Dependence of cumulative CO 2 emission and microbial diversity on the wetting intensity in drying-rewetting cycles in agriculture soil on the Loess Plateau

Altered drying-rewetting (DRW) procedures due to climate change may influence soil microbial properties and microbially-mediated carbon cycling in arid and semi-arid regions. However, the effects of DRW of different intensities on the microbial properties and respiration are not well understood. Thus, the responsive patterns of microbial communities and carbon mineralization in agriculture soil on the Chinese Loess Plateau to DRW treatments with different wetting intensities (5%–25% and 5%–36%) and frequency (1-cycle to 4-cycle) were investigated. Continuous moisture levels of 5%, 25% and 36% were used as control. Results revealed that the reduction of bacterial diversity and richness were greater for 5%–36% than 5%–25% treatment, while diversity of fungi was similar for different wetting intensities. Bacterial communities became clustered by wetting intensity rather than cycle number, however fungal community was unaffected by DRW. The complexity of bacterial co-occurrence network increased because of higher nodes, edges, average degree, diameter and average cluster coefficient after 4-cycles, and the interaction was more complex after 1-cycle for fungi. Rewetting caused a pulse-like increase of respiration rate, and the pulse amplitude was greater for DRW with high rewetting intensity and decreased with the increase of cycle number. The cumulative CO 2 emission for DRW treatments was lower than that for the continuous moisture conditions. The net reduction of carbon release for 5%–36% treatment was 1.18 times higher than that for 5%–25% treatment. Our study provides experimental evidence of the positive potential of DRW processes for maintaining soil carbon stock in an agriculture system on the Loess Plateau.