Effects of soil fauna on litter decomposition and soil carbon content in Caragana korshinskii shrub microhabitats

Litter decomposition is one of the main sources of soil carbon content, and it plays an important role in the material cycle and energy flow of desert steppe ecosystems. The objective of the present study was to investigate the contribution of litter decomposition (associated with soil fauna) to soil carbon content in shrub microhabitats. In this study, the decomposition of Caragana korshinskii shrub litter, soil fauna communities, and soil carbon content were examined using the litterbag method (mesh sizes: 4, 2, and 0.01 mm) in microhabitats having different shrub sizes, including large, medium, small, and extremely small crown canopies. The results were as follows. 1) There was a significantly higher contribution of meso-micro soil fauna to litter decomposition than that of soil macrofauna, and the total soil fauna had a positive effect on litter decomposition at an early stage. However, the contribution rate of total soil fauna tended to be negative at 570 d. 2) When total soil fauna was involved in litter decomposition, soil carbon content in the shrub microhabitats of large and medium crown canopies was higher than that in the shrub microhabitats of small and extremely small crown canopies; it was insignificant only at 150 and 570 d of decomposition (P < 0.05). 3) Pearson correlation analysis showed that there was a significant positive correlation between soil carbon content and litter lignin content in shrub microhabitats (P < 0.01), but no significant correlation between soil carbon content and soil fauna contribution rate (P > 0.05). In conclusion, meso-micro soil fauna could indeed promote litter decomposition; however, the carbon generated by litter decomposition did not cause significant changes in soil carbon content.