Sand dune fixation enhances the contribution of microbial necromass carbon to soil organic carbon: A case study of Mu Us Sandy Land in China

Restoration of vegetation, soil, and biodiversity is key crucial for managing desertified ecosystems; however, whether desertification restoration promotes the accumulation of microbial necromass carbon (NC) remains unclear. In this study, four dune types (mobile, semi-mobile, semi-fixed, and fixed) were selected to represent different desertification restoration stages, and the accumulation mechanism of microbial NC and its contribution to soil organic carbon (SOC) were analyzed. The results showed that since the plant diversity, soil water content, and microbial activity of semi-mobile, semi-fixed, and fixed dunes were higher than those of mobile dunes, the SOC in semi-mobile (2.63 g kg- 1), semi-fixed (2.98 g kg- 1), and fixed (3.82 g kg- 1) dunes were significantly higher than that in mobile dune (0.98 g kg- 1). Moreover, sand dune fixation promoted microbial NC accumulation and increased microbial NC/SOC ratio but decreased fungal NC/bacterial NC ratio. In addition, our study showed that plant diversity is the main factor influencing microbial NC, which has direct and indirect effects on microbial NC accumulation. In conclusion, sand dune fixation enhances microbial NC accumulation and its contribution to SOC, and the change is driven mainly by plant diversity. This study enhances our understanding of the microbial NC accumulation mechanism during dune restoration.