Impacts of targeted grazing, controlled burning, and strip seeding on soil microbial communities

Increased vegetation management efforts are crucial due to the magnitude of global land degradation. Most modern land management projects focus on either controlling undesirable plant species or attempting to reconstruct the historical plant community. While most strategies are generally expected to enhance native vegetation establishment and diversity, there may be unintended impacts on vital soil microbial communities. Soil microbial communities play a crucial role in biogeochemical processes like nutrient cycling, organic matter decomposition, and the development of soil structure, all of which influence plant productivity, nutrient acquisition, and the regulation of plant diversity and composition. We sought to investigate the consequences of different combinations of vegetation management strategies used to restore a former cropland to a perennial grassland in Davis, California, USA. Specifically, we assessed soil microbial community diversity, composition, and putative functional group abundances across different combinations of (1) targeted sheep grazing, (2) low and high frequency controlled burning, and (3) native plant strip seeding. We found that microbial taxonomic diversity was largely unchanged across vegetation management practices, but grazing, burning, and seeding led to shifts in soil microbial community composition. Microbial community shifts were primarily associated with changes in plant community composition; however, indirect modifications to carbon: nitrogen and pH were also differentially associated with compositional shifts in bacteria and fungi, respectively. Overall, our findings highlight that soil bacterial communities are resistant to increasing management intensities. Future studies should investigate how changes in soil microbial communities within managed ecosystems impact ecosystem processes and whether these processes align with land management objectives.