Drivers of understory plant communities in Sierra Nevada mixed conifer forests with pyrodiversity

• Published in: Fire ecology Vol. 17; no. 1
• Main Authors: Wilkin, Kate, Ponisio, Lauren, Fry, Danny L., Collins, Brandon M., Moody, Tadashi, Stephens, Scott L.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 09-11-2021; Springer Nature B.V
• Subjects: Biomedical and Life Sciences; Canopies; Coniferous forests; Coniferous trees; Conifers; Ecology; Forestry; Forests; Herbivores; Life Sciences; Mixed forests; Neighborhoods; Original Research; Plant communities; Species composition; Species diversity; Species richness; Understory; United States > US; Nevada; Restoration; Biodiversity; Frequent fire; Sierra Nevada
• ISSN: 1933-9747; 1933-9747
• DOI: 10.1186/s42408-021-00111-6

Background
Fire suppression in western North America increased and homogenized overstory cover in conifer forests, which likely affected understory plant communities. We sought to characterize understory plant communities and their drivers using plot-based observations from two contemporary reference sites in the Sierra Nevada, USA. These sites had long-established natural fire programs, which have resulted in restored natural fire regimes. In this study, we investigated how pyrodiversity—the diversity of fire size, severity, season, and frequency—and other environment factors influenced species composition and cover of forest understory plant communities.
Results
Understory plant communities were influenced by a combination of environmental, plot-scale recent fire history, and plot-neighborhood pyrodiversity within 50 m. Canopy cover was inversely proportional to understory plant cover, Simpson’s diversity, and evenness. Species richness was strongly influenced by the interaction of plot-based fire experience and plot-neighborhood pyrodiversity within 50 m.
Conclusions
Pyrodiversity appears to contribute both directly and indirectly to diverse understory plant communities in Sierra Nevada mixed conifer forests. The indirect influence is mediated through variability in tree canopy cover, which is partially related to variation in fire severity, while direct influence is an interaction between local and neighborhood fire activity.