Effects of plant and microbial biodiversity on soil nitrogen and phosphorus accumulation under ecological restoration of Alpine Sandy Land in Northwest Sichuan

Abstract

The accumulation patterns of soil Nitrogen (N) and phosphorus (P), and the mechanisms through which they are influenced by plant, microorganisms, and extracellular enzymes during the ecological restoration of alpine semi-humid sandy lands remain unclear. Therefore, this study focused on the alpine semi-humid sandy land in northwest Sichuan, employing the method of spatial-for-temporal substitution, selected the shrub-grass restoration research sample plots for periods of 5, 10, 15, and 20 years (a), with natural sandy land without artificial intervention serving as the control group (CK), to investigate the variation characteristics of soil N and P storage across different shrub-grass restoration periods, and reveal the mechanisms of soil N and P accumulation by plant, microbial biodiversity, and N and P cycle enzyme activities. The results showed that: The shrub-grass restoration significantly increased soil N and P storage, and the Margalef, Shannon-Wiener, and Simpson biodiversity indices of herbaceous plants, meanwhile increased the species quantity of Poaceae and Fabaceae, Observed, Chao1, ACE, Shannon-Wiener biodiversity indices of soil microorganisms, the relative abundances of Proteobacteria and Bacteroidetes, and the soil N and P cycling enzymes activities in each soil layer. During the process of shrub-grass restoration, the vegetation biomass influenced soil microbial biodiversity by affecting vegetation biodiversity, which in turn fostered an increase in the abundance of specific microbial phylum. Ultimately, this process impacted the accumulation of soil N and P by modulating the activities of N and P cycling enzymes. The coverage of Salix cupularis served as a fundamental factor in promoting soil N and P accumulation, while the plant Margalef index and microbial Chao1 index were crucial factors influencing soil N and P storages. The research findings address the gaps in desertification control studies and offer a scientific foundation for ecological restoration measures targeting sandy lands in such areas.