Dynamics of litter decomposition rate and soil organic carbon sequestration following vegetation succession on the Loess Plateau, China

Litter quality determines the decomposability of litter and the proportion of recalcitrant residues, which in turn can affect the accumulation of soil organic carbon (SOC). However, the impact of litter decomposition on SOC turnover following vegetation succession has not been systematically studied. To clarify the dynamics and mechanisms of litter decomposition and SOC sequestration following vegetation succession, this study conducted a decomposition experiment across four successional stages: grassland (∼30 years), shrubland (∼60 years), pioneer forest (∼110 years), and climax forest (∼160 years). This study also analyzed the litter quality and the SOC turnover rate. The results showed that litter decomposition rates gradually decreased with vegetation succession. Litter lignin content (LC), and nitrogen content (LN) were the major factors controlling the change of litter decomposition rate. Litter with a high LC: LN ratio and lignin: LN ratio exhibited a lower decomposition rate, whereas the opposite was found for litter with a higher LN content. The increase in the SOC content mainly occurred in the early successional stage (<110 years), with a higher litter decomposition rate and SOC turnover rate. At the later stage (≥110 years), the SOC was close to saturation, together with low rates of litter decomposition and SOC turnover. The variation trend of the mineral-associated organic carbon (MAOC) content was the same as that of the SOC content, resulting from continuous litter inputs. Based on the above results, litter inputs can significantly increase the SOC content in the early successional stage, and soil carbon sequestrations gradually reach saturation in the late successional stage. The findings of this study strengthen our understanding of the changes in litter decomposition and its contribution to SOC sequestration following vegetation succession.