Abstract: Land tillage disturbances and nutrient enrichment severely alter ecosystem processes and functions. Previous studies have investigated the effects of tillage disturbance and nutrient enrichment on plant communities and soil properties. However, integrated studies of the effects of tillage disturbance and nutrient enrichment on multiple below-ground ecological processes and functions are needed. Here, we conducted a field experiment in the Hulunber grassland, setting up four treatments (control, tillage disturbance (D), nutrient enrichment (NPKμ) and tillage disturbance plus nutrient enrichment (NPKμD)) to study the effects of tillage disturbance and nutrient enrichment on plant communities, soil microbial communities, and carbon mineralization. Compared to D treatment, NPKμD treatment increased plant community biomass through a significant 13-fold rise in annual and biennial plant biomass (p < 0.01). D treatment and NPKμD treatment significantly decreased the Shannon index of plant communities (p < 0.05). Microbial network complexity increased under NPKμ treatment whereas D treatment decreased it. Both D treatment and NPKμ treatment significantly reduced soil carbon mineralization, and NPKμ exacerbated the negative effects of tillage disturbance (p < 0.05). Partial Least Squares Path Modeling showed that plant diversity, biomass and soil properties influenced soil carbon mineralization directly and indirectly through soil bacterial and fungal communities. Our study suggests that nutrient enrichment promotes the recovery of plant community productivity after disturbance, while the recovery of plant diversity and soil microbial community structure may take a longer period. Therefore, achieving comprehensive ecological integrity characterized by stable plant community structure and healthy soil microbial communities requires long-term monitoring and targeted management measures.

Key words: Tillage disturbance, nutrient enrichment, plant communities, microbial communities, carbon mineralization