The Influence of Burn Severity on Post-Fire Spectral Recovery of Three Fires in the Southern Rocky Mountains

Jaclyn Guz,Dominik Kulakowski,Florencia Sangermano

doi:10.3390/rs14061363

Abstract

Increased wildfire activity and altered post-fire climate in the Southern Rocky Mountains has the potential to influence forest resilience. The Southern Rocky Mountains are a leading edge of climate change and have experienced record-breaking fires in recent years. The change in post-fire regeneration and forest resilience could potentially include future ecological trajectories. In this paper, we examined patterns of post-fire spectral recovery using Landsat time series. Additionally, we utilized random forest models to analyze the impact of climate and burn severity on three fire events in the Southern Rocky Mountains. Fifteen years following the fires, none of the burned stands fully recovered to their pre-fire spectral states. The results suggested that burn severity significantly impacted post-fire spectral recovery, but that influence may decrease as time since fire increases. The biggest difference in forest recovery was among fire events, indicating that post-fire climate may be influential in post-fire recovery. The mean and minimum growing-season temperatures were more significant to post-fire recovery than the variability in precipitation, which is consistent with field-based analysis. The present study indicated that, as warming continues, there may be changes in forest density where forests are not regenerating to their pre-fire spectral states. Additionally, this study emphasizes how high-elevation forests continue to regenerate after fires, but that regeneration is markedly affected by post-fire climate.

Highlights

We examined patterns of post-fire spectral recovery following three fires in the Southern Rocky Mountains
Increased disturbances have been especially prominent in forests dominated by lodgepole pine
Post-fire %normalized burn ratio (NBR) recovery increased annually in areas burned at both medium and low severities (Table 4). This may be because the fire thinned out the stand and allowed other trees to grow more or because the fire was intense enough to release some seeds from serotinous cones. [6]

Summary

Introduction

Wildfires are burning in the Southern Rocky Mountains (e.g., Northern Colorado and Southern Wyoming), 22% more than any other time in the past 2000 years [1]. During the MCA, the Northern Hemisphere was 0.3 ◦ C (0.5 ◦ F) warmer than the 20th-century average and subalpine forests, ranging from 9000 to 10,000 ft, burned on average every 150 years. In 2020, the Northern Hemisphere was 1.28 ◦ C (2.3 ◦ F) above the 20th-century average, and fires are expected to occur, on average, every 117 years. This dramatic increase in the wildfire activity is directly related to the warmer–drier weather caused by climate change [1]

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Discussion

Conclusion