Central Appalachians Forest Ecosystem Vulnerability Assessment

This chapter describes the forests and related ecosystems across the Central Appalachian Broadleaf Forest-Coniferous Forest-Meadow and Eastern Broadleaf Forest Provinces of Ohio, West Virginia, and Maryland and summarizes current threats and management trends. This information lays the foundation for understanding how shifts in climate may contribute to changes in forest ecosystems, and how climate may interact with other stressors on the landscape.

• The assessment area of the Central Appalachians region contains about 29 million acres, of which 18.9 million acres are forest land. Private individuals and organizations own more than 85 percent of forest land.
• The existing climates within the Central Appalachians are strongly influenced by atmospheric circulation patterns, latitude, topography, and abrupt changes in elevation. The primary factors influencing the climate are latitude and proximity to Lake Erie (warmer), and elevation and complex topography in the (cooler) mountainous eastern sections.
• Oak/hickory and maple/beech/birch are the most abundant forest-type groups across the area.
• Current major stressors and threats to Central Appalachians forest ecosystems include fragmentation and land-use change, natural disturbances (e.g., extreme weather, fire, drought, or flood), forest diseases and insect pests, and nonnative invasive plant species.
• The forest products and forest-related recreation industries are major contributors to the regional economy, and an increasing amount of forest land is managed according to a sustainability certification standard.
• Nine forest ecosystems are used to describe the forests in the Central Appalachian region. The descriptions of forest communities were based on NatureServe terrestrial ecosystems and crosswalked to FIA forest type groups.

Many of the climatic changes that have been observed across the world over the past century are also evident in the assessment area. This chapter summarizes our current understanding of observed changes and current climate trends across the Central Appalachians region, with a focus on the last 100 years.

• Annual minimum temperatures increased over the past century, with summer and fall minimum temperatures warming the most rapidly. April, June, July, August, and November had the greatest increases in minimum temperature. Maximum temperatures decreased during July, September, and October. Hot days are occurring more frequently.
• Precipitation patterns have changed across the region, with the most change occurring in fall (increase of 2.3 inches). The number of intense precipitation events has increased.
• Snowfall decreased across the assessment area, and lake ice duration has declined.
• Climate change is also indicated by positive trends in growing season length, shifts in flowering phenology, and changes in wildlife emergence and migration.

This chapter describes climate projections for the assessment area over the 21st century. Temperature and precipitation projections are derived from downscaled simulations of climate models. Published scientific literature provides the basis for describing possible trends in a range of climate-driven processes, such as extreme weather events and snowfall.

• Temperatures are expected to increase over the next century, under a range of climate scenarios and in all seasons.
• Precipitation is projected to increase in winter and spring across a range of climate scenarios. Projections of summer and fall precipitation are more variable.
• Localized soil moisture deficits are expected to become more frequent.
• The growing season length is expected to increase by up to 1 month.
• The number of hot days is expected to increase and the number of cold days is projected to decrease.
• Intense precipitation events are expected to become more frequent. Streamflow and flooding potential are expected to increase in the winter and spring, and decrease in the summer and fall.

This chapter summarizes the potential impacts of climate change on forests in the assessment area, drawing on information from a coordinated series of model simulations and published research.

• Many temperate tree species present within the assessment area are expected to tolerate a mild degree of warming, but are expected to decline under higher rates of warming.
• Many mesic species, including American beech, eastern hemlock, eastern white pine, red spruce, and sugar maple are among those projected to have reductions in suitable habitat, growth potential, and biomass under a high degree of warming over the next century.
• Many species are expected to lose establishment and regeneration potential over the next century, but in the absence of other mortality factors, may persist as mature individuals that continue to grow for much longer. Species with ranges that extend largely to the south such as eastern redcedar, post oak, and shortleaf pine may have increases in suitable habitat and biomass. Loblolly pine, currently only in plantations in the assessment area, is also expected to fare well under the future climate.
• The model projections used in this assessment do not account for many other factors that may change under a changing climate. Scientific literature was used to provide additional information on drought stress, wildfire, acid deposition and nutrient cycling, pests and pathogens, herbivory, and many interactions between factors.

This chapter focuses on the vulnerability of nine major forest ecosystems in the Central Appalachians region to climate change, with an emphasis on shifts in dominant tree species, features that define a system (drivers), and features that disturb a system (stressors). The adaptive capacity of each forest ecosystem was also examined as a key component to overall vulnerability. Adaptive capacity is the ability of a species or ecosystem to accommodate or cope with potential climate change impacts with minimal disruption (Glick et al. 2011, IPCC 2007). We further rated the evidence used in assessing vulnerability as well as the level of agreement between sources of evidence. We consider a system to be vulnerable if it is at risk of a species composition change leading to a substantially different character for the forest system, or if the system is anticipated to suffer substantial declines in acreage, health, or productivity. General trends in climate change impacts and adaptive capacity factors for the Central Appalachians region are also captured in overarching synthesis statements.

Potential impacts of climate change on ecosystem drivers and stressors

• Temperatures will increase (robust evidence, high agreement). All downscaled climate models agree that temperatures will increase across much of the assessment area.
• Growing seasons will get longer (robust evidence, high agreement). There is high agreement among evidence that projected temperature increases will continue to lengthen growing seasons in the region.
• The amount and timing of precipitation will change (medium evidence, high agreement). All downscaled climate models agree that there will be changes in precipitation patterns, but the direction of changes will depend on the season.
• Intense precipitation events will continue to become more frequent (medium evidence, medium agreement). There is some agreement among climate models that the number of heavy precipitation events will continue to increase in the region. If so, impacts from flooding and soil erosion may become more damaging.
• Severe storms will increase in frequency and severity (medium evidence, medium agreement). Climate change is expected to destabilize atmospheric circulation patterns and processes, leading to increased risk of severe weather.
• Soil moisture patterns will change (medium evidence, high agreement). Studies show that climate change will have impacts on soil moisture, but there is uncertainty about the direction and magnitude of the changes at specific locations, especially during the growing season.
• Climate conditions will increase wildfire risk by the end of the century (medium evidence, medium agreement). Some national and global studies suggest that conditions favorable for wildfire will increase, but few studies have specifically looked at wildfire risk in the Central Appalachians region. Wildfire risk will also depend on ignition, fire weather, ecosystem type, topography, fragmentation, and other regional characteristics.
• Certain insect pests and pathogens will increase in occurrence or become more damaging (medium evidence, high agreement). Evidence indicates that an increase in temperature will lead to increases in certain pest and pathogen outbreaks, but research to date has examined relatively few species.
• Many invasive plants will increase in extent or abundance (medium evidence, high agreement). Evidence indicates that increases in temperature and more frequent disturbances will lead to increases in many invasive plant species.

Potential impacts of climate change on forest communities

• Suitable habitat for northern tree species will decline (medium evidence, high agreement). All three impact models project a decrease in suitability for northern species such as eastern hemlock, red spruce, and sugar maple.
• Habitat is projected to become more suitable for southern species (medium evidence, high agreement). All three forest impact models project an increase in suitability for southern species such as eastern red cedar and loblolly pine.
• Species composition will change across the landscape (limited evidence, high agreement). Although few models have specifically examined species composition may change, model results from individual species, paleoecological data, and ecological principles suggests that recognized communities may disaggregate to form new mixes of species. Forest disturbance (e.g., increased fire frequency, harvesting, land use change) is expected to accelerate the pace of climate-related changes.
• Climate change is expected to affect early growth and regeneration conditions (medium evidence, medium agreement). Seedlings are more vulnerable than mature trees to changes in temperature, moisture, and other seedbed and early growth requirements.
• Net change in forest productivity is expected to be minimal (medium evidence, low agreement). Few studies have examined the impact of climate change on forest productivity, but they disagree on how multiple factors such as species composition, stand age, disturbance, or pollution may interact to influence productivity. Changes are not expected to be consistent within a species, and the diversity of forest site conditions across the landscape suggests that changes will be spatially variable.

Adaptive capacity factors

• Low-diversity forest communities are at greater risk (medium evidence, high agreement). Studies have consistently shown that diverse systems are more resilient to disturbance, and low-diversity ecosystems are more vulnerable to change.
• Species in fragmented landscapes will have less opportunity to migrate to long distances in response to climate change (limited evidence, high agreement). Evidence suggests that species may not be able to disperse over the distances required to keep up with climate change, but little research has been done in the region on this topic.
• Ecosystems that are highly limited to by hydrologic regime or geological features may be topographically constrained (limited evidence, medium agreement). Our current ecological understanding indicates that migration to new areas may be impossible for tree species and forest communities with narrow habitat requirements.
• Ecosystems that are tolerant to disturbance will be at lower risk of decline (medium evidence, high agreement). Basic ecological theory and other evidence suggest that communities adapted to disturbance will be at lower risk of declining on the landscape.
• Fire-adapted ecosystems will be more resilient to climate change (high evidence, medium agreement). Studies have shown that fire-adapted ecosystems are better able to recover after disturbances and can promote many of the species that area expected to do well in a changing climate.
• Ecosystems occupying habitat in areas of high landscape complexity have more opportunities for persistence in pockets of refugia (medium evidence, medium agreement). The diversity of landscape positions occupied by forest may provide opportunities for natural refugia, for example where cool air and moisture accumulate in valley bottoms.

This chapter summarizes the implications of potential climate change impacts on important facets of forest management and planning in the Central Appalachians region, such as impacts on wildlife or cultural resources. We point out key implications, ongoing research, and sources for more information on how climate change is expected to affect these topics. This chapter does not make recommendations as to how management should be adjusted to cope with these impacts, because impacts and responses will differ by ecosystem, ownership, and management objective.

• Management of endemic plants and animals that depend on forests may face additional challenges as the climate shifts.
• Prevention and eradication of nonnative invasive plant species are expected to become more difficult and require more resources.
• The timing of activities, including prescribed fire, recreation, or timber removal may need to be shifted as temperatures and precipitation patterns change.
• Responses to increased risk of wildfire or large-scale wind and storm events may require reassessing emergency response plans, water resource infrastructure, and available resources.
• Climate change may present opportunities for the forest products industry, recreation, and other sectors if resource managers are able to anticipate and respond to changing conditions.