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Vermonts Changing Forests
Key Findings on theHealth of Forested Ecosystems from the
Vermont Monitoring Cooperative
O 2009
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VMC S
Donnie Ager, Web & Data Assistant
Lawrence Forcier, Principal Investigator
Joanna Grossman, Web & Data Manager
Mim Pendleton, Monitoring Technician & Site Operator
Judy Rosovsky, Monitoring Assistant
Carl Waite, Program Coordinator
2009 VMC S C MAnne Archie, USDA Forest Service
Douglas Lantagne, University o Vermont
Ed OLeary, Vermont Agency o Natural Resources
Dennis May, USDA Forest Service
Steve Roy, USDA Forest Service
Robert Paquin, USDA Farm Service Agency
Charles Scott, USDA Forest Service
Steven Sinclair, Vermont Agency o Natural Resources
Mary Watzin, University o Vermont
2009VMC A C M
Barbara Burns, Vermont Agency o Natural Resources
Nancy Burt, USDA Forest ServiceBrian Keel, USDA Forest Service
Bill Keeton, University o Vermont
Jim Kellogg, Vermont Agency o Natural Resources
Rich Poirot, Vermont Agency o Natural Resources
Beverley Wemple, University o Vermont
Deane Wang, University o Vermont
Sandy Wilmot, Vermont Agency o Natural Resources
Vermont Monitoring Cooperative
Providing the information needed to understand, manage, and protect Vermonts forested ecosystems
in a changing global environment.
The Vermont Monitoring Cooperative (VMC) was established in 1990. In 1996, a memorandum o understanding
was signed by the Vermont Agency o Natural Resources, the University o Vermont, and USDA Forest Service.
The partners agreed to work together to operate VMC to better coordinate and conduct long-term natural resource
monitoring and research within Mount Manseld State Forest, the Lye Brook Wilderness Area o the Green
Mountain National Forest, and other relevant areas in Vermont.
The Vermont Monitoring Cooperative works in partnership with the USDA Forest Service State & Private Forestry as
part o the Cooperative Lands Forest Health Management Program. The majority o VMC operations are handled by
sta aliated with the Rubenstein School o Environment and Natural Resources at the University o Vermont, the
Vermont Department o Forests, Parks & Recreation in the Vermont Agency o Natural Resources, and the USDA
Forest Service Green Mountain National Forest.
VMC C j:
James S. Andrews, Vermont Reptile and
Amphibian Atlas Project
Lesley-Ann Dupigny-Giroux, University o Vermont
Steve Faccio, Vermont Center or Ecostudies
Jennier Jenkins, University o Vermont
William Keeton, University o Vermont
Ron Kelley, Vermont Agency o Natural Resources
Jim Kellogg, Vermont Agency o Natural Resources
Trish Hanson, Vermont Agency o Natural Resources
Kent McFarland, Vermont Center or Ecostudies
Eric Miller, Ecosystems Research Group, Ltd.
Heather Pembrook, Vermont Agency o Natural Resources
Rich Poirot, Vermont Agency o Natural Resources
Chris Rimmer, VermontCenter or EcostudiesDonald Ross, University o Vermont
Jamie Shanley, U.S. Geological Survey
Tom Simmons, Vermont Agency o Natural Resources
Christopher Still, University o Caliornia, Santa Barbara
Thomas Villars, Natural Resources Conservation Service
Beverley Wemple, University o VermontSandy Wilmot,Vermont Agency o Natural Resources
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V A N R
U V
U S F S
Vermonts Changing Forests
Key Findings on the
Health of Forested Ecosystems from the
Vermont Monitoring Cooperative
October 2009
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A B H V M C
A major Vermont Forest Health Task Force assembled by then-Governor MadeleineKunin determined that Vermont needed to continuously monitor orest health andimportant environmental variables. In 1990, there were very ew models on which to build astatewide monitoring and research program. That year, through the eorts o VermontSenator Patrick Leahy and his sta, the U.S. Congress appropriated $250,000 or the
establishment o VMC. Leaders o the three ounding organizationsthe Vermont Agency
o Natural Resources, the University o Vermont, and the U.S. Department o AgricultureForest Serviceagreed to jointly orm, nurture, and administer VMC as a long-term naturalresource monitoring program. VMC prided itsel on a collaborative approach toorganization and administration, in both its daily operations and its longer-term monitoringinitiatives. VMC encouraged and embraced involvement and guidance rom caring andknowledgeable individuals working outside o the immediate partner organizations. In1996, the three ounding partners signed a ormal memorandum o understanding in whichthey agreed to work together to operate VMC with the goal to better coordinate and
conduct long-term ecological monitoring and research within the Mt. Manseld StateForest, the Lye Brook Wilderness Area o the Green Mountain National Forest, and otherrelevant areas in Vermont. In the process o developing the memorandum, the broad andecient involvement o many Vermonters and other proessionals was recognized as an
important outcome o this phase o the Vermont Monitoring Cooperative, and an elementthat should be promoted as VMC continued to evolve.
VMCs mission is: To provide the inormation needed tounderstand, manage, and protect Vermonts orested ecosystems
within a changing global environment. VMC seeks to serveVermont through improved understanding o annual conditions,long-term trends, and interrelationships o the physical, chemical,and biological components o orested ecosystems by collectingand disseminating Vermont environmental data. VMC alsopromotes the ecient communication and coordination omulti-disciplinary environmental monitoring and researchactivities among ederal, state, university, and private entities
with common interests in the long-term health, management,and protection o Vermonts orests.
VMC has become an important database and inormationmanagement service or Vermonts study o orest ecosystemsand environmental quality. The VMC data library contains 300research and monitoring projects and datasets, collected overnearly two decades by dozens o cooperators on a wide array o environmental topics (seepage 38 or a sampling o VMC projects and datasets; a more complete listing can be oundat the VMC web site: www.uvm.edu/vmc). VMCs cooperators range rom undergraduateand graduate students doing research or class projects and theses to university, state,
ederal, and private-sector research and monitoring scientists. Through VMC, all results areassembled in a collaborative eort to advance knowledge and understanding o the
environment and Vermonts orests. VMC data and inormation resources are used bystudents, natural-resources managers, scientists, lay citizens, and policy makers. VMCaccomplishes its mission through a small proessional sta, many other committedproessionals and volunteers, contemporary data management systems, education andoutreach programs, and continuing eorts to support and help coordinate Vermontsenvironmental data interests. VMC continually upgrades its data services to provide the
best data quality and accessibility possible.
VMCs mission:To provide theinormation neededto understand,manage, and protectVermonts orestedecosystems withina changing globalenvironment.
VMC cooperators have
conducted research
on Vermont orests or
18 years, amassing a
wealth o long-term
data.
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A Steering Committee, whose members represent the three ounding partnerorganizations, guides the planning, administration, and policy development or VMC. AnAdvisory Committee, with members rom Vermonts scientic research, monitoring, andresource-management communities, helps inorm decisions about operations, unding,and support needs or research and monitoring projects, and advises on direction or the
organization in general.Mount Manseld was the rst o two study sites selected by VMC or intensive orest
ecosystem monitoring and research (Figure 1). This site comprises over 5,500 acres o stateand university-owned land located between 1,300 and 4,300 eet in elevation. It includesthree watersheds, northern hardwoods and montane spruce-r orest types, as well as analpine ecosystem. VMC utilizeson-site laboratory acilities at theUniversity o Vermonts ProctorMaple Research Center (PMRC).
At PMRC, VMC operates eldcollection sites or the NationalAtmospheric Deposition Program(NADP)/National TrendsNetwork, NADP/AtmosphericIntegrated Research Monitoring
Network, NADP/MercuryDeposition Network, U.S.Department o Agriculture
UV-B Monitoring and ResearchProgram, and the Vermont AcidPrecipitation Monitoring Program.Other VMC acilities andinrastructure include a 66-ootwalkup canopy tower; thelongest continually operating wetatmospheric mercury monitoring
station that we are aware o in the
world; ve meteorologicalstations; three stream-gage stations; and a remotely accessed soil climate station. TheVermont Air Pollution Control Division also operates aco-located air quality monitoring station at PMRC.
The Lye Brook Wilderness Area, the second VMC intensive study site, provides asouthern Vermont complement to Mount Manseld. It encompasses 15,000 acres o GreenMountain National Forest land, ranges in elevation rom 900 to 2,900 eet, and supportsnorthern-hardwood, spruce-r, and paper-birch orests. The Lye Brook areas surace waters
identiy it as being sensitive to acid deposition. Lye Brook supports a remotely accessedatmospheric monitoring station (ozone, wet and dry deposition, and meteorology), airvisibility monitoring, and a soil climate station.
VMC data collected and archived during the past 18 years have made signicant
contributions toward our knowledge about climate change, land-use ragmentation, andthreats rom insects, diseases, invasive plants, and air pollution. VMC data have been usedin Vermont to determine the best time to spray or orest tent caterpillars in order to protecteconomically and ecologically important sugar maple trees, while minimizing the negativeeects on the endangered Indiana bat. Data collected by herpetologists tell us that while
numbers o the smooth greensnake may be declining in Vermont, the only viable populationo the North American racer may have already disappeared within the last two years. VMCresearchers ound that Bicknells thrush tend to avoid crossing open areas such as openski trails and that male thrushes may be more vulnerable to predation when crossing theseopen areas.
Mount Manseld
Lye Brook
Figure 1: The majorVMC study sites at
Mt. Manseld and
Lye Brook Wilderness
Area, indicated by
dots, are shown here
within the context o
the biophysical regions
o Vermont.
Source: Sandy Wilmot and
Beverley Wemple
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VMC-supported projects have shown that high-elevation developments increase annualwater, sediment, and chloride yields over undeveloped watersheds. Also, we now know that,on average, sugar maple budbreak is three days earlier and lea-out ve days earlier this decadethan in the 1990s; the 2008 budbreak was 12 days earlier and lea-out was nine days earlierthan the baseline. A map o orest soil carbon assembled by VMC researchers which shows
areas o high or low carbon may suggest uture guidelines or managing soil carbon. In a 2007lawsuit led by the U.S. Environmental Protection Agency and eight northeastern statesagainst a large midwestern utility company, data rom PMRC in Underhill helped providecompelling evidence that the company was keeping outdated power plants in service to avoidthe costs o producing cleaner power; in an out-o-court settlement, the company agreed tospend $4.6 billion to retrot several old power plants. Because o the pioneering work doneby VMC cooperators, Vermont is a strong candidate or a role as a pilot site in an anticipatednational mercury biomonitoring network. The Underhill monitoring site known as VT99 wasrecently selected and unded by EPA as one o the initial sites in the new NADP/Mercury
Trends Network.The work o VMC has helped Vermonts leadership role on the national stage in certain
environmental issues. During the potentially uncertain times brought about by climate change,continuing threats rom air pollution, and changes in land use both locally and nationally, it ismore important than ever to support monitoring o environmental variables and conditionsand to eciently and eectively share scientically robust data among scientists, resource
managers, policy makers, and the public in an unselsh spirit o cooperation. Ecosystemhealth is an essential element to achieve sustainability. The need or useul indicators oorest ecosystem health recognized by Vermont and ederal leaders 20 years ago is even
more important in 2009.
8
7
6
5
4
3
2
1
0
1989
Hermit Thrush Decline
1990
1991
19
92
1993
19
94
1995
19
9619
97 1998
1999 20
00
2001
2002
2003
20
04
2005
2006
AnnualIndex
Annual Trend = -6.3% (SE 0.024)
P= 0.011
T S V S B: H T D
R
Figure 2: Populations o hermit thrush havedeclined by 6.3 percent annually at more than
two dozen VMC study sites.
Source: FBMP
esults rom the VMC-supported Vermont ForestBird Monitoring Program (FBMP) indicate thatVermonts state bird, the hermit thrush, declined by
an average o 6.3 percent annually between 1989 and 2006(Figure 2). FBMP monitors breeding birds at more than twodozen orested study sites throughout the state, includingsites at Mt. Manseld and Lye Brook. Several actors mayhave contributed to this long-term decline, including habitatalterations rom deer overbrowse, soil calcium depletion
due to acid rain, andhabitat loss, especially onthe birds southeastern
U.S. wintering grounds.
n Hermit Thrush
During thepotentiallyuncertain timesbrought aboutby climate change,continuing threats
rom air pollution,and changes inland use bothlocally andnationally, it ismore importantthan ever tosupport monitoringo environmental
variables andconditions.
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Figure 3: More than 80 percent o Vermontsorests are privately owned.
Source: Adapted rom Wharton et al. 2003
T L O T
T
Distribution of Timberland Area by Ownership
Individuals:
63%
Federal: 6%
Other Public: 8%
Forest Industry: 6%
Farmers: 6%
Corporations: 11%
he history o the Vermont landscape is marked by the inuence o geologic orces that gave rise to the states
mountains over 400 million years ago and climatic orces that have produced dramatic changes in
environmental conditions. Roughly 11,000 years ago, glacial ice that had extended over the state or nearly two
million years began to retreat and trees began to appear on a landscape stripped bare o vegetation. These earliestorests were dominated by black spruce and paper birch. Animal communities became established in new habitats
made available in the emerging orests. As the climate warmed, tundra vegetation retreated to only the states
highest peaks, while spruce and r dominated the higher elevations and northern mountains. Lower elevations came
to be dominated by eastern white pine, maple, birch, hemlock, beech, oak, and hickory, creating todays mosaic o
the mixed northern hardwood orest. Today orests cover roughly 4.6 million acres or roughly 78 percent o the state
(Wharton et al. 2003).
The current predominance o young to mature orests is an artiact o 19 th-century clearing, subsequent
land abandonment, and secondary orest redevelopment on old-elds. With these changes have come shits in the
types o ecosystem services provided by orested landscapes. For example, young to mature northern hardwood
orests provide less desirable habitats or late-successional wildlie species, lower levels o biomass and associated
carbon storage, and less dramatic eects on aquatic habitat structure in orest streams (Keeton et al. 2007). On the
other hand, a young, maturing orest has higher growth rates, providing opportunities or sustained yield timber
production. In addition, open lands and young orests provide abundant habitats or early-successional species,
some o which are now declining due to orest redevelopment.
Compared to the primary (or never cleared) orest systems, the secondary orests that have recovered across
Vermonts landscape tend to have less complex canopies, lower densities o large trees (both live and dead), lower
volumes and densities o downed logs, smaller canopy gaps, and less horizontal variation in stand density (McGee
1999, Keeton et al. 2007). At larger scales, our land-use and orest-management history has converted landscapes
with complex patch mosaics, which are shaped by wind and other disturbances, to simpler congurations. Forest
patches are now less diverse in size and less complex in shape (Mladeno and Pastor 1993). The relative abundance
o dominant tree species has also shited as a result o land-use history (Cogbill et al. 2002). As we evaluate the
current conditions and trends in orest ecosystem health indicators, we need to keep in mind that land-use history
has prooundly shaped our current orested landscape.
Modern changes to the Vermont landscape accompany dramatic changes in the states population over the
last ew decades. The population boom in the United States ollowing the Second World War did not reach Vermont
until later, with a 14 percent population growth in the 1960s and a 15 percent growth in the 1970s, and rates slowing
to 10 percent or less in more recent decades. With this population growth, came a change in urbanized land,which has grown by roughly 20 percent since 1960. Nearly one-third o urbanized land has come rom conversion
o agricultural land and nearly two-thirds rom conversion o orest land. Although much o this population and
development pressure has been ocused in the Champlain Valley and more populous towns o the state,
a signicant eature o Vermonts recent growth has been a growth
in recreational development and second homes in Vermonts
resort towns. Demographic changes and pressures associated
with property taxation have led to changes in land ownership and
increased parcelization o orest land across the state. Today, more
than 80 percent o Vermonts orests are privately owned (Figure 3).
These changes in population, land ownership, and land use have
important implications or orest ecosystem health.
A 1999 EPA report estimates a loss o approximately 35
percent o our wetlands since European settlement, with morerecent annual losses o 200 to 400 acres per year (EPA 1999).
Undeveloped land provides valuable ecosystem services.
Degradation, ragmentation, or loss o these natural systems
adversely impacts orest ecosystem health and compromises the
ability o orests to provide habitat, clean water, pure air, and other
critical resources upon which we rely.
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istorically orests were considered healthy simplyi they supported an abundance o healthy trees.In a broader context, orests are ecosystems
supporting many organisms in addition to trees, and whoseunctions are more inclusive than just human exploitationo its resources. Forest ecosystems provide services tohumans without which we could not live. They puriyour air by capturing pollutants. They provide shade and
windbreaks that regulate and moderate temperatures. Theyprotect waters by puriying and keeping them cool. Whenstorms come, they mitigate the impacts rom fooding.They capture nutrients rom the air, and renew soil ertility.Tree roots adhere to soils and prevent major soil erosionand sediments leaching into streams and lakes. Forestsprovide habitats or game and nongame animals, harbornatural control agents against pests, provide resilience
rom disturbances. And they allow humans to beneteconomically rom recreation, aesthetics, wood harvesting
and other orest products. A healthy orest ensures theprovision o these ecosystem services. A healthy orestsystem is also dynamic in response to natural climatevariability, disturbances, and succession. But changesin structure or unction outside the historical range ovariability may signal stress.
Recent international agreements known as the Montreal
Process Criteria and Indicators o Forest Sustainabilityhave ormed a oundation or describing and measuringorest sustainability across the landscape. Five o theseindicators pertain to orest ecosystem health: biodiversity,productivity, soil and water resources, carbon cycles, and
disturbances. These provide a ramework or describingcurrent conditions and trends in orest ecosystem healthwith particular ocus on studies by the Vermont MonitoringCooperative (VMC).
THE HEALTH OF OUR FORESTS
H BBiodiversity encompasses not only the composition ospecies, but also the complexity o structural eatures withina orest stand and across landscapes. Vermont hillsides area patchwork o orests with trees o various sizes and ages.
This diversity o tree sizes and ages makes orests adaptable,dynamic, better situated to recover rom disturbance, andalso provides a broader range o habitats or otherorganisms. One advisory group o Vermont oresters andecologists suggested that a healthy proportion o tree sizesin a mature orest would be approximately 50 percentsaplings, 30 percent pole-sized trees, and 20 percentsawtimber-sized trees (VTFPR 1999). Two time periods ostatewide orest inventory data show an increasing proportiono trees in the smaller tree category (Figure 4).
Special characteristics o orests can make them suitableas habitat or animal species. Vernal pools, caves, coarse
woody material, and legacy trees are examples o uniquestructural elements that provide habitat or animals andallow greater potential diversity. When animal survey dataare not available, habitat measures can be used as predictorso potential species diversity. VMC data have been valuablein building connections between animal-species diversity
and habitat eatures. Among other examples o this dataare VMCs orest bird survey and moth-host plant database,both o which are discussed in this report.
Composition of Tree Sizes in Vermont Forests
80
60
40
20
0
24.3
8.219.1
7.9
1983 1997
67.5 73
Figure 4: Studies in 1983 and 1997 show an increasingpercentage o Vermont trees are in smaller-size categories.
Source: VTFPR 1999
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N- P I P
ermont has been subject to many introductions o exotic insectand disease organisms that have caused damage to orests(Table 1). Some organisms have ecosystem-altering eects,
such as those responsible or Dutch elm disease and chestnut blight.
In other cases the impacts are slower, oering opportunities to developmanagement strategies to mitigate impacts. VMC has been instrumentalin providing ongoing detailed inormation on non-native organisms, suchas pear thrips, gypsy moths, and beech bark disease, which are now wellestablished in Vermont, and has helped in understanding relationshipsbetween these pests and environmental actors. For example, pear thripshave been ound to cause more damage when cold weather slows thedevelopment o sugar maple leaves.
Other non-native insects are moving toward Vermont, and could causesignicant ecological eects. These include the emerald ash borer, with newnds in Quebec; the Asian long horned beetle, a maple pest now in Worcester,MA; and the hemlock woolly adelgid, now in orests in southeastern Vermont.Long-term monitoring by VMC provides baseline data which will help assess
the impact o these insects on host species and associated organisms.Invasive non-native plants, such as barberry, buckthorn, and honeysuckle,
continue to expand northward in Vermont orests, causing negative impacts on biodiversity and orest regeneration.Forest monitoring plots, such as those measured at the VMC research sites, provide a mechanism to survey trendsin invasive plants and their long-term eects on orest health. The North American Maple Project survey resultshighlight the growing incidence o invasive plant species in orests across Vermont (Figure 5). At the VMC sites atMt. Manseld and Lye Brook, which are more removed rom residential areas and their associated plantings o
non-native plants,no exotic invasive plants were ound in a 2005 survey at 20 monitoring plots.
Table 1:This list
indicates
the status onon-native
insects and
diseases in
Vermont.
Source:VTFPR
60
50
40
30
20
10
0
Barberry Buckthorn Honeysuckle Multiflora Rose
Non-native Invasive Plant Species
PresenceonPlo
ts(%)
Figure 5: There is a growingincidence o non-native invasive
plant species on monitoring plots
statewide.
Source: North American Maple Project
V
N- S VJapanese beetle Popillia japonica EstablishedElm lea beetle Pyrrhalta luteola Established
Pine shoot beetle Tomicus piniperda Recently detectedEastern spruce gall adelgid Adelges abietis EstablishedBalsam woolly adelgid Adelges piceae EstablishedHemlock woolly adelgid Adelges tsugae Recently detectedBeech scale Cryptococcus fagisuga EstablishedIntroduced pine sawfy Diprion similis EstablishedBirch leaminer Fenusa pusilla EstablishedEuropean spruce sawfy Gilpinia hercyniae EstablishedMountain-ash sawfy Pristiphora geniculata EstablishedLarch casebearer Coleophora laricella EstablishedGypsy moth Lymantria dispar EstablishedPear thrips Taeniothrips inconsequens EstablishedIntroduced basswood thrips Thrips calcaratus EstablishedSirex wood wasp Sirex noctilio Recently detected
Emerald ash borer Agrilus planipennis Not detectedAsian long horned beetle Anoplophora glabripennis Not detected
N- Scleroderris canker Ascocalyx abietina EstablishedChestnut blight Cryphonectria parasitica EstablishedWhite pine blister rust Cronartium ribicola EstablishedDogwood anthracnose Discula destructive EstablishedBeech bark disease Nectria coccinea EstablishedDutch elm disease Ophiostoma ulmi EstablishedButternut canker Sirococcus clavigignenti-juglandacearum EstablishedSudden oak death Phytophthora ramorum Not detected
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Vermont is estimated to be home to 441 species o birds, mammals, amphibians,and reptiles. A majority o these species are dependent on orests or all or part o theirlie cycles. As we struggle to balance procurement o orest products with conservationo wildlie, new models o orest management are emerging that protect specicocus animal species. At VMC research sites, we have documented many orested
species and their associated habitat requirements. Biodiversity audits can help assessthe relative environmentalimpacts o various orestry and land-development practicesand o climate change. While biodiversity in communities is oten seen as desirable,it is important to remember that some ecosystems, such as in bogs or sandplains,may have relatively low diversity but harbor highly valued species that are unusualrom a regional perspective.
Insect Diversity
While the enormous diversity and sheer numbers o insects excites entomologists, thegeneral public is amiliar with only a relatively ew species that have economic or healthimpacts. Comparatively little or nothing is known about other insects. Insects comprise overtwo-thirds o the approximately 2 million known species o living things on the earth, andmillions more species remain to be discovered. There are about as many species o butterfiesand moths on Mt. Manseld as there are breeding bird species in all o Canada!
There are currently known to be approximately 2,000 species o butterfies and moths(Lepidoptera) in Vermont, which refects the great variety o habitats ound here. The long,
varied, and sometimes arduous work that has produced this number involves methodical eldprocedures combined with meticulous record-keeping. Additionally, existing curated insectcollections have been an invaluable source o baseline environmental data, with each specimenvouching or the historical occurrence o a species at a particular time and place. Collectively,this inormation allows us to retroactively track local arrivals and extinctions o various species,and rames the study o the eects o human disturbance and climate change. For severalyears in the 1990s, and again a decade later, Lepidoptera were surveyed at three elevations onVMC sites on Mt. Manseld. These eorts resulted in a count o close to 400 butterfy andmoth species. In the ood-web, Lepidoptera larvae are a primary ood source during the nesting
periods o the majority o birds that breed in Vermont.
What can insect communities tell us about the relative ecological health o an area?Among other things, insects have roles in orests as pollinators, decomposers o lea litter, andas prey or breeding birds. Documenting the insect species living in a given habitat, along withtheir immediate networks o organisms, brings us closer to evaluating the health o that naturalcommunity. Monitoring indicator species may shed light on the vigor o a natural habitat. Forexample,we know that the aquatic larvae o certain species o black fy are associated withclean water, or that given species o springtails occur within a specic pH range.
PForest productivity, usually thought o as growth and abundance, is an endpoint o many
unctional processes o orests that in one way or another contribute to growth. Measures
o orest processes include plant growth (biomass), reproductive success, timing odevelopmental stages (phenology), and nutrient dynamics in air, biota, soil, and water.
Forest biomass is a measure o the eectiveness o the photosynthetic process. Whengrowth exceeds mortality, biomass accumulation increases. But i disturbances impact thebalance o growth to mortality, biomass accumulation decreases. At VMCs Mt. Manseldsite, there has been a decrease in above-ground live tree biomass on the east slope andsummit since 1997 (Figure 6), evidence o the impacts rom a variety o stress events on
orest productivity. These events included the ice storm in January 1998 ollowed by excessivemoisture in the summer o 1998 and marked drought in 1999.
There are as manyspecies o butterfiesand moths on Mt.
Manseld as thereare breeding birdspecies in all oCanada.
Atlantis ritillary
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The timing o developmental stages provides abaseline or comparing annual changes and allowsevaluation o stress impacts on unctional processeso plants and animals. When managing orest pests,the timing o developmental stages o pest and host
is essential (see page 23 or a discussion o phenologymonitoring).
S W RThe soils supporting orests play a crucial role
in orest health, providing a myriad o servicesranging rom nutrient recycling to physical support.Characteristics important to orest health include
soil texture, drainage, depth, and ertility. With theexception o soil ertility, these soil characteristicsdont change signicantly over time. Tunbridge soilsare typical o Vermont uplands, and not surprisinglysupport the majority o northern hardwood orests (Table 2). Depth to bedrock or hardpan andsoil drainage aect root growth and availability o soil moisture, and determine areas that will
be most aected by droughts. Forest lands have been altered through time or a wide varietyo uses, and not all orests are growing in sites that represent their ideal growing conditions.
Soil-nutrient availability is a common measure o orest health, and where soil pH, base cations,or aluminum concentrations are abnormal, ecological impacts can occur (see page 34 oncritical loads).
VMC supports a program o research and long-term monitoringo streamfow and water quality dynamics o high-elevation orestedstreams within the Lye Brook Wilderness Area and on the slopes oMt. Manseld. These studies have shown that both the fow o waterand concentration o some solutes such as nitrate are highest duringsnowmelt. As a result, most o the annual loss o these solutes rom
orest to stream system is ound during a relatively short time period
in the spring. This ongoing VMC monitoring will aid the detection oenvironmental change due to changing climate and high-elevationdevelopment such as ski resorts.
C COne o the major greenhouse gases is atmospheric carbon in
the orm o carbon dioxide. Through photosynthesis, CO2
is removedrom the air by trees and orest plants, and stored as carbon in roots,stems, and oliage. Forests play a huge role in carbon dioxide mitigationin Vermont, so knowledge o current carbon storage and release is
essential to learning how to better manage our carbon budget. Carbon
can be stored or long time periods in live tree biomass, below ground in roots, in soils, andin trees harvested or durable wood products. Vermont orests are being considered or uturepolicies aimed at sequestration o additional carbon emissions in attempts to reduce ourcarbon ootprint. In calculating carbon sequestration, researchers must consider a variety ocomplex actors, including amount o carbon stored in orests, rate o carbon accumulation,amount o biomass extracted or uel, biomass used or durable wood products, impacts oorest management on above- and below-ground orest carbon, and disturbances such as
insect deoliation.
160
140
120
100
80
60
40
20
0
Biomass(Mg
/ha)
East West Summit
Above-ground Live Tree Biomass
Years
1993
1997
2001
2005
Natural Community Type Soil Name
Northern Hardwoods TunbridgeCabotBerkshire
LymanPeruMarlow
Rich Northern Hardwoods BucklandVershireDutchess
Oak-hickory GeorgiaStockbridgePaxtonPittseld
Table 2: Common soil
series associated withsome o Vermonts
orest communities, in
order o importance.
Source: Report by the
Governors Task Force on
Climate Change, 2007
Figure 6: At VMCs Mt.Manseld site, there
has been a decrease in
above-ground live tree
biomass on the east slope
and summit since 1997.
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G G M
R apidly developing domestic and internationalcarbon markets recognize three general possibilitiesor orest carbon management. These are reorestation/aorestation, avoided deorestation, and improved orest
management (Ruddell et al. 2007). The latter is concerned
with the carbon stored in managed orests, and ocuses on
the concept o additionality or the potential or increasing
net carbon storage over a baseline level. But this has
proved challenging or scientists and orest managers alike,
particularly because o the complex carbon accounting
required to determine the net eects o a particular
management approach (Ray et al. 2009).
Actively managed orests provide carbon sequestration
benets both within the orest ecosystem and in harvested
wood products. Biomass uel produced as a by product o
orest management activities can help oset greenhouse
gas emissions rom ossil uels. Ongoing research isexploring how to design orest management strategies
that optimize storage among these sinks. Rapidly growing,
younger or well spaced orest stands may have higher
rates o carbon uptake, but they have lower biomass per
unit area compared to older or less intensively managed
orests (Figure 7), and thus actually store less carbon than
high biomass orests with lower or stable rates o carbon
uptake (Harmon and Marks 2002). Research has shown
that as orests age they store more carbon, due to very high
levels o accumulated above and belowground biomass
(Keeton et al. 2007; Luyssaert et al. 2008). Forested
landscapes recovering toward an older, higher biomass
condition will store much higher quantities o carbon thanlandscapes dominated by young to mature hardwood
orests (Rhemtullaa et al. 2009). Dierent management
approaches (requency and intensity) result in dierent
amounts o average carbon storage over the long term.
Thus the choice o harvesting approach directly aects
not only emissions osets but also long-term carbonstorage dynamics.
Research at UVM by VMC cooperators has used
simulation modeling to examine the impact o harvesting
requency and proportion o post-harvest structural
retention on carbon storage and the signicance o
including harvested wood products in carbon accounting
(Nunery and Keeton, in review). Carbon dynamics were
simulated under nine orest management scenarios,
spanning a range o increasing structural retention
and decreasing harvesting requencies, including no
harvest. The simulations incorporated carbon ux
between aboveground orest biomass (dead and live
pools) and harvested wood products. The results
suggest that intensied regeneration cutting reducesnet carbon storage. Conversely, extended rotations or
entry cycles, high levels o post-harvest retention, and
practices avoring production o durable wood products
enhance average storage over multiple rotations or
entry cycles. The highest levels o storage are actually
achieved by passive management, even actoring in the
oregone storage in wood products. These conclusions
are valid only so long as the analysis does not include
the greenhouse gas emissions that would result rom
substituting non-wood construction materials or wood
i production o the latter were reduced. Other work has
shown that actoring in substitution eects can make
some intensive management scenarios comparable tothe least intensive in terms o net carbon sequestration,
depending on the assumptions built into the analysis
(Malmsheimer et al. 2008).
TotalCarbonS
tored
Stand Development Over Time
Figure 7: This gure shows carbon sequestration andstorage in relation to orest stand development. Note
that the highest rates o uptake occur in early to mid
stages o development, but the greatest levels o storage
are achieved late in development, resulting in a
substantial carbon reservoir.
Source: Jared Nunery and Bill Keeton, UVM
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The estimated annual,statewide accumulation o CO
2
in orests is 9.63 million metrictons o carbon dioxide equivalent)(Table 3). Keep in mind that in1990, Vermont CO
2emissions
were 8.1 million metric tons,
and by 2005 had increased to9.1. Without emission-reductionpolicies, emissions could grow to10.67 million metric tons by 2030,beyond orest-sequestration rates.
The two major carbon pools in orests are live trees andsoil. Forests that continue to increase live tree biomass areconsidered sinks or atmospheric carbon. When the rateo sequestration decreases to a point where net growth isless than mortality and decomposition, such as in areas oorest decline, orests become a source o carbon dioxide
emission. The VMC plot data shows that some locations onMount Manseld may currently be a source o carbon dioxideemissions, due to drought-induced mortality and a trendtoward decreasing biomass. This, however, could be reversedas existing trees grow and new trees replace dead trees.
Soil carbon is less well studied. Vermont estimates maybe low because temperate orests are estimated to store nearly
double that o above-ground vegetation. Most o the soilcarbon in Vermont is organic carbon, allowing estimates o
soil carbon based on organic matter content. VMC researchersassembled a map o orest soil carbon or Vermont (Figure 8);areas o high or low carbon may suggest uture guidelinesor managing soil carbon.
DForest health monitoring measures the ability o trees to
recover rom damages inficted by natural and anthropogenicdisturbances. Natural disturbances are an ecologically
important and intrinsic part o Vermonts orested ecosystems. They shape the types, quantities,and spatial distributions o habitats and strongly infuence successional processes. Incontemporary ecology, natural disturbances are viewed as a subsidy to the system, creatingcritical habitat structures and driving a host o ecological processes, including soil and nutrientturnover, organic matter recruitment into streams, and carbon storage dynamics. But whendisturbance dynamics are perturbed by humans (or example, when peoples actions contributeto severe fooding or large-scale insect outbreaks), then deleterious stress can be induced.Disturbances also interact with human-induced stressors, such as acid deposition and climatechange, in determining trajectories o orest ecosystem change (North and Keeton 2008).
Vermont Forests Stored Carbon Annual
(MMt) Accumulation
o CO2 (MMt)
Soil 139 0.7
Forest foor 45.7 0.5
Down dead 12.2 0.4
Understory 3.2 0.03Standing dead 11.4 0.3
Live trees 172.2 6.3
Wood products 1.4
T 383.7 9.63
Table 3: Estimates o carbon stored in Vermont orestsand the annual removal o CO
2rom the atmosphere
through orest sequestration.
Figure 8: This map o
orest soil carbon inVermont, assembled by
VMC researchers, may
help develop guidelines
or managing orest
carbon in the uture.
Source:Wilmot et al. 2008
V F S C
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A variety o natural disturbance agents, including wind, ice,insects, ungal pathogens, beavers, foods, and re, have sculptedour orested landscapes or centuries. Events that create gaps inthe canopy are the most common type o disturbance in Vermontsorests. Disturbance gaps usually involve death or damage to
individual or small groups o trees. Depending on size andorientation, gaps can result in regeneration o intermediate to shadetolerant species, release o advanced regeneration, or competitiverelease and accelerated growth in proximate overstory trees.
In 1985, surveys o Vermonts hardwood resources showednearly 14,000 acres o dead trees (Figure 9). Although subsequentresurveys showed that acres o dead trees decreased and percento healthy trees improved to 90 percent or better, concern aboutsugar maple tree health across the regioncaused potentially by
impacts o acid deposition and the ill eects o tapping trees ormaple syrup productionled to the establishment o a Canada-United States sugar maplehealth monitoring program (NAMP). In Vermont, one o the monitoring sites was at the base
o Mount Manseld.Sugar maple health monitoring has
provided solid inormation on trends in stress
events and recovery or this prominent treein Vermont orests. While initially this surveyshowed areas o tree decline, with only 81
percent o sugar maples in Vermont plotsconsidered healthy, tree health improved inthe early 1990s (Figure 10). Tree health dippedagain in recent years ollowing an outbreak oorest tent caterpillar.
In 1990, a systematic orest health detectionprogram started in New England and grew tobecome the national Forest Health Monitoring
program, aimed at detecting emerging
regionally signicant orest health problems.We have adopted key ecosystem methodsrom this program or use on many o ourVMC monitoring plots. VMC provided a uniqueopportunity to co-locate these orest health
measurements with those o atmospheric, weather, wildlie, water, and soils conditions, whichhas improved our understanding o relationships among environmental changes, orest health,and ecological dynamics (see Ozone, page 36).
A massive ice storm in
1998 devastated large
portions o Vermonts
orests.
17,500
14,000
10,500
7,000
3,500
0
1985 1990 1995 2000
Acres of Hardwood Mortality in Vermont
Year
Figure 9: In 1985, a survey o Vermonts
hardwood resources showed nearly14,000 acres o dead trees. In later years
this acreage decreased dramatically.
Source: Kelley et al. 2002
25
20
15
10
5
0
Sugar Maple Health
Average %
1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Dieback
Foliage Transparency
Mortality
Figure 10: Sugarmaple health
monitoring has
provided long-term inormation
on trends in stress
events and recovery.
While initially only
81 percent o sugar
maples were healthy,
tree health improved
in the early 1990s.
Source: Vermont Plots,
NAMP
Forest tent caterpillar
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Precipitation is one o the key drivers oorest health, both directly and indirectly. Treesneed adequate moisture or growth, but lowprecipitation has also been correlated with risingpopulations o insect deoliators. Periods o poorsugar maple tree health have corresponded withbelow-normal precipitation over the past twodecades. Following the 1999 and 2001 droughts,orest tent caterpillar populations exploded,
resulting in extensive deoliation. Stress rom avariety o disturbances has aected sugar maplehealth at Mt. Manseld and around Vermont asseen in the percent o trees with thinner thannormal oliage (Figure 11).
Monitoring has been instrumental indetermining thresholds or tree recovery. Periods o stress oten lead to crown dieback, but treeshave the ability to recover i the stresses abate. Fertile sites high in calcium tend to recover more
quickly. This ability also varies with species. Sugar maple is good at recovering; yellow birch hasa moderate ability to recover, but paper birch has poor stress recovery. This inormation hashelped orest managers determine how and when to thin orests to maintain healthy, vigorous
trees, and was especially helpul in salvage cutting ollowing the destruction rom the 1998 icestorm (Kelley et al. 2002). Tree recovery at VMC sites has ollowed this same trend; sugar maplerecovery rom the ice storm and rom orest tent caterpillar deoliation has been good, but whitebirch recovery rom ice damage and drought has not been as successul.
At the VMC study sites, weather actors play a signicant role in shaping the growingconditions o orests. Mt. Manseld has elevations ranging rom 1,300 to 4,300 eet and Lye
Brook Wilderness Area peaks at nearly 3,000 eet.Winter storms are severe, with high winds and icecovering trees. Soils are quite shallow in portionso upper elevation orests. Also, air at these upperelevations is laden with high amounts o acidiccompounds, ozone, and mercury. So monitoring
the health o these orests can show the mostextreme orest impacts rom stress events, but
can also provide early indications o potentialproblems that will aect a wider area oVermonts orests.
Forests o the high-elevation spruce-rzone on Mt. Manseld have been more proneto mortality than other locations. The balsamr-dominated orests consistently have highdieback and damage rom broken branches.Annual monitoring has also shown that heavy cone-producing years, while beneting squirrel
populations, is detrimental to crown health and indirectly to bird reproduction, as squirrels are
predators o bird eggs. Birch trees are particularly vulnerable to drought. On the east slope oMt. Manseld, birch condition has declined since the severe drought o 1998-99 (Figure 12).
50
45
40
35
30
25
20
15
10
5
0
1992
Percent of Trees with High Dieback
1993
19
9419
95
1996
19
97
1998
19
99
2000
20
01
2002
20
03
2004
2005
2006
20
07
2008
Balsam fir
Birch
Figure 12: This gureindicates dieback o
birch and balsam r
on Mt. Manseld. Adecade o balsam r
recovery ollows a past
disturbance. Birch
trees are particularly
vulnerable to drought,
shown here in the
decline o birch since
the severe drought o
1998-99.
Source: Sandy Wilmot,VTFPR
50
45
40
35
30
25
20
15
10
5
0
1988
Percent of Sugar Maple Trees on Monitoring Plots with Thin Foliage
Pear Thrips Ice Storm
Drought Forest Tent Caterpillar
1989
1990
19
9119
9219
9319
94
1995
1996
19
97
1998
19
99
2000
2001
2002
2003
20
04
2005
2006
20
07
Figure 11: Stresses roma variety o events have
aected sugar maple
health. Following the
1999 and 2001 droughts,
or example, orest tentcaterpillar populations
exploded, resulting in
extensive deoliation.
Source: Vermonts Plots,
NAMP
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orest managers in Vermont must contend withmyriad hot button issues. These include how to deal
with exotic diseases and insects, adapt to climate change,
saeguard riparian systems, minimize impacts associated
with orest roads, manage competing recreational interests,
and conserve orest biodiversity. Keeping working orests
economically viable, conserving open space, and
discouraging parcelization and sprawl are major concerns.
But 21st century oresters also ace new opportunities, such
as growing interest in community-based orestry, orest
certication, rapidly developing carbon markets, and rising
demand or sustainably produced biomass uels. These
opportunities may create economic and other incentives
or sustainable orest management, but also require
balancing tradeos between competing resource values.
An example is the inherent difculty o how best to allocate
biomass among uses such as on-site carbon storage,wood products, uel, and habitat structure.
A central challenge in sustainable orest management
has been determining the best mix o management
approaches most capable o providing a broad array o
ecosystem unctions while meeting landowner objectives.
VMC scientists are conducting research on a promising area
known as disturbance based silviculture, which emulates
naturally occurring orest processes (Keeton 2006).
A general nding o this research is that late-
successional characteristics in northern hardwood
including vertically complex canopies and gapscan be
promoted through a variety o modied silvicultural
approaches. But these management techniques are lesseective in other ways, tending to signicantly inhibit certain
stand development processes, such as recruitment o large
trees, downed coarse woody debris, and the highest levels o
biomass and carbon storage. The results signal that
treatments can be modied to retain and even enhance
important elements o stand structural complexity, but o
course this involves tradeos in terms o reduced harvest
volumes (Figure 13).
The VMC-sponsored Forest Ecosystem Management
Demonstration Project (FEMDP) has also shown that low-
intensity, disturbance-based management can provide an
intermediate level o carbon storage, providing a margin o
enhanced on-site carbon sequestration compared toconventional selection harvesting. Aboveground biomass is
predicted to increase over the next 50 years under all the
treatments, including controls. None o the experimental
stands is likely to attain the biomass they would have without
treatment, but some techniques are projected to attain 91.4
percent o the biomass levels o untreated stands.
FEMDP researchers have monitored a variety o wildlie
as indicators o biodiversity responses to sustainable orest
management. As predicted, responses to the silviculturaltreatments vary according to the habitat associations o
dierent groups o species. For instance, some early
successional bird species appear to have beneted rom the
variably sized openings created by group selection logging,
while all the treatments have been eective in maintaining
the habitat needed by interior dwelling and late-successional
birds (Strong, unpublished data).
There are clear economic tradeos involved in modiying
silvicultural treatments to promote stand structural complexity
(Keeton and Troy 2006). FEMDP assessments examined
timber-related revenue only, whereas a more complete
economic analysis might include other potential revenue
sources, such as carbon credits.The prot margins incurred
by all the treatments were highly sensitive to site quality andmarket conditions. Where these are poor, lower intensity
harvesting may generate only enough prot to cover expenses.
This might be acceptable in a limited number o settings,
or instance where disturbance-based approaches are employed
or restoration purposes in reserves. For commercial harvests,
however, the experimental approaches would be marketable
only where site quality is moderate to high and market
conditions are avorable. Under those conditions the
experimental treatments oer alternatives that provide
revenue rom low-intensity harvest while also meeting
ecological management objectives.
R S F M
F
P r e - H a r v e s t
P r e - H a r v e s t
P o s t - H a r v e s t
P o s t - H a r v e s t
Single-Tree Selection Unit
Structural Complexity Enhancement Unit
Figure 13: Visualization o stand structure changesassociated with two o the experimental treatments in
the VMC Forest Ecosystem Management Demonstration
Project.
Source: Keeton 2006
PRE-HARVEST
PRE-HARVEST
POST-HARVEST
POST-HARVEST
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Biomonitoringdata collected onmountain streamsbelow ski resortsshow that increased
sediment andfuctuating pH canaect the productivityabundance, andspecies richness omacroinvertebrates.
Ski Resorts and Land-Use Disturbance
Disturbances caused by conversion o upland orests to developed uses may have moreserious environmental implications than at low elevations. As Vermont ski resorts expand anddiversiy activities over our seasons, their ecological impacts may be intensiying. Mountain
ecosystems are also increasingly subject to other disturbances and stresses such as climatechange, mercury deposition, acid precipitation, and development o wind and communicationtowers. VMC-supported wildlie research has ocused on three aspects o mountain
development: direct habitat loss, ragmentation, and modication. Hydrologic and aquaticstudies have examined the role o mountain development on streamfow, water quality, andaquatic biota.
The response o wildlie species to orest ragmentation and loss is dictated by actorssuch as home range size, sensitivity to habitat edge eects, and gap-crossing ability. Theoretical
modeling o bird species on two existing Vermont ski resorts, Stratton Mountain and MountManseld, showed dramatic decreases in population sizes as ragmentation and edge eectsincreased (Strong et al. 2009). Modeling habitat requirements, using current ski resortmanagement scenarios, shows that species with one-hectare territories declined by 32-41percent, while population declines in species with ten-hectare territories ranged rom64-73 percent. These results underscore the need to investigate actual impacts o ski resortdevelopment on wildlie, in particular high-elevation orest birds like Bicknells thrush.
Research on songbirds has repeatedly shown that increased habitat ragmentation causesedge eects which can lead to higher rates o nest predation and lower rates o nest survival.
Because ski trails and associated work roads ragment and increase the amount o edge habitat,an important question is whether these modications aect the nesting success o Bicknellsthrush. VMC researchers examined potential dierences in nest predation and adult survivor-ship on ski resorts compared to natural orest areas on Manseld and Stratton (Rimmer etal. 2004). Overall there was no strong evidence or a ski resort eect on nest predation orsurvivorship. There was some evidence that male thrushes may be more vulnerable to predationwhen crossing open ski trails. Radio telemetry data indicate that Bicknells thrushes tend toavoid crossing large openings. Other species may also be reluctant to cross open ski trails,
as shown in research involving orest beetles (Strong 2009) and six species o songbirds(Holmgren 2002).
Mountain watersheds are high energy settings, where water, solutes and sediment moverapidly over steep slopes and thin soils. Decades o study in orests o the northeastern U.S.and elsewhere indicate that logging and road construction aect annual water yields, peakfows, sediment production, water quality, and aquatic habitat quality. The eects o ski resortdevelopment, however, are not well known. In 2000, a team o VMC cooperators established a
Aerial inrared
photography showing
an increase in road
inrastructure and
land-use changes
in Charlotte over a
15-year period.
Source: Kelley et al. 2002
1985 2000
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watershed study on Mt. Manseld to examine the hydrologic eects o ski resortdevelopment. The study uses a paired-watershed approach to compare streamfow,water chemistry, and sediment yields or two adjacent watersheds on the easternslopes o Mt. Manseld (Wemple et al. 2007; Shanley and Wemple 2009). Evenater accounting or small dierences in watershed size and articial snowmaking,
study results show that water runo rom the ski resort watershed consistentlyexceeds that o the unmanaged watershed to a greater extent than orest harvestingincreased runo over unmanaged orests in regional watershed studies. Thegreater runo appears to result rom the combined eects o the more prodigioussnowall in the ski-resort watershed and to dierences in snowmelt delivery tostreams during spring runo, and has important implications or storm watermanagement in mountain development projects. Annual sediment yield rom theski-resort watershed exceeds that rom the unmanaged watershed by roughly threetimes (Figure 14), with much larger dierences documented during periods o
construction and ground disturbance. Annual chloride yield is ten times higher inthe developed watershed, presumably due to road salting, relative to the control(Figure 15).
VMC-sponsored research on ski resort development also ocuses on aquaticbiota. Biomonitoring data collected on mountain streams below ski resorts showthat increased sediment and fuctuating pH can aect the productivity, abundance,
and species richness o macroinvertebrates. Increased fows oten will cause ascour eect temporarily decreasing macroinvertebrate abundance, results that areseen in monitoring data across the state.
The three species o stream salamanders which inhabit the mountain orests o Vermontserve as useul bioindicators o stream habitat quality. Salamander abundance and body sizeswere quantied within seven Vermont ski resorts and in adjacent undisturbed orest areas,including Mt. Manseld (Hagen 1998; Strong et al. 2009). Ski resort streams supportedsignicantly lower populations o spring salamanders and northern dusky salamanders, andbody lengths o northern dusky salamanders were shorter within ski resorts. These dierencesmay have resulted rom clearing streamside vegetation and increased siltation rates instreams within ski resorts.
VMC-supported research has shown that the eects o upland development, when
reerenced against traditional orest practices o logging and road construction, have provedto be larger than expected. Some o these eects can be mitigated through good managementpractices, including storm water detention structures, waterbars on ski trails, and increasedriparian buer widths. Other eects are an inevitable outcome o habitat ragmentationassociated with development o the mountain landscape.
Fragmentation Eects on Reptiles and Amphibians
Land conversion and ragmentation are key disturbances that adversely aectthe ability o animals to move saely through the landscape. As a result othe statewide reptile and amphibian studies unded by VMC, we have rened
our knowledge o the distribution o all o Vermonts reptiles and amphibians
and the eects o habitat ragmentation on these species. One o thesespecies, the eastern ratsnake, is among the largest snakes in the UnitedStates, commonly reaching six eet in length. The eastern ratsnake has anisolated northern population and a connected population in western RutlandCounty. The northern population on the Monkton/New Haven/Bristol borderis entirely disconnected rom any other eastern ratsnakes; hence, thereis no introduction o new genes into the population and no possibility o
recolonization ater a local population extirpation. Consequently, it is at amuch greater risk o permanent loss than the Rutland County population.
250
200
150
100
50
0
Annual Suspended Sediment Yield
WY01 WY02 WY03
150
100
50
0
Annual Chloride Yield
WY01 WY02 WY03
Ranch Brook West Brook
Ranch Brook West Brook
Wood turtle
Figures 14 and 15:In a paired-watershed
study at Mt. Manseld
conducted in water
years 2001-2003,
both annual sediment
yield and annual
chloride yield were
higher on a ski-resort
watershed than on an
unmanaged watershed.
Source: Wemple et al. 2007;Shanley and Wemple 2009
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Among the best known migrating wildlie in Vermont are those specieso amphibian that breed in the early spring. With the rst warm rains o lateMarch and early April, thousands o spotted salamanders and wood rogs thathave spent the winter in upland deciduous orests, head to the nearest beaverponds, vernal pools, and swamps to breed and lay their eggs. VMC-unded
work has discovered a ew, large, remaining populations o the blue-spottedsalamander. One o these populations currently crosses a major shortcut to theWilliston big-box shopping malls. As a result, hundreds o adult blue-spottedsalamanders are killed on this road every spring. Eventually the amount omortality on the road will surpass the ability o the population to replace them,and the population will disappear. Another amphibian, the eastern newt, relieson a contiguous mosaic o oten shiting ponds and orested uplands or its liecycle. As these ponds and orests become isolated rom each other by orest ragmentation,the newts become increasingly at risk.
Wood turtles exempliy another conservation issue aecting long-lived species. Woodturtles may live 30 years or more and do not become sexually mature until reaching about 14years o age. Their survival as a species depends upon the turtles laying eggs or many years.The long-lived strategy worked well or wood turtles until the introduction o cars, mechanizedhaying equipment, and turtle collectors. Consequently, both their longevity and their terrestrialbehavior put them more at risk rom increased development, habitat ragmentation, and human
population growth.Another example o the impact o changing orested landscapes on reptiles is loss o
early successional habitat. Both smooth greensnakes and North American racers preer open
grasslands or a mix o shrubs and grasses. Historically these might have been extensive beavermeadows, food plains, or areas cleared by rockslides, hurricanes, or other natural events. Ashilltop arms were abandoned, open areas rst returned to orests, and now many are beingdeveloped. Most o the lands that remained open were maintained by regular mowing, or usedas cropland. The machines that keep these lands open today have become aster and more
ecient over the years. Wildlie o all kinds ismowed, raked, and baled along with the crops.As a result, smooth greensnakes and North
American racers no longer inhabit cropland
or regularly mowed and baled areas. Theyare, however, ound along open power lines,cleared margins o roadways, pastures (keptopen by animals), wet elds, and elds keptopen by occasional brush-hogging to maintain
views. Consequently, populationso the smooth greensnake areincreasingly dicult to nd. We know
o only one recent populationo North American racers and eventhat one may have disappeared inthe last two years.
Blue-spotted salamander
Smooth greensnake
Eastern rat snake
VMC-unded workhas discovereda ew, large,remaining
populations othe blue-spottedsalamander.Eventually theamount omortality on theroad will surpassthe ability o thepopulation to
replace them.
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R
Nearly two decades o VMC-supported research and monitoring provides a rich pictureo the health o our orests and a window into things to come. Strengths and weaknessesin the health o our orest ecosystems have been highlighted in this report. Productivitymonitoring indicates stresses caused by air pollution, extreme weather events, and perhapschanging climate conditions. Our orests produce an abundant supply o clean water, butstudies suggest that development will produce impacts on fows and water quality that will
have measureable eects on aquatic organisms. Biodiversity in our orests is high, but VMCstudies show clear eects o a landscape increasingly pressured by a growing population andland-use practices that consume and ragment natural habitats.
VMC researchers studying orest-health issues recommend the ollowing:
Continuetostudycarbondynamicsinmanagedandunmanagedforests,andtheir
relationship to long-term orest recovery rom historic land uses, anthropogenic stress,natural disturbance dynamics, and orest management.
Investinequipmenttobetterunderstandcarbonuxandinteractionsbetweencarbonand other atmospheric pollutants as climate changes.
UtilizeVMCexpertiseanddatatoaddresstheecologicaleffectsofexpandingbiomassharvesting or energy.
Createdemonstrationareasforforestmanagerstomeasureforestcarboncyclingandunderstand carbon accounting and management options.
Continuemonitoringtheresponsesofterrestrialandaquaticspeciestodevelopmentpressures leading to habitat ragmentation.
CollectbaselinedataonnewhumanandanimalhealthrisksemerginginVermont,including especially the deer tick, a vector o Lyme disease.
Monitornaturaldisturbanceimpactstobetterunderstandbaselineecosystemdynamicsand evaluate regime changes related to global climate disruption.
UtilizeVMC-supportedwatershedresearchtoinformstatepermittingstandardsfornewmountain development projects.
Providedatatoinformguidelinesforskiresortsandothersconductinghabitat-mitigation
eorts to maintain or restore ecosystem structure and unction.
VMC I D I B
ndiana bats are listed as an endangered species at state andederal levels. Populations in Vermont depend on large old sugarmaple trees or nesting and rearing their young. A recent population
explosion o orest tent caterpillars deoliated thousands o acres osugar maple orest. Proposed control eorts to protect sugar maple
stands included aerial applications o a bacterial biological control agent,Bacillus thuringiensis (Bt). Because Bt is known to kill Lepidoptera larvae ingeneral, concerns were raised about the eects o such treatments on thebats ood supply, which would have placed an additional stress on batsduring a critical lie stage. Data on moth presence and abundance,generated through VMC and other studies, were used to help time theaerial sprayings so that eects on the Indiana bat populations wouldbe minimized.
I
Indiana bat
Nearly twodecades oVMC-supportedresearch andmonitoringprovides a richpicture o thehealth o ourorests.
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WEATHER AND CLIMATE IN VERMONT
ituated just south o the 45th parallel, Vermontexperiences a humid, continental climate that
is characterized by a high degree o variability. Thestates latitude and location relative to air masses androntal systems that originate to its northwest, west, andsouth are key actors in both the weather fuctuations thatare observed seasonally and annually, as well as the natureo the storms that move across it. Precipitation is equallydistributed throughout the year and the cloud shield thataects most o the region makes Vermont one o the
cloudiest places in the United States.Weather and climate reer to two very dierent
phenomena. Weather describes the condition o theatmosphere (or example, temperature, precipitation,cloud cover, and humidity) over a short time rame ominutes to about a week. Climate, on the other hand, reersto the longer-term averagesmonths to millennia andlongero the variations in the atmosphere, biosphere,
and hydrosphere over time. Climate variability incorporatesthe naturally occurring fuctuations in the atmosphere overthese long time periods, while climate change reers toa long-term change in the statistics o climate variables(such as winds and temperature) due to either naturalclimatic processes, changes in earth-sun characteristics,or anthropogenic mechanisms (American MeteorologicalSociety 2000).
Natural climatic hazards that plague Vermont includetemperature extremes, fooding, drought, tornadoes,
damaging winds, severe thunderstorms, winter storms andorest res. Each hazard has seasonal characteristics and
temporal cycles, with some occurring more requently incertain decades than others. Hazards can be exacerbated bythe states terrain and mountain barriers (its orography), inparticular the north-south trending Green Mountains andTaconics. Orographic precipitation reers to the enhancedprecipitation totals that occur when a storm system is
orced to rise as it encounters a mountain barrier. This isoten observed across Vermont and can lead to foodingepisodes in the summer or areas o increased snowallaccumulation in the winter. On a local and regional scale,
Vermonts mountains and valleys also aect the unnelingo wind fow, the creation o cold/rost hollows in valleys,and the line between reezing precipitation and rain or snowduring complex winter storms. These terrain infuences aretranslated into the distribution and diversity o species types
as well as the location and magnitude o storm damage onorests (Dupigny-Giroux 2002).
M TIn Vermont there is a saying that one extreme ollows
another. This is particularly true or droughts and foods.Very severe droughts are rare and tend to be statewide,spanning a number o years. These include the severedroughts o the mid-1960s, 1998-1999, and 2001-2002all were noteworthy in terms o their eects on the statesorests. The 1998-1999 event aected 85,000 acres (34,425hectares) statewide with symptoms such as lea scorch, leayellowing, and early lea color. Less severe droughts occur
more requently and tend to be localized in extent. Speciesthat are susceptible to drought include red and sugar maple(Dupigny-Giroux 2002). Temperature extremes can occurin every season, including extreme cold and rost duringthe summer which can be detrimental during the growingseason. In the spring, marked fuctuations ollowingbudding can infuence fowering in species such as crabapples. In 2001, spring temperatures varied rom at least
90 degrees F to about 20 degrees F. This accelerated theproduction o apple blossoms, which were then destroyedby the low nocturnal temperatures. Moisture extremes
can be conducive to insect outbreaks as well as diseasessuch as tar spot that repeatedly struck Norway maples in2007 and 2008.
Storms and other severe weather can act asdisturbances in orested ecosystems, the most noteworthyo which in recent decades was the ice storm o January
1998, which damaged more than 951,000 acres in Vermontalone. Other stressors such as drought and hurricane-induced rainall have also caused physical and chemicalchanges in plant response. When these stressors and
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disturbances occur consecutively or coincidentally, they raise questions aboutlong-term orest health and viability.
Meteorological observations are taken at six Vermont Monitoring Cooperative(VMC) sites. The lowest in elevation are Colchester Ree (125 eet or 38 meters)and Diamond Island (148 eet or 45 meters), located on Lake Champlain. Both
stations report 15-minute averages with Colchester Ree beginning in July 1996and Diamond Island in May 2004. In September 1996, the station on the westernslopes o Mt. Manseld began operations at an elevation o 2,800 eet (853meters). A second station, also at 2,800 eet on the eastern side o Mt. Manseld,became operational in July 1999. Fiteen-minute data are available or these stationsas well as or the Proctor Maple Research Center Air Quality site (1,309 eet or399 meters). Finally the National Weather Service supervises daily records at thesummit o Mt. Manseld (4,300 eet or 1,310 meters), which has been in operationsince 1954.
Daily readings o temperature and relative humidity taken at the ColchesterRee station versus Mt. Manseld West highlight the stations physical andgeographical dierences (Figures 16 and 17). The moderating infuence o LakeChamplain is clearly observed at Colchester Ree in contrast to the more continental andhigher elevation on Mt. Manseld. Variations in relative humidity between these two sites aredetermined by both the temperature and water vapor pressure o air and largely refect the
dierent air characteristics at the sites. The range o relative humidity values is larger at
40
30
20
10
0
-10
-20
-30
1997
Air Temperature Colchester Reef
1998
19
99
2000
2001
20
02
2003
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2005
20
06
2007
20
08
2009
Year
AirTemperature(C)
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0
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1997
Air Temperature Mt. Mansfield
1998
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2001
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02
2003
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04
2005
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06
2007
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08
2009
Year
AirTemperature(C)
Figure 16: Daily average air temperatures atColchester Ree (top) and Mt. Manseld West.Source: Christopher Still
100
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2010
0
1997
Relative Humidity Colchester Reef
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2009
Year
RelativeHumidity(%)
Relative Humidity Mt. Mansfield
100
90
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0
1997
1998
20
00
2001
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02
2003
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2005
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06
2007
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08
2009
Year
Relativ
eHumidity(%)
Figures 17: Daily average relative humidity at ColchesterRee (top) and Mt. Manseld West.Source: Christopher Still
The Colchester Ree
monitoring station.
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Mt. Manseld than it is at Colchester Ree, with substantially more100 percent relative humidity observations at the ormer site. Also,while the mean daily relative humidity is rarely below 50 percent atColchester Ree, it requently dips below this threshold at the Mt.Manseld station.
Cloud data comprise another meteorological elementmeasured at these stations. Clouds infuence several environmentalactors important or orest carbon and water cycling and oresthealth. For example, clouds are strong determinants o suraceclimate, particularly intercepted solar radiation (insolation), airtemperature, and relative humidity. Clouds diuse sunlight. Studieso orests have documented how increasing this so-called diuseinsolation can increase canopy photosynthesis up to a point. Thereason is thought to be due to enhanced photosynthesis o leaves
deep in the canopy that are otherwise shaded by upper-canopyleaves. Clouds also decrease radiant heating and thus temperatureso upper canopy leaves. Finally, increased cloudiness is alsoassociated with higher relative humidity via decreases in air and leatemperature and increases in specic humidity.
As a result o all these processes, temperate broadlea orests
oten have the highest photosynthesis rates under partly cloudyconditions, as they benet rom lowered temperatures, higherrelative humidities, and increased diuse insolation (Freedman et
al. 2001; Min and Wang 2008; Still et al. 2009). However, cloudscan also negatively impact orests through delivery o acidityand pollutants rom cloudwater deposition. Cloudwater is otencontaminated with pollutants like mercury and other trace elements. Given the importanceo clouds or orest processes and health, we analyzed long-term data on cloud requencyand height rom the Burlington International Airport. Seasonal cycles o cloud requency areshown in the two charts in Figure 18, which indicate clearly how cloudy the Burlington area is,with the highest cloud requency in winter and the lowest requency in the summer months.
Cloud data going back to the late 1940s document an apparent downward trend in the
requency o cloudy periods observed in Burlington starting in the mid-1990s and continuingto the present. Notably, when we examine the requency o clouds with bases below 1,000meters over this same time period, no downward trend appears,so the variation must be driven by higher elevation clouds.Interestingly the downward trend in cloud requency may underliethe insolation patterns observed at Colchester Ree. As can be seenin Figure 19, there is an increase through time in the summertimemaximum insolation values measured at Colchester Ree. This is
exactly what would be expected rom declining cloud cover overthis period, with reduced refection, scattering, and absorption osolar radiation rom cloud droplets.
In order to place these observations into perspective, it
is useul to look at averages over the entire western region oVermont or an extended period o time. Again, climate variabilitycomes to the ore with marked temperature and precipitationfuctuations over the last century at both a regional scale (westernVermont) as well as statewide. Several droughts o larger
magnitude and intensity than those observed in the VMC period o record are noted onFigure 20, as are the decades that have been warmer and colder than those o the 1998-2008time rame.
Figure 18: Cycleso cloud requency
at the Burlington
International Airport.
Source: Christopher Still
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Average Seasonal Cycle of Cloud Frequency
Month
C
loud
Frequency
1 2 3 4 5 6 7 8 9 10 11 12
Mean Monthly Frequency Clouds < 1000mMean Monthly Frequency All Clouds
0.8
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Year
Cloud
Frequency
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1952
1955
1958
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6119
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1988
19
91
1994
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00
2003
2006
Annual Mean Cloud Frequency Since 1949
600
500
400
300
200
100
0
Insolation Values at Colchester Reef
Insolation(W/m2)
1996
1997
1997
1997
1998
1999
1999
2000
2000
2001
2002
2002
2002
2003
2003
2004
2004
2005
2005
2006
2006
2007
2007
2008
2008
2009
Date
Figure 19: There is anincrease through time in
the summertime maximum
insolation values measured
at Colchester Ree.
Source: Christopher Still
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F P SForests are dynamic. Thus, understanding and measuring
what is normal can be challenging, requiring a long-timecommitment. One measure o orest processes is the timingo spring events such as tree lea and fower development,ephemeral plant fowering, and pear thrips (a orest insectpest) emergence and eeding. Over the past 18 years, sugar
maple lea and fower development have been monitoredannually, and other spring phenological events have beenmonitored periodically, at Mt. Manseld, Lye Brook, and other
locations, as indicators o orest health.Forests in spring are teeming with activity as trees, plants,
and animals come alive rom their long winters dormancy.Everything happens quickly and the timing o eventsdetermines an organisms survival and propagation. Herbaceous ephemeral plants (plants thatare only seen in the spring) are a clear example o a quick, well timed orest process. Sunshinepenetrates orest canopies that havent yet produced their leaves, warming the orest foor.This provides an opportunity or plants that normally live in the shade o orest trees to takeadvantage o the warmth and open canopy to quickly emerge, gather sunlight or energy,
fower, and set seeds. By the time tree leaves have come out, these plants are nished theircrucial lie stages and retreat into dormancy once more. The timing o these events has beenmonitored over the last 18 years at the base o Mt. Manseld in a sugar maple-dominatedorest, providing a baseline or monitoring change over time (Table 4).
Pear thrips was discovered as a new sugar maple pest in 1987, and in 1988 thrips deoliatednearly 250,000 acres o orestland inVermont. This tiny insect emergesrom the soil in the early spring and
searches or open sugar maple budsto enter and eed upon. I spring buddevelopment is rapid, thrips havelittle time to enter buds, eed, and
damage lea tissue. But i weatherconditions stall bud development,thrips can destroy young leaves,causing signicant orest injury. In theearly 1990s, research on pear thrips
at the UVM Entomology ResearchLaboratory produced monitoringmethods or sugar maple lea andfower development. Subsequent treeand insect monitoring at the VMCMt. Manseld site have contributedto understanding population andmanagement strategies o this insect
in relation to sugar maple processes. In 1993 and 1995, pear thrips populations were signicant,emergence and eeding developed sooner than sugar maple lea development, and this resultedin large areas o orest injury. Normally, sugar maple lea emergence outpaces thrips eedingand little lea injury occurs.
Additional monitoring o other hardwood species has increased our understanding o theprogression o spring development among species, at dierent elevations and within orestcanopies. Managing orest health in Vermont requires answering questions about the timingo tree species development. For example, when VMC researchers received a request orinormation on the timing o sugar maple pollination, the answer was readily available: between
April 28th and May 15th. Another request or inormation came rom the maple syrup industry,
Figure 20: StandardizedPrecipitation Index (SPI)
or the western climate
division o Vermont
1895-2008. Periods o
excessive precipitation
and droughts have beennoted.
Source: Courtesy the National
Drought Mitigation Center
4
3
2
1
0
-1
-2
-3
-4
Standardized Precipitation Index 1895-2008
SPI
values
1895
1899
1903
1907
1911
1915
1919
1923
1927
1931
1935
1939
1943
1947
1951
1955
1963
1967
1971
1975
1979
1983
1987
1991
1995
1999
2003
2007
Months
1927 1938
1955
1998,19992005
199519871980
197819631915
Table 4:Floweringdates o understory
spring plants at
Proctor Maple
Research Center in
Underhill. Data results
are rom 18 years o
monitoring (1991-
2008).
Source: Sandy Wilmot andTom Simmons, VTFPR
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which was interested in expanding tapping to include red maple trees and needed inormation
on the timing o red maple bud development in comparison to sugar maple. Red maple hasbeen traditionally thought o as fowering early in spring and so could potentially add a buddyfavor i mixed with sugar maple sap. Although red maple fower buds begin to swell onaverage two days earlier than sugar maples, budbreak (when leaves start to emerge) is actuallylater. Sugar maple bud development is on average 37 days rom bud swell to ull lea out,
whereas red maple is 51 days. Monitoring results indicated that red maple, on average, leaedout 14 days later that sugar maple, so timing o lea out was not a valid reason or excludingred maple sap.
Spring development, however, is highly variablerom year to year and location to location, dependingon temperature, precipitation, snow pack, and otherenvironmental actors. On Mount Manseld with itscolder temperatures, increased snow pack, and otherenvironmental dierences, lea development o sugar
maple orests located at 2,200 eet was 7-10 days laterthan at 1,400 eet.
Because o interest in climate change, researchersare oten asked i the timing o lea development isearlier or later than normal. Sugar maple budbreak(green tip o lea emerging rom buds) and lea out(ull lea development) have been earlier in the decadeo the 2000s compared to the 1990s. While there is
much variability rom year to year, eight o the nineyears o earlier than normal lea development occurred since 2000. On average, budbreak isthree days earlier and lea out is ve days earlier this decade than in the 1990s (Figure 21). In
2008, monitoring show