Data for: Prescribed versus wildfire impacts on exotic plants and soil microbes in California grasslands

Prescribed burns are often used as a management tool to decrease exotic
plant cover and increase native plant cover in grasslands. These changes
may also be mediated by fire impacts on soil microbial communities, which
drive plant productivity and function. Yet, the ecological effects of
prescribed burns compared to wildfires on either plant or soil microbial
composition remain unclear. Grassland fires account for roughly 80% of
global annual fires, but only roughly 12% of research on belowground
impacts of fires occurs in grasslands, limiting our understanding of
aboveground belowground connections in these important habitats. Here, we
took advantage of the serendipitous opportunity of a wildfire burning
through the same reserve where we had previously sampled a prescribed
burn. This enabled us to investigate the impacts of a spring prescribed
burn versus a fall wildfire on plant cover and community composition and
bacterial and fungal richness, abundance, and composition. Our California
grassland sites were thus within the same reserve, limiting environmental,
vegetation, or climate variation between the sites. We used qPCR of 16S
and 18S to assess impacts on bacterial and fungal abundance and Illumina
MiSeq of 16S and ITS2 to assess impacts on bacterial and fungal richness
and composition. Wildfire had stronger impacts than prescribed burns on
microbial communities and both fires had similar impacts on plants with
both prescribed and wildfire reducing exotic plant cover but neither
reducing exotic plant richness. Fungal richness declined after the
wildfire but not prescribed burn, but bacterial richness was unaffected by
either. Yet, fire exposure in both fire types resulted in reduced
bacterial and fungal abundance and altered bacterial and fungal
composition. Plant diversity differentially impacted soil microbial
diversity, with exotic plant diversity positively impacting bacterial
richness and having no effect on arbuscular mycorrhizal richness. However,
the remainder of the soil microbial communities were more related to
aspects of soil chemistry including cation exchange capacity, organic
matter, pH and phosphorous. Our coupled plant and soil community sampling
allowed us to capture the sensitivity to fire of the fungal community and
highlights the importance of potentially incorporating management actions
such as soil or fungal amendments to promote this critical community that
mediates native plant performance.