Plant Communities Under a Changing Wildfire Regime

In 2020, two of Colorado’s largest wildfires, the Cameron Peak and East Troublesome fires, burned in Rocky Mountain National Park (RMNP) and the surrounding region₅. The size and severity of these fires follow a broader trend of larger, more frequent, and more severe wildfires in Rocky Mountain forests and the Western United States_{5 6 8 10}. Elevations above ~8,000 ft have seen the highest increase in burned sites between 1984-2017₁. Alpine and subalpine forests are found above this elevation, and sustain a high diversity of plant communities due to their unique environmental conditions₇. Species richness in temperate alpine regions has been compared to that of tropical environments₉, providing various ecosystem services such as soil retention and recreational aesthetics.

Heartleaf arnica (Arnica cordifolia) at a burned site in Rocky Mountain.

Photo courtesy of Christopher Maienza.

Burned lodgepole pine in Rocky Mountain.

Photo courtesy of Christopher Maienza.

Historically, the fire regime of subalpine forests is known to have infrequent yet high severity fires. Due to changing fire regimes, higher elevation fires are becoming more frequent and more severe. Plant communities are often adapted to the historic fire regimes of their local ecosystem. Therefore, the mismatch between current and historical fire regimes may impact plant community composition and diversity. In some studies, plant communities in subalpine and alpine regions show greater species diversity and richness in burned versus unburned areas decades after a fire_{2 3 4}. Less is known about post-fire succession the first few years following a fire.

Understanding Wildfire Impacts on Plant Communities

Researchers from Idaho State University are conducting a multi-part research study looking at the impact of wildfires on plant communities. The first goal of this research is to survey plant composition and diversity at locations that burned during the 2020 wildfires compared to unburned locations. This research could help identify plants that are positively and negatively impacted by changing fire regimes and help identify the potential spread of non-native plant species in burned areas. Researchers expect to find plant diversity will decrease as burn severity increases. They also expect to find plants that are better adapted to frequent fires in burned areas.

Fireweed (Chamaenerion angustifolium) at a burned site in Rocky Mountain.

Photo courtesy of Christopher Maienza.

The second goal of this study is to create a model that can predict wildfire burn severity based on landscape characteristics like plant composition and diversity, elevation, slope, and others. This type of model can be used by park managers to identify what areas of the park might experience high burn severity during future wildfire events. Park managers can use this model to identify locations where predicted high burn severity and plant communities of management concern overlap.

Lastly, researchers will analyze the how wildfires influence the genetic diversity of certain plant species. Researchers will study the genetics of subalpine fir trees (Abies lasiocarpa) by collecting and analyzing foliage samples. Researchers expect to find a decrease in genetic diversity as fire frequency increases.

The information learned from this research can be used by park managers to help guide conservation strategies in the context of fire and climate change and inform post-fire recovery efforts.

This research is funded, in part, by the Rocky Mountain Conservancy through the Scholar-in-Residence Program.

Plot with lodgepole pine delineated by measuring tape for plant surveys at a burned site from East Troublesome Fire (2020).

Photo courtesy of Christopher Maienza.

References

1. Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118. https://doi.org/10.1073/pnas.2009717118
2. Coop, J. D., Massatti, R. T., & Schoettle, A. W. (2010). Subalpine vegetation pattern three decades after stand-replacing fire: Effects of landscape context and topography on plant community composition, tree regeneration, and diversity. Journal of Vegetation Science, 21(3), 472–487. https://doi.org/10.1111/j.1654-1103.2009.01154.x
3. Douglas, G. W., & Ballard, T. M. (1971). Effects of Fire on Alpine Plant Communities in the North Cascades, Washington. Ecology, 52(6), 1058–1064. https://doi.org/10.2307/1933813
4. Doyle, K. M., Knight, D. H., Taylor, D. L., Barmore, W. J., & Benedict, J. M. (1998). Seventeen Years of Forest Succession Following the Waterfalls Canyon Fire in Grand Teton National Park, Wyoming. International Journal of Wildland Fire, 8(1), 45–55. https://doi.org/10.1071/wf9980045
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