Project Summary
Preparing forests for a changing climate is a growing concern for forest managers. To provide examples of how to integrate climate change adaptation into on-the-ground forest management, the Adaptive Silviculture for Climate Change (ASCC) project established a series of experimental silvicultural trials in different forest ecosystem types. By implementing site-specific treatments based on local conditions and management objectives, the trials are designed to help future forests respond to a changing climate.
The San Juan National Forest in Colorado is a dry, mixed-conifer forest with a historical fire interval of about 30 years. It has been selectively logged in past decades and has experienced various insect and disease outbreaks. The forest’s dense understory contributes to ladder fuels that increase the threat of extreme fires. Climate change is expected to increase average annual temperatures, decrease snowpack, cause earlier snowmelt, increase drought and insect outbreaks, and change the composition and abundance of the forest’s tree species.
A team of natural resource specialists and researchers developed a set of desired future conditions, objectives, and tactics for the San Juan National Forest based on three climate adaptation approaches.
For the resistance option, management strategies include thinning while maintaining even and consistent tree spacing, retaining the existing stand structure, and retaining the same species composition to maintain relatively unchanged conditions over time. For the resilience option, management strategies include favoring fire-adapted and drought-tolerant species, and creating variable stand openings to allow changes in current conditions, but to encourage an eventual return to prior conditions. Finally, under the transition option, management strategies include retaining the most fire-adapted and drought-tolerant species, removing white fir (which serves as a ladder fuel), and creating high variability in canopy openness. Subsequent monitoring that focuses on tree regeneration, forest growth, and forest health will evaluate the forest’s response to these treatments as the climate changes, and will inform future forest management.
The San Juan National Forest in Colorado is a dry, mixed-conifer forest with a historical fire interval of about 30 years. It has been selectively logged in past decades and has experienced various insect and disease outbreaks. The forest’s dense understory contributes to ladder fuels that increase the threat of extreme fires. Climate change is expected to increase average annual temperatures, decrease snowpack, cause earlier snowmelt, increase drought and insect outbreaks, and change the composition and abundance of the forest’s tree species.
A team of natural resource specialists and researchers developed a set of desired future conditions, objectives, and tactics for the San Juan National Forest based on three climate adaptation approaches.
For the resistance option, management strategies include thinning while maintaining even and consistent tree spacing, retaining the existing stand structure, and retaining the same species composition to maintain relatively unchanged conditions over time. For the resilience option, management strategies include favoring fire-adapted and drought-tolerant species, and creating variable stand openings to allow changes in current conditions, but to encourage an eventual return to prior conditions. Finally, under the transition option, management strategies include retaining the most fire-adapted and drought-tolerant species, removing white fir (which serves as a ladder fuel), and creating high variability in canopy openness. Subsequent monitoring that focuses on tree regeneration, forest growth, and forest health will evaluate the forest’s response to these treatments as the climate changes, and will inform future forest management.
Project background and scope
To help inform forest managers who are coping with the vagaries of a changing climate, a team of scientists, land managers, and collaborators formed the Adaptive Silviculture for Climate Change (ASCC) project, which has established a series of experimental silvicultural trials in a network of different forest ecosystems across the U.S and Canada. Each trial is focused on understanding and evaluating management options designed to enable forests to respond to a changing climate. The silvicultural treatments that prepare forests for these different scenarios are tailored to the local conditions of the ecosystem in which each forest is located.
The San Juan National Forest ASCC site is a dry, mixed-conifer forest in southwest Colorado. The warmer, drier conditions that climate change is likely to bring will make this forest more vulnerable to catastrophic fires, as well as to insect and disease outbreaks. To deal with these eventualities, silvicultural prescriptions focus on reducing ladder fuels and creating more open stands. The response of the various treatments to actual climate conditions in the coming years will help inform future forest management for this type of forest.
The San Juan National Forest ASCC site is a dry, mixed-conifer forest in southwest Colorado. The warmer, drier conditions that climate change is likely to bring will make this forest more vulnerable to catastrophic fires, as well as to insect and disease outbreaks. To deal with these eventualities, silvicultural prescriptions focus on reducing ladder fuels and creating more open stands. The response of the various treatments to actual climate conditions in the coming years will help inform future forest management for this type of forest.
Project Process and Implementation
To begin to answer ASCC Network’s core question—what actions can be taken to enhance an ecosystem’s ability to adapt to change while still meeting management goals and objectives—the group brought together a core team of scientists and managers interested in integrating climate change adaptation into their silvicultural planning and management. To accommodate the uncertainty of climate change impacts, the ASCC experiment looks at a spectrum of adaptation options.
Each ASCC Network site begins with a workshop to familiarize local managers and scientists with adaptation approaches and tactics for forest management and design specific climate change adaptation experimental treatments for their ecosystem. While experimental elements are consistent across all study sites, management activities at individual sites are tailored to achieve desired future conditions and to meet local management goals.
Management Objectives
- Test experimental silvicultural approaches to climate change adaptation that can serve as models for similar types of forest ecosystems
- Select for drought-tolerant and fire-adapted species to successfully navigate a warming, drying climate
- Open stands (through selective cutting) and reduce ladder fuels to reduce the chance of extreme wildfire events and outbreaks of damaging insects and diseases
Adaptation Approaches
Forest Vegetation Approaches
- Protect genotypic and phenotypic diversity Tactics:
- Protect trees that are fire adapted
- Protect trees that are drought tolerant
- Increase drought resilience in forests Tactics:
- Increase the amount of thinning and alter thinning prescriptions as needed to meet management objectives
- Create high variability in spacing and canopy openness
- Increase resilience of forest stands to disturbance by increasing tree vigor Tactic:
- Thin to decrease stand density and increase tree vigor
- Increase forest landscape resilience to large and extensive insect or pathogen outbreaks Tactic:
- Expand openings off of existing natural openings in the stand structure
- Promote diversity of forest age and size classes Tactic:
- Retain trees in closely spaced legacy groups with multiple size classes and species in resilience plots
- Increase resilience of existing vegetation by reducing hazardous fuels and forest density and maintaining low densities Tactic:
- Remove all white fir (a ladder fuel) from transition plots
- Manage forest vegetation to reduce severity and patch size; protect refugia (e.g., old trees) Tactic:
- Use gaps in silvicultural prescriptions
- Create landscape patterns that are resilient to past and expected disturbance regimes Tactic:
- Manage for diversity of structure and patch size with mechanical thinning
- Promote disturbance-resilient species Tactic:
- Thin to favor disturbance-resilient species
- Decrease density within stands, and increase structural diversity across the landscape Tactic:
- Reduce density by thinning, with density and structural goals based on past and predicted future conditions
Wildlife Approaches
- Maintain current habitat, restore historical habitat, promote potential future habitat, and increase resilience of these habitats and surrounding habitats Tactic:
- Conduct strategic thinning to create different adaptation strategies for forests under different climate change options: resistance, resilience, transition, and no action
- Increase resilience of late-successional habitat and structure (shrub and forest) and surrounding habitat Tactic:
- Retain trees in closely spaced legacy groups with multiple size classes and species
- Maintain spatial patterns that are resilient to disturbance. Promote habitat and structural heterogeneity and diversity. Maintains landscape permeability. Tactic:
- Create high variability in spacing with variably sized canopy openings
Project Outcomes
The ASCC Network process provides scientists and managers with the necessary tools for integrating climate change considerations into their decision-making. The Network also helps managers to address locally appropriate adaptation actions to address the uncertainties of climate change. In the case of the San Juan National Forest, various prescriptions are being implemented to reduce the potential for extreme wildfire and insect and disease outbreaks in the face of a warming and drying climate. The treatments and resultant findings from the San Juan National Forest’s climate-related management activities along with those of other ASCC Network sites are based on a robust experimental design and will provide a suite of adaptation actions that managers can use in future silvicultural planning.