Soil structure and nutrient supply drive changes in soil microbial communities during conversion of virgin desert soil to irrigated cropland

Abstract

AbstractSoil microorganisms are critical to soil health and environmental functions; however, the dynamics of microbial communities and their response to soil variables following conversion of desert soils to oasis farmland have not been well documented. We used high‐throughput pyrosequencing to investigate the dynamics of soil microbial communities along an irrigated cultivation chronosequence (cultivated for 16, 33, 45 and 60 years) and in adjacent non‐cultivated soil in a desert‐oasis ecotone in northwestern China. Additionally, we explored which soil variables may be responsible for shifts in microbial communities. Generally, cultivation in desert soil increased microbial community abundance and diversity; however, bacterial abundance and diversity increased along the cultivation chronosequence, whereas fungal abundance and diversity initially increased and then decreased. Continuous crop cultivation also resulted in a shift in microbial community composition, notably with a decrease in nitrogen (N)‐fixing microbes (Proteobacteria and Cyanobacteria) and an increase in ammonia‐oxidizing (Nitrosomonadales) and nitrite‐oxidizing microbes (Nitrospirae). Redundancy analysis showed that soil organic carbon, total N, available N, available phosphorus and bulk density explained over 80% of the variation in both bacterial and fungal communities; this indicated the critical roles of nutrient supply and soil structure in shaping the composition and diversity of microbial communities during the conversion of native desert soils to irrigated croplands.Highlights Cultivation in desert soil increased microbial community abundance and diversity. Cultivation decreased N‐fixing microbes. Cultivation increased ammonia‐oxidizing and nitrite‐oxidizing microbes. Soil structure and nutrient supply shaped the diversity of microbial communities.