Soil Bacterial Biodiversity in Drylands Is Dependent on Groundcover Under Increased Temperature

ABSTRACT Introduction Drylands are a major terrestrial biome, supporting much of the earth's population. Soil microbial communities maintain drylands’ ecosystem functions but are threatened by increasing temperature. Groundcover, such as vegetation or biocrust, drives the patchiness of drylands' soil microbial communities, reflected in fertile islands and rhizosphere soil microbial associations. Groundcover may shelter soil microbial communities from increasingly harsh temperatures under climate change, mitigating effects on microclimate, but few data on the microbial response exists. Understanding the fine‐scale interactions between plants and soil is crucial to improving conservation and management of drylands under climate change. Materials and Methods We used open‐top chambers to experimentally increase the temperature on five key groundcover species found in arid Australia, and are commonly present in drylands worldwide; bareground (controls), biocrust, perennial grass, Maireana sp . shrub, Acacia aneura trees, testing soil bacterial diversity and community composition response to the effects of increased temperatures. Results We found that groundcover was a stronger driver of soil bacterial composition than increased temperature, but this response varied with groundcover type. Larger groundcover types ( Acacia and Maireana ) buffered the impact of heat stress on the soil bacterial community. Bacterial diversity and species richness declined with heat stress affecting the bacterial communities associated with perennial grass, Maireana and Acacia . We identified 16 bacterial phyla significantly associated with groundcover types in ambient treatment. But, under heat stress, only three phyla, Verrumicrobiota, Patescibacteria, and Abditibacteriota, had significantly different relative abundance under groundcovers, Acacia and Maireana , compared to bareground controls. The soil bacterial community associated with perennial grass was most affected by increased temperature. Conclusion Our findings suggest soil communities may become more homogeneous under climate change, with compositional change, rather than diversity, tracking soil response to heat stress.