Search
Browse by Subject
Contact Information

Northern Research Station
11 Campus Blvd., Suite 200
Newtown Square, PA 19073
(610) 557-4017
(610) 557-4132 TTY/TDD

You are here: NRS Home / Research Programs / Sustaining Forests / Conserve and Enhance Forest Resources / Biodiversity and Structural and Functional Complexity of Forests
Sustaining Forests

Conserve and Enhance Biodiversity and Structural and Functional Complexity of Forests

Biodiversity and structural and functional complexity of forests have relatively recently been recognized as critical concerns for public and private land management. The health and stability of ecosystems are closely related to their biodiversity. Land-use planners, land managers and policy makers frequently do not understand the full complexities inherent in the concept and NRS scientists have developed a conceptual framework that relates the different types of diversity and the different social stakes and stakeholders to scales ranging from the gene to the planet. Other NRS scientists are examining the effects of various silvicultural treatments on wildlife and forest diversity, forest dynamics, nutrient cycling, and disturbance processes, particularly those from destructive invasive insect and plant species.

Research Studies

[photo:] Artificially regenerated red and white oak and shortleaf pine in the Missouri Long-Term Soil Productivity Study on a site in the Missouri Ozarks.Long-Term Soil Productivity
The USDA Forest Service’s Long-Term Soil Productivity (LTSP) program began in 1989 in the Southern Research Station to address land managers’ concerns about the long-term consequences of soil disturbance on fundamental forest productivity.  It eventually grew into a national program of the USDA Forest Service.

 

[photo:] Shortleaf pine commonly grows with hardwoods in the Missouri Ozarks and elsewhere in the Central Hardwood Region.  Management of pine with hardwoods in natural stands is a new line of research to develop silvicultural systems for regenerating pine and sustaining it in forest and woodland systems.Agroforestry Practices for Biodiversity Conservation
Agroforestry in the temperate region is the intentional integration of trees and shrubs with livestock or crops into intensive land management systems. It can include practices such as alley-cropping, silvopastural, and riparian buffers. Integrating woody vegetation with grasses and forbs provides a wider range of habitats than would typically be found in most agricultural systems and can also enhance the production of clean water.

 

[photo:] [photo:] Shortleaf pine commonly grows with hardwoods in the Missouri Ozarks and elsewhere in the Central Hardwood Region.  Management of pine with hardwoods in natural stands is a new line of research to develop silvicultural systems for regenerating pine and sustaining it in forest and woodland systems.The Role of Fire in Restoration of Woodlands and Savannas
Our research is focused on understanding the role of fire in sustaining woodland and savanna composition and structure. Our goals are to develop fundamental information about how to manage and regenerate oak and oak-pine woodlands and savannas with timber harvests and prescribed fire and to use this information to develop management guidelines to be applied on both public and private land.

 

[photo:] [photo:] Shortleaf pine commonly grows with hardwoods in the Missouri Ozarks and elsewhere in the Central Hardwood Region.  Management of pine with hardwoods in natural stands is a new line of research to develop silvicultural systems for regenerating pine and sustaining it in forest and woodland systems.The Ecology and Silviculture for Restoration of Shortleaf Pine
There is renewed interest in restoring shortleaf pine throughout its native range in the Ozark Highlands and elsewhere in the Central Hardwood Forest Region and in the southeastern United States. Restoring shortleaf pine on former pine and oak-pine sites is viewed as a long-term strategy for mitigating chronic oak decline. There also is an increasing interest in restoring native oak-pine woodland communities where they once were abundant.

 

Computer-Coded Content Analysis as a Research Method
Analysis of news media content has repeatedly produced results that parallel the findings of attitude surveys for many public policy issues, including environmental and natural resource issues. Studies have found that the news media strongly influence agenda setting for public policy issues; that is, there is a relationship between the emphasis that the media give to an issue and how prominent the topic is among the general public. Therefore, analysis of the public debate about social issues in the news media is not simply ‘‘media analysis’’; it is a window into the broader social debate and a way to gauge, indirectly, public attitudes and values.

 

Forest Value Orientations in Australia
We used computer-coded content analysis to explore forest values expressed in the public news media discussion in Australia between 1997 and 2004. The final database included 14,413 paragraphs from 4034 relevant stories over the eight-year period.

 

[photo:] TIonesta long term research area 1943 - 1942 Hobblebush and browsed hemlockLong-term Change at Hearts Content and Tionesta Scenic and Research Natural Area
Our ability to understand how unmanaged forests develop over time through various climatic and environmental changes depends on long-term data from unmanaged forests, especially remnants of the forest that predated European settlement of our region. Impacts of acid deposition, deer overabundance, beech bark disease, recovery of vegetation after windthrow, climate change, invasive plants – all are better understood by examining their effects in forests that have not been directly manipulated by humans, as well as those that have been managed.

 

[photo:] Intensively managed pecan sapling with weed control, deer protection, and pruning to maintain central stem.Intensive Management of Hardwood Plantings
In the 1960s the diminishing supply of quality hardwood saw timber, especially black walnut, raised the question of how best to grow hardwoods in plantations to assure future supplies.  At the time, we determined the most promising native hardwood for timber production in intensively managed plantings was black walnut, white ash, and several of the oak species.  

 

[photo:] Deer overbrowsing has dramatically reduced the plant diversity of eastern US forests. Hay-scented fern (Dennstaedtia punctilobula) dominates the understory of this forest in Pennsylvania, which would make it difficult for many plant species to recover even if deer populations were eventually brought under control.Native Invasive Species
Recent changes in disturbance and browsing regimes have strongly impacted species composition in forest understories worldwide.  In some cases, these changes have led to large increases in the density and cover of a small number of native understory plant species which may then expand to form interfering vegetation layers. 

 

[photo:] Gap created following a severe windstorm in July 2003.Catastrophic Wind Disturbance
In eastern forests, severe wind disturbances are common and salvaging occurs after these disturbances.  The Allegheny Plateau region alone receives an average of 11 high wind events and one tornado per year (National Climate Data Center) making wind the predominant natural disturbance event.  Given the ubiquity of storm damage and salvaging on the Allegheny and elsewhere, there is a surprising paucity of experimental work demonstrating the impact of salvage logging on post-disturbance forest regeneration patterns. 

 

[photo:] Photo shows regeneration of multiple speciesRegeneration of Northern and Allegheny Hardwoods
The Allegheny hardwood forest type is a variant of the northern hardwood type consisting primarily of black cherry, red maple, sugar maple and American beech. Associated species include white ash, yellow‑poplar, black birch, yellow birch, cucumber magnolia and hemlock. Black cherry and the maples usually dominate stands in Pennsylvania and southward; white ash and sugar maple tend to be more important, and red maple less important, in the New York portion of the range.

 

[photo:] Researcher lighting a prescribed burn fire on the Vinton Furnace Experimental Forest.Restoration of Mixed Oak Forests in Southern Ohio with Prescribed Fire
In the eastern U.S., fire suppression has been implicated as a primary factor facilitating shifts in forest composition from oak to other species, often maples. The state of Ohio began suppressing fires in 1923. Oaks are considered well-adapted to a regime of frequent low- to moderate-intensity fires because they possess thick bark, the ability sprout repeatedly after being topkilled, and are intermediate in shade tolerance.

 

[image:] Map depicting presence or absence of red spruce at individual corner locations on the Monongahela National Forest.Central Appalachian Forests: Past and Present
There is increasing acceptance of the historical role of fire in shaping the composition and structure of oak forests in the eastern United States.  There is evidence that fires in the Central Appalachians occurred at intervals of 5 to 15 years during the previous four centuries. 
 

 

[photo:] Dense second-growth red spruce dominated forest on the Monongahela National Forest.Restoration of Red Spruce Ecosystems
Central Appalachian montane red spruce (Picea rubens) forests have been greatly reduced in extent and integrity over the past century.  This decline has put several species at risk from habitat loss, most notably the Virginia northern flying squirrel and the Cheat Mountain salamander.  Also, these forests are no longer considered a commercially viable forest type in the region.   

 

[photo:] First growing season after a spring-time prescribed fire on the Fernow Experimental Forest.  A 90 percent reduction in sapling density was caused by two prescribed fires.   Understanding and Using Prescribed Fire
There is increasing acceptance of the historical role of fire in shaping the composition and structure of oak forests in the eastern United States.  There is evidence that fires in the Central Appalachians occurred at intervals of 5 to 15 years during the previous four centuries.   

 

[photo:] Forester using the point relascope method for sampling coarse woody debris.Coarse Woody Debris
A proportion of the carbon in forest ecosystems is contained in coarse woody debris on the forest floor. Estimating the carbon stock and other attributes of coarse woody debris can be time consuming and error-prone. New methods for field sampling of coarse woody debris are needed for efficient estimation of the carbon stock in this forest pool.

 

[photo:] The forest landscape of the Missouri Ozark Highlands in the Central Hardwood Region is diverse with a mixture of oak/mixed hardwood/shortleaf pine forests and woodlands.Sustaining Central Hardwood Forests
A number of challenges to sustain central hardwood forests face managers today. For example, it is difficult to sustain the current level of oak stocking in mature forests in many areas, especially on more productive sites. Oak species are often replaced by either more shade-tolerant species such as maples, or by fast growing species such as tulip tree (yellow-poplar) when forests are regenerated either by managed harvesting or natural disturbances. This is a problem in both upland and bottomland forests.

 

[photo:] Swamp white oak 8 years after being planted as a large container seedlings grown by the Root Production Method (RPM®) in a former agricultural crop field along the Missouri River.  Trees were planted with redtop grass to control competition.Restoring Forests in Bottomland Fields
We have identified several promising practices and seedling types that can be used to successfully restore oak to future bottomland forests when bringing marginal agricultural lands back into forest production.

 

[image:] The Tionesta Research Natural Area as seen in 2004 with beech mortality over 40%. The mortality reached 52% in 2006 and shows no sign of diminishing (see figure below). The foreground is an old Tornado swath of a much younger age class.Contrasting Silvicultural Systems
In order to provide science-based guidance to society and landowners to support their silvicultural decisions, scientists must implement replicated examples of different silvicultural treatments and assess their outcomes. Such research often requires decades of measurements, and outcomes and outputs vary by forest type and ecoregion. Results can also be complicated by interactions among silvicultural systems and treatments and other landscape scale disturbances

 

[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.

 

[image:] Graph shows relation of basal area, umber of trees, and average tree diameter to stocking percentage for upland central hardwoods.Thinning in Mixed Hardwood Forests
Very little was known about managing the growth and quality of hardwood forests in the east as the second- and third-growth forests were developing. Studies of “growth and yield” were established to quantify the growing capacity of these 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. 

 

[photo:] Dense understories formed following co-occurring fire and gaps in the absence of browsing.  These plots are dominated by browse intolerant shrubs and tree species and contain high regenerating tree species richness, but lower herbaceous species richness.Interactions between Fire, Gaps, and Deer Browsing
In eastern deciduous forests, low-intensity understory fires, canopy gaps, and ungulate browsing are generally regarded as the main forces influencing vegetation dynamics.  Over the past 100 years, all three of these historic disturbance and herbivory regimes have been altered to some extent (e.g., fire suppression, smaller, less frequent gap formation in 2nd growth forests, and overabundant deer herds) and have been putatively linked to observed changes in regeneration patterns and losses in understory herbaceous diversity. 

 

[image:]  Participants in a SILVAH Training Session conduct a systematic inventory of forest overstory and understory as part of a field exercise in the course. SILVAH - Training Sessions and Computer Software
The SILVAH framework has been adopted by many public and private forest management agencies, and many depend upon the decision-support software to analyze inventory data and recommend prescriptions.  Initially developed for Allegheny hardwood forests, much of the focus in recent years has been expanding the SILVAH framework to incorporate recommendations for sustaining the oak component of mixed oak forests. 

 

[image:] Primary, secondary, and tertiary impacts of deer on forest understory communitiesDeer Impacts: Primary, Secondary (Interfering Plants), Tertiary (Faciltated Seed Predation)
Overabundant white-tailed deer (Odocoileus virginianus) herds have been shown to be a key determinant of understory plant species composition in  many parts of eastern North America over the last century.   The primary, direct effect of chronic overbrowsing is the reduction in growth and survival of browse-intolerant plant species which ultimately shifts species composition towards a few highly browse-tolerant or unpalatable species.  Such shifts in plant dominance patterns may secondarily result in altered plant-plant competitive dynamics in forests understories.  Finally, through modification of plant composition and structure, deer overbrowsing may also exert indirect effects on the habitat and foraging patterns of other animal species.

 

[image:] Shows the Racoon Ecological Management Area (Thin and Burn treatment) in 2000, before thinning and two burns, for 'competitiveness' for oaks and hickories.Landscape-level Effects of Thinning and Burning
Oak regeneration continues to be a problem in the Central Hardwoods region of the US. In the absence of regular fire (as was common before European settlement and fire regulatory agencies in the ~1920’s), the canopy closes and oak regeneration is often preempted by more shade-tolerant species like maples. The Fire and Fire Surrogates Study (FFS) is aimed to better understand the influence of multiple fires and thinning on oak regeneration. This research is a component of the FFS work in Ohio.

 

[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.   

 

image:] Data entry screen for SILVAH’s non-native invasive species inventory and information module. SILVAH NNIS
As we have planned to increase our SILVAH training and decision support in Ohio, several of our partners suggested that ignoring NNIS was not an option.  Pending development of better guidelines for recognizing when NNIS are abundant enough to pose a threat to management objectives and treatment options, SILVAH currently provides a format for recording presence absence and frequency data about several NNIS that are important in Ohio and elsewhere in the mixed hardwood forests of the east.  SILVAH flags the presence of such species and encourages users to investigate treatment options for NNIS before undertaking the silvicultural treatments that SILVAH recommends. 

 

[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:] Whole-tree chipping operation by Michael J. Lietz .Impacts of harvesting forest residues for bioenergy on nutrient cycling and community assemblages in northern hardwood forests
The increasing demand to utilize slash for bioenergy purposes will compete with other ecological services forests provide.  Current site-level guidelines emphasize retaining large diameter coarse woody debris (CWD) based on many studies documenting the important role it plays in managing biodiversity and contributing to nutrient cycling.   However, little information exists to help guide land managers on appropriate levels of fine woody debris (<6 inch diameter) retention for biodiversity and nutrient cycling concerns. 

 

[photo:] Landscape Diversity, Vegetation types, National Wildlife Federation, GLA websiteConserving Wildlife in Managed Forests
Public land managers are mandated to sustain viable populations of all species on their lands, which requires an understanding how wildlife populations respond to forest management practices. Our research focuses on forest birds, as populations of many species of eastern deciduous forests are declining across their range, raising concerns over possible negative effects of timber management.  

 

[photo:] Damage caused by the butternut cankerSaving the Butternut
The butternut canker disease is killing butternut and threatening the future of this important hardwood species throughout its range in North America.

 

[photo:] Amatina jacksonianaTropical Forest Mycology
The Center for Forest Mycology Research (CFMR, part of the Northern Research Station of the US Forest Service) leads critical research on the biology of tropical fungi native to Hawaii, US territories in the Caribbean (Puerto Rico and the US Virgin Islands) and to other countries in the Caribbean Basin.

 

[photo:] Cyptotrama chrysopeplum, a wood-inhabiting fungus.  Photo by Daniel Lindner. Collections at the Center for Forest Mycology Research
Forest fungi are critically important for forest health and productivity. Of the estimated 1.5 million species of fungi worldwide, only about 5% have been described and named. Key characteristics used to identify species and the relationships among species are in a critical period of change. 

 

[photo:]   Lake Baikai, Siberia by Eric GustafsonDesigning Pest-Resistant Forest Landscapes: The Importance of Spatial Pattern
Defoliating insects damage millions of acres of forested land annually in the United States.  The balance of evidence suggests forest insect outbreaks today are more damaging than ever because of changes in forest composition and structure induced by fire suppression and post-harvest proliferation of tree species intolerant to herbivory.  Our central hypothesis is that landscape connectivity of acceptable host types increases defoliator population connectivity, altering the dynamics and spatial structure of defoliator populations, and thus increasing forest susceptibility to insect pest damage.   

 

[photo:] 2008 Wildfire on Council Grounds, Wisconsin by Richard LaValleyStudying fire mitigation strategies in multi-ownership landscapes: Balancing management of fire-dependent ecosystems and fire risk.
Fire risk mitigation within multi-owner landscapes containing flammable but fire-dependent ecosystems epitomizes the complexities of managing public lands.  The cumulative effects of fire and forest management over the last century have exacerbated fire risk in some regions and threatened fire-dependent systems in many others.  The issue is further complicated by the recent encroachment of human homes into fire prone ecosystems that simultaneously increase fire ignitions and increase demands on fire suppression agencies to protect lives and property.  Consequently, the balance between forest restoration, human rural development, and fire risk remains an issue of major concern to natural resource agencies.

 

Photo The Working Forest Initiative: Simulating the cumulative effects of the forest management strategies of multiple landowners on landscape pattern and biodiversity
Sustainable forestry involves the extraction of forest products while maintaining ecosystem integrity to conserve biodiversity and to provide other non-commodity benefits to society.  Population viability is a function of the combined actions of multiple landowners, which create a dynamic mosaic of forest types, stand structures and age distributions.  Consequently, it is necessary to understand how the actions of individual land owners interact with the actions of others to determine the spatial pattern of the landscape mosaic, and therefore its ability to maintain biodiversity. 

 

[photo:] Soil respiration measurements in this northern hardwood stand are used to understand the impact of exotic earthworms on forest carbon dynamics.Earthworm Invasion
Populations of exotic European earthworms have been expanding into formerly worm-free forests in the north central and northeastern United States.  These earthworms consume the organic horizons of the forest floor, often removing leaf litter within several years of invasion.  This leads to changes in soil carbon, nutrients (e.g. nitrogen and calcium), soil microclimate, hydrology, soil organisms, and plant community assemblages. 

 

Photo: Entrance to Houghton's rhizotronTree roots made visible in "Rhizotron"
Trees contribute massive amounts of organic matter to forest soils in the form of fine root inputs and litterfall. Soils, in turn, supply trees with water and nutrients essential for growth. All of this is mediated by an intricate web of interactions between tree roots and soil organisms. NRS scientists are studying how forest management and environmental change affect these biological processes, which will help us determine what can be done to increase the productivity and sustainability of our forests

 

Last Modified: 05/22/2013