为了解亚热带天然次生林保护对森林土壤有机碳库的影响,研究了湘中丘陵区杉木人工林和3种天然次生林(马尾松+石栎针阔混交林、南酸枣落叶阔叶林、石栎+青冈常绿阔叶林)土壤水溶性有机碳(DOC)含量季节动态及其与土壤自然含水率、p H、养分含量的相关性。结果表明:土壤DOC含量0~15 cm土层高于15~30 cm土层,秋季土层之间的含量差异最小,土壤DOC的分配比例15~30 cm土层高于0~15 cm土层;马尾松+石栎针阔混交林、南酸枣落叶阔叶林、石栎+青冈常绿阔叶林土壤DOC含量分别较杉木人工林高3.15%~9.81%,3.85%~8.19%和11.24%~12.00%,夏季不同森林类型之间的含量差异最大;4种森林土壤DOC的分配比例在2.00%~2.54%之间,杉木人工林土壤DOC的分配比例高于3种次生林;4种森林土壤DOC含量季节变化明显,均表现为:春、夏、冬季较高,秋季最低,秋季与春(除杉木人工林外)、夏季之间差异显著;各森林土壤DOC含量与土壤自然含水率、有机碳(SOC)、全N、全P、全K、水解N、有效P、速效K含量之间呈极显著或显著正相关。可见,地带性常绿阔叶林或天然次生林转变为杉木人工林后,土壤DOC含量下降,土壤DOC含量可作为衡量土壤潜在生产力的敏感指标。 In order to understand the impact of subtropical natural secondary forest conservation on forest soil organic carbon pool, the effects of subtropical natural forests on soil organic carbon pool were studied. The effects of subtropical natural forest protection on Chinese fir plantation and three natural secondary forests (Pinus massoniana + Quercus mongolica mixed forest, Seasonal dynamics of soil water - soluble organic carbon (DOC) content in evergreen broadleaved forest and its relationship with soil natural water content, p H and nutrient contents. The results showed that the contents of soil DOC in 0 ~ 15 cm soil layer were higher than those in 15 ~ 30 cm soil layer, and the contents of DOC in soil layers in autumn were the lowest. The distribution proportion of soil DOC in 15 ~ 30 cm soil layer was higher than that in 0 ~ 15 cm soil layer ; DOC content of Pinus massoniana + Quercus mongolica mixed forest, Jujube deciduous broad-leaved forest, Lithocarpus glauca and Cyclobalanopsis glauca forest were 3.15% ~ 9.81%, 3.85% ~ 8.19% and 11.24% ~ 12.00%, the difference between the different forest types in summer was the largest; the distribution proportion of DOC in the four kinds of forest soils was between 2.00% ~ 2.54%, the distribution proportion of DOC in the Chinese fir plantation was higher than that in the three kinds of secondary forests; The contents of DOC were significantly different in the seasons. The contents of DOC were significantly higher in spring, summer and winter, lowest in autumn, autumn and spring (except for Chinese fir plantation) Total SOC, total P, total K, hydrolyzed N, available P and available K were significantly or significantly positively correlated. Therefore, the DOC content of soil decreased after the zonal evergreen broad-leaved forest or natural secondary forest was transformed into Chinese fir plantation, and the soil DOC content could be used as a sensitive index to measure the potential productivity of soil.