Effects of controlled burns on flowering resources for pollinators

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Presenting Author(s)

SW

Samuel Wilhelm

Austin, TX

Co-Author(s)

Sean R. Griffin

University of Texas at Austin
Austin, Texas
EL

Elinor Lichtenberg

University of North Texas
Denton, Texas
KB

Kristen A. Baum

Oklahoma State University
Stillwater, Oklahoma
Shalene Jha

University of Texas at Austin
Austin, Texas

Grasslands represent critical but declining habitat for pollinators. They are currently threatened by overgrazing, fire suppression, human development, and other factors. Within grassland ecosystems, flowering forb (herbaceous non-grass) communities provide food and nesting resources for native pollinators. A better understanding of the mechanisms by which forb abundance and diversity respond to fire and seeding will inform the development of future pollinator habitat restoration projects. We focus on the Cross Timbers ecotype of the Southwestern U.S., where we sought to understand the flowering dynamics of forbs in a controlled burn restoration experiment. In winter of 2018, we applied three treatments within plots at 10 different sites (30 plots): burn, burn + forb seed, and control (no burn or seed). Following the treatments, we surveyed all sites across three seasons (spring, summer, fall) in 2018, yielding 3 collection periods, where we counted all inflorescences within 30 quadrats per site. There was a significant effect of season, (p-value< 0.0001), treatment (p-value = .009), and their interaction (p-value < 0.0001), on floral abundance. Seeded plots contained the most flowers of all treatments. We found no effect of season or treatment on floral diversity or community composition. We posit that, unlike floral abundance, shifts in diversity and composition are not likely to occur within one year of treatment, as many of the forbs responding to the burns are slow-growing perennials. Our results suggest that while burn and seed treatments can have immediate impacts on floral abundances, shifts in floral richness may be slower to occur.