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 resilient 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.