• Start-up
  • Planning
  • Action
  • Evaluation
The Colorado State Forest is participating in a study called the Adaptive Silviculture for Climate Change (ASCC) Network. The goals of this project are to test different silvicultural approaches to climate change and forest health adaptation that will also serve as useful examples across the U.S. and Canada.

Project Area

Clearing in the Colorado State Forest. Photo Credit: Courtney Peterson, Colorado State University.
The Colorado State Forest Service is leading the development of an ASCC project site targeting high-elevation spruce-fir forests located in the north central area of Colorado. The Colorado State Forest is a 71,000-acre cooperatively managed State Trust property west of Fort Collins, near Cameron Pass. With miles of trails, wildlife, alpine lakes, and abundant outdoor recreational activities this beautiful area provides an array of ecosystem services. The State Forest is part of the Headwaters of the North Platte River and provides additional water to the Cache La Poudre River via the Michigan Ditch Interbasin Transfer. Maintaining healthy forests in these high-elevation spruce-fir forests is critical in protecting these watersheds.

Management Goals

Area with large amount of standing dead trees. Photo Credit: Courtney Peterson, Colorado State University.

A team of natural resource specialists from the Colorado State Forest, regional managers, and scientists came together for a virtual three-day workshop in December 2020 to develop the study design for the ASCC project site.  The team developed a set of Desired Future Condition statements, Objectives, and Tactics for each major climate adaptation trajectory (resistance, resilience, transition). These three trajectories are briefly summarized below:

 

Resistance:

  • Reduce stand density to build resistance to windthrow, beetles, and drought
  • Promote tree vigor and release, increase wind firmness, and remove dead trees
  • Provide ecosystem services, including wood products, watershed health, recreation opportunities, carbon sequestration potential, and cultural resources
  • Provide lynx habitat (large trees required)
  • Maintain aesthetics / recreation value

Resilience:

  • Build resilience to drought, fire, white pine blister rust, windthrow, and bark beetles
  • Promote future-adapted native tree species and genotypes, promote lodgepole pine for serotiny (fire resilience), promote rust-resistant limber pine
  • Retain genotypes on site (refugia-like)
  • Create a heterogeneous structure and reduce fuels in the matrix
  • Promote wildlife habitat by retaining large diameter trees and snags
  • Provide ecosystem services, including wood products, watershed health, recreation opportunities, and cultural resources
  • Create opportunities for carbon sequestration by retaining larger trees

Transition:

  • Create firebreaks, break up dense forest to limit insect outbreaks, and promote natural regeneration opportunities to create heterogenous forest structure
  • Favor future-adapted species that tolerate variable environmental conditions/disturbances (temperature extremes, drought, mixed-severity fire, insects, etc.)
  • Create a variety of regeneration microsites: focus on topography and drier/wetter microsites (i.e., topographic wetness index; heat load index), CWD/slash retention
  • Increase wind firmness
  • Reduce surface fuels to be appropriate for an upper montane-mixed conifer forest (10-20 tons/ac)
  • Increase shrub component for wildlife habitat
  • Provide ecosystem services, including wood products, watershed health, recreation opportunities, and cultural resources
  • Create opportunities for carbon sequestration through large tree retention

Climate Change Impacts

Key projected climate change impacts that the project team considered for the Colorado State Forest include:
Warmer temperatures, particularly hotter and drier summers
Longer growing seasons – shorter and milder winters and earlier snowmelt in the spring
Uncertain changing precipitation patterns – potentially decreased snow during winter months and less rain during spring/summer months. Potential to impact seedling regeneration and survival
Elevated drought risk
Increased potential for wildfires
Increased risk of disturbances such as pest, pathogens, invasive species, deer herbivory, and weather

Challenges and Opportunities

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

Challenges

Changing vegetation dynamics – difficulties in tree regeneration for spruce-fir forest due to compound disturbances (wildfire, insects, disease, and drought)
Increased susceptibility to bark beetle attacks
Increased drought conditions
Changes in tree species habitat

Opportunities

Increased habitat range for Douglas-fir, aspen, and ponderosa pine (possible assisted migration)
Species respond individually. Meaning we may not lose all species at once and can possibly replace the niches of the shifted species
Fire promotes species diversity and resilient systems due to more diverse sets of genes in the ecosystem that react to fires differently
Increased drought conditions hinder fungi growth and promote tougher leaves that are less palatable to pest

Adaptation Actions

The ASCC project was designed to explicitly test three different adaptation options: resistance, resilience, and transition. A detailed silvicultural prescription was designed for each adaptation option, which was replicated several times across the study site. Detailed silvicultural prescriptions can be found in the Adaptation Workbook. Some of the adaptation tactics employed in this project include:

Area/Topic
Approach
Tactics
Resistance
Mechanical thinning
Release cut to reduce density and encourage advance regeneration
Alter species proportions through favoring healthy spruce and lodgepole
Create surface fuels for soil moisture retention and surface roughness (20-35 tons/acre)
Maintenance of snags for wildlife use by keeping at least 4/acre ≥ 10 inches DBH for Engelmann spruce and subalpine fir, or ≥ 8 inches DBH for lodgepole pine
Resilience
Group selection to encourage natural lodgepole pine regeneration: Remove 20-30% of the basal area creating 3 2-acre groups and 3 1/2-acre groups. Place groups near overstory lodgepole pine to facilitate natural regeneration
Thin the matrix to promote healthier stands: overall reduce stand density by 10-20%; remove Engelmann spruce <10” dbh, while maintaining mature/live spruce; remove subalpine fir across all size classes >5” dbh; keep lodgepole pine and any aspen present
Passively allow any natural regeneration to establish within matrix. Favor aspen and lodgepole in open areas
Plant Douglas-fir (local source) and rust-resistant limber pine
Maintain snags to help promote wildlife. Minimum of 4 snags/acre, retained in larger clumps, if possible
Reduce ladder fuel build-up while leaving some to promote roughness, soil moisture, and nutrient cycling
Lop and scatter (20-35 tons/acre) to encourage lodgepole pine height growth and seedling survival during drought years; allow for regeneration of spruce
Transition
Group selection: create an overstory mosaic through gaps and thinning
Create one large 4 acre opening, multiple small ½ acre gaps within thinned matrix
Lower residual density: Remove subalpine fir and Engelmann spruce to create 0.25-acre gaps for planting in matrix; keep lodgepole pine and large trees in matrix; promote quaking aspen if already growing, especially in moist topographic areas
Weed around remaining trees and maintain open areas with brush cutter, creating structures from upper montane mixed-conifer forests
Allow any natural regeneration
Details of tree species composition to be planted: Plant future adapted species with a different seed source than resilience treatment. Details of spacing grid for planting: Douglas-fir 40%; ponderosa pine 30%; bristlecone pine 20%; blue spruce 10%
Plant Douglas-fir across the site in gaps and matrix; plant ponderosa pine in the drier microsites within the gaps; plant limber pine across the site in gaps, matrix, ridgetops; plant some bristlecone pine; plant blue spruce on wetter microsites in matrix
Retain snags of varying sizes in clumps to help windfirm the area and create wildlife habitat (minimum number of 4 snags/acre)
Plant shrubs such as mountain ash, rocky mountain maple, mountain mahogany, bitterbrush, and ceanothus shrubs in the persistent tree-less openings
Reduce surface fuels to promote surface roughness, moisture retention, and nutrient cycling. Whole trees will be harvested, fuels will be reduced to 10-20 tons/acre

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:
Residual tree survival and growth
Natural regeneration survival and growth
Planted regeneration survival and growth
Microclimate conditions
Understory plant cover and diversity
Pollinator abundance
Nutrient cycling

Next Steps

Each of the adaptation treatments will be replicated 4 times across a 400-acre (160-hectare) area on the Colorado State Forest. The Colorado State Forest Service is collaborating with key partners, including the Colorado State Forest Service Nursery, to determine potential seedlots for future-adapted seedlings. Pre-treatment forest inventory data is currently being collected on the study site and the treatment units will be implemented in the summer of 2023/2024. Future data will be collected at 1,2,3,5, and 10 years post set-up. It will focus on tree regeneration, forest growth, forest health, and carbon and nutrient fluxes, wildlife habitat, and water quality.

Keywords

Drought
Fire and fuels
Forest threats
Insect pests
Management plan
Planting
Recreation
Regeneration
Research
Water resources
Wildlife habitat

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