Bacteria are more sensitive than fungi to moisture in eroded soil by natural grass vegetation restoration on the Loess Plateau.

Community composition and respiration rates of bacterial and fungal communities from grass-covered eroded soils of the Loess Plateau responded differently to constant and increasing soil moisture (SM) regimes. The soils were incubated with SM contents of 5%, 30%, and 45% and with wetting processes in the SM ranges from 5% to 30% (5-30%), from 5% to 30% to 45% (5-30-45%) and from 30% to 45% (30-45%); high-throughput sequencing and co-occurrence network analyses were applied to investigate the different responses of the bacterial and fungal communities to changed SM. Our results showed that bacteria were more sensitive than fungi to changes in SM. The dominant bacterial communities converted from Actinobacterial to Proteobacteria and Acidobacteria in 5-30-45% wetting procedure. Firmicutes preferred wet condition and exhibited slow resilience. However, no difference was observed for the Chloroflexi communities across any sample. The obvious difference in fungal composition was found between the wetting process of 5-30-45% and constant 45% SM. During the 5-30-45% procedure, the respiration rate was higher than that at 30-45% procedure after incubation for 24 days. The respiration rate in 5-30% procedure was lower than that of 5-30-45% process after incubation for 16-27 days. The larger effects on bacterial response than on fungi were verified in network analysis. Multiple stepwise regression analysis showed that 84.40% of the variation in bacterial richness and diversity as well as fungal diversity can be explained by changes in soil respiration rate in response to wetting procedure. Understanding the response of difference between bacterial and fungal community composition, phylum-levels networks and respiration rate to changes in SM is essential for the management of plant-soil-water relationship in the ecosystem after natural vegetation restoration on the Loess Plateau.