Dead-fallen shrubs exhibit beneficial effects in enhancing soil microbial activity and soil fertility in arid sandy...

Shrub death occurs during arid sandy land restoration in northern China. However, the role of these shrubs in sandy soil restoration remains underexplored. In this study, soil samples were collected from areas with bare sand, standing living shrubs, and dead-fallen shrubs (at decay stages of 3-5, 7-9, and 11-12 years) in China's Mu Us Sandy Land. Soil samples (0-5 and 5-10 cm) were analyzed for moisture, pH, carbon/nitrogen fractions, extracellular enzyme activities, and microbial communities. Compared with bare sand, fallen shrubs increased soil moisture by 19.75-36.94 % and lowered soil pH by 0.06-0.20 in 0-10 cm soil depths. Concurrently, soil enzyme activity and microbial community structure were notably improved by fallen shrubs, leading to an average 129 % and 67 % increase in soil carbon and nitrogen fractions, respectively. Structural equation model revealed that the accumulations of carbon and nitrogen at the two soil depths was primarily driven by soil enzymes and fungal communities. Additionally, dead-fallen shrubs also enhanced microbial network stability and increased predicted functional abundances. However, standing living shrubs showed less potential than dead-fallen shrubs in enhancing soil microbial activity and fertility during arid sandy land restoration, primarily due to the living shrubs' failure to increase soil moisture or add organic materials to sandy soils. In summary, these findings emphasize that retaining dead shrubs as natural soil amendments can significantly improve restoration outcomes in arid sandy ecosystems.