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Forest Disturbance Processes

Fish and Wildlife Habitat and Viability

The northern tier of the Northeast and Midwest, which was covered by Ice Age glaciers, is filled with an extensive system of lakes, rivers, and streams. These have long influenced local and regional ecological and social systems. Historically, Native Americans and European explorers used waterways as travel corridors, and relied upon fish, mussels, and waterfowl as important food sources. Following settlement by Europeans, rivers and streams were used to transport logs and were dammed to provide power for sawing lumber, milling grain, and powering the mills of the industrial revolution, first mechanically and later by generating electricity. Disturbances to these streams, lakes, and rivers have taken many forms in the past and present—stream down-cutting and bank damage from the early logging era (and still not healed), pollution, damming, shoreline development, overfishing, the invasion of exotic species, and recreational overuse have lessened the ability of these bodies of water to support healthy populations of their former residents.

Selected Research Studies

[photo:] California myotis (Myotis californicus) Photo Credit:  Norman Barrett, Rogue River-Siskiyou National Forest, Habitat for Bats in the Face of Development Pressure
Most bats in temperate climates have a strategy for survival where part of the time is spent foraging for food and water, while the remaining time (daytime in summer, or for extended periods in winter) is spent in roosts.  Some species are suffering population declines and are vulnerable to habitat loss associated with urban development.  One strategy to mitigate the problem is to protect areas that provide bat habitat by outright purchases or by acquiring conservation easements on areas before they fall victim to development.  Guidance is needed to help organizations prioritize areas for habitat protection where development pressure is high.


[image:] Output from a havitat suitability simulation.Cumulative Effects of Succession, Management, and Disturbance on Forest Landscapes
Multi-resource forest planning and management requires knowledge of the long-term, large-scale cumulative effects of alternative management strategies.  For common management goals such as sustaining forest biodiversity, providing habitat for desired wildlife species, and reducing forest fragmentation this requires spatially explicit forecasting tools that enable resource managers to map the spatial arrangement of forest size structure, species composition, wildlife habitat suitability, timber volume, and other attributes over time for large forest landscapes.   


[image:] An example of how models are linked to understand climate and disturbance impacts on forested landscapes.  Linking Population, Ecosystem, Landscape, and Climate Models to Evaluate Climate Adaptation Strategies
Climate change and forest mortality from disturbance agents such as fire and insects are among the top challenges facing natural resource management.  Landscape change will result from interactions among climate change; land use and management; and population, ecosystem, and landscape processes.  Approaches to forecasting landscape change have commonly addressed a subset of these factors but rarely have they all be considered.  Land managers and planners need knowledge of how these factors will interact and modeling tools to assess the effects of mitigation strategies.   


[photo:]  Red maple stem heating experiment.Fire Effects in Eastern Forests
Understanding fire effects requires consideration of the processes by which the effects occur.  We are applying process-based (mechanistic) approaches to modeling fire effects on endangered Indiana bats and fire-caused tree injury and mortality.  Fires pose risks for bats but also provide opportunities for improving bat roosting habitat, our project considers both sides of the problem. 


[image:]  Map of contigous USA - shows locations of FFS sitesFire and Fire Surrogate Treatments: The Central Appalachian Plateau Site
Current forests in many fire-dependent ecosystems of the United States are denser and more spatially uniform, have many more small trees and fewer large trees than did their presettlement counterparts. Causes include fire suppression, past livestock grazing and timber harvests, and changes in land use. The results include a general deterioration in forest ecosystem integrity and the threat of losing important, widespread forest types. Such conditions are prevalent nationally, especially in forests with historically short-interval, low- to moderate-severity fire regimes, such as the upland oak forests of the central hardwoods region.   


[photo:] Moderate-intensity surface fire in mixed-oak forestEcosystem Management Study: Restoration of Mixed-oak Forests with Prescribed Fire
Historically, fire was a frequent disturbance process in the mixed-oak forests of the central hardwoods region. Fire control has altered forest structure and composition. Forests are more dense and the sustainability of oak and hickory dominance is now threatened by an abundance of shade-tolerant and fire sensitive tree species such as red maple, sugar maple, and beech. Prescribed fire has been advocated to promote and sustain open-structured mixed-oak forests and the plants and animals that have adapted to these communities. However, long-term research on fire effects is lacking.


[photo:] Redring milkweed (Asclepias variegata), growing in an Ohio mixed-oak forest after repeated prescribed fires.Plant Diversity in Managed Forests
The great majority of plant diversity in forests is contained in the herbaceous layer, comprised of both herbaceous and woody species.  We seek a better understanding of how forest management activities affect plant diversity.  NRS-2 scientists are investigating the direct and indirect effects of timber harvesting, prescribed burning, herbicide application, and deer browsing (alone and in combination) on plant composition and diversity in mixed oak, Allegheny, and Northern Hardwood forests.


[photo:]  Sugar Maple Decline on the unglaciated Allegheny Plateau in northern PennsylvaniaSite, Stress, Nutrition, and Forest Health Interactions
A range of stressors including defoliating insects, pathogens, droughts, inadequate soil base cations, and changing climate have interacted to affect the health and regeneration of selected northern and central hardwood forest species. In the 1980s and 1990s sugar maple dieback and mortality was extensive across the unglaciated Allegheny Plateau in northern Pennsylvania. 


[image:] Aerial view of jack pine planting pattern used in Kirtland's warbler habitat management programSpatiotemporal response of the male Kirtland’s warbler population to changing landscape structure over 26 years
Species conservation remains an important challenge for ecologists and managers given the rate of habitat transformations occurring worldwide.  Strategic planning for wildlife restoration programs over broader geographic regions will become the standard rather than the exception as increasing numbers of populations become smaller and more isolated.  However, there continues to be a lack of synthesis between general principles of the fragmentation process and field evidence.  To further our understanding of habitat loss/fragmentation, we need to examine how populations that currently exist in patchy environments respond to increasing habitat amounts and changing arrangements over long time periods and broad spatial scales simultaneously.    


Photo: Atlantic salmonAtlantic Coast rivers and salmon
The Atlantic salmon, for example, was plentiful in all northeastern rivers from the Connecticut River to Hudson Bay. Now it is present in severely reduced numbers in its middle range and in healthy numbers only in northern Canada. A small experimental restocking being attempted in the Connecticut River is supported by the work of the NRS fisheries biologist.


Photo: San Joaquin kit fox pupsHabitat Protection Modeling
Expanding habitat protection is a common tactic for species conservation. When unprotected habitat is privately owned, decisions must be made about which areas to protect by land purchase or conservation easement. To address this problem, we developed an optimization framework for choosing the habitat protection strategy that minimizes the risk of population extinction subject to an upper bound on funding. NRS scientists tested the framework to address the problem of expanding the protected habitat of a core population of the endangered San Joaquin kit fox (Vulpes macrotis mutica) in central California. The application showed that the results of a complex demographic model of population viability can be synthesized for use in optimization analyses to determine cost-efficient habitat protection strategies and risk-cost tradeoffs.



Last Modified: 03/11/2020