Drying-rewetting cycles reduce bacterial diversity and carbon loss in soil on the Loess Plateau of China

Abstract

Soil drying-rewetting (DRW) events became intensified and occurred frequently on the Loess Plateau with the global climate change. However, the extent to which the DRW cycles with different intensity and number alter microbial community and respiration is rarely understood. Therefore, indoor DRW treatments on the soil samples obtained from Loess Plateau involving soil moisture that accounted for 10% water holding capacity (WHC) increasing to 60% WHC and 90% WHC (i.e., 10%–60% WHC and 10%–90% WHC) with 1 or 4 cycles, respectively, were implemented. Constant soil moistures of 10%, 60% and 90% WHC were set as control. Results showed that the bacterial diversity and richness were decreased and those of fungi remained unchanged under DRW treatments compared to those under constant moisture conditions. At the bacterial and fungal phylum level, Actinobacteriota and Ascomycota were the most dominant in all the different moisture treatments, respectively. The bacterial network was more complex than fungi, indicating that the bacteria had a greater potential for interaction and niche-sharing under DRW treatment. The pulse of respiration rate was declined as DRW cycle was increased under 10%−60% WHC treatment, but remained similarly in different cycles under 10%−90% WHC treatment. Moreover, the DRW treatments could reduce the overall carbon loss and the direct carbon release under 10%−60% WHC treatment was larger than that under 10%−90% WHC treatment. The cumulative CO2 emission after four cycles were positively correlated with microbial biomass carbon (MBC) and negatively correlated with fungal Chao 1 richness with great significances.