Abstract:

Aims: Arbuscular mycorrhizal (AM) fungi are key plant symbionts in terrestrial ecosystems. Investigating the responses of AM fungal communities to precipitation changes and their relationships with vegetation and soil factors is of great theoretical importance for understanding the stability of desert steppe ecosystems. 

Methods: A precipitation manipulation experiment was conducted in Yanchi County, Ningxia, China, from 2019 to 2021 using a completely randomized design. Five precipitation treatments were established: D50 (natural precipitation −50%), D25 (natural precipitation −25%), CK (natural precipitation), I25 (natural precipitation +25%), and I50 (natural precipitation +50%). Based on Illumina high-throughput sequencing combined with Mantel analysis, random forest analysis, and partial least squares path modeling (PLS-PM), we examined the effects of altered precipitation regimes on the diversity, richness, and community composition of soil AM fungi in the desert steppe ecosystems and identified their main driving factors. 

Results: Vegetation cover, biomass, and Shannon diversity index of the desert steppe were sensitive to precipitation changes. Compared with CK, the D50 treatment significantly reduced the Shannon, Sobs, ACE, and Chao1 indices of AM fungi by 31.6%, 53.3%, 62.4% and 58.7%, respectively. However, the relative abundances of dominant AM fungal genera did not differ significantly among precipitation treatments. Non-metric multidimensional scaling analysis indicated that precipitation gradients significantly affected AM fungal community composition. Random forest analyses revealed that plant diversity and cover were the primary determinants of AM fungal diversity, AM fungal richness was mainly regulated by soil pH, and AM fungal community composition was primarily influenced by precipitation and NO₃^–-N. The PLS-PM results further showed that precipitation directly affected AM fungal community composition by altering soil moisture, indirectly increased AM fungal diversity through vegetation communities, and indirectly increased AM fungal richness through changes in soil pH. 

Conclusion: Precipitation changes regulate the coupling relationships between vegetation and soil factors, thereby driving shifts in the diversity, richness and composition of AM fungal communities in desert steppe ecosystems. These findings highlight the sensitive response of the mycorrhizal symbiosis system to precipitation variation and provide new insights into the mechanisms underlying the regulation of desert steppe ecosystems under climate change.

Key words: Arbuscular mycorrhizal fungi, precipitation gradient, plant communities, soil properties, desert steppe, global climate change