• Start-up
  • Planning
  • Action
  • Evaluation

The San Juan National Forest has worked with partners to design and implement a silvicultural study for climate change adaptation. 

The San Juan National Forest is participating in a multi-region study called Adaptive Silviculture for Climate Change (ASCC). The goals of this project are to test different silvicultural approaches to climate change adaptation that will also serve as useful examples across the country.

Project Area

San Juan National Forest ASCC Site
The San Juan National Forest Adaptive Silviculture for Climate Change (ASCC) study site was established on Jackson Mountain in Southwestern Colorado, ranging in elevation from 7,400 to 8,600 feet. The site has deep, well-drained, loamy soils, and variability in aspect with deep drainages and slopes from 0 to 35%.

The San Juan ASCC project is located within a dry mixed conifer forest type, containing various tree species including ponderosa pine, Douglas-fir, white fir, aspen, and a shrubby component of Gambel oak. Each species has specific strategies and tolerances to cope with drought, fire, insects, and disease, and provides an excellent opportunity to test various management treatment strategies to inform future management of these forests.

Prior to 1873, the mean fire interval was about 30 years in the San Juan National Forest. The area was lightly logged over 50 years ago as indicated by large ponderosa pine stumps. In the mid-1970s through early 1980s, a prep cut of a two-stage shelterwood was implemented removing mainly large diameter ponderosa pine and Douglas-fir. Over the past several decades, the area has been subjected to a range of insects such as western pine beetle, fir engraver, and Douglas-fir beetle, as well as root diseases and dwarf mistletoe.

Management Goals

A team of natural resource specialists and researchers from the region came together for a three-day workshop to develop the silviculture prescriptions for the San Juan National Forest ASCC site. The team developed a set of desired future conditions, management objectives, and tactics for the San Juan National Forest based on three climate adaptation approaches (resistance, resilience, and transition). These three treatments are summarized briefly below:

Resistance

  • Retain the same species composition as in pre-harvest stand of ponderosa pine, Douglas-fir, and aspen, with a slight reduction in white fir, and maintain all species, especially if poorly represented. 
  • Maintain even and consistent spacing.
  • Retain stand structure to resist the increase of growing space for shrub components and the likelihood of creating a new cohort of conifers that would act as ladder fuels to the existing co-dominants and dominants in the stands.    

Resilience

  • Heavily favor fire-adapted and drought tolerant species across all size classes and create openings in the stand.
  • Create high variability in spacing with openings up to 1 acre. 
  • Expand openings off of existing natural openings in the stand structure. 
  • Retain trees in closely spaced legacy groups with multiple size classes and species. 
  • Increase drought-tolerant and fire-adapted species (ponderosa pine and Douglas-fir). 

Transition

  • Increase drought-tolerant and fire-adapted species (ponderosa pine and Douglas-fir). Remove all white fir. 
  • Create high variability in spacing with a canopy openness target of 30-40%, average 40 ft2/acre of basal area.
  • Maintain aspen in swales on north slopes. 

Climate Change Impacts

Key projected climate change impacts that the project team considered for the San Juan National Forest include:
A warming trend and increased average annual temperatures
Variable precipitation patterns with decreased snowpack and earlier snowmelt and peak runoffs
Increased drought that may drive fires and insect outbreaks
The relative proportions of component species may change

Challenges and Opportunities

Climate change will present challenges and opportunities for accomplishing the management objectives of this project, including:

Challenges

The dense understory of white fir and Gambel oak currently acts as ladder fuels contributing to wildfire hazard in the area
The forest has been subjected to a range of insects and diseases, such as western pine beetle, fir engraver, Douglas-fir beetle, root disease, and dwarf mistletoe

Opportunities

Interactions of climate change, fire, drought, and insect outbreaks may lead to changes in species dominance for novel species
Increasing structural heterogeneity will break up fuels and reduce the chance of large, catastrophic wildfires

Adaptation Actions

Project participants used the Adaptation Workbook to develop several adaptation actions for this project, including:

Area/Topic
Approach
Tactics
Resistance
retain the same species composition as in pre-harvest stand of ponderosa pine, Douglas-fir, and aspen, with a slight reduction in white fir
retain stand structure to resist the increase of growing space for shrub components and the likelihood of creating a new cohort of conifers that would act as ladder fuels to the existing co-dominants and dominants in the stands
Resilience
thin to 60-80 ft2/acre
create high variability in spacing with openings up to 1 acre
increase drought-tolerant and fire-adapted species (ponderosa pine and Douglas-fir)
Transition
create high variability in spacing with a canopy openness target of 30-40%, average 40 ft2/acre of basal area
increase drought-tolerant and fire-adapted species (ponderosa pine and Douglas-fir)
maintain aspen in swales on north slopes
remove all white fir

Monitoring

Monitoring is an essential component of the ASCC study. Research partners from several institutions are working together to investigate the effectiveness of different silvicultural treatments aimed at creating adaptive ecosystems. Some of the monitoring items include:
Natural regeneration in gaps and harvest areas
Soil nutrients and microclimate sampling
Inventory of fuels and understory plants

Next Steps

Each of the adaptation treatments is replicated 4 times across a 400-acre area on the San Juan National Forest. Pre-treatment forest inventory data has been collected on the study site. The treatment units have been marked for harvest and are scheduled to be cut. Future data collection will focus on tree regeneration, forest growth, and forest health.

Learn more about this project at: https://www.adaptivesilviculture.org/project-site/san-juan-national-forest.

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Keywords

Fire and fuels
Forest types
Management plan