest environment 

can be detected and monitored by using these plants as 

indicators. The FIA program uses these indicator plants 

to monitor changes in air quality across a region and to 

evaluate the relationship between ozone air quality and 

the indicators of forest condition.

The ozone-induced foliar injury on indicator plants 

is used to describe the risk of impact in the forest 

environment, using a national system of sites (Smith 

et al. 2003, 2007). These sites are not co-located with FIA 

samples. Ozone plots are chosen for ease of access and 

optimal size, species, and plant counts. As such, the ozone 

plots do not have set boundaries and vary in size. At 

each plot, between 10 and 30 individual plants of three 

or more indicator species are evaluated for ozone injury. 

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

4,000 

0-2 6-8 12-14 20-22 

Seedlings and Saplings

(average number per acre) 

Invasive Plant Cover (percent) 

Seedlings 

Saplings 

Figure 72.—Average number of seedlings and saplings per acre by invasive 

plant cover class for invaded P2 Invasive and P3 FIA plots in New Hampshire 

and Vermont, 2007-2008.

Each plant is rated for the proportion of leaves with 

ozone injury and the mean severity of symptoms, using 

break points that correspond to the human eye’s ability to 

distinguish differences. A biosite index is calculated based 

on amount and severity ratings where the average score 

(amount * severity) for each species is averaged across all 

species at each site and multiplied by 1,000 to allow risk 

to be defi ned by integers (Smith et al. 2007).

What we found

The majority of the plants sampled were milkweed 

(Asclepias spp.) or blackberry (Rubus spp.) (Table 12). 

The fi ndings for Vermont indicate that risk of foliar 

injury due to ozone has been trending downward since 

the mid-1990s (Table 13 and Fig. 73) as have ozone 

exposure levels (Fig. 74). 

Table 12.—Distribution of plants sampled for ozone injury by species, Vermont, 

1994-2007

Milkweed 5,933 32.9

Blackberry 4,420 24.5

Black cherry 3,137 17.4

White ash 2,138 11.9

Spreading dogbane 1,934 10.7

Pin cherry 458 2.5

Species Number Percent

0 4 10 15 20 25 30 35

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

1994

Biosite Index 

Inventory Year 

Figure 73.—Biosite index, Vermont, 1994-2007.
51

FOREST INDICATORS

What this means

Ozone exposure rates have been decreasing with 

corresponding decreases in foliar injury. This fi nding 

contrasts with evidence of medium and high risk 

in portions of the Mid-Atlantic region (Coulston 

et al. 2003).

A typical summer ozone exposure pattern for Region 

9 (the Eastern Region of the U.S. Forest Service) is 

shown in Figure 75 (USDA For. Serv. 2002). The 

term SUM06 is defi ned as the sum of all valid hourly 

ozone concentrations that equal or exceed 0.06 ppm. 

Controlled studies have found that high ozone levels 

Number of biosites 

evaluated 14 18 16 17 17 21 22 18 15 16 17 14 12 11

Number of biosites 

with injury 12 5 13 9 9 7 6 4 5 5 4 4 5 1

Average biosite 

index score 16.01 3.84 29.4 20.28 13.46 0.86 2.73 0.6 1.24 0.89 0.82 2.39 1.2 0.99

Number of plants 

evaluated 858 1,169 1,049 1,092 946 1,382 1,544 1,335 1,409 1,639 1,752 1,435 1,235 1,186

Number of 

plants injured 195 22 200 139 98 40 74 29 23 25 18 8 13 15

Maximum SUM06

value (ppm-hr)2

 15.54 14 10.44 13.11 9.33 16.92 5.46 13.57 17.23 11.59 7.58 9.59 7.45 9.12

Parameter 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Table 13.—State-level summary statistics for ozone bioindicator program, Vermont, 1994-2007

0 2 4 6 8 10 12 14 16 18 20

Year 

Maximum SUM06 Exposure (ppm-hr)2

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

1994

Figure 74.—Maximum SUM06 exposure levels (ppm-hr)2, Vermont, 1994-2007.

Figure 75.—Typical ozone exposure rates in Region 9.

Projection: Albers, NAD83.

Sources: NLCD 1992, EPA 2006. 

Geographic base data are provided 

by the National Atlas of the USA. FIA 

data and Tools are available online at 

http://www.fi a.fs.fed.us/tools-data/

Cartography: R.S. Morin. Apr. 2011

SUM06 Ozone 

Exposure (ppm-hrs)

 < 10

 10 -15

 15 - 20

 > 20

 Water

 Nonforest

(shown in orange and red) can lead to measurable 

growth suppression in sensitive tree species (Chappelka 

and Samuelson 1998). Smith et al. (2003) reported 

that even when ambient ozone exposures are high, the 

percentage of injured plants can be lower in dry years.
52

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DVD Contents

Vermont’s Forests 2007 (PDF)

Vermont’s Forests: Statistics and Quality Assurance (PDF)

Vermont’s Inventory Database (CSV fi le folder)

Vermont’s Inventory Database (Access fi le)

Field guides that describe inventory procedures (PDF)

Database User Guides (PDF)
Vermont’s Forests 2007:

Statistics and Quality Assurance

 United States 

Department of 

Agriculture

Forest Service

 Resource Bulletin 

NRS-51

Morin, Randall S.; Barnett, Chuck J.; Brand, Gary J.; Butler, Brett J.; De Geus, Robert; Hansen, Mark H.; 

Hatfi eld, Mark A.; Kurtz, Cassandra M.; Moser, W. Keith; Perry, Charles H.; Piva, Ron; Riemann, Rachel; 

Widmann, Richard; Wilmot, Sandy; Woodall, Chris W. 2011. Vermont’s Forests 2007. Resour. Bull. 

NRS-51. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 

56 p. [DVD included].

The fi rst full annual inventory of Vermont’s forests reports more than 4.5 million acres of forest land with 

an average volume of more than 2,200 cubic feet per acre. Forest land is dominated by the maple/beech/

birch forest-type group, which occupies 70 percent of total forest land area. Sixty-three percent of forest 

land consists of large-diameter trees, 27 percent contains medium-diameter trees, and 9 percent contains 

small-diameter trees. The volume of growing stock on timberland has been rising since the 1980s and 

currently totals nearly 9 billion cubic feet. The average annual net growth of growing stock on timberland 

from 1997 to 2007 is approximately 180 million cubic feet per year. Additional information is presented 

on forest attributes, land use change, carbon, timber products, and forest health. Detailed information on 

forest inventory methods and data quality estimates is included in a DVD at the back of the report. Tables 

of population estimates and a glossary are also included.

KEY WORDS: forest resources, forest health, forest products, volume, biomass
http://www.nrs.fs.fed.us