Contribution of plant litter and soil variables to organic carbon pools following tropical forest development after slash-and-burn agriculture

Tropical forest development after slash-and-burn agriculture crucially affects soil carbon accumulation. However, it remains unclear how the dynamics of soil organic carbon (SOC) pools are regulated following tropical forest restoration. Our study aims to quantify the contribution of litter and soil variables to alterations in carbon pools during tropical forest restoration on slash-and-burn agricultural land in Xishuangbanna, Yunnan, China. This study observed a significant increase in soil carbon pools along forest restoration. The extent of the increase in labile fractions (1.9-2.5-times) was higher than that of SOC (1.5-times) during the restoration from early to later stages. The proportion of microbial carbon to total carbon increased from 3.0 to 7.7% during forest restoration, while those of dissolved (5.3-3.1%) and readily oxidizable (42.9-29.6%) fractions decreased. Clay content determined the accumulation dynamics of SOC (10.5%) and labile fractions (6.0-13.5%) in the later stage, while free Fe oxides (10.4-15.4%) contributed to these pools mainly in the early stage. Microbial carbon explained 22.4-26.7% and 20.6-28.3% of the variation in SOC stocks and labile fractions, respectively, whereas litter carbon accounted for 9.5-15.3% of the change in microbial carbon stock. The contribution (8.2-17.1%) of litter-soil nutrient interactions to carbon pools increased during forest restoration. Our data suggest that carbon dynamics are mainly determined by variations in the clay content, free Fe oxides, and litter and microbial carbon, possibly through nutrient-level interactions between the litter and soil during tropical forest restoration.