Ecological effects of root exudates from five plant species within a desert steppe community

Root exudates are important mediators of plant–soil–microbe interactions by influencing rhizosphere microbial communities and soil nutrient conditions. To elucidate the ecological effects of root exudates from different plant species within the same community, we collected five coexisting plant species from a desert steppe in Inner Mongolia, including one constructive species (Stipa breviflora), two dominant species (Artemisia frigida and Cleistogenes songorica), and two accompanying species (Convolvulus ammannii and Heteropappus altaicus). Root exudates were collected using a hydroponic approach and applied to in situ soil in a three-week incubation experiment. Changes in soil microbial communities were assessed using high-throughput sequencing, while major soil properties were determined using standard soil analyses. The addition of root exudates generally reduced bacterial diversity and significantly altered microbial community composition, while exerting relatively minor effects on fungal communities. Root exudate inputs also resulted in a decrease in soil pH and significant increases in available nitrogen and available phosphorus. Distinct ecological effects were observed among plant species, with plant species occupying similar functional positions exerting more similar influences on soil microbial communities and nutrient characteristics. Specifically, root exudates from the constructive and dominant species jointly promoted the enrichment of the phylum Actinobacteria, particularly Rubrobacter, Arthrobacter, and Solirubrobacter, taxa associated with nitrogen and phosphorus transformation processes, which coincided with increased soil nutrient availability. In contrast, root exudates from the accompanying species did not induce significant enrichment of Actinobacteria. Collectively, these results show that root exudates from different coexisting plant species differentially influence soil microbial communities and nutrient dynamics in desert steppe ecosystems.