Precise assessment of soil organic carbon (SOC) storage requires understanding how vegetation and soil physicochemical properties differ in SOC fractions. Therefore, we aimed to analyze the dynamics of aggregate-associated, liable organic carbon (LOC) fractions corresponding to depth to clarify the effect of vegetation and soil properties on water stable aggregate (WSA) mineral adsorption in subtropical, red soil with five vegetation restoration regimes. The results showed that the large macro-aggregate fraction dominated the degraded red soil, which had the highest content of dissolved organic carbon (DOC). WSA-associated, easily oxidized organic carbon (EOC) varied from 6.26 to 20.02 g/kg and was not affected by vegetation types. Schima superba pure forest (SP) significantly increased DOC (0.38 g/kg on average) and particulate organic carbon (POC, 7.92g/kg on average), which had the highest biomass. Along with soil depth, WSA-associated POC declined, while exhibiting a growth trend with decreasing particle size, e.g., the highest POC was found in silt + clay fraction. The RDA ordination indicated that soil porosity and TN were the main soil parameters that explained the most variance. Meanwhile, the vegetation biomass, except for litter, were all significantly positively correlated with silt + clay fractions. Leaf biomass played the most important role on DOC in macro-aggregate with a 53.42% contribution. For aggregate-related POC, the largest contribution was from the interactions between branch biomass and pH (47.78%) followed by TN (35.1%) of micro-aggregate-related POC. Leaf biomass, silt + clay fractions, and TN can be used as indicators to evaluate the impact of vegetation restoration on WSA-associated SOC fractions. Broad leaved forest or combined with indigenous coniferous species was a better choice for SOC sequestration improvement in the study area.

The conversion of natural forests to planted forests has become a global trend, and the practice has wide-ranging effects on soil. This study aimed to explore the differences in soil water movement after the conversion of evergreen and deciduous broad-leaved mixed forests (natural forest, NF) to Chinese fir (Cunninghamia lanceolate (Lamb.) Hook.) plantations (CFP, 20–21 years old). Soil samples from five layers (0–5, 5–10, 10–20, 20–30, and 30–50 cm) were collected from NF and CFP before and after rainfall event in the Peng Chongjian watershed, Jiangxi Province. The physical properties of the soils, including the mean and coefficient of variation (CV) of soil moisture content and the soil particle composition, were determined in both forest types. The δD of soil water and the litter water-holding capacity were also measured. The results showed that the variation ranges of moisture content in each soil layer after the rainfall was 21.13%–49.40% in CFP and 21.33%–43.87% in NF. There were no significant differences in soil bulk density or porosity; the clay and silt contents were significantly increased in topsoil, while the sand was significantly decreased (P < 0.05). After the rainfall, soil water in CFP responded more promptly than NF. In the process of infiltration, the contribution of rainfall to soil moisture gradually decreased with increasing soil depth. Topsoil (0–5 cm) in NF responded promptly to rainfall, but the response showed a lag effect with the increase of soil depth. With the extension of infiltration time, the contribution of precipitation to deep soil gradually increased. The results showed that the soil did not degrade after the conversion of NF to CFP, a significant guiding result for plantation cultivation.