Understanding the effects of wildfire on biodiversity is crucial for planning pre- and post-fire management activities. Herbaceous plant communities play important roles in forest ecosystems but their responses to wildland fire remain incompletely understood. Previous research on how fire affects understory plant communities has focused largely on prescribed fires, which often do not represent the full range of fire severity that characterizes wildfires. In addition, previous research on fire effects on plant communities has generally focused on small geographic areas (e.g., a single fire), making it difficult to identify generalizable patterns across ecological gradients. Pyrodiversity—or spatial heterogeneity in fire history—may be one important driver of post-fire plant communities, but its effects have rarely been studied for plants. To understand the relative effects of local fire severity and heterogeneity of fire severity in the surrounding landscape on plant communities, we sampled plant communities in ~250 study plots across eight different wildfires in the Sierra Nevada and Warner Mountains of California. We used remotely sensed fire severity data to characterize spatial heterogeneity in fire severity within 100 m of study plots (hereafter pyrodiversity).
Results/Conclusions
Pyrodiversity had a positive effect on plant diversity, and in some cases was a stronger predictor of plant species richness than local fire severity. These findings indicate that fires that burn at heterogeneous severity may benefit plant diversity. The increasing prevalence of large, homogenous, high-severity burn patches, however, may eliminate fire-sensitive species from the landscape. Our findings suggest that pre-fire management that leads to heterogeneous burn mosaics is likely to benefit plant diversity and, potentially, the higher trophic levels that plants support.