Microbial-derived C increased more than plant-derived in soil under plantation versus grassland 11 years after landslide

Vegetation restoration can improve soil carbon (C) sink capacity, and is considered an effective approach for restoring degraded ecosystems. As an important component of soil organic carbon (SOC), microbial- and plant-derived C affect the size and turnover of the SOC pool; however, the effects of different vegetation types on SOC sequestration capacity remains controversial due to the lack of long-term systematic observations in restoration areas.

Amino sugars and lignin phenols (as biomarkers of microbial- and plant-derived C, respectively), together with several soil basic physicochemical properties in the topsoil (0–10 cm) and subsoil (40–50 cm) were investigated in an afforested (AF) and naturally restored grassland (NRG) of a shallow landslide ecological restoration area in the Bailong River Basin, China, following 11 years of restoration.

In the topsoil, SOC sequestration efficiency of AF was 28.18% higher than that of NRG; Whereas AF was 6.69% lower than NRG in the subsoil. Further, the enrichment of amino sugars in soil was more favorable to SOC accumulation than lignin phenols, and the environmental factors affecting SOC and amino sugar accumulation showed relative uniformity. The more suitable environment for microbial survival within AF regions promoted the decomposition of lignin phenols, and increased the contribution of microbial-derived C to SOC compared with NRG; Further, the more stable SOC components in AF facilitated its resistance to external disturbances.

Our results demonstrated when compared with NRG, the contribution of plant-derived C to SOC was lower in the AF plots, while the contribution of microbe-derived C was both higher and more stable. These results provide novel information regarding the accumulation pathways of SOC in shallow landslide areas, and emphasize the importance of microbial-derived C in SOC sequestration, as well as suggesting that AF is more effective than NRG in SOC sequestration.