Collaboration Supports Prescribed Burning on the Colorado Front Range – Part 2

by Hannah Brown, Science Communication Specialist, Colorado Forest Restoration Institute, Colorado State University

Using prescribed fire as a tool on forest restoration projects in fire-adapted forests helps to achieve ecological objectives that you can’t accomplish without putting fire on the ground. Fire can reduce the buildup of fine fuels like the layer of needles, twigs, and sticks that cover the ground and create fuel for wildfire, control regeneration of small seedlings to keep the forest from becoming overcrowded, and recycle nutrients to replenish soil. In 2019, The Nature Conservancy and 12 other agencies came together to complete the Elkhorn Unit 4 prescribed burn as part of the Elkhorn Creek Forest Health Initiative. This project was designed to reintroduce fire to historically fire-adapted ponderosa pine ecosystems, and reduce the potential for high severity wildfire in this area. The Colorado Forest Restoration Institute (CFRI) collected monitoring data before and after the fire that shows how the project accomplished restoration goals and contributed to improving future fire science.

Field monitoring data shows very positive outcomes from the fire, where all restoration goals were basically met or exceeded.

This treatment impacted the forest by removing mostly small trees, and leaving behind large
ones.

Field monitoring can tell us whether the ecological objectives of the burn were met. To determine whether a treatment has impacted potential future fire behavior, you either have to wait and see what happens when the treatment encounters a wildfire, or you can use fire modeling programs that are informed by field monitoring data. Though the 2020 Cameron Peak Fire came within two miles of this treatment area, it did not burn through the Elkhorn 4 unit, so we used the Fire and Fuels Extension to the Forest Vegetation Simulator to make predictions about how this area would respond to fire in the future.

Overall, the fire behavior shifted from passive crown fire (torching of individual and small groups of trees) to surface fire burning along the ground. The windspeed needed to make flames long enough to carry fire into the tree crown increased from 9 to 46mph. This big increase is largely driven by the fact that the prescribed fire increased the tree canopy base height. Canopy base height is the height of the lowest living branches from the ground—a tree with a high canopy base height is harder to ignite!

Information from fire modeling and field data collection is used to improve the performance of an analytical tool called the Watershed Investment Tool, which was developed by the Peaks to
People Water Fund and CFRI as a planning tool that estimates benefits of fuels reduction projects, and helps decision-makers choose where and how to treat forests. We continue to refine this tool by incorporating field monitoring data from actual projects on the Front Range, so it becomes more accurate and useful over time. One way this project has improved our future
modeling with the Watershed Investment Tool has to do with the increased canopy base height
that we saw after this prescribed fire.

The WIT incorporates a stack of models about vegetation, erosion potential, and wildfire
likelihood and behavior. There are parameters built into each of these layers that work together
to define how prescribed fire is likely to impact mixed conifer forests like those on the Front
Range. The parameters in the vegetation layer are informed by research from mixed conifer
forests in the Sierras of California. While forests in the Southern Rockies do share many
similarities with these forests, forests on the Front Range grow in tougher conditions, and are
shorter overall. Because the lowest branches on a Colorado ponderosa may start off lower than
those on a Sierra ponderosa, prescribed fire is more likely to burn lower branches and raise
canopy base height. (If you want to get into all the modeling distinctions, check out the 2018
Ecological Monitoring Report for Peaks to People Water Fund Demonstration Sites, or the
Elkhorn 4 Prescribed Fire Monitoring Report). The outcome is that the WIT underestimates the
benefits of prescribed fire for achieving restoration goals and reducing future wildfire risk, and
prescribed fire can be an even more effective tool than the WIT currently predicts. When our
models are better informed with localized data, we can support better prioritization and decision
making. Collaborative partnerships in which forest restoration practitioners and researchers
adaptively manage their methods together improve outcomes on the ground, and in the science.

For more about the collaborative process that supported this project, check out part 1 of this blog series.