1. Wildfire Effects on Forest Cover in Ponderosa Pine Forest
Bollinger, Justin J.1,2, Malone, Sparkle L.1, Battaglia, Michael.1, Fornwalt, Paula1
1 USFS, Rocky Mountain Research Station, Fort Collins, CO
2 Colorado State University, Fort Collins, CO
Introduction
Fire is an essential component of ecosystem structure and function.
Ponderosa pine (Pinus ponderosa) dominated forest historically had two major fire regimes:
Low elevation forest ( m) were maintained by high frequency, low to moderate severity summer fires every 5 to 20 years (Figure 1a).
High elevation ( m) forest were maintained by mixed severity fire every 30 to 40 years (Figure 1b).
Fire suppression in ponderosa pine dominated forests have led to higher fuel loads and increases in forest cover.
Considering that wildfire size and severity is likely to increase into the future with drier climate, It is important that we understand how wildfire effects ponderosa pine forests.
The objective of this research is to understand wildfire effects on forest cover.
Questions
How does forest cover change following wildfire?
How does burn severity influence forest cover?
Methods
Accuracy Assessment:
Figure 4. Accuracy for the pre-fire forest layer was 97% with a kappa value of 0.74.
We mapped pre and post fire forest cover in the High Park fire (Figure 3).
Randomly generated 1000 points.
Points were classified as forested or non-forested based on NAIP imagery and compared to the forest layers (Figures 4-5).
Figure 3. Supervised classification of aerial imagery (National Agriculture Imagery Program: NAIP) was used to identify live forested area within the High Park Fire.
Figure 5. Accuracy for the post-fire forest layer was 92% with a kappa value of 0.40.
Results
How does forest cover change following wildfire?
How does burn severity influence forest cover?
Figure 1. (a.) The low elevation fire regime often maintained monospecific stands of ponderosa pine while the (b.) mixed severity fire regime is associated with mixed conifer forest. v a. b.
Figure 6. Shows the Pre-Fire aerial imagery (NAIP).
Figure 7. Shows the Post-Fire aerial imagery (NAIP).
Figure 8. Comparison of pre and post fire forested area.
Forest cover went from 84% to 63% postfire (Figures 6-8).
Figure 2. Elevation (m) thresholds in the High Park fire.
Low and high elevation ponderosa pine forest represent 40% and 35% of the study area, respectively (Figure 2).
Figure 9. Burn severity map of the High Park Fire. (
Figure 10. Relative cover for severity classes for the entire fire and estimates of forested area within each severity class.
Relative Frequency (%)
Unburned areas had the lowest pre fire forest cover.
Post fire forest cover was greatest for low and moderately burned areas (Figures 9-10).
Conclusions
Wildfire reduced forest cover by 21% in ponderosa pine forest (Figure 8).
Post fire forest cover was lowest for high severity areas (Figure 9).
Low pre-fire forest cover was associated with low burn severity.
Acknowledgements: This research was funded in part by the USFS Rocky Mountain Research Station and directly builds upon an ongoing USFS Rocky Mountain Research Station National Fire Plan Study (RMRS-NFP FWE-43), which is improving our understanding of forest recovery from wildfire.