Forests in the semiarid southwestern U.S. are expected to be highly vulnerable to increasing aridity anticipated with climate change. In particular, low elevation forests and the processes of tree regeneration and mortality are likely to be highly susceptible to climate change. This work seeks to characterize how, where and when forest ecosystems will change and identify management strategies to promote resilience.
Background & Importance
Climate change, as well as elevated climatic extremes, represents a major challenge facing forest managers, policy makers and forest scientists today. In particular, severe drought events cause widespread tree mortality and decreased growth in forest habitats across the globe, including areas with cool and mesic climates where drought impacts are not widely recognized. As the reality of climate change and increasing drought frequency and severity become clear, forest managers seek strategies to increase adaptation capacity, specifically by promoting forest resistance (minimizing negative impacts during the drought) and resilience (maximizing recovery rates following drought). Ecological theory suggests that forests with greater complexity and biodiversity should have greater capacity to resist change and or recover ecosystem function in the face of drought. However, the applicability of this theory to practical habitat conservation and forest management are unclear.
General Methods
Forest managers and policy makers need actionable results about management practices that enhance forest adaptation to increasing aridity. Approaches to filling these interacting knowledge gaps are largely undeveloped, especially approaches for identifying and developing management strategies. SBSC researchers, in cooperation with researchers at universities and the US Forest Service, are working to characterize how climate change will impact forest regeneration, growth and mortality over broad climatic gradients, and to quantify the efficacy of forest management strategies designed to promote resistance and resilience to drought. This work includes several projects supported by funding from the U.S. Forest Service, the Western Wildland Environmental Threat Center and the National Science Foundation.
Important Results
Tree regeneration is highly sensitive to soil moisture conditions and may already be reflecting tree migration
Our regional-scale study indicated that regeneration of many tree species is already shifting upslope and to wetting conditions, setting the stage for future tree distribution changes.
However, many species have nowhere to go
Mountainous terrain has very limited migration options for higher-elevation species. Our work quantified that subalpine fir and Engelmann spruce, in particular, have very limited opportunity for migration to maintain climatic suitability, while ponderosa pine has more potentially suitable future locations.
Forest management can promote drought resistance and minimize future tree mortality
Our research indicated that reducing forest density, an easily manipulated forest structural condition may allow remaining individual trees to more effectively survive harsh drought conditions. Results indicate that thinning can decrease drought-induced growth declines and tree mortality, providing an opportunity for forest managers to guide transitions to future forests.
Future Directions
Identifying forest management strategies that maximize climate resilience
Building upon several long-term forest management experiments, this project is identifying characteristics that can help trees sustain growth and avoid mortality despite changing climate and increasing climatic variability.
Describing west-wide patterns and controls over tree mortality
This project is teasing apart the individual and combined effects of climate, weather, disease and competition on aspen mortality.
Lower forest ecotones: the key to forest sustainability
This project will assess how lower forest boundaries in dryland ecosystems respond to changing climate and disturbance and assess forest vulnerability and sustainability. Results will provide valuable information for land managers about the future distribution and abundance of forests in the southwest U.S.
Quantifying future changes in ecosystem carbon stocks
This work will quantify how shifts in the distribution of forests in the western U.S. will impact carbon cycling and storage, potentially providing a feedback to increasing atmospheric CO2.
Incorporating drought extremes into tree niche modeling
This work will enhance niche models by integrating the influence of extremes in ecological drought – both unusually wet conditions that facilitate episodic regeneration and unusually dry conditions that cause tree mortality.
Below are other science projects associated with this project.
Colorado Plateau Futures: Understanding Agents of Change on the Colorado Plateau to Facilitate Collaborative Adaptation
Southwest Energy Exploration, Development, and Reclamation (SWEDR)
Dryland Forest Sustainability
Plant Responses to Drought and Climate Change in the Southwestern United States
Aeolian Dust in Dryland Landscapes of the Western United States
RAMPS: Restoration Assessment & Monitoring Program for the Southwest
Chronic Drought Impacts on Colorado Plateau ecosystems (Rain-Out Experiment)
Big Sagebrush Ecosystem Response to Climate & Disturbance
Colorado Plateau Extreme Drought in Grassland Experiment (EDGE)
- Overview
Forests in the semiarid southwestern U.S. are expected to be highly vulnerable to increasing aridity anticipated with climate change. In particular, low elevation forests and the processes of tree regeneration and mortality are likely to be highly susceptible to climate change. This work seeks to characterize how, where and when forest ecosystems will change and identify management strategies to promote resilience.
Background & Importance
Climate change, as well as elevated climatic extremes, represents a major challenge facing forest managers, policy makers and forest scientists today. In particular, severe drought events cause widespread tree mortality and decreased growth in forest habitats across the globe, including areas with cool and mesic climates where drought impacts are not widely recognized. As the reality of climate change and increasing drought frequency and severity become clear, forest managers seek strategies to increase adaptation capacity, specifically by promoting forest resistance (minimizing negative impacts during the drought) and resilience (maximizing recovery rates following drought). Ecological theory suggests that forests with greater complexity and biodiversity should have greater capacity to resist change and or recover ecosystem function in the face of drought. However, the applicability of this theory to practical habitat conservation and forest management are unclear.
A wildfire burned this area in northern Arizona more than 20 years before the picture was taken, but regeneration is extremely limited. Our research is working to understand this episodic regeneration and forecast the consequences of climate change for dryland forests. (Credit: John Bradford, USGS. Public domain.) General Methods
Forest managers and policy makers need actionable results about management practices that enhance forest adaptation to increasing aridity. Approaches to filling these interacting knowledge gaps are largely undeveloped, especially approaches for identifying and developing management strategies. SBSC researchers, in cooperation with researchers at universities and the US Forest Service, are working to characterize how climate change will impact forest regeneration, growth and mortality over broad climatic gradients, and to quantify the efficacy of forest management strategies designed to promote resistance and resilience to drought. This work includes several projects supported by funding from the U.S. Forest Service, the Western Wildland Environmental Threat Center and the National Science Foundation.
Important Results
Tree regeneration is highly sensitive to soil moisture conditions and may already be reflecting tree migration
Our regional-scale study indicated that regeneration of many tree species is already shifting upslope and to wetting conditions, setting the stage for future tree distribution changes.
However, many species have nowhere to go
Mountainous terrain has very limited migration options for higher-elevation species. Our work quantified that subalpine fir and Engelmann spruce, in particular, have very limited opportunity for migration to maintain climatic suitability, while ponderosa pine has more potentially suitable future locations.
Forest management can promote drought resistance and minimize future tree mortality
Our research indicated that reducing forest density, an easily manipulated forest structural condition may allow remaining individual trees to more effectively survive harsh drought conditions. Results indicate that thinning can decrease drought-induced growth declines and tree mortality, providing an opportunity for forest managers to guide transitions to future forests.
Future Directions
Identifying forest management strategies that maximize climate resilience
Ponderosa pine stand in northern Arizona destroyed by fire about 20 years past. There has been very little regeneration by ponderosa pine since the fire. (Credit: John Bradford, USGS. Public domain.) Building upon several long-term forest management experiments, this project is identifying characteristics that can help trees sustain growth and avoid mortality despite changing climate and increasing climatic variability.
Describing west-wide patterns and controls over tree mortality
This project is teasing apart the individual and combined effects of climate, weather, disease and competition on aspen mortality.
Lower forest ecotones: the key to forest sustainability
This project will assess how lower forest boundaries in dryland ecosystems respond to changing climate and disturbance and assess forest vulnerability and sustainability. Results will provide valuable information for land managers about the future distribution and abundance of forests in the southwest U.S.
Quantifying future changes in ecosystem carbon stocks
This work will quantify how shifts in the distribution of forests in the western U.S. will impact carbon cycling and storage, potentially providing a feedback to increasing atmospheric CO2.
Incorporating drought extremes into tree niche modeling
This work will enhance niche models by integrating the influence of extremes in ecological drought – both unusually wet conditions that facilitate episodic regeneration and unusually dry conditions that cause tree mortality.
- Science
Below are other science projects associated with this project.
Colorado Plateau Futures: Understanding Agents of Change on the Colorado Plateau to Facilitate Collaborative Adaptation
The objective of this interdisciplinary research effort is to 1) characterize agents of change important to land management decision makers on the Colorado Plateau; 2) identify and analyze relationships between agents of change and key landscape attributes and processes; 3) collectively assess the influence of agents of change and attributes and processes on the services provided by the ecosystem...Southwest Energy Exploration, Development, and Reclamation (SWEDR)
Approximately 35% of the US and approximately 82% of DOI lands are “drylands” found throughout the western US. These lands contain oil, gas, oil shale, shale oil, and tar sand deposits and the exploration for and extraction of these resources has resulted in hundreds of thousands of operating and abandoned wells across the West. These arid and semi-arid lands have unique soil and plant communities...Dryland Forest Sustainability
Forests in the semiarid southwestern U.S. are expected to be highly vulnerable to increasing aridity anticipated with climate change. In particular, low elevation forests and the processes of tree regeneration and mortality are likely to be highly susceptible to climate change. This work seeks to characterize how, where and when forest ecosystems will change and identify management strategies to...Plant Responses to Drought and Climate Change in the Southwestern United States
Land managers face tremendous challenges in the future as drought and climate change alter the abundance, distribution, and interactions of plant species. These challenges will be especially daunting in the southwestern US, which is already experiencing elevated temperatures and prolonged droughts, resulting in reduced soil moisture in an already water-limited environment. These changes will...Aeolian Dust in Dryland Landscapes of the Western United States
Dust emission caused by wind erosion has received considerable attention because of its far-reaching effects on ecosystems, including the loss of nutrients and water-holding capacity from source areas, changes to climate and global energy balance in areas where dust is entrained in the atmosphere, fertilization of terrestrial and marine ecosystems, in addition to decreases in snow albedo, causing...RAMPS: Restoration Assessment & Monitoring Program for the Southwest
The Restoration Assessment and Monitoring Program for the Southwest (RAMPS) seeks to assist U.S. Department of the Interior (DOI) and other land management agencies in developing successful techniques for improving land condition in dryland ecosystems of the southwestern United States. Invasion by non-native species, wildfire, drought, and other disturbances are growing rapidly in extent and...Chronic Drought Impacts on Colorado Plateau ecosystems (Rain-Out Experiment)
In drylands, chronic reductions in water availability (press-drought) through reduced precipitation and increased temperatures may have profound ecosystem effects, depending on the sensitivities of the dominant plants and plant functional types. In this study, we are examining the impacts of moderate, but long-term chronic drought using a network of 40 drought shelters on the Colorado Plateau...Big Sagebrush Ecosystem Response to Climate & Disturbance
Big sagebrush ecosystems are a major component of landscapes in the western U.S. and provide vital habitat to a wide array of wildlife species. However, big sagebrush ecosystems have been dramatically impacted by disturbances in the past several decades. This collaborative research between USGS and the University of Wyoming focuses on understanding how climatic and soil conditions influence big...Colorado Plateau Extreme Drought in Grassland Experiment (EDGE)
In drylands, short-term extreme droughts can have profound ecosystem effects, depending on the timing (seasonality) of drought and the sensitivities of the dominant plants and plant functional types. Past work suggests that cool season drought may disproportionately impact regionally important grass and shrub species. In this study, we are examining the impacts of extreme seasonal drought on... - Publications
- Partners