Adaptive Silviculture for Climate Change In San Juan National Forest

Introduction

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Forest ecosystems across the United States are facing multiple climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.

Learn more about climate change related stressors including an increase in drought, wildfire, insect, and disease pressure. Developing usable management strategies to help forests adapt to these stressors requires an understanding of the ecological, social, and economic impacts of climate change. Individual natural resource managers require support accessing the knowledge, skills, and resources needed to develop effective climate adaptation strategies for the forests they manage. Resource managers have also expressed the need for more examples of effective adaptation projects that they can learn from to inform management strategies.

The Adaptive Silviculture for Climate Change (ASCC) project is a multi-region network of research sites that responds to these needs by developing and testing climate adaptation strategies across diverse forest ecosystems. The ASCC sites develop and test three climate adaptation strategies along a gradient according to the level of desired change and method of adaptation. Each ≥25 acre treatment is replicated four times (for statistical significance) and the total study area of each site extends over 400-500 acres, matching the size of most forest management contracts. The management strategies span from resistance–which seeks to maintain forest composition, structure structure
Something temporarily or permanently constructed, built, or placed; and constructed of natural or manufactured parts including, but not limited to, a building, shed, cabin, porch, bridge, walkway, stair steps, sign, landing, platform, dock, rack, fence, telecommunication device, antennae, fish cleaning table, satellite dish/mount, or well head.

Learn more about structure , and function–to transition, which facilitates change in forest composition, structure, and function by enabling the ecosystem to adaptively respond to climate change (Nagel et al., 2017; Swanston et al. 2016; Millar et al. 2007). In 2014 a diverse group of regional scientists, land managers, climate experts, and non-governmental organization (NGO) personnel participated in a three day collaborative workshop to discuss adaptation approaches and tactics for forest management treatments at the San Juan National Forest (SJNF) in Southwestern Colorado. During the three-day workshop, participants identified desired future conditions and developed climate adaptation treatments that align with the SJNF’s overarching forest plan and help the Forest adapt to the impacts of climate change. 

The SJNF Adaptive Silviculture for Climate Change (ASCC) study site includes dry mixed-conifer forest types, rare for Colorado but common in Arizona and New Mexico. These forests contain ponderosa pine (Pinus ponderosa; PP), Douglas-fir (Pseudotsuga menziesii; DF), white fir (Abies concolor; WF), aspen, and a shrubby component of Gambel oak (Quercus gambelii). Each species has specific strategies and tolerances to cope with drought, fire, insects, and disease. The history of fire exclusion and logging of larger ponderosa pine trees increase the risk of large fires. Prior to 1873, the mean fire interval was between 10 and 30 years with a mean fire interval of 24 years at the ASCC site in the San Juan National Forest. This fire interval has been dramatically reduced since policies of fire suppression and other land management factors reduced fire frequency. Furthermore, the SJNF is surrounded by residential communities in the Wildland Urban Interface (WUI) that are at risk of damage if severe wildfires burn through the forest. This management history and mix of species provides an excellent opportunity to test various management strategies for dry mixed-conifer forests. Since the SJNF has already experienced significant climate-driven and human impacts it is representative of many of the challenges similar forests will face in the future as climate change accelerates. 

Key Issues Addressed

The climate impacts that the ASCC management strategies at the SJNF seek to address include increased pressure from insects such as bark beetles, and fir engraver, as well as root diseases and dwarf mistletoe. Additionally, reduced fire frequency has increased the density of young coniferous trees in the SJNF. In combination with increased density of shrub-like Gambel oak, these young trees act as ladder fuels when fire occurs, allowing fire to reach the canopy of larger and older conifers that increases fire severity. They also increase competition for limited water resources further exacerbating impacts of drought, disease, and insect damage.

Because there are few examples of effective large-scale management strategies to help forests adapt to the impacts of climate change, managers often do not know how to start designing and implementing effective forest management. By developing operational-scale research treatments, the San Juan ASCC site will provide a real-world example of implementable forest prescriptions that managers for similar forests can learn from.

Developing, monitoring, and implementing forest treatments that can help the SJNF respond to the pressures it is facing from climate change requires knowledge and resources that may not be available to individual forest managers. Creating implementable treatments therefore requires input from a variety of experts and forest managers with specialized knowledge and experience that can provide additional contemporary resources, knowledge, and examples to supplement the work that forest managers are already doing to support forest health in the face of climate pressures.

Project Goals

• Introduce natural resource managers to conceptual tools and approaches that help integrate climate change into resource management and silvicultural decision making.
• Identify desired future conditions, management objectives and on-the-ground actions for dry mixed-conifer stands in the San Juan National Forest for three climate adaptation options (resistance, resilience, and transition) that can help respond to the impacts of climate change including drought, fire, insect and disease pressures.
• Provide real-world examples of climate adaptation strategies for forest managers through robust, operational-scale treatments at the San Juan National Forest.

Project Highlights

Opening Doors: The scale and statistical rigor of this project will allow other researchers, including The Nature Conservancy and USDA, to pursue related research questions at the site. For example, how treatments will affect snowpack.

• Broad Representation in Workshops & Leadership: Planning for each ASCC site begins with a collaborative workshop that brings together managers, regional scientists, and climate experts to discuss adaptation approaches and tactics for forest management treatments. Engaging a core team of managers, researchers, and other stakeholders with diverse expertise was critical to workshop success. Similarly, participation from subject matter specialists (wildlife biologists, fuels and suppression specialists, silviculturists, soil scientists, biogeochemists, hydrologists, and more) helped workshop participants learn about climate impacts and develop effective and realistic silvicultural prescriptions.
• Workshop and Prescription Plans: Guided by the Northern Institute of Applied Climate Science (NIACS) Adaptation Workbook process, a team of natural resource specialists and researchers developed three forest prescriptions to help the San Juan National Forest adapt to the impacts of climate change during a three-day workshop. 
  • Resistance: This prescription helps the San Juan National Forest resist the impacts of climate change (fire, disease, insects) while maintaining the current tree species composition, structure, and function. To reduce drought stress, insect and disease pressure, and chances of catastrophic fires, managers will reduce the basal area of trees to 60-90 ft²/ac. When reducing basal area, managers will preferentially remove young and small trees, especially white fir, and trees affected by disease or insects while maintaining consistent spacing between trees throughout the forest. Removing small and diseased trees and reducing tree density will allow for regular fires to pass through the forest and knock back the shrubs and young conifers that act as ladder fuels. 
  • Resilience: The resilienceprescription will help the San Juan National Forest become more resilient to fire by creating a heterogeneous structure with openings from 1/2 acre up to 2 acres in size, expanding existing openings in the forest canopy and retaining trees in closely spaced groups with different sizes and species. This breaks up connected fuels during fires and reduces stress from drought, insects, and diseases. Additionally, managers will reduce tree density to a similar basal area as the resistance prescription (60-90 ft²/ac), preferentially retaining ponderosa pine, a more fire-adapted and drought tolerant species, and cutting young and diseased white fir and Douglas-fir.
  • Transition: This prescription was developed to actively support the transition of the forest towards a more heterogeneous structure, and species composition dominated by drought-tolerant and fire-adapted ponderosa pine. This will be achieved by removing nearly all (80-90%) white fir as well as most of the smaller Douglas-fir and ponderosa pine trees. The basal area will be reduced more than the resistance and resilience prescriptions to an average of 40 ft²/ac. When removing trees, managers will create openings of up to 2 acres, similar to the resilience prescription. Additionally, aspens will be retained in swales on north slopes.
• Forest Modeling for Scenario Planning: Forest Vegetation Simulator (FVS) models (Crookston and Dixon, 2005) allowed workshop participants to evaluate how future climate conditions will alter forest structure and composition up to 30 years in the future. This allowed participants to evaluate tradeoffs between implementation costs, forest health considerations, and other management benefits and drawbacks of the different forest prescriptions, as well as to determine when follow up actions might be needed after initial implementation to maintain desirable forest conditions. The FVS models also help participants design prescriptions likely to result in a forest that can support economically sustainable timber harvesting in 30 years. This could allow the management to “pay for itself” in the long-run. 

Lessons Learned

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The forest prescriptions developed during the initial workshop in 2014 have yet to be implemented. Due to the large scale of the San Juan ASCC project and the absence of a robust timber industry in the region at the time of the workshop, prescriptions needed to be implemented under a “long-term stewardship contract”. These long-term stewardship contracts are carried out over an extended timeline instead compared to shorter-term stand-alone projects but allowed for a larger scope of work. Therefore, in situations when there is not a robust local timber industry, undertaking smaller-scale demonstration projects that can be implemented as stand-alone projects might be able to result in more immediate implementation compared to longer-term and larger-scale long-term stewardship contracts.

The planning workshop was an introduction for staff at the San Juan National Forest and surrounding lands to learn about “Ecological Forestry” that takes social, biophysical, and economic factors into account. Staff were already thinking along these lines in their forest restoration and timber management projects and the workshop brought in additional resources, knowledge, and expertise to continue along this track. 

During the three-day workshop where participants developed silviculture prescriptions for the San Juan National Forest ASCC site, there was no representation from the timber industry, and only a few soil scientists with expertise in biogeochemistry. The timber industry is a key partner in many forest management projects because of their access to the equipment, capital, and knowledge that enables treatment of large acreages for management activities such as thinning. However, because there was not a robust forest industry in Southern Colorado at the time of the original workshops in 2014, organizers were unable to find timber industry representatives to attend. In future workshops, organizers could seek participation of timber industry representatives from other regions if no local industry exists. Because soil scientists and biogeochemists are able to understand how treatments implemented in areas with different soils are likely to succeed or fail depending on soil conditions, their participation is highly valuable. Outreach to staff soil scientists at organizations such as the National Resource Conservation Service and USDA Agricultural Research Service would benefit future workshops.

In 2014, the forestry, restoration, and silviculture community were just beginning to consider the concept of assisted migration, where managers plant species that will do better in projected future climate conditions than current species compositions. In retrospect, some members of the San Juan ASCC project wish they had considered assisted migration strategies that consider planting species more common in Arizona and New Mexico into the San Juan National Forest that is in the northernmost extent of this forest bioregion.

Being able to get out into the field together is a valuable part of planning land management treatments. Unfortunately, because of high snowpack at the San Juan National Forest in early March, workshop participants were unable to gather together on the land when discussing treatments. Because of how valuable it is to get together on the land, it is best to plan workshops and other in-person events at a time of year where it is likely that participants will be able to visit the study site. 

The treatments developed during the workshop meet the ASCC network’s goals of developing climate adaptation strategies and the SJNF overarching goals related to protecting wildlife, reducing erosion, and protecting nearby communities from fire. This was achieved by bringing together managers, scientists, and climate experts to share conceptual tools and approaches that integrate climate change into resource management and forest decision making. The results can be used by forest managers in dry mixed-conifer forests across the Southwestern USA to ensure forests provide key ecosystem services and values in the future despite uncertain climate projections.

Next Steps

• Work with partners to implement the three climate adaptation management strategies developed during the 2014 workshop as the long-term stewardship contract approach their end date.
• Once the treatments are implemented, monitoring is an essential component of the ASCC study design. Managers and researchers will be monitoring natural regeneration in gaps and harvest areas, soil nutrients and microclimates, and ladder fuels and understory plants at the San Juan National Forest ASCC site. 
• Add fire simulations to the current Forest Vegetation Simulation model to help understand future fire behavior in the three climate adaptation management strategies.
• Partnering with other sites in the ASCC Network, the San Juan National Forest ASCC site can begin to ask cross-site management and research questions to determine how resistance, resilience, and transition compare across forest types and if they are achieving local management goals and objectives into the future under a changing climate. 

Funding Partners

• USDA Forest Service, Rocky Mountain Research Station
• USDA Forest Service, Western Wildland Environmental Threat Assessment Center

Resources

• Adaptive Silviculture for Climate Change website

• San Juan National Forest ASCC

• NIACS Adaptation Workbook
• Climate Change Response Framework: Summary of San Juan National Forest ASCC project 
• San Juan Adaptive Silviculture for Climate Change Forest Prescriptions 
  • Overview
  • Resistance
  • Resilience
  • Transition
  • Map
• Nagel L.M., et al. (2017) “Adaptive Silviculture for Climate Change: A National Experiment in Manager-Scientist Partnerships to Apply an Adaptation Framework”. Journal of Forestry 115(3):167-178 
• Swanston et al. (2016) ”Forest Adaptation Resources: Climate Change Tools and Approaches for Land Managers, 2nd edition” USDA Forest Service Northern Research Station General Technical Report NRS-GTR-87-2 
• Millar C.I., Stephenson N.L., and Stephens S.L. (2007) “Climate Change and Forests of the Future: Managing in the Face of Uncertainty” Ecological Applications 17(8):2145-2151
• Crookston, N.L., and Dixon, G.E. (2005) “The forest vegetation simulator: A review of its structure, content, and applications” Computers and Electronics in Agriculture 49(1):60-80

Contacts

• Mike Battaglia, USDA Forest Service: michael.battaglia@usda.gov
• Timothy Leishman, USDA Forest Service: timothy.leishman@usda.gov
• Courtney Peterson, Colorado State University, Northern Institute of Applied Climate Science: courtney.peterson@colostate.edu

CART Lead Author

Ariel Léger, CART: arielleger@arizona.edu

Suggested Citation

Léger, A., M., and Rumble, M. (2022). “The Adaptive Silviculture for Climate Change Project in the San Juan National Forest.” CART. Retrieved from https://www.fws.gov/project/adaptive-silviculture-climate-change-san-juan-national-forest.