Silviculture

Overview

Silviculture refers to practices that are used to manage the growth and composition of forest vegetation for an array of objectives, such as wildlife habitat, timber, water resources, recreation, and much more. Many silvicultural practices are potentially valuable tools for helping forests respond to a changing climate.

This set of papers discusses some of the expected impacts on forest vegetation as a result of climate change, and how silviculture may be used to help forests adapt. Some detailed regional examples are discussed, and additional resources are provided to allow additional exploration.

Overview

Silviculture refers to practices that are used to manage the growth and composition of forest vegetation for an array of objectives, such as wildlife habitat, timber, water resources, recreation, and much more. Many silvicultural practices are potentially valuable tools for helping forests respond to a changing climate.

This set of papers discusses some of the expected impacts on forest vegetation as a result of climate change, and how silviculture may be used to help forests adapt. Some detailed regional examples are discussed, and additional resources are provided to allow additional exploration.

Silviculture for Climate Change

K. Schmitt

Topics Horizontal Tabs

Synthesis

Synthesis

Preparers

Paul Anderson, Pacific Northwest Research Station; Brian Palik, Northern Research Station

An archived version of this topic paper is available.

Issues

There is a growing consensus that management decisions need to consider how actions either enhance or detract from a forest's potential to adapt to changing climate. Uncertainty regarding the specifics of future climate conditions increases this need.

Silvicultural planning needs to embrace managing forests for adaptation to new conditions by promoting the resistance of a forest to change, resilience of a forest in the face of change, and response options that facilitate the transition of forests to new conditions (1). This may involve actions that restore or sustain compositional, structural, and functional diversity in stands. This diversified investment portfolio concept applied to forests, provides more management flexibility and capacity for forests to adapt to changing environmental conditions and societal values. Managing for adaptability is applicable to all uncertainties associated with forests, not only climate change.

Silvicultural planning considers factors that influence a forest stand's potential response to manipulation, including the structure of the ecosystem (2), current and potential range of variation in stand composition, history of disturbance or disturbance suppression, and stand development dynamics over time. It considers habitat suitability for threatened or endangered species that need to be sustained and exotic invasive species that must be discouraged. The landscape context of a stand, how its current and desired composition and structure compare to other stands in the surrounding landscape, informs how to meet broader landscape management objectives. Climate change warrants additional silvicultural considerations such as future habitat suitability for tree species currently comprising the stand, or for those species desired for the future.

The silviculturist must also consider how threats may increase under a changing climate. Warmer, drier growing seasons may reduce fuel moisture levels and increase risk of catastrophic wildfire. Milder winter temperatures and longer growing seasons may increase the risk of attack from insect and disease pests. Sustained climatic stress can increase the threat to overcrowded, older-aged forests predisposed to insect epidemics(3), as may be evidenced by the recent devastating impact of mountain pine beetle in western North America.

Societal expectations for ecosystem goods and services from forests may change little in the face of climate change. Silviculturists may be challenged to develop prescriptions that enhance adaptability to climate change, while still providing desired or expected ecosystem goods and services, such as merchantable wood, game species, native plants and animals, and forest composition and structure.

Likely Changes

Although climate is changing globally, changes in temperature, precipitation, and atmospheric composition will vary over time and among continents, among regions, and locally. Climate changes will modify the environment and cause disturbances affecting forest communities. If these modifications override the adaptive capacity of the forest ecosystem, these forests and the goods and services they provide are vulnerable.

Silvicultural approaches to climate adaptation will be effective when they focus on stress factors that pose the greatest risks to forests. An awareness of how environmental stresses result in altered tree vigor and stand dynamics is critical to understanding these risks, including:

  • Which physiological and developmental processes are most sensitive to a particular stress or suite of stressors?
  • How do changes in these sensitive processes affect the survival, growth and productivity of individual trees and stands?
  • At what temporal and spatial scales do stressors act and forests respond?
  • What are the consequences for various goods and services expected from forests?

With climate change, an objective for silviculture is to manage the composition and structure of stands and landscapes to alleviate climate-related stresses and to enhance forest capacity to resist, tolerate and adapt to a dynamic environment. When and where silvicultural adaptation strategies are employed will be influenced by overarching management objectives, perceived risks, and the confidence that intervention will be effective, given various ecological, economic or social criteria.

Management Options

Density management

Density management based on characteristics explicitly related to site resource demand may be an effective means to mitigate climate-related stressors. Silviculturists have long recognized the value of thinning and other forms of vegetation manipulation to maintain a desired balance between site resource availability and utilization. Conventional thinning commonly targets stand productivity and focuses on allocating site resources from a large number of smaller, less desirable trees to a smaller number of larger, more desirable trees. Thinnings may be repeated over time to maintain stand densities at levels that sustain cumulative productivity and preclude periods of low stand vigor. Density management can be practiced to achieve not only a balance of site resource availability and demand, but also to modify species composition and other environmental and structural features that influence climate-related stresses. For example, thinning may target the release or recruitment of species that provide diversity of adaptation traits. Recent studies are beginning to demonstrate the usefulness of variable density thinning to achieve more varied plant communities that provide a broader array of habitats and potentially greater biodiversity (4).

Changes in stand structure also may alter local environmental conditions that influence biotic and abiotic disturbance agents. Maintaining lower tree density can increase wind speeds within a canopy, making controlled flight difficult for some bark beetles (5). Thinning may decrease relative humidity, creating conditions less favorable to some pathogenic fungi, but potentially promoting infection by others such as white pine blister rust (6). Removing shrubs and other ground vegetation may decrease site resource demand, as well as reduce the risk of severe wildfire by decreasing the abundance and depth of fuels. It may be important to couple density management with understory vegetation control, so gains in site moisture balance are not negated by understory growth (7). Density management also may substantially decrease risks to individual tree and stand vigor (5, 8).

Managing composition

Restoring component species
Species composition has been altered in many forested areas by management and change in disturbance regimes, so that some species well-adapted to the historic range of variation have been diminished, while other poorly-adapted species have been added. Climate change may take decades to generate discernible effects. For the near-term, those plant communities best adapted to transitional climatic extremes will be comprised of the species and populations that evolved on site. Restoring species that have been lost due to land-use, management practices, or exclusion by invasive species is a reasonable objective for silvicultural intervention. The time to restore community composition is before substantial changes in climate occur, while there is still a relatively strong match between current site conditions and the adaptive potential of the species being restored. Approaches to restore target species include retention during thinning or other vegetation removal operations, removing competing or inhibiting invasive and non-native species, or active regeneration by planting or seeding.

Favoring adaptable species and genotypes
Promoting resistant and resilient forest communities includes favoring those species and genotypes that are adaptable to projected environmental changes. Adaptive characteristics that vary along climatic gradients, and are therefore likely to be of importance, include traits that permit a plant to survive and function when subjected to water deficits, temperature extremes or uncharacteristic disturbance (9). Drought stress is an important contributor to seedling mortality in many ecosystems and can be a limiting factor to successful reforestation (10). If fires become more severe, those species that have thick, insulating bark or that regenerate by sprouting from below-ground root systems may be more resistant and resilient.

A major issue is the degree to which current seasonal patterns of growth and development will remain synchronized in the face of rapidly changing and increasingly variable weather and climate patterns. For example, if pollen dispersal occurs out of synchrony with flower receptivity, then decreased seed production may limit natural regeneration for seed-regenerating species.

The limitation of this strategy is that capacity for adaptation has evolved in response to historical pressures, and may not be sufficient for dealing with projected future conditions. There may not be enough time for new adaptations to evolve in place, given the rapid changes in climate we are experiencing (9).

Adding new species and genotypes
An active approach to facilitate adaptation may be intentionally moving species or genotypes to match known adaptive characteristics with locations where these traits may be beneficial in the future environment (11). This "assisted migration" can be practiced with varying intensity and risk. Initially, movements of species or genotypes can be limited to relatively short "ecological" distances along a climatic gradient and focused on the transition zones from one ecotype to another. Caution must be used, because in the near term, some transferred sources may not be as well adapted to the current environment as local sources.

A more subtle approach to building resilience may be planting or sowing a greater variety of species and genotypes when reforesting after a harvest or natural disturbance event. The premise is the same - expand the gene pool, and therefore the probability of having adapted individuals on a site. Regeneration harvests and stand-replacing disturbances may be opportunities to enhance the adaptive capacity of the regenerated forest.

Reducing threats

Silviculture can also be used to decrease some threats to vulnerable forest stands and landscapes. Biotic threats include some insects and diseases, pathogen vectors, and invasive plants or animals. Physical threats include fire ignition sources such as lightning strikes, windstorms, flooding or landslides. Silvicultural approaches to biotic threats include treatment of incipient infestation centers through "sanitation" harvests, chipping or burning excessive down wood accumulations from harvest or disturbance events, and integrated pest management for invasive plants and animals.. Silvicultural regimes can minimize slope destabilization and moderate runoff to mitigate potential landslides and flooding.

Effective silvicultural regimes address site specific issues in the broader temporal and landscape contexts. The treatment of threats across a landscape can be influenced by the spatial and temporal application of stand-level treatments. For example, fuels management is integral to restoration of fire resilience in some western forests. For fuels reduction to be effective, at least 20-30% of a landscape needs treatment in designed spatial patterns, with retreatment occurring after 15-20 years; random spatial application requires approximately twice the area treated to get the same effect (12). These larger-scale contexts are useful to prioritizing site and stand level actions to reduce threats.

Silviculture for Climate Change: Generalities Common to all Regions

Vulnerabilities differ by forest type and stage of development.
Individual trees and species differ in their degree of adaptability to any given suite of stresses. Capacity to cope with a stress depends on the physiology of individuals and how individuals interact as a forest community. For the individual, changes in size and maturation can influence resource demand, acquisition and storage, and the ability to buffer environmental challenges. Stage of stand development will influence the degree of inter-tree competition and the susceptibility of forest stands to various disturbances.

Interactions between climate and other biological and physical stressors will be important in determining forest response to climate change.
Forest ecosystems are complex. Stresses imposed by climate that decrease tree and stand vigor will often result in increased damage by secondary stress agents. Climate may also directly influence the abundance and voracity of pests, as well as promote physical disturbances such as fire.

Opportunities exist for vegetation management to enhance balance between site occupancy and resource availability.
Silviculture aims to manipulate the composition and structure of forests to meet an array of management objectives. If sustaining vigorous forests is a primary challenge imposed by a changing climate, then silvicultural activities that maintain a balance between the supply and demand for site resources or that mitigate local environmental stresses will have an important adaptation role.

Restoring composition and structure now will enhance adaptation capabilities for the future.
Adaptation to a changing climate will be facilitated by starting with communities that are diverse and resistant and resilient to the range of environmental conditions historically encountered. Most managed ecosystems are simplified in composition relative to their un-managed, reference condition. A near-term strategy is to restore a portion of the landscape to native plant community composition and structure within the natural range of variation.

Silvicultural treatments at a stand scale are most effective when conceived and applied in a landscape context.
Climate-related stresses occur at stand and landscape scales. To have a major adaptation impact, silviculture must be practiced strategically to best target threats and responses that occur at multiple spatial and temporal scales. The opportunity to do everything needed, everywhere, all of the time, is rare. Silviculturists must understand how vulnerabilities and threats operate at multiple scales in order to be most effective in using limited adaptation resources.

 

References

  1. Millar, C.I.; Stephenson, N.L.; Stephens, S.L. 2007. Climate change and forests of the future: managing in the face of uncertainty. Ecological Applications. 17: 2145-2151.
  2. Palik, B. J.; Goebel, P.C.; Kirkman, L. K.; West, L. 2000. Using landscape hierarchies to guide restoration of disturbed ecosystems. Ecological Applications. 10: 189-202.
  3. Trzcinski, M.K.; Reid, M.L. 2009. Intrinsic and extrinsic determinants of mountain pine beetle population growth. Agricultural and Forest Entomology. 11: 185-196.
  4. Peterson, C.E.; Anderson, P.D. 2009. Large-scale interdisciplinary experiments inform current and future forestry management options in the U.S. Pacific Northwest. Forest Ecology and Management 258: 409-414.
  5. Whitehead, R.J.; Safranyik, L.; Russo, G.L.; Shore, T.L.; Carroll, A.L. 2003. Silviculture to reduce landscape and stand susceptibility to the mountain pine beetle. In Shore, T.L., Brooks, J.L., and J.E. Stone (eds). Mountain Pine Beetle Symposium: Challenges and Solutions. October 30-31, 2003, Kelowna, British Columbia. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Information Report BC-X-399, Victoria, BC. 298 p.
  6. Jactel. H.; Nicoll, B.C.; Branco, M.; Gonzalez-Olabarria, J.R.; Grodzki, W.; Lanngstrom, B.; Moreira, F.; Netherer, S.; Orazio, C.; Piou, D.; Santos, H.; Schelhaas, M.J.; Tojic, K.; Vodde, F. 2009. The influences of forest stand management on biotic and abiotic risks of damage. Annals of Forest Science. 66: 701, 18 p.
  7. Kurpius, M.R.; Panek, J.A.; Nikolov, N.T.; McKay M.; Goldstein, A.H. 2003. Partitioning of water flux in a Sierra Nevada ponderosa pine plantation. Agricultural and Forest Meteorology. 117: 173–192.
  8. McDowell, N.G.; Adams, H.D.; Baily, J.D.; Hess, M.; Kolb, T.E. 2006. Homeostatic maintenance of ponderosa pine gas exchange in response to stand density changes. Ecological Applications. 16: 1164-1182.
  9. Aitken, S.N.; Yeaman, S.; Holliday, J.A.; Wang, T.; Curtis-McLane, S. 2008. Adaptation, migration or extirpation: climate change outcomes for tree populations. Evolutionary Applications. 1: 95-111.
  10. McDowell, N.; Pockman, W.T.; Allen, C.D.; Breshears, D.D.; Cobb, N.; Kolb, T.; Plaut, J.; Sperry, J.; West, A.; Williams, D.G.; Yepez, E.A. 2008. Mechanisms of plant survival and mortality during drought: why do some plants survive while others succumb to drought? New Phytologist. 178: 719–739.
  11. St.Clair, J.B.; Howe, G.T. 2007. Genetic maladaptation of coastal Douglas-fir seedlings to future climates. Global Change Biology. 13: 1441-1454.
  12. Finney, M.A.; Seli, R.C.; McHugh, C.W.; Ager, A.A.; Bahro, B.; Agee, J.K. 2007. Simulation of long-term landscape-level fuel treatment effects on large wildfires. International Journal of Wildland Fire. 16:712-727.

How to cite

Anderson, P.; Palik, B. 2011. Silviculture for Climate Change. (October, 2011). U.S. Department of Agriculture, Forest Service, Climate Change Resource Center. www.fs.usda.gov/ccrc/topics/silviculture

Reading
Research

Research

There is extensive Forest Service research on silviculture and climate change - some examples are available below via the CCRC Research Roundup.

 

PINEMAP: Mapping the future of southern pine management in a changing world
Southern Research Station, Eastern Forest Environmental Threat Assessment Center
Project website: http://pinemap.org/

The PINEMAP project integrates research, extension, and education to enable southern pine landowners to manage forests to increase carbon sequestration; increase efficiency of nitrogen and other fertilizer inputs; and adapt forest managment approaches to increase forest resilience and sustainability under variable climates.

Contact:
Cumulative Effects of Succession, Management, and Disturbance on Forest Landscapes
Northern Research Station

For more than 15 years we have worked together with collaborators from other institutions to develop and apply methods to forecast landscape-scale forest change in response to tree growth and species succession as well as disturbance from timber harvest and fire. Much of this work has utilized the LANDIS model to forecast changes in forest conditions for management and disturbance scenarios applied. We have demonstrated the capabilities of these tools to analyze the cumulative effects of management scenarios applied to real forest landscapes in Indiana and Missouri.

Contact:
Addressing Climate Change in the Forest Vegetation Simulator
Rocky Mountain Research Station

The Forest Vegetation Simulator (FVS) is a family of forest growth simulation models that allow a user to explore forest growth and yield at the stand level. This research incorporates climatic effects into FVS to produce a new extension called Climate-FVS, providing managers with a tool that allows climate change impacts to be incorporated in forest plans.

Jerry Rehfeldt
Regeneration dynamics during oak decline with prescribed fire
Southern Research Station

Researchers are looking at how forest management practices - including controlled fire - can help give certain oak species in the Boston Mountains of northern Arkansas an advantage under possible conditions created by climate change.

Contact:
Impacts of Land Management on the Climate System
Northern Research Station

Research is needed to examine the potential impacts of land cover changes, including afforestation, on the climate system. This can provide a scientific basis for adopting land use decisions that are meant to mitigate global warming.

Contact:
Tools

Tools

USFS Climate Change Atlas
The Atlas uses downscaled climate projections for the eastern US to project potential future suitable habitats for 134 tree species and 147 bird species. It also models and maps current species habitats.

Videos

Videos

An overview of a set of tools that assess how climate change might influence tree distributions in the eastern U.S.

Presenter : Louis Iverson

The Alder Spring project in the Mendocino National Forest is a case study in climate change mitigation.

Presenter : Mark Nechodom

Forest management options for reducing carbon emissions and enhancing carbon sequestration in forests.

Presenter : Maria Janowiak

Andrea Tuttle takes a look at forest carbon markets and how these can be used to capture and hold carbon on the landscape.

Presenter : Andrea Tuttle

Presents a western U.S. perspective on forest management for carbon sequestration, and the above and below- ground carbon consequences of different management strategies.

Presenter : Bernard Bormann

The Eastern U.S. forest perspective on carbon sequestration and examples of forest carbon management projects.

Presenter : Richard Birdsey

Three key factors make old redwood forests stable: topography, buffering marine influence and special species attributes. Active management may be required to maintain old growth redwood forests.

Presenter : Steve Norman

Andrea Tuttle discusses the drivers of deforestation, current international approaches to reducing emissions and lessons learned from REDD pilot programs.

Presenter : Andrea Tuttle

The 5Rs + 1 strategy for forest management in the face of climate change: resist, resile, respond, realign, reduce and prioritize.

Presenter : Connie Millar

Regional Example - Pacific Northwest

P. Anderson

Topics Horizontal Tabs

Synthesis

Synthesis

Regional examples of silvicultural adaptation strategies: Western hemlock/ Douglas-fir Forests of the Pacific Northwest

Preparers

Paul Anderson, Pacific Northwest Research Station; Brian Palik, Northern Research Station

Geographic and Climatic extent

Douglas-fir forests of the western hemlock zone in the Pacific Northwest are some of the most productive in the world. Douglas-fir (Pseudotsuga menziesii) typically dominates as a result of disturbance over the past 150 years, however, the shade-tolerant western hemlock (Tsuga heterophylla) is a potential climax species and several conifer associates occur in varying abundance (19). Hardwood associates including red alder (Alnus rubra), bigleaf maple (Acer macrophyllum) and others occur in relatively low abundance.

The western hemlock zone is extensive, encompassing the west slopes of the Cascade Range and all but the most coastal portions of the Coast Range (19). It extends from southern Oregon northward through Washington into British Columbia. The zone is generally characterized by a wet, mild maritime climate but it encompasses a great deal of climatic variation arising from latitude, elevation and location in relation to mountain ranges. Mean annual precipitation varies from 150 to 300 cm, with only 6 to 9% of precipitation occurring in summer. The amount of precipitation occurring as snow varies with elevation and ranges from a trace to an excess of 200 cm. Average annual temperatures range from 8 to 9 °C, with neither winter minimums nor summer maximums considered extreme.

Potential Vulnerabilities

Increasing temperatures combined with unchanging or decreasing summer available moisture will lead to more frequent water deficits when evaporative demand exceeds seasonal moisture availability. With increasing temperatures, productivity in water-limited systems is expected to decrease as water deficits constrain photosynthesis (1). Elevated CO2 concentrations may have a fertilization effect that may increase carbon gain per unit of water transpired. However, limited water supply could negate CO2 fertilization benefits (2). Much of the Douglas-fir forest at mid-to upper elevations is currently considered energy-limited rather than moisture-limited; productivity is constrained predominantly by light and temperature (1). Climate induced changes in energy-limited ecosystems may include warming effects of decreased snowpack depth and duration, coupled with increasing temperature. The fundamental limiting factors driving ecosystem composition, processes and productivity may be altered - particularly at ecotones between energy and moisture limited environments.

Douglas-fir is wide-ranging but displays substantial local adaptation, making the species responsive to climatic changes (3, 4). Current populations within the western hemlock zone differ considerably for adaptive traits, particularly bud phenology and emergence. Variation in bud-set, emergence and growth is strongly related to elevation and cool-season temperatures. Variation in bud-burst and growth partitioning to stem diameter versus height is related to latitude and summer drought. With increasing temperatures, suboptimal timing of growth may lead to water deficit susceptibility, failure to adequately develop autumn cold-hardiness leading to frost damage, and failure to achieve requisite chilling and forcing needed to break winter dormancy (5). Based on statistical models of climate suitability, by the 2060s, climate changes west of the Cascade crest will be sufficient to put Douglas-fir at risk of maladaptation, particularly at low elevations throughout its current distribution (1).

Climate-related vulnerabilities will arise not only from effects on tree vigor, but also from alterations of disturbance regimes associated with insects, diseases and fire. Across western North America there have been examples of large-scale insect epidemics causing vast areas of forest mortality. Although suitable climate for bark beetles exists throughout much of the Douglas-fir region west of the Cascade crest, typically bark beetle outbreaks have been less extreme than in the drier forest types east of the Cascades. Nonetheless, outbreaks of Douglas-fir beetles (Dendroctonus pseudotsugae) have occurred in the western Cascades of Oregon as recently as the early 1990's (6). Historical analysis revealed that landscape-scale factors such as prolonged drought and windstorm events were more important predictors of local outbreaks than were fine-scale factors such as individual tree growth rate, a proxy for host-tree vigor (6). Douglas-fir beetle epidemics occurred more in areas with a greater abundance of mature and old-growth conifer vegetation. Beetle densities were sufficient to overcome the resistance associated with individual tree and stand vigor.

Foliar diseases are among the pathogen groups most likely to be affected by changing climate. Swiss needle cast (Phaeocryptopus gaeumannii) was historically a minor leaf pathogen that has since the 1990s been a substantial pathogen of Douglas-fir plantations in the coastal fog belt of Oregon (7). Warmer winter and spring temperatures, if combined with potential increases in winter and spring moisture, could sustain high levels of Swiss needle cast infection (7). While typically non-lethal, Swiss needle cast can have major impacts on Douglas-fir growth and production in heavily infected stands (8).

Various root rot pathogens (e.g. Phellinus weirii) are tied to the distribution of Douglas-fir and other conifers. Because soil temperatures may be somewhat buffered from changes in air temperature, it is difficult to assess how a changing climate, coupled with altered species distribution, will affect the occurrence of root pathogens. However, one concern is that warmer winter temperatures could eliminate a climatic barrier to the widespread infection of Douglas-fir by Phytophthera cinnamomi, a root and stem pathogen that has severe impact on Douglas-fir in New Zealand (7).

Fire regimes of the relatively moist Douglas-fir forests of the western hemlock zone are historically characterized by low frequency, moderate to high severity events. While a regional average fire return interval of 230 years has been estimated, studies suggest variable return intervals over this geographically large and ecologically diverse area (9, 10). The great extent of Douglas-fir dominated forests arising between the 1850's and 1930's was due in large part to stand replacing fire events (10). With climate change, area burned in west-side Douglas-fir regions is projected to increase about threefold by the 2040's, but will still remain a relatively small portion of landscape (1).

It is important to recognize that potential vulnerabilities change with the stage of forest development. Regeneration is often considered the developmental stage most vulnerable to climate related stresses such as drought or high evaporative demand (2). Individual seedlings can lack the root system development and water and nutrient storage capacities to buffer against seasonal resource limitations. Natural regeneration may be hindered at a more fundamental level as alterations of weather patterns may result in a disruption of the coordinated processes of pollen dispersal and flower receptivity leading to poor seed set. Established stands may experience vulnerabilities that arise at the community level, such as competition for resources that is intensified by climate dynamics and associated stresses, such as insect or disease infestations. Older-aged stands may be buffered to some extent from climate variability but the vulnerabilities may be more subtle. Tree species may be differentially impacted by climate changes - potentially leading to a simplification of composition in mixed-species older-aged forests. It can be postulated that some elements of the diverse biological communities of arthropods and bryophytes that comprise distinct old-growth canopy communities may be threatened without detection.

  • Map showing western hemlock and Douglas-fir zones of Washington and Oregon

    The western hemlock and Douglas-fir zones of Washington and Oregon. Adapted from a map by Jan Henderson, USDA Forest Service.

  • Douglas-fir tree plantation

    This Douglas-fir tree plantation is in a stage of growth where a dense canopy results in low levels of light and minimal growth of understory vegetation. Credit: Paul Anderson

  • Douglas-fir plantation

    A Douglas-fir plantation five years following thinning from 325 trees per acre to 185 trees per acre. Thinning is one possible strategy for increasing forest resilience to climate change. Credit: Paul Anderson

  • Understory of an old-growth western hemlock, Douglas-fir forest

    Understory of an old-growth western hemlock/Douglas-fir forest, H.J. Andrews Experimental Forest, Blue River, Oregon. Credit: Paul Anderson

  • Planted western hemlock and Douglas-fir

    Planted western hemlock and Douglas-fir seedlings develop into a second cohort of trees in a heavily thinned plantation on the Siuslaw National Forest. Planting can increase forest stand diversity. Credit: Paul Anderson

  • Thinning of a Douglas-fir plantation

    Thinning of a Douglas-fir plantation in western Oregon provides opportunity for diverse species to get established in the understory, through natural tree regeneration and planting. Credit: Paul Anderson

Management Options - Silvicultural Strategies

Density management

Density management to avoid excessive inter-tree competition may be one of the most useful means for increasing tree and stand vigor, and therefore forest resistance and resilience to climate related stresses. Relationships between stand density, growth, and site quality have been well-characterized for Douglas-fir forests of the Pacific Northwest. Degree of crowding and potential demand on site resources has been characterized by stand density indices such as Curtis Relative Density (11) or Reineke's SDI (12). Density management guidelines based on stand density indices have been useful for regulating stand productivity and for identifying thresholds for bark-beetle epidemics. Assuming that climate stresses are manifest as lower site potentials and lower thresholds for competition-related mortality, a conservative approach may be to maintain stands within a lower range of stand densities.

Management of overstory density alone may not be sufficient to enhance vigor and resilience. With overstory thinning, increased light and moisture resources can provide an opportunity for regeneration and growth of understory vegetation that places demands on site resources, offsetting to some extent the benefits derived from thinning. If untreated, biomass residues from thinning may provide breeding opportunities for insects (13), and fuel loads that increase flammability and fire risk (14). Silvicultural strategies need to account for the unintended consequences of any harvest operation.

Silviculturists have relied on site index to communicate differences in the potential productivity of a location. However, changes in climate may lead to altered site productive capacity. In the absence of sophisticated climate-site models, correlations between existing plant associations and site indices can provide a simple means to visualizing future changes in site productive capacity. A rudimentary sense of possible growth or production response to altered site capacity can be deduced from the site indices with plant associations occupying slightly drier or warmer environments.

Increasing Diversity

One way to manage uncertainty is to increase within-stand and landscape diversity by regenerating with mixtures of species. In stands or landscapes simplified by forest management practices or altered disturbance regime, encouraging the regeneration of a variety of species consistent with the potential natural vegetation may enhance the adaptive capacity. Alternatively at lower elevations where summer water deficits are likely to become more frequent, planting a proportion of drought tolerant species such as ponderosa pine (Pinus ponderosa), incense cedar (Calocedrus decurrens), or Oregon white oak (Quercus garryana) may provide a greater breadth of adaptive characteristics than a monoculture of Douglas-fir. Mixed species regeneration opportunities are not limited to clearcuts or burns, but may occur with partial overstory removals or forest gaps created in variable density thinning. Recent studies are beginning to provide useful information on the survival, growth and productivity of various conifer and hardwood species planted under the residual overstory of thinned Douglas-fir and western hemlock forests (e.g. 15). Root rot pockets and small windthrow gaps can provide local, small-scale opportunities to manage for alternative species, including more light demanding species or root rot resistant hardwoods, often at relatively low risk to near-term stand productivity. Furthermore, novel approaches to seedling deployment, such as small, widely dispersed clusters of various species can be embedded within conventional plantations or areas of natural regeneration.

Another approach to enhancing diversity and adaptability is planting seedlings comprised of mixtures of local and lower elevation or more southerly seed sources. For Douglas-fir, the analysis of St. Clair and Howe (4) suggests that to match current populations to the prospective climate of 2100, one might plant seedlings from sources that are 450 to 600 meters lower in elevation, or 1.8 to 2.5 degrees southerly in latitude, or a combination thereof. Similar relationships for species other than Douglas-fir are only beginning to emerge. However, for the 20 or so Northwest species with defined seed zones, the general guidelines for seed transfer are the same - from lower to higher elevation or from southern to northern latitudes. It is also important to recognize species differences in their degree of local adaptation. Whereas Douglas-fir demonstrates a relatively high degree of localized population adaptation, other widely distributed species such as western white pine are broadly adapted and show little localized adaptive population structuring. Initially, seed transfers for species with strong local adaptation might be restricted to adjacent seed zones, or perhaps more conservatively, to shifts between distant locations within a seed zone. Seed transfer guidelines could be more relaxed for those species demonstrating weak adaptive population structuring.

As with planting species mixtures, introductions of new seed sources should be practiced judiciously, either as a small proportion of any regeneration effort, or focused on those areas where the current population is most likely to become stressed. There is always some risk that introduced seed sources may be less fit than local sources in the near-term, and therefore they will only provide a future benefit if they survive. Where the expected lifespan of a stand is relatively short, such as a commercial forest plantation of Douglas-fir with a rotation age of 35 to 50 years, the risks associated with seed transfer may be offset by a relatively rapid population turnover. In contrast, the risks may be greater for forests managed with an extended rotation or late-successional reserve strategy in which population turnover opportunities arise infrequently or through unintended disturbance.

Maintain riparian ecosystems

Maintaining the integrity of aquatic and riparian ecosystems is a critical consideration for silvicultural adaptation strategies in the Pacific Northwest. Streamside vegetation is important to sustaining the distinct microclimate and habitat conditions associated with streams and riparian areas. The functionality of species composition and structure and width of streamside vegetation buffers is an active area of research. It is increasingly apparent that buffers are important to mitigating the near stream impacts of forest harvesting. The buffer configurations required will differ with stream orientation, flow regime, presence or absence of fishes, amphibians and other aquatic dependent organisms, local topography, vegetation composition and structure, and the intensity of harvest or other forest disturbance (16, 17). With projected warming and decreases in summer stream flow, fishes and other aquatic and riparian dependent organisms will potentially face contracting stream networks, increased stream temperatures, altered food supplies and other habitat conditions that challenge population fitness and ecosystem resilience (18).

 

References

  1. Littell, J.S.; Oneil, E.E.; McKenzie, D.; Hicke, J.A.; Lutz, J.A.; Norheim, R.A.; Elsner, M.M. 2010. Forest ecosystems, disturbance and climate change in Washington State, USA. Climatic Change. 102:129-158.
  2. Chmura, D.J.; Anderson, P.D.; Howe, G.T.; Harrington, C.A.; Halofsky, J.E.; Peterson, D.L.; Shaw, D.C.; St.Clair, J.B. 2011. Forest responses to climate change in the northwestern United States: ecophysiological foundations for adaptive management. Forest Ecology and Management.261: 1121-1142.
  3. St.Clair, J.B.; Mandel, N.L.; Vance-Boland, K.W. 2005. Geneology of Douglas fir in western Oregon and Washington. Annals of Botany. 96: 1199-1214.
  4. St.Clair, J.B.; Howe, G.T. 2007. Genetic maladaptation of coastal Douglas-fir seedlings to future climates. Global Change Biology. 13: 1441-1454.
  5. Harrington, C.A.; Gould, P.J.; St. Clair, J.B. 2010. Modeling the effects of winter environment on dormancy release of Douglas-fir. Forest Ecology and Management. 259: 798-808.
  6. Powers, J.S.; Sollins, P.; Harmon, M.E.; Jones, J.A. 1999. Plant-pest interactions in time and space: A Douglas-fir bark beetle outbreak as a case study. Landscape Ecology. 14: 105-120.
  7. Kliejunas, J.T.; Geils, B.W.; Glaeser, J.M.; Goheen, E.M.; Hennon, P.; Kim, M.-S.; Kope, H.; Stone, J.; Sturrock, R.; Frankel, S.J. 2009. Review of literature on climate change and forest diseases of western North America, General Technical Report, PSW-GTR-225. U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station, Albany, CA, USA
  8. Maguire D.A.; Kanaskie A.; Voelker W.; Johnson R.; Johnson, G. 2002. Growth of young Douglas-fir plantations across a gradient in Swiss needle cast severity. Western Journal of Applied Forestry. 17: 86-95.
  9. Agee, J.K. 1993. Fire Ecology of Pacific Northwest Forests. Island Press, Washington D.C.
  10. Poage, N.J.; Weisberg, P.J.; Impara, P.C.; Tappeiner, J.C.; Sensenig, T.S. 2009. Influences of climate, fire, and topography on contemporary age structure patterns of Douglas-fir at 205 old forest sites in western Oregon. Canadian Journal of Forest Research. 39: 1518-1530.
  11. Curtis, R.O. 1982. A simple index of stand density for Douglas-fir. Forest Science. 28: 92-94.
  12. Reineke, L.H. 1933. Perfecting a stand-density index for even-aged forests. Journal of Agriculture Research. 46:627-638.
  13. Walker, R.F.; Fecko, R.M.; Frederick, W.B.; Murphy, J.D.; Johnson, D.W.; Miller, W.W. Thinning and prescribed fire effects on forest floor fuels in the east side Sierra Nevada pine type. Journal of Sustainable Forestry. 23: 99-115. (abstract)
  14. Fettig, C.J.; McMillin, J.D.; Anhold, J.A.; Hmud, S.M.; Borys, R.R.; Dabney, C.P.; Seybold, S.J. 2006. The effects of mechanical fuel reduction treatments on the activity of bark beetles (Coleoptera: Scolytidae) infesting ponderosa pine. Forest Ecology and Management. 230: 55-68.
  15. Maas-Hebner, K.G.; Emmingham, W.M.; Larson, D.J.; Chan, S.S. 2005. Establishment and growth of native hardwood and conifer seedlings underplanted in thinned Douglas-fir stands. Forest Ecology and Management. 208: 331-345.
  16. Anderson, P.D.; Larson, D.J.; Chan, S.S. 2007. Riparian buffer and density management influences on microclimate of young headwater forests of Western Oregon. Forest Science. 53: 254-269.
  17. Olson, D.H.; Anderson, P.D.; Frissell, C.A.; Welsh, H.H. Jr.; Bradford, D.F. 2007. Biodiversity management approaches for stream-riparian areas: perspectives for Pacific Northwest headwater forests, microclimates, and amphibians.  Forest Ecology and Management. 246: 81-107.
  18. Bisson, P.A.; Dunham, J.B.; Reeves, G.H. 2009. Freshwater ecosystems and resilience of Pacific Salmon: habitat management based on natural variability. Ecology and Society. 14: 45.
  19. Franklin, J.F.; Dyrness, C.T. 1988. Natural vegetation of Oregon and Washington. Oregon State University Press, Corvallis, OR.

How to cite

Anderson, P.; Palik, B. (October, 2011). Regional examples of silvicultural adaptation strategies: Western hemlock/ Douglas-fir Forests of the Pacific Northwest. U.S. Department of Agriculture, Forest Service, Climate Change Resource Center. www.fs.usda.gov/ccrc/topics/silviculture/pacific-northwest

Regional Example - Western Great Lakes

M. Janowiak

Topics Horizontal Tabs

Synthesis

Synthesis

Regional examples of silvicultural adaptation strategies: Western Great Lakes Mixed-Pine Ecosystem

Preparers

Paul Anderson, Pacific Northwest Research Station; Brian Palik, Northern Research Station

Geographic and Climatic extent

The forested portion of the western Great Lakes region of the continental United States includes the northern half of the Lower Peninsula of Michigan, the entire upper peninsula of Michigan, northern Wisconsin, and north central Minnesota. Historically, a mixed-pine ecosystem was an important upland component on dryer sites in the region, occupying nearly 4 million hectares (ha) prior to significant Euro-American settlement (9 - see map below). Red pine (Pinus resinosa) and eastern white pine (Pinus strobus) were the dominant tree species in this system, with varying amounts of other conifers and hardwoods, including balsam fir (Abies balsamea), jack pine (Pinus banksiana), trembling and bigtooth aspens (Populus tremuloides, P. grandidentata), and paper birch (Betula papyrifera) (see map below). In the contemporary landscape, the abundance and area occupied by red pine and eastern white pine are reduced to less than 1 million ha, while trembling and bigtooth aspens have greatly increased. While the mixed pine component of this ecosystem is greatly reduced in the contemporary landscape (10), it is still important ecologically and economically and is the target of restoration efforts on most public and some private lands.

The physiographic setting of the Great Lakes mixed pine ecosystem is generally characterized by a moist low boreal and subhumid low boreal climate (11). Mean annual precipitation varies from 50 cm in the west to 70-80 cm in the eastern parts of the region. Annual summer temperatures average 14oC to 15.5oC, while winter temperatures average -13oC. Climatic variation arises from location relative to the Great Lakes. Lake influences on temperature and precipitation occur closer to shorelines of all the Great Lakes, increasing the length of the growing season and influencing average temperatures, extreme temperatures, and the amount and timing of precipitation. The lake effect results in moderated temperature regimes in the eastern part of the region. The climate is considerably more "continental," with extreme minimum winter temperatures and short growing seasons in the western part of the region.

Potential Vulnerabilities

The Great Lakes mixed pine ecosystem occurs on sand to loamy sand soils derived from glacial outwash and ice-contact topography (1). The soil moisture regime is dry-mesic to xeric and as such, a decrease in growing season soil moisture under a warmer, drier climate could negatively impact the system in several ways. Higher growing season temperatures, combined with reduced summer precipitation, will result in greater plant water deficits, if evapotransporation demand exceeds moisture availability more frequently and for longer duration. Reduced photosynthetic capacity, growth, and tree vigor are likely consequences. Increasing atmospheric CO2 concentration may increase growth in the short term, but the long-term response is not clear at present. For example, increasing ground-level ozone concentrations, which can damage forest trees, as well as soil moisture limitations, may offset the positive effect of CO2 fertilization on growth.

Odocoileus virginianus) is a significant problem in many parts of the region (2). In Minnesota, for example, it is virtually impossible to regenerate eastern white pine, and often jack and red pines, without browse protection of some type (3). It is difficult to predict how white tail deer will respond to a climate that is expected to be warmer, with potentially deeper snowpack in winter.

Dryer conditions during the growing season may result in reduced moisture of woody fuels more frequently in space and time, with a concurrent increased risk of wildfire. While the Great Lakes mixed-pine ecosystem is fire dependent, fuels build up due to long-term fire suppression poses a significant risk of catastrophic wildfire in many locations. This may be particularly true if fuels are drier. Soil moisture deficits during the growing season will also exacerbate the potential for wildfire. More frequent heavy rainstorms accompanied by high winds may result in increased blowdown, particularly of older pines, as both red and eastern white pine can reach super-dominant crown positions, with high wind exposure.

  • Pre-settlement distribution of Great Lakes pine forest within the Lake States.

    Pre-settlement distribution of Great Lakes pine forest within the Lake States.

  • Red pine stand thinned

    Red pine stand thinned and maintained at 13.8 m2/ha (60 ft2/ac). Thinning may help increase forest resilience to climate change. Credit: Christel Kern.

  • Prescribed surface fire during the growing season controls understory shrub proliferation in pine forests.

    Prescribed surface fire during the growing season controls understory shrub proliferation in pine forests. Credit: Christel Kern.

  • multi-cohort pine forest

    Early settlement example of a structurally complex, mixed-species, multi-cohort pine forest. Greater diversity may lead to greater resilience to climate changes.

Warmer, drier growing season conditions, along with milder winter temperatures, may shift competitive advantage towards more generalist species, and those currently at the northern edge of their distribution in the region. For instance, habitat suitability for several currently minor oak (Quercus) species is projected in increase (4), as is that for species that currently do not occur in the region, such as eastern red cedar (Juniperus virginiana). In contrast, predictions suggests a moderate reduction in habitat suitability for eastern white pine and substantial reductions for red pine throughout much of the region, with both low and high emission scenarios (4). Other species that occur in the mixed-pine ecosystem, including trembling aspen, paper birch and balsam fir, are projected to have large declines in habitat suitability as well.

Potential compositional changes may lead to long-term effects on fuels and fire risk that are complex and unpredictable. If CO2 fertilization and milder temperatures increase productivity, fuel loadings may increase and potentially fire risk along with this. Alternatively, drier growing season conditions could reduce productivity and thus the standing crop of fuels. Additionally, shifts in composition to species producing less flammable fine fuels, such as maples, could lead to decreased fire risk.

Insect and disease pests of red and eastern white pine may respond to climate change in ways that increase tree mortality. Changes in pest populations could result directly from changes in climatic factors. For example more frequent drought could increase bark beetle outbreaks, a potentially serious threat to eastern white and red pines. Climate change may result in more complex interaction with other environmental changes. For example, populations of Ips bark beetles are greater on red pine with bole scorch from surface fire, resulting in increased mortality (5). If fire is more frequent with climate change, bark beetle-induced loss of vigor and mortality may increase as well.

Management Options

Several of the general strategies outlined in ‘Silviculture for climate change’ may have relevance for managing Great Lakes mixed pine ecosystems in the face of climate change. These strategies can be broadly segregated into resistance, resilience, and response or facilitation strategies (6), although there is some ambiguity in assigning specific approaches to a broad strategy.

Resistance

Resistance strategies may include activities that, at least in the short-term, greatly increase regeneration of species that are expected to have reduced habitat suitability in the future, such as red pine and eastern white pine. Increased use of prescribed surface fire to create appropriate seedbeds and reduce competing understory vegetation may be one such strategy.

Corylus Americana, Corylus cornuta). This response may negate potential enhancement of soil moisture availability to overstory trees. As such understory control may need to be more widely practiced than it currently is. Greater use of growing season prescribed fire would help reduce hazel populations (7). As with other forest types, thinning may also help to reduce the potential outbreaks of density dependent pest species, such as bark beetles.

Resilience

A primary resilience strategy involves restoring and sustaining the native species and structural conditions currently associated with reference conditions for the Great Lakes mixed-pine ecosystem. The specific magnitudes of climate changes, especially for precipitation, are still uncertain and the exact response of various tree species is not well understood. As such, hedging one’s bet and increasing options for the future by maintaining the full suite of native species in the ecosystem is appropriate. There is tremendous opportunity to restore native species composition in the Great Lakes mixed pine ecosystem (8), as much of the current resource occurs in near mono-specific stands (often plantations) of either red pine or eastern white pine. Generalist species, such as red maple (Acer rubrum), and those with a more southerly distribution such as some oaks (Quercus spp.), that currently are a minor components of a stand may be favored by a resilience strategy, under the premise that conditions for their survival, growth, and fecundity may be enhanced in the future. Density management may be a tool to promote resilence of these species if they already occur in a stand. Specifically, thinning during the stem exclusion stage of stand development may prevent their competitive exclusion and allow them to recruit to the overstory.

The structural condition of many pine stands in the region is greatly simplified, relative to reference conditions. The later is inclusive of multi-cohort stands (8), as well as "even-aged" stands composed of one dominant cohort, along with a smaller population of older individuals. Concurrent with these age structures is greater complexity and heterogeneity in vertical and horizontal canopy distribution, greater amounts of large dead wood, and greater ranges of tree sizes, including very large individuals. The greater diversity of tree age and sizes may allow more flexibility of a species to persist in the face of climate change, if certain age or size classes are less susceptible to drought or other negative influences. As such, a resilience strategy may involve restoration of more complex age and size structures in forest of the region.

Response

Managing native species composition, as a strategy to adapt the system to climate change may meet with limited success in the long-term. Red pine, along with most of the associated "boreal" species, are predicted to face habitat conditions that are not suitable for long-term sustainability of populations. Thus, as a response strategy to facilitate the transition of forests to a new state, the silviculturist may also begin considering compositional manipulation that is currently outside the norm of practice. Initially, this may include the introduction of more southerly genotypes of contemporarily occurring species. This should be fairly straightforward when the species under consideration is widely regenerated artificially, as are both eastern white and red pines and some oaks. However, this approach may require relaxing seed source regulations, so as to allow material from outside of currently acceptable ranges.

A more controversial approach, but one that is gaining attention, is assisted migration of species not currently part of the contemporary ecosystem. In the Great Lakes mixed pine ecosystem, this might include, for example, eastern red cedar and short leaf pine. Assisted migration of species not currently part of the ecosystem should only be "experimented" with on a limited basis in the short-term. The problem with habitat suitability projections for these species is that the occurrence and magnitude of extreme climatic events, particularly extreme low temperatures, may not be well predicted in models. While average temperature or precipitation may begin to coincide with a species range requirements, the occurrence of even one deep freeze could decimate populations of these "formerly" southern species.

References


  1. MN DNR. 2003. Field Guide to the Native Plant Communities of Minnesota: The Laurentian Mixed Forest Province. Minnesota Department of Natural Resources. St. Paul, MN. Order through
  2. Rooney, T. P.; Waller, D. M. 2003. Direct and indirect effects of white-tailed deer in forest ecosystems. Forest Ecology and Management. 181: 165-176.
  3. Palik, B.; Johnson, J. 2007. Constraints on pine regeneration in northern Minnesota: causes and potential solutions. Report to the Minnesota Forest Resources Council, St. Paul, MN.
  4. Prasad, A.M.; Iverson, L.R. 1999-ongoing. A Climate Change Atlas for 80 Forest Tree Species of the Eastern United States [database]. http://www.fs.fed.us/nrs/atlas/, Northeastern Research Station, USDA Forest Service, Delaware, Ohio.
  5. Santoro, A.E.; Lombardero, M.J.; Ayres, M.P.; Ruel, J. J. 2001. Interactions between fire and bark beetles in an old growth pine forest. Forest Ecology and Management. 144: 245-254.
  6. Millar, C.I., Stephenson, N.L., Stephens, S.L. 2007. Climate change and forests of the future: managing in the face of uncertainty. Ecological Applications 17: 2145-2151.
  7. Buckman, R. E. 1964. Effects of prescribed burning on hazel in Minnesota. Ecology. 45: 626-629.
  8. Palik, B.; Zasada, J. 2003. An Ecological Context for Regenerating Multi-cohort, Mixed-species Red Pine Forests. USDA Forest Service Research Paper NC-382.
  9. Frelich, L.E. 1995. Old forest in the Lake States today and before European settlement. Nat. Areas J., I5: 157- 167.
  10. Schmidt, T. L.; Spence, J. S.; Hansen, M.H. 1996. Old and potential old forest in the Lake States, USA. Forest Ecology and Management. 86: 81-96.
  11. Kling, G.W.; Hayhoe, K.; Johnson, L.B.; Magnuson, J.J.; Polasky, S.; Robinson, S.K.; Shuter, B.J.; Wander, M.M.; Wuebbles, D.J.; Zak, D.R.; Lindroth, R.L.; Moser, S.C.; Wilson, M.L. 2003. Confronting Climate Change in the Great Lakes Region: Impacts on our Communities and Ecosystems.Union of Concerned Scientists, Cambridge, Massachusetts, and Ecological Society of America, Washington, D.C.

How to cite

Anderson, P.; Palik, B. (October, 2011). Regional examples of silvicultural adaptation strategies: Western Great Lakes Mixed-Pine Ecosystem. U.S. Department of Agriculture, Forest Service, Climate Change Resource Center. www.fs.usda.gov/ccrc/topics/silviculture/western-great-lakes

Silviculture

Silviculture for Climate Change

K. Schmitt

Topics Horizontal Tabs

Synthesis

Synthesis

Preparers

Paul Anderson, Pacific Northwest Research Station; Brian Palik, Northern Research Station

An archived version of this topic paper is available.

Issues

There is a growing consensus that management decisions need to consider how actions either enhance or detract from a forest's potential to adapt to changing climate. Uncertainty regarding the specifics of future climate conditions increases this need.

Silvicultural planning needs to embrace managing forests for adaptation to new conditions by promoting the resistance of a forest to change, resilience of a forest in the face of change, and response options that facilitate the transition of forests to new conditions (1). This may involve actions that restore or sustain compositional, structural, and functional diversity in stands. This diversified investment portfolio concept applied to forests, provides more management flexibility and capacity for forests to adapt to changing environmental conditions and societal values. Managing for adaptability is applicable to all uncertainties associated with forests, not only climate change.

Silvicultural planning considers factors that influence a forest stand's potential response to manipulation, including the structure of the ecosystem (2), current and potential range of variation in stand composition, history of disturbance or disturbance suppression, and stand development dynamics over time. It considers habitat suitability for threatened or endangered species that need to be sustained and exotic invasive species that must be discouraged. The landscape context of a stand, how its current and desired composition and structure compare to other stands in the surrounding landscape, informs how to meet broader landscape management objectives. Climate change warrants additional silvicultural considerations such as future habitat suitability for tree species currently comprising the stand, or for those species desired for the future.

The silviculturist must also consider how threats may increase under a changing climate. Warmer, drier growing seasons may reduce fuel moisture levels and increase risk of catastrophic wildfire. Milder winter temperatures and longer growing seasons may increase the risk of attack from insect and disease pests. Sustained climatic stress can increase the threat to overcrowded, older-aged forests predisposed to insect epidemics(3), as may be evidenced by the recent devastating impact of mountain pine beetle in western North America.

Societal expectations for ecosystem goods and services from forests may change little in the face of climate change. Silviculturists may be challenged to develop prescriptions that enhance adaptability to climate change, while still providing desired or expected ecosystem goods and services, such as merchantable wood, game species, native plants and animals, and forest composition and structure.

Likely Changes

Although climate is changing globally, changes in temperature, precipitation, and atmospheric composition will vary over time and among continents, among regions, and locally. Climate changes will modify the environment and cause disturbances affecting forest communities. If these modifications override the adaptive capacity of the forest ecosystem, these forests and the goods and services they provide are vulnerable.

Silvicultural approaches to climate adaptation will be effective when they focus on stress factors that pose the greatest risks to forests. An awareness of how environmental stresses result in altered tree vigor and stand dynamics is critical to understanding these risks, including:

  • Which physiological and developmental processes are most sensitive to a particular stress or suite of stressors?
  • How do changes in these sensitive processes affect the survival, growth and productivity of individual trees and stands?
  • At what temporal and spatial scales do stressors act and forests respond?
  • What are the consequences for various goods and services expected from forests?

With climate change, an objective for silviculture is to manage the composition and structure of stands and landscapes to alleviate climate-related stresses and to enhance forest capacity to resist, tolerate and adapt to a dynamic environment. When and where silvicultural adaptation strategies are employed will be influenced by overarching management objectives, perceived risks, and the confidence that intervention will be effective, given various ecological, economic or social criteria.

Management Options

Density management

Density management based on characteristics explicitly related to site resource demand may be an effective means to mitigate climate-related stressors. Silviculturists have long recognized the value of thinning and other forms of vegetation manipulation to maintain a desired balance between site resource availability and utilization. Conventional thinning commonly targets stand productivity and focuses on allocating site resources from a large number of smaller, less desirable trees to a smaller number of larger, more desirable trees. Thinnings may be repeated over time to maintain stand densities at levels that sustain cumulative productivity and preclude periods of low stand vigor. Density management can be practiced to achieve not only a balance of site resource availability and demand, but also to modify species composition and other environmental and structural features that influence climate-related stresses. For example, thinning may target the release or recruitment of species that provide diversity of adaptation traits. Recent studies are beginning to demonstrate the usefulness of variable density thinning to achieve more varied plant communities that provide a broader array of habitats and potentially greater biodiversity (4).

Changes in stand structure also may alter local environmental conditions that influence biotic and abiotic disturbance agents. Maintaining lower tree density can increase wind speeds within a canopy, making controlled flight difficult for some bark beetles (5). Thinning may decrease relative humidity, creating conditions less favorable to some pathogenic fungi, but potentially promoting infection by others such as white pine blister rust (6). Removing shrubs and other ground vegetation may decrease site resource demand, as well as reduce the risk of severe wildfire by decreasing the abundance and depth of fuels. It may be important to couple density management with understory vegetation control, so gains in site moisture balance are not negated by understory growth (7). Density management also may substantially decrease risks to individual tree and stand vigor (5, 8).

Managing composition

Restoring component species
Species composition has been altered in many forested areas by management and change in disturbance regimes, so that some species well-adapted to the historic range of variation have been diminished, while other poorly-adapted species have been added. Climate change may take decades to generate discernible effects. For the near-term, those plant communities best adapted to transitional climatic extremes will be comprised of the species and populations that evolved on site. Restoring species that have been lost due to land-use, management practices, or exclusion by invasive species is a reasonable objective for silvicultural intervention. The time to restore community composition is before substantial changes in climate occur, while there is still a relatively strong match between current site conditions and the adaptive potential of the species being restored. Approaches to restore target species include retention during thinning or other vegetation removal operations, removing competing or inhibiting invasive and non-native species, or active regeneration by planting or seeding.

Favoring adaptable species and genotypes
Promoting resistant and resilient forest communities includes favoring those species and genotypes that are adaptable to projected environmental changes. Adaptive characteristics that vary along climatic gradients, and are therefore likely to be of importance, include traits that permit a plant to survive and function when subjected to water deficits, temperature extremes or uncharacteristic disturbance (9). Drought stress is an important contributor to seedling mortality in many ecosystems and can be a limiting factor to successful reforestation (10). If fires become more severe, those species that have thick, insulating bark or that regenerate by sprouting from below-ground root systems may be more resistant and resilient.

A major issue is the degree to which current seasonal patterns of growth and development will remain synchronized in the face of rapidly changing and increasingly variable weather and climate patterns. For example, if pollen dispersal occurs out of synchrony with flower receptivity, then decreased seed production may limit natural regeneration for seed-regenerating species.

The limitation of this strategy is that capacity for adaptation has evolved in response to historical pressures, and may not be sufficient for dealing with projected future conditions. There may not be enough time for new adaptations to evolve in place, given the rapid changes in climate we are experiencing (9).

Adding new species and genotypes
An active approach to facilitate adaptation may be intentionally moving species or genotypes to match known adaptive characteristics with locations where these traits may be beneficial in the future environment (11). This "assisted migration" can be practiced with varying intensity and risk. Initially, movements of species or genotypes can be limited to relatively short "ecological" distances along a climatic gradient and focused on the transition zones from one ecotype to another. Caution must be used, because in the near term, some transferred sources may not be as well adapted to the current environment as local sources.

A more subtle approach to building resilience may be planting or sowing a greater variety of species and genotypes when reforesting after a harvest or natural disturbance event. The premise is the same - expand the gene pool, and therefore the probability of having adapted individuals on a site. Regeneration harvests and stand-replacing disturbances may be opportunities to enhance the adaptive capacity of the regenerated forest.

Reducing threats

Silviculture can also be used to decrease some threats to vulnerable forest stands and landscapes. Biotic threats include some insects and diseases, pathogen vectors, and invasive plants or animals. Physical threats include fire ignition sources such as lightning strikes, windstorms, flooding or landslides. Silvicultural approaches to biotic threats include treatment of incipient infestation centers through "sanitation" harvests, chipping or burning excessive down wood accumulations from harvest or disturbance events, and integrated pest management for invasive plants and animals.. Silvicultural regimes can minimize slope destabilization and moderate runoff to mitigate potential landslides and flooding.

Effective silvicultural regimes address site specific issues in the broader temporal and landscape contexts. The treatment of threats across a landscape can be influenced by the spatial and temporal application of stand-level treatments. For example, fuels management is integral to restoration of fire resilience in some western forests. For fuels reduction to be effective, at least 20-30% of a landscape needs treatment in designed spatial patterns, with retreatment occurring after 15-20 years; random spatial application requires approximately twice the area treated to get the same effect (12). These larger-scale contexts are useful to prioritizing site and stand level actions to reduce threats.

Silviculture for Climate Change: Generalities Common to all Regions

Vulnerabilities differ by forest type and stage of development.
Individual trees and species differ in their degree of adaptability to any given suite of stresses. Capacity to cope with a stress depends on the physiology of individuals and how individuals interact as a forest community. For the individual, changes in size and maturation can influence resource demand, acquisition and storage, and the ability to buffer environmental challenges. Stage of stand development will influence the degree of inter-tree competition and the susceptibility of forest stands to various disturbances.

Interactions between climate and other biological and physical stressors will be important in determining forest response to climate change.
Forest ecosystems are complex. Stresses imposed by climate that decrease tree and stand vigor will often result in increased damage by secondary stress agents. Climate may also directly influence the abundance and voracity of pests, as well as promote physical disturbances such as fire.

Opportunities exist for vegetation management to enhance balance between site occupancy and resource availability.
Silviculture aims to manipulate the composition and structure of forests to meet an array of management objectives. If sustaining vigorous forests is a primary challenge imposed by a changing climate, then silvicultural activities that maintain a balance between the supply and demand for site resources or that mitigate local environmental stresses will have an important adaptation role.

Restoring composition and structure now will enhance adaptation capabilities for the future.
Adaptation to a changing climate will be facilitated by starting with communities that are diverse and resistant and resilient to the range of environmental conditions historically encountered. Most managed ecosystems are simplified in composition relative to their un-managed, reference condition. A near-term strategy is to restore a portion of the landscape to native plant community composition and structure within the natural range of variation.

Silvicultural treatments at a stand scale are most effective when conceived and applied in a landscape context.
Climate-related stresses occur at stand and landscape scales. To have a major adaptation impact, silviculture must be practiced strategically to best target threats and responses that occur at multiple spatial and temporal scales. The opportunity to do everything needed, everywhere, all of the time, is rare. Silviculturists must understand how vulnerabilities and threats operate at multiple scales in order to be most effective in using limited adaptation resources.

 

References

  1. Millar, C.I.; Stephenson, N.L.; Stephens, S.L. 2007. Climate change and forests of the future: managing in the face of uncertainty. Ecological Applications. 17: 2145-2151.
  2. Palik, B. J.; Goebel, P.C.; Kirkman, L. K.; West, L. 2000. Using landscape hierarchies to guide restoration of disturbed ecosystems. Ecological Applications. 10: 189-202.
  3. Trzcinski, M.K.; Reid, M.L. 2009. Intrinsic and extrinsic determinants of mountain pine beetle population growth. Agricultural and Forest Entomology. 11: 185-196.
  4. Peterson, C.E.; Anderson, P.D. 2009. Large-scale interdisciplinary experiments inform current and future forestry management options in the U.S. Pacific Northwest. Forest Ecology and Management 258: 409-414.
  5. Whitehead, R.J.; Safranyik, L.; Russo, G.L.; Shore, T.L.; Carroll, A.L. 2003. Silviculture to reduce landscape and stand susceptibility to the mountain pine beetle. In Shore, T.L., Brooks, J.L., and J.E. Stone (eds). Mountain Pine Beetle Symposium: Challenges and Solutions. October 30-31, 2003, Kelowna, British Columbia. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Information Report BC-X-399, Victoria, BC. 298 p.
  6. Jactel. H.; Nicoll, B.C.; Branco, M.; Gonzalez-Olabarria, J.R.; Grodzki, W.; Lanngstrom, B.; Moreira, F.; Netherer, S.; Orazio, C.; Piou, D.; Santos, H.; Schelhaas, M.J.; Tojic, K.; Vodde, F. 2009. The influences of forest stand management on biotic and abiotic risks of damage. Annals of Forest Science. 66: 701, 18 p.
  7. Kurpius, M.R.; Panek, J.A.; Nikolov, N.T.; McKay M.; Goldstein, A.H. 2003. Partitioning of water flux in a Sierra Nevada ponderosa pine plantation. Agricultural and Forest Meteorology. 117: 173–192.
  8. McDowell, N.G.; Adams, H.D.; Baily, J.D.; Hess, M.; Kolb, T.E. 2006. Homeostatic maintenance of ponderosa pine gas exchange in response to stand density changes. Ecological Applications. 16: 1164-1182.
  9. Aitken, S.N.; Yeaman, S.; Holliday, J.A.; Wang, T.; Curtis-McLane, S. 2008. Adaptation, migration or extirpation: climate change outcomes for tree populations. Evolutionary Applications. 1: 95-111.
  10. McDowell, N.; Pockman, W.T.; Allen, C.D.; Breshears, D.D.; Cobb, N.; Kolb, T.; Plaut, J.; Sperry, J.; West, A.; Williams, D.G.; Yepez, E.A. 2008. Mechanisms of plant survival and mortality during drought: why do some plants survive while others succumb to drought? New Phytologist. 178: 719–739.
  11. St.Clair, J.B.; Howe, G.T. 2007. Genetic maladaptation of coastal Douglas-fir seedlings to future climates. Global Change Biology. 13: 1441-1454.
  12. Finney, M.A.; Seli, R.C.; McHugh, C.W.; Ager, A.A.; Bahro, B.; Agee, J.K. 2007. Simulation of long-term landscape-level fuel treatment effects on large wildfires. International Journal of Wildland Fire. 16:712-727.

How to cite

Anderson, P.; Palik, B. 2011. Silviculture for Climate Change. (October, 2011). U.S. Department of Agriculture, Forest Service, Climate Change Resource Center. www.fs.usda.gov/ccrc/topics/silviculture

Reading
Research

Research

There is extensive Forest Service research on silviculture and climate change - some examples are available below via the CCRC Research Roundup.

 

PINEMAP: Mapping the future of southern pine management in a changing world
Southern Research Station, Eastern Forest Environmental Threat Assessment Center
Project website: http://pinemap.org/

The PINEMAP project integrates research, extension, and education to enable southern pine landowners to manage forests to increase carbon sequestration; increase efficiency of nitrogen and other fertilizer inputs; and adapt forest managment approaches to increase forest resilience and sustainability under variable climates.

Contact:
Cumulative Effects of Succession, Management, and Disturbance on Forest Landscapes
Northern Research Station

For more than 15 years we have worked together with collaborators from other institutions to develop and apply methods to forecast landscape-scale forest change in response to tree growth and species succession as well as disturbance from timber harvest and fire. Much of this work has utilized the LANDIS model to forecast changes in forest conditions for management and disturbance scenarios applied. We have demonstrated the capabilities of these tools to analyze the cumulative effects of management scenarios applied to real forest landscapes in Indiana and Missouri.

Contact:
Addressing Climate Change in the Forest Vegetation Simulator
Rocky Mountain Research Station

The Forest Vegetation Simulator (FVS) is a family of forest growth simulation models that allow a user to explore forest growth and yield at the stand level. This research incorporates climatic effects into FVS to produce a new extension called Climate-FVS, providing managers with a tool that allows climate change impacts to be incorporated in forest plans.

Jerry Rehfeldt
Regeneration dynamics during oak decline with prescribed fire
Southern Research Station

Researchers are looking at how forest management practices - including controlled fire - can help give certain oak species in the Boston Mountains of northern Arkansas an advantage under possible conditions created by climate change.

Contact:
Impacts of Land Management on the Climate System
Northern Research Station

Research is needed to examine the potential impacts of land cover changes, including afforestation, on the climate system. This can provide a scientific basis for adopting land use decisions that are meant to mitigate global warming.

Contact:
Tools

Tools

USFS Climate Change Atlas
The Atlas uses downscaled climate projections for the eastern US to project potential future suitable habitats for 134 tree species and 147 bird species. It also models and maps current species habitats.

Videos

Videos

An overview of a set of tools that assess how climate change might influence tree distributions in the eastern U.S.

Presenter : Louis Iverson

The Alder Spring project in the Mendocino National Forest is a case study in climate change mitigation.

Presenter : Mark Nechodom

Forest management options for reducing carbon emissions and enhancing carbon sequestration in forests.

Presenter : Maria Janowiak

Andrea Tuttle takes a look at forest carbon markets and how these can be used to capture and hold carbon on the landscape.

Presenter : Andrea Tuttle

Presents a western U.S. perspective on forest management for carbon sequestration, and the above and below- ground carbon consequences of different management strategies.

Presenter : Bernard Bormann

The Eastern U.S. forest perspective on carbon sequestration and examples of forest carbon management projects.

Presenter : Richard Birdsey

Three key factors make old redwood forests stable: topography, buffering marine influence and special species attributes. Active management may be required to maintain old growth redwood forests.

Presenter : Steve Norman

Andrea Tuttle discusses the drivers of deforestation, current international approaches to reducing emissions and lessons learned from REDD pilot programs.

Presenter : Andrea Tuttle

The 5Rs + 1 strategy for forest management in the face of climate change: resist, resile, respond, realign, reduce and prioritize.

Presenter : Connie Millar

Pacific Northwest

Grasslands and Climate Change

US Fish & Wildlife Service

Topics Horizontal Tabs

Overview

Overview

The grassland ecosystems we see today have an extensive history of human activity and disturbance. In response to these alterations, many native U.S. grasslands and grassland species are in decline and climate change is expected to add to or exacerbate existing stressors that threaten these ecosystems. Although there are serious causes for concern, climate change may represent an opportunity to develop a broader, more responsive, and collaborative management paradigm. Read the synthesis to learn more.

Synthesis

Synthesis

Preparers

Karen Bagne, Paulette Ford, and Matt Reeves; Rocky Mountain Research Station

Issues

Grasslands cover a broad expanse of the U.S. and encompass a diverse set of environmental conditions and ecological communities. Grasslands are major contributors to U.S. food production and provide many other services valuable to humans including aquifer recharge, pollination, and recreational opportunities. While typically defined as lands on which the existing plant cover is dominated by grasses, undeveloped grasslands consist of more than just grass. They are highly diverse communities of grasses, forbs, and non-vascular and woody plants, punctuated by wetlands that provide critical wildlife habitat. Although climate is an important driver of grassland ecosystems, disturbances such as fire and grazing also play a key role in sustaining grasslands. Some systems, such as temperate savannas commonly grade into grasslands, and are maintained as grasslands principally by human-caused disturbance [1].

The largest U.S. grassland region is the Great Plains, a vast area of prairie, agriculture, and rangelands extending from the Dakotas through Iowa, Nebraska, Kansas, Oklahoma and parts of Texas, and including the eastern parts of Montana, Wyoming, Colorado, and New Mexico (see grasslands map below).

Grasslands are also an important component in other regions including the Central Valley of California, the western coast of the Gulf of Mexico, parts of the Great Basin, and arid regions of the Southwest. Temperate savannas (used frequently to describe temperate grasslands with scattered trees) include pine savannas of the southeastern Gulf Coastal Plain, California oak savannas, piñon/juniper savannas of the Southwest, and aspen parklands of Canada. We do not discuss marshes, alpine meadows, or tundra for this topic page.

The grassland ecosystems we see today have an extensive history of human activity including burning, hunting, crop production, livestock grazing, and urban development. In response to these alterations, many native grasslands and grassland species are in decline and climate change is expected to add to or exacerbate existing stressors that threaten these ecosystems. As climate conditions shift geographically so will the distributions of many plants and animals. The relatively flat terrain of grasslands increases vulnerability to climate change impacts, because habitats and species must migrate long distances to compensate for temperature shifts. This contrasts sharply with mountainous terrain, where conditions change over short distances due to steep increases in elevation [2]. Warmer temperatures bring greater evaporation and alter rainfall patterns, which will further deplete aquifers and threaten water-dependent habitats. Of particular concern are the small isolated wetlands that facilitate groundwater recharge, support a critical component of diversity in many grassland ecosystems (e.g., vernal pools, playa lakes, prairie potholes) and are already threatened by current land use practices [3].

History and human values influence not only how grassland ecosystems will respond to climate change but also what management options will be available. The extensive fragmentation that already characterizes grassland ecosystems will limit opportunities for species to disperse in concert with climate. Global market trends affect local human activities in grassland ecosystems, often with important consequences. For example, changing commodity prices can alter crop choice and subsequent aquifer withdrawals [4]. In some grasslands, ecosystem engineers (e.g., bison and prairie dogs), are missing from much of their former range [5], and fragmentation and agricultural practices have reduced pollinator species. Because these species play an active role in ecosystem dynamics, this will further limit ecosystem resilience to climate change impacts.

  • GIS Map showing estimated distribution of major grasslands in the US.

    Estimated distribution of major grasslands of the Contiguous U.S before Euro-American settlement.

  • Oaks and grassland

    A mix of oaks and grassland on the San Joaquin Experimental Range in central California established in 1934. This and other experimental ranges contribute significantly to longterm research. Credit: Kathryn Purcell.

  • Black Kettle National Grassland wildfire

    A wildfire burning through mixed grass prairie on the Black Kettle National Grassland, OK. Fires are important to maintaining grasslands, but can also threaten human life and property. Credit: Chuck Milner.

Likely Changes

On a large scale grassland-suitable habitat in the U.S. is expected to increase, but projections vary by grassland type. Model projections for grasslands are at a broad scale (1km) and give a sense of likely changes summarized below [6]:

  • Climate suitable for Great Plains grasslands is expected to remain relatively stable with some expansion to the north in Canada and retraction on the eastern and southern boundaries.
  • Climate suitable for semi desert grasslands in the southwestern U.S. is expected to expand while contracting in Mexico.
  • Climate suitable for Great Basin shrub-grasslands is expected to decline with contraction primarily along the eastern boundary in Colorado, Montana, and eastern Idaho.
  • Climate suitable for California valley grasslands is likely to have significant declines, shifting towards oak woodlands and desert scrub, along with a high proportion of no analog climates (i.e., projected climates do not match any contemporary biomes).
  • Climate suitable for Gulf Coastal grasslands is expected to contract towards southeastern Texas and have a high proportion of no analog climates.

Other expected changes not captured by the distribution models include effects of CO2 and nitrogen availability.

When not limited by other factors, increasing CO2 increases plant growth, as well as water use efficiency, which is especially important in drier regions. However, the benefits of elevated CO2 will be limited by factors including water availability [7, 8] and available nutrients, particularly nitrogen [9]. Thus effects of elevated CO2 on plant growth will vary with local climate patterns,species adaptations to water limitations, and nitrogen availability. Studies indicate that nutrient depletion may happen faster in drier regions, and with factors such as plant community composition and grazing [8]. Nitrogen deposition from air pollutants and increased mineralization from higher temperatures can increase plant productivity, but increases are often accompanied by a reduction in biodiversity as faster growing plants outcompete others [10]. A study of a California grassland found that global change may speed reductions in diversity and forb species are most vulnerable to this process [11].

Grassland community composition will likely be affected by climate change, but complex interactions make predictions problematic. For example, some experiments have shown that under certain conditions elevated CO2 favors woody plants, herbaceous forbs, and legumes over many grasses, because of their different photosynthetic pathways, (C4, warm-season versus C3, cool-season) [12] or possibly differences in root depth and groundwater uptake [13]. Shrub encroachment of montane meadows under warmer temperatures has also been supported [14]. But other evidence suggests that C4 grasses may be favored in arid areas with reduced precipitation because of their greater ability to resist desiccation, high temperatures, and low nitrogen levels [15]. Although a number of expanding exotic grass species are C4, any competitive disadvantage from elevated CO2 so far is not universally apparent. Changes in species composition will likely vary by region and by year and will depend on depth and timing of available soil water as well as disturbance factors such as grazing, fire, and disease, which can have strong influence on plant communities.

Extreme weather conditions can induce a rapid and severe response that alters both ecosystems and human communities [16]. Increasingly severe and frequent droughts, floods, fires, and hurricanes are likely to affect U.S. grassland ecosystems. Drought exacerbates soil erosion and aquifer depletion. Greater variability in precipitation will favor more frequent fires, which can reduce encroachment of woody plants into grasslands[17]. Fires are a natural element in grassland ecosystems, but extreme conditions, along with land use variables, can encourage fires that impact very large areas in a short period of time, such as the Texas fires of 2011. Similarly, floods occur regularly, recharge aquifers, transport nutrients, and provide habitat for some wildlife species, but greater intensity of run-off events will also decrease retention of organic matter and flush out aquatic organisms in wetlands [18]. Other widespread disturbance events, such as insect outbreaks, can speed the conversion of forests and woodlands to grasslands [19].

The extent and duration of open water in wetlands is expected to decrease even in regions where precipitation is expected to be higher, because of the greater evaporation expected with warmer temperatures [20]. Greater evaporation also increases salinity. Sea level rise will inundate coastal grasslands with salt water and increase erosion. These changes will impact wetland plants as well as migratory bird populations that breed, winter, or migrate through grassland habitats, which are significant components along the Pacific, Central, and Mississippi Flyways. Although the distribution and timing of available water in aquatic habitats will be sensitive to climate change, regional effects, such as geomorphology, water demand, and soils, have not been well explored [21].

Options for Management

Management options to sustain grassland ecosystems under global change are many, but are mostly untested in their ability to maintain or enhance resource values into the future. Tenants of managing climate change response, also called adaptation, include evaluating the success of current management programs, implementing anticipatory actions, and maintaining the flexibility to modify strategies. Local climate alterations may also affect management decisions such as when prescribed fires can be applied. Low risk and "no regrets" options include actions that are expected to have benefits on valued resources now. Examples include management to reduce current stressors that threaten the ecosystem services from grasslands and actions that increase ecosystem resilience such as altering grazing patterns to increase biodiversity. More drastic measures include assisted migration, where species are moved to new regions expected to have favorable climates, and assisted transition, where managers encourage conversion of an area to a projected state [22]. Managers need to consider the expected impacts to key resources at a relevant temporal and spatial scale as well as uncertainty surrounding those expectations. For example, wetlands suitable for breeding waterfowl in the northern Great Plains are projected to shift in location to wetter regions in the northeast where few wetlands are protected, thus conservation efforts for these species needs to shift focus [23].

Connectivity

Landscape connectivity and species’ dispersal ability are important concepts in climate change adaptation because of the expected spatial shifts in suitable habitat for plants and animals. The widespread fragmentation of grasslands makes this an especially critical consideration for anticipating species response. Dispersal can be manipulated through establishment of corridors and translocations. Shifts of geographic distributions should anticipate not just emigration but also immigration of new species to a defined location.

Livestock

Productivity and changes to growth periods, both in their duration and timing, will need to be taken into consideration for livestock management. Livestock management can include altering of stocking rates, livestock breeds, and livestock species to better match new conditions, along with monitoring of indicators that practices are compatible with sustaining healthy grasslands.

Restoration

Restoration of degraded grasslands can increase resilience to climate change along with providing protection from soil erosion, carbon loss, and other negative impacts. In regions where climate is expected to no longer support current communities, restoration can focus on a function such as aquifer recharge or on species expected to be more tolerant of new conditions. Conservation of native grasslands often focuses on localized areas at a small spatial scale, but a focus on the surrounding matrix becomes increasingly important as climate and natural communities shift, especially for grasslands because of their intensive human use and fragmentation. Genetic diversity incurs greater resilience to changing and uncertain conditions and should be considered in restoration or translocation of species. Greater biodiversity and redundancy of species functional roles creates greater stability of ecosystems and is associated with greater resilience in the face of changing conditions [24, 22]. Intermediate levels of disturbance, including soil disturbance, fire, and grazing, can encourage greater biodiversity. Disturbance, however, is also conducive to invasion by exotic plants [25]. Control of invasive species can reduce stress on the system making it better able to resist climate change.

Extreme events

Extreme events should be anticipated and steps taken to mitigate their impacts. This may take the form of building infrastructure or reducing fuel for fires, but could also be addressed through contingency plans that can be put into action quickly when the need arises. Providing for redundancy in habitats across a large spatial scale can also increase resilience to extreme events. Extreme weather events can also have positive effects. Hurricanes, in part, prevent forest establishment and maintain grasslands in coastal areas [26,27].

Management tools

Many decision support tools are available for managers. Scenario planning, where impacts are assessed across a range of climate futures, can identify actions that are robust under multiple projections. Where and how to direct management resources can be guided by vulnerability assessments, because they identify priorities and areas of vulnerability where effective actions can be directed. Risk and decision analysis can help evaluate the potential outcomes and uncertainty surrounding possible management actions. Find more tools in the "tools" tab.

Opportunities

Although there are many reasons for concern, some climate change impacts may be positive. Increases in plant productivity and longer growing seasons in some regions may support more livestock, increase wildlife species, and increase economic benefits. Increases in fires may reduce encroachment by woody species and further encourage conversion to grasslands. Native grassland restoration efforts may get a boost from the expected increase in carbon sequestration these sites provide. In some cases, climate change may incur negative impacts to problematic invasive species in favor of natives [28]. The variability in climate expected can be an opportunity for effective management, such as invasive control and revegetation, as actions can be timed to the most effective conditions [29]. For example, native plants can be more tolerant of drought conditions than non-natives allowing for control measures to be applied when populations are low [30]. Finally, climate change is a good motivator for developing a broader, more responsive, and collaborative management paradigm.

References

  1. Ford, P.L. 2002. Grasslands and savannas. In: Encyclopedia of Life Support Systems. UNESCO. 20pp. Available at http://www.eolss.net/.
  2. Loarie, S.R.; Duffy, P.B.; Hamilton, H.; Asner, G.P.; Field, C.B.; Ackerly, D.D. 2009. The velocity of climate change. Nature. 462:1052-1057.
  3. Murkin, H.R. 1998. Freshwater Functions and Values of Prairie Wetlands. Great Plains Research: A Journal of Natural and Social Sciences. Paper 362.
  4. Joyce, L.A.; Ojima, D.; Seielstad, G.A.; Harriss, R.; Lackett, J. 2009. Potential consequences of climate variability and change for the Great Plains. In Global Change Impacts in the United States. U.S. Global Change Research Program. p 191-217.
  5. Fahnestock, J. T.; Detling, J. K. 2002. Bison-prairie dog-plant interactions in a North American mixed-grass prairie. Oecologia. 132:86-95.
  6. Rehfeldt, G.E.; Crookston, N. L.; Saenz-Romero, C.; Campbell, E. M. 2012. North American vegetation model for land-use planning in a changing climate: a solution to large classification problems. Ecological Application. 22:119-141.
  7. Polley, H. W. 1997. Implications of rising atmospheric carbon dioxide concentration for rangelands. Journal of Range Management. 50:562-577.
  8. Morgan, J.A.; Derner, J.D.; Machunas, D.G.; Pendall, E. 2008. Management implications of global change for Great Plains rangelands. Rangelands. 18-22.
  9. Hungate, B.A.; Dukes, J.S.; Shaw, M.R.; Luo, Y.; Field, C. B. Nitrogen and climate change. Science. 302:1512-1513.
  10. Weiss, S.B. 1999. Cars, Cows, and Checkerspot Butterflies: Nitrogen Deposition and Management of Nutrient-Poor Grasslands for a Threatened Species. Conservation Biology 13: 1476-1486.
  11. Zavaleta, E.S.; Shaw, M.R.; Chiariello, N.R.; Mooney, H.A.; Field, C.B. 2003. Additive effects of simulated climate changes, elevated CO2, and nitrogen deposition on grassland diversity. Proceedings of the National Academy of Sciences, USA. 100: 7650-7654.
  12. Morgan, J.A.; Milchunas, D.G.; LeCain, D.R.; West, M.; Mosier, A.R. 2007. Carbon dioxide enrichment alters plant community structure and accelerates shrub growth in the shortgrass steppe. Proceedings of the National Academy of Sciences USA.104:14724-14729.
  13. Barron-Gafford, G.A.; Scott, R.L.; Jenerette, G.D.; Hamerlynck, E.P.; Huxman, T.E. 2012. Temperature and precipitation controls over leaf- and ecosystem-level CO2 flux along a woody plant encroachment gradient. Global Change Biology. 18:1389-1400.
  14. Harte, J.; Shaw, R. 1995. Shifting dominance within a montane vegetation community: results of a climate-warming experiment. Science. 267:876-880.
  15. Esser, G. 1992. Implications of climate change for production and decomposition in grasslands and coniferous forests. Ecological Applications. 2:47-54.
  16. Allen, C.D.; Breshears, D.D. 1998. Drought-induced shift of a forest-woodland ecotone: Rapid landscape response to climate variation. Proceedings of the National Academy of Sciences. USA 95: 14839-14842.
  17. McLaughlin, S. E.; Bowers, J.P. 1982. Effects of wildfire on a Sonoran Desert plant community. Ecology. 63:246-248.
  18. Mulholland, P.J.; Best, G.R.; Coutant, C.C.; Hornberger, G.M.; Meyer, J.L.; Robinson, P.J.; Stenberg, J.R.; Tuner, R.E.; Vera-Herrera, F.; Wetzel, R.G. 1997. Effects of climate change on freshwater ecosystems of the south-eastern United States and the gulf coast of Mexico. Hydrological Processes. 11: 949-970.
  19. Williams, A.P.; Allen, C.D.; Millar, C.I.; Swetnam, T.W.; Michaelsen, J.; Still, C.J.; Leavitt, S.W. 2010. Forest responses to increasing aridity and warmth in the southwestern United States. Proceedings of the National Academy of Sciences, USA. 107: 21289-21294.
  20. Poiani, K.A.; Johnson,W.C.; Kittel, T.G.F. 1995. Sensitivity of a prairie wetland to increased temperature and seasonal precipitation changes. Water Resources Bulletin. 31, 283-294.
  21. Covich, A.P.; Fritz, S.C.; Lamb, P.J.; Marzolf, R.D.; Matthews, W.J.; Poiani, K.A.; Prepas, E.E.; Richman, M.B.; Winter, T.C. 1997. Potential effects of climate change on aquatic ecosystems of the Great Plains of North America. Hydrological Processes. 11:993-1021.
  22. Heller, N.E.; Zavaleta, E.S. 2009. Biodiversity management in the face of climate change: A review of 22 years of recommendations. Biological Conservation. 122:14-32.
  23. Johnson, W.C.; Millett, B.V.; Gilmanov, T.; Voldseth, R.A.; Guntenspergen, G.R.; Naugle, D.E. 2005. Vulnerability of Northern Prairie Wetlands to Climate Change. BioScience. 55:863-872.
  24. Tilman, D.; Downing, J.A. 1994. Biodiversity and stability in grasslands. Ecosystem management: selected readings 367: 363-365.
  25. Vujnovic, K.; Wein, R.W.; Dale, M.R.T. 2002. Predicting plant species diversity in response to disturbance magnitude in grassland remnants of central Alberta. Canadian Journal of Botany. 80: 504-511.
  26. Schroeder, P.M; Hayden, B.; Dolan, R. 1979. Vegetation changes along the United States east coast following the Great Storm of March 1962. Environmental Management 3.4: 331-338.
  27. Beckage, B.; Gross, L. J.; Platt, W. J. 2006. Modelling responses of pine savannas to climate change and large-scale disturbance. Applied Vegetation Science. 9: 75-82.
  28. Bradley, N.L.; Leopold, A.C.; Ross, J.; Huffaker, W. 1999. Phenological changes reflect climate change in Wisconsin. Proceedings of the National Academy of Sciences of the United States of America. 96:9701-9704.
  29. Holmgren, M.; Scheffer, M. 2001. El Niño as a window of opportunity for the restoration of degraded arid ecosystems. Ecosystems. 4: 151-159.
  30. Salo, L.F. 2004. Population dynamics of red brome (Bromus madritensis subsp. rubens): times for concern, opportunities for management. Journal of Arid Environments 57:291-296.

     

How to cite

Bagne, K.; Ford, P.; Reeves, M. (November 2012). Grasslands. U.S. Department of Agriculture, Forest Service, Climate Change Resource Center. www.fs.usda.gov/ccrc/topics/grasslands/

Reading
Research

Research

Shrub Encroachment, Wildland Fire, Climate Change, and Carbon Sequestration in Three Southwestern Grassland Ecosystems
This multifaceted research program addresses the impacts of shrub encroachment, precipitation variability, and warming on carbon and nitrogen dynamics of arid grasslands along a latitudinal gradient from northeastern Colorado to southern New Mexico.
Contact: Paulette Ford, RMRS, in collaboration with Scott Collins, University of New Mexico, Sevilleta LTER.

Long-term implications of prescribed fire in the western Great Plains
Environmental influences on responses of soil, vegetation, fuel loads and modeled fire behavior.
Contacts: Paulette Ford, Matt Reeves, Jamie Sanderlin, Bob Keane, RMRS, in collaboration with Justin Derner and David Augustine, USDA-ARS.

Ecology, Management, and Restoration of Great Basin Meadow Ecosystems
Researchers are using a multi-scale approach to examine geomorphic, hydrologic, and vegetation influences on Great Basin meadow complexes, how these influences might change under future climates, and to develop guidelines and methods for maintaining and restoring sustainable riparian ecosystems.
Contact: Jeanne Chambers, David Board

Exploring the Potential for Cheatgrass Biocontrol with Naturally Occurring Fungal Pathogens.
This research group seeks to understand why cheatgrass (Bromus tectorum) is such a successful invader in the Intermountain West, and how it might be controlled using a fungal seed pathogen (Pyrenophora semeniperda).
Contact: Susan Meyer

Classical Biological Control of Dalmatian (Linaria dalmatica), Yellow (L. vulgaris) and Hybrid (L. dalmatica x L. vulgaris) Toadflax.
Identify factors affecting the abundance and distribution of weevil used for biocontrol of toadflax, a noxious weed affecting range quality.
Contact: Sharlene Sing

Predicting the Effects of Climate Change on Avian Abundance.
Using a longterm dataset (27+ years), researchers are examining the effect of weather patterns on avian abundance at the San Joaquin Experimental Range, an oak woodland savanna in California, to reveal potential climate change effects on demography and identify species at risk.
Contact: Kathryn Purcell, Sylvia Mori

Grassland restoration species for central New Mexico
Researchers are looking at long-term population dynamics, germination characteristics, response to disturbance, and climate manipulations for a suite of forbs found in central New Mexican grasslands.
Contact: Rosemary Pendleton, Esteban Muldavin

Tools

Tools

Short course on forest and grassland carbon (CCRC)

CVal: Carbon calculator to assess the economic profitability of participating in carbon markets.

COASTER: Customized Online Aggregation & Summarization Tool for Environmental Rasters. Historical climate data (1980-2009) for conterminous U.S.

SAVS: System to Assess Vulnerability of Species. Scoring tool to assess climate change vulnerability for individual terrestrial vertebrate species.

Southern Plains Wind and Wildlife Planner: science-based site selection and mitigation for priority resources in Colorado and New Mexico.

SGP CHAT: Southern Great Plains Crucial Habitat Assessment Tool. Identify crucial habitat and corridors for the Lesser Prairie Chicken.

UNICOR: Universal Corridor Network Simulator. Species connectivity and corridor identification.

TACCIMO: Template for Assessing Climate Change Impacts and Management Options. Web-based information delivery tool.

Identification of invasive plants in Southern forests: mobile device app to identify invasive plants in forests and grasslands in the southern U.S.

Western Great Lakes

Regional Example - Western Great Lakes

M. Janowiak

Topics Horizontal Tabs

Synthesis

Synthesis

Regional examples of silvicultural adaptation strategies: Western Great Lakes Mixed-Pine Ecosystem

Preparers

Paul Anderson, Pacific Northwest Research Station; Brian Palik, Northern Research Station

Geographic and Climatic extent

The forested portion of the western Great Lakes region of the continental United States includes the northern half of the Lower Peninsula of Michigan, the entire upper peninsula of Michigan, northern Wisconsin, and north central Minnesota. Historically, a mixed-pine ecosystem was an important upland component on dryer sites in the region, occupying nearly 4 million hectares (ha) prior to significant Euro-American settlement (9 - see map below). Red pine (Pinus resinosa) and eastern white pine (Pinus strobus) were the dominant tree species in this system, with varying amounts of other conifers and hardwoods, including balsam fir (Abies balsamea), jack pine (Pinus banksiana), trembling and bigtooth aspens (Populus tremuloides, P. grandidentata), and paper birch (Betula papyrifera) (see map below). In the contemporary landscape, the abundance and area occupied by red pine and eastern white pine are reduced to less than 1 million ha, while trembling and bigtooth aspens have greatly increased. While the mixed pine component of this ecosystem is greatly reduced in the contemporary landscape (10), it is still important ecologically and economically and is the target of restoration efforts on most public and some private lands.

The physiographic setting of the Great Lakes mixed pine ecosystem is generally characterized by a moist low boreal and subhumid low boreal climate (11). Mean annual precipitation varies from 50 cm in the west to 70-80 cm in the eastern parts of the region. Annual summer temperatures average 14oC to 15.5oC, while winter temperatures average -13oC. Climatic variation arises from location relative to the Great Lakes. Lake influences on temperature and precipitation occur closer to shorelines of all the Great Lakes, increasing the length of the growing season and influencing average temperatures, extreme temperatures, and the amount and timing of precipitation. The lake effect results in moderated temperature regimes in the eastern part of the region. The climate is considerably more "continental," with extreme minimum winter temperatures and short growing seasons in the western part of the region.

Potential Vulnerabilities

The Great Lakes mixed pine ecosystem occurs on sand to loamy sand soils derived from glacial outwash and ice-contact topography (1). The soil moisture regime is dry-mesic to xeric and as such, a decrease in growing season soil moisture under a warmer, drier climate could negatively impact the system in several ways. Higher growing season temperatures, combined with reduced summer precipitation, will result in greater plant water deficits, if evapotransporation demand exceeds moisture availability more frequently and for longer duration. Reduced photosynthetic capacity, growth, and tree vigor are likely consequences. Increasing atmospheric CO2 concentration may increase growth in the short term, but the long-term response is not clear at present. For example, increasing ground-level ozone concentrations, which can damage forest trees, as well as soil moisture limitations, may offset the positive effect of CO2 fertilization on growth.

Odocoileus virginianus) is a significant problem in many parts of the region (2). In Minnesota, for example, it is virtually impossible to regenerate eastern white pine, and often jack and red pines, without browse protection of some type (3). It is difficult to predict how white tail deer will respond to a climate that is expected to be warmer, with potentially deeper snowpack in winter.

Dryer conditions during the growing season may result in reduced moisture of woody fuels more frequently in space and time, with a concurrent increased risk of wildfire. While the Great Lakes mixed-pine ecosystem is fire dependent, fuels build up due to long-term fire suppression poses a significant risk of catastrophic wildfire in many locations. This may be particularly true if fuels are drier. Soil moisture deficits during the growing season will also exacerbate the potential for wildfire. More frequent heavy rainstorms accompanied by high winds may result in increased blowdown, particularly of older pines, as both red and eastern white pine can reach super-dominant crown positions, with high wind exposure.

  • Pre-settlement distribution of Great Lakes pine forest within the Lake States.

    Pre-settlement distribution of Great Lakes pine forest within the Lake States.

  • Red pine stand thinned

    Red pine stand thinned and maintained at 13.8 m2/ha (60 ft2/ac). Thinning may help increase forest resilience to climate change. Credit: Christel Kern.

  • Prescribed surface fire during the growing season controls understory shrub proliferation in pine forests.

    Prescribed surface fire during the growing season controls understory shrub proliferation in pine forests. Credit: Christel Kern.

  • multi-cohort pine forest

    Early settlement example of a structurally complex, mixed-species, multi-cohort pine forest. Greater diversity may lead to greater resilience to climate changes.

Warmer, drier growing season conditions, along with milder winter temperatures, may shift competitive advantage towards more generalist species, and those currently at the northern edge of their distribution in the region. For instance, habitat suitability for several currently minor oak (Quercus) species is projected in increase (4), as is that for species that currently do not occur in the region, such as eastern red cedar (Juniperus virginiana). In contrast, predictions suggests a moderate reduction in habitat suitability for eastern white pine and substantial reductions for red pine throughout much of the region, with both low and high emission scenarios (4). Other species that occur in the mixed-pine ecosystem, including trembling aspen, paper birch and balsam fir, are projected to have large declines in habitat suitability as well.

Potential compositional changes may lead to long-term effects on fuels and fire risk that are complex and unpredictable. If CO2 fertilization and milder temperatures increase productivity, fuel loadings may increase and potentially fire risk along with this. Alternatively, drier growing season conditions could reduce productivity and thus the standing crop of fuels. Additionally, shifts in composition to species producing less flammable fine fuels, such as maples, could lead to decreased fire risk.

Insect and disease pests of red and eastern white pine may respond to climate change in ways that increase tree mortality. Changes in pest populations could result directly from changes in climatic factors. For example more frequent drought could increase bark beetle outbreaks, a potentially serious threat to eastern white and red pines. Climate change may result in more complex interaction with other environmental changes. For example, populations of Ips bark beetles are greater on red pine with bole scorch from surface fire, resulting in increased mortality (5). If fire is more frequent with climate change, bark beetle-induced loss of vigor and mortality may increase as well.

Management Options

Several of the general strategies outlined in ‘Silviculture for climate change’ may have relevance for managing Great Lakes mixed pine ecosystems in the face of climate change. These strategies can be broadly segregated into resistance, resilience, and response or facilitation strategies (6), although there is some ambiguity in assigning specific approaches to a broad strategy.

Resistance

Resistance strategies may include activities that, at least in the short-term, greatly increase regeneration of species that are expected to have reduced habitat suitability in the future, such as red pine and eastern white pine. Increased use of prescribed surface fire to create appropriate seedbeds and reduce competing understory vegetation may be one such strategy.

Corylus Americana, Corylus cornuta). This response may negate potential enhancement of soil moisture availability to overstory trees. As such understory control may need to be more widely practiced than it currently is. Greater use of growing season prescribed fire would help reduce hazel populations (7). As with other forest types, thinning may also help to reduce the potential outbreaks of density dependent pest species, such as bark beetles.

Resilience

A primary resilience strategy involves restoring and sustaining the native species and structural conditions currently associated with reference conditions for the Great Lakes mixed-pine ecosystem. The specific magnitudes of climate changes, especially for precipitation, are still uncertain and the exact response of various tree species is not well understood. As such, hedging one’s bet and increasing options for the future by maintaining the full suite of native species in the ecosystem is appropriate. There is tremendous opportunity to restore native species composition in the Great Lakes mixed pine ecosystem (8), as much of the current resource occurs in near mono-specific stands (often plantations) of either red pine or eastern white pine. Generalist species, such as red maple (Acer rubrum), and those with a more southerly distribution such as some oaks (Quercus spp.), that currently are a minor components of a stand may be favored by a resilience strategy, under the premise that conditions for their survival, growth, and fecundity may be enhanced in the future. Density management may be a tool to promote resilence of these species if they already occur in a stand. Specifically, thinning during the stem exclusion stage of stand development may prevent their competitive exclusion and allow them to recruit to the overstory.

The structural condition of many pine stands in the region is greatly simplified, relative to reference conditions. The later is inclusive of multi-cohort stands (8), as well as "even-aged" stands composed of one dominant cohort, along with a smaller population of older individuals. Concurrent with these age structures is greater complexity and heterogeneity in vertical and horizontal canopy distribution, greater amounts of large dead wood, and greater ranges of tree sizes, including very large individuals. The greater diversity of tree age and sizes may allow more flexibility of a species to persist in the face of climate change, if certain age or size classes are less susceptible to drought or other negative influences. As such, a resilience strategy may involve restoration of more complex age and size structures in forest of the region.

Response

Managing native species composition, as a strategy to adapt the system to climate change may meet with limited success in the long-term. Red pine, along with most of the associated "boreal" species, are predicted to face habitat conditions that are not suitable for long-term sustainability of populations. Thus, as a response strategy to facilitate the transition of forests to a new state, the silviculturist may also begin considering compositional manipulation that is currently outside the norm of practice. Initially, this may include the introduction of more southerly genotypes of contemporarily occurring species. This should be fairly straightforward when the species under consideration is widely regenerated artificially, as are both eastern white and red pines and some oaks. However, this approach may require relaxing seed source regulations, so as to allow material from outside of currently acceptable ranges.

A more controversial approach, but one that is gaining attention, is assisted migration of species not currently part of the contemporary ecosystem. In the Great Lakes mixed pine ecosystem, this might include, for example, eastern red cedar and short leaf pine. Assisted migration of species not currently part of the ecosystem should only be "experimented" with on a limited basis in the short-term. The problem with habitat suitability projections for these species is that the occurrence and magnitude of extreme climatic events, particularly extreme low temperatures, may not be well predicted in models. While average temperature or precipitation may begin to coincide with a species range requirements, the occurrence of even one deep freeze could decimate populations of these "formerly" southern species.

References


  1. MN DNR. 2003. Field Guide to the Native Plant Communities of Minnesota: The Laurentian Mixed Forest Province. Minnesota Department of Natural Resources. St. Paul, MN. Order through
  2. Rooney, T. P.; Waller, D. M. 2003. Direct and indirect effects of white-tailed deer in forest ecosystems. Forest Ecology and Management. 181: 165-176.
  3. Palik, B.; Johnson, J. 2007. Constraints on pine regeneration in northern Minnesota: causes and potential solutions. Report to the Minnesota Forest Resources Council, St. Paul, MN.
  4. Prasad, A.M.; Iverson, L.R. 1999-ongoing. A Climate Change Atlas for 80 Forest Tree Species of the Eastern United States [database]. http://www.fs.fed.us/nrs/atlas/, Northeastern Research Station, USDA Forest Service, Delaware, Ohio.
  5. Santoro, A.E.; Lombardero, M.J.; Ayres, M.P.; Ruel, J. J. 2001. Interactions between fire and bark beetles in an old growth pine forest. Forest Ecology and Management. 144: 245-254.
  6. Millar, C.I., Stephenson, N.L., Stephens, S.L. 2007. Climate change and forests of the future: managing in the face of uncertainty. Ecological Applications 17: 2145-2151.
  7. Buckman, R. E. 1964. Effects of prescribed burning on hazel in Minnesota. Ecology. 45: 626-629.
  8. Palik, B.; Zasada, J. 2003. An Ecological Context for Regenerating Multi-cohort, Mixed-species Red Pine Forests. USDA Forest Service Research Paper NC-382.
  9. Frelich, L.E. 1995. Old forest in the Lake States today and before European settlement. Nat. Areas J., I5: 157- 167.
  10. Schmidt, T. L.; Spence, J. S.; Hansen, M.H. 1996. Old and potential old forest in the Lake States, USA. Forest Ecology and Management. 86: 81-96.
  11. Kling, G.W.; Hayhoe, K.; Johnson, L.B.; Magnuson, J.J.; Polasky, S.; Robinson, S.K.; Shuter, B.J.; Wander, M.M.; Wuebbles, D.J.; Zak, D.R.; Lindroth, R.L.; Moser, S.C.; Wilson, M.L. 2003. Confronting Climate Change in the Great Lakes Region: Impacts on our Communities and Ecosystems.Union of Concerned Scientists, Cambridge, Massachusetts, and Ecological Society of America, Washington, D.C.

How to cite

Anderson, P.; Palik, B. (October, 2011). Regional examples of silvicultural adaptation strategies: Western Great Lakes Mixed-Pine Ecosystem. U.S. Department of Agriculture, Forest Service, Climate Change Resource Center. www.fs.usda.gov/ccrc/topics/silviculture/western-great-lakes