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Northern Research Station
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Sustaining Forests

Understanding the Ecological Roles of Natural Disturbance


The key to sustaining forests is successfully renewing all their elements after disturbance, across landscapes and through time. NRS scientists are working to strengthen our understanding of the relationships of certain elements of forest communities in stands and forests of different ages, species compositions, and disturbance history and patterns. Many forest types result from natural disturbances such as fire, storm blowdown, and native tree pests. Generally these are not devastating disturbances; those usually result from non-native pests.

Research Studies

[photo:]  Red maple stem heating experiment.Fire Effects
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.  Ecologists and land managers would like to predict tree injury and mortality from fire behavior, but the tools available are not sufficiently process-based to be general, that is, applicable across a wide range of species and locations.  In our tree injury and mortality work, we seek to develop general models.      


[image:] Contigous US - 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.   


[image:]   Burned area determined from multiple infrared heat release images taken from an aircraft during a prescribed fire in the Ohio Hills.Fuels and Fire Behavior in Eastern Hardwoods
An ability to predict fuel loads and fire behavior are needed to improve prescriptions for prescribed fire and answer questions about smoke emissions and transport and fire effects on flora and fauna. Our fuels and fire behavior research seeks to develop process-based (mechanistic) approaches to predicting fuel characteristics and fire behavior, with particular focus on hardwoods in Appalachian topography. Areas of emphasis have been fuel production and decomposition through seasons and across years, topographic variability in fuel moisture, and fire behavior monitoring. 


Ecosystem 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. Our Ecosystem Management Study was initiated in 1995 to quantify the effects of frequent and periodic prescribed fires on the structure, composition, and function of oak forest ecosystems.


[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.  Subsequent research established the critical role of landscape position and soil base cation nutrition (calcium and magnesium) as predisposing stresses, and defoliation from elm spanworm and forest tent caterpillar as inciting stressors that caused this extensive sugar maple dieback and mortality.  Other factors such as poor seed production and antagonistic cations (manganese and aluminum) may also be affecting sugar maple health and regeneration. 


[image:]logo of the North Atlantic Fires Science ConsortiumWitness Trees as Indicators of Past Fire
Understanding and mapping presettlement fire regimes is vitally important for ecosystem restoration, helping ensure the return of fire into ecosystems that formerly burned.  Witness trees can support this endeavor by serving as pyro-indicators of the past. 


Carbon Cycling Research at Silas Little Experimental Forest
An understanding of carbon, water, and energy exchanges between forests and the atmosphere at multiple scales in time and space is necessary to better inform decisions that are made concerning forest management, carbon sequestration, fire management, and the climate system.


PhotoPredicting global change effects on forest biomass and composition in south-central Siberia
We use a landscape succession and disturbance model (LANDIS-II) to study the relative effects of climate change, timber harvesting and insect outbreaks on forest composition, biomass (carbon) and landscape pattern on a 316,527 ha landscape in south-central Siberia


Fire in Northern hardwood forest.Modeling silvicultural treatments after natural disturbance
Modeling silviculture after natural disturbance to maintain biodiversity is a popular concept., yet its application remains elusive. We discuss difficulties inherent to this idea, and suggest approaches to facilitate implementation, using longleaf pine (Pinus palustris). In this species, natural disturbances such as lightning, hurricanes, surface fires, and windthrow all lead to similar structures, but at different rates. The outcomes of natural disturbances are inherently different from those of silviculture (for example, harvesting always removes boles) and it is instructive to think of silvicultural disturbances along a gradient in structural outcomes, reflecting degree of disparity with natural disturbance. Interactions of frequency, severity, intensity, seasonality, and spatial pattern define a disturbance regime and these components may not have equal weight in affecting biodiversity and some are easier to emulate with silviculture than are others.


Tree branches coated in ice.Ice storms
Northern New England forests were heavily damaged by a severe ice storm in January 1988. Many branches were broken off and trees were toppled due to the weight of thick layers of ice. Trees’ response to injury, infection, and environmental change is based on dynamic changes in tree form and function. These changes in trees provide the resilience to disturbance that is the foundation of healthy forests. NRS scientists who study the effects of various disturbances— whether natural, mechanical, or stress induced (from pollutants and drought)—used this opportunity to follow the healing process in these damaged trees.


Last Modified: 09/18/2015