Abstract: Cyperus esculentus is characterized by rapid growth and strong tolerance to drought and low soil fertility. However, its potential as a pioneer species for restoring desertified grasslands has received limited attention, and the effects of C. esculentus cultivation on soil fertility and the underlying mechanisms remain poorly understood. In this study, we assessed changes in soil nutrient contents, enzyme activities, soil respiration rates, microbial biomass, bacterial community structure and composition, and predicted functional potential using PICRUSt2 before and after C. esculentus cultivation. The results showed that: (1) C. esculentus cultivation increased the soil dissolved organic carbon to dissolved organic nitrogen ratio by 1.3-fold and the soil carbon availability index by 40.6%, indicating its positive impact on soil carbon availability. (2) C. esculentus cultivation increased microbial biomass nitrogen by 75.3% and protease activity by 58.8%, and elevated soil nitrate content by 13-fold, suggesting its role in enhancing microbial nitrogen immobilization and soil nitrogen mineralization. (3) C. esculentus cultivation significantly altered soil bacterial community composition, with increased relative abundances of copiotrophic taxa, including Bacteroidetes and Acidobacteria subgroup Gp1, whose relative abundances increased from 3.7% to 5.0% and from 1.4% to 7.6%, respectively. This pattern was consistent with faster nutrient turnover. In conclusion, C. esculentus cultivation in desertified grasslands can activate soil nutrients through multiple pathways, including enhancing microbial activity, improving bacterial community structure, and regulating soil carbon and nitrogen turnover, thereby facilitating soil organic matter accumulation. This study provides important mechanistic evidence for the promotion of C. esculentus cultivation in ecological restoration and soil fertility improvement in sandy semi-arid regions.

Key words: desertified grassland, soil nutrient, microbial community composition, oligotrophic/copiotrophic microorganisms, functional prediction