δ¹³C characteristic of soil organic carbon under different vegetation restoration in subtropical red soil region

To explore effect of different vegetation restoration types on soil organic carbon turnover in degraded red soil, δ¹³C of vegetation and soil organic carbon were analyzed in the natural restoration grassland, Pinus massoniana forest and Schima superba forest. The results showed that C₄ plants were dominated in the natural restoration grassland, while C₃ plant mainly occurred in the Pinus massoniana and Schima superba forest. The δ¹³C increase of soil organic carbon from litter to soil was beyond the normal range from current research in both stands, indicating that sources of soil organic carbon were the mixture of the pasture and the currently restored forest. Soil organic carbon from the surface soil was lower than that from the original grass carbon. The δ¹³C of soil organic carbon increased with the depth in both stands. The decomposition rate of soil organic carbon in the Schima superba forest was lower than that of soil in the Pinus massoniana forest, but the retention time of SOC was the opposite in two forests. Although the proportion of soil organic carbon from new carbon in the Pinus massoniana forest was higher than that in Schima superba forest, the soil organic carbon decomposes more solwly in muhe forests. In the long run, the carbon sequestration process of Pinus massoniana and Schima superba soils needs more reasonable evaluation. This study provides a theoretical basis for the selection of tree species for vegetation restoration and enriches the research for soil organic carbon of vegetation restoration in degenerated red soil regions. (authors)