The Characteristic Of Surface Soil Organic Carbon Of Different Vegetation Types In Rainy Area Of West China

Since the Industrial Revolution in Britain, the global natural resources have been diminishing. As people pay attention to the importance of issue, plantation area has been increased significantly. But comparing planted forests to natural forests, there are still some gaps in protecting species diversity, maintaining the soil fertility, disease resistance. Rainy area of West China plays a very important role in ecological barrier function in our country. Study on the soil organic carbon and its active carbon components of seven vegetation types, which are Cinnamomum camphora, mixed forest, Metasequoia glyptostroboides, Cryptomeria fortunei Hooibrenk, orchard, Neosino calamus affinis and farmland, the results as follows:(1) The amount of total organic carbon was between1.64～33.64g/kg. The amount of total organic carbon decreased with the increasing soil depth.(2) The amount of particulate carbon (POC) was between0.68～19.75g/kg, the amount of readily oxidizable carbon was between0.23～6.66g/kg, the amount of water-soluble organic carbon (WSOC) was between10.98～98.08mg/kg, the amount of microbial biomass soil carbon (SMBC) was between65.46～374.17mg/kg, and the light fraction organic carbon (LFOC) was between0.46～7.89g/kg. The order of ratios of POC to SOC was between32.58～66.32%. The order of ratios of ROC to SOC was between8.44～29.95%. The order of ratios of WSOC to SOC was between0.16～1.14%. The order of ratios of SMBC to SOC was between0.97～3.58%. The order of ratios of LFOC to SOC was between10.69～36.78%. The amount of POC, ROC, SMBC, LFOC, WSOC were all decreased with the increasing soil depth. SOC and each kinds of active organic carbon correlated positively with each other. The size of the order between the active carbon components was POC>LFOC>ROC>SMBC>WSOC.(3) Different vegetation types in soil organic carbon content exhibited different seasonal changes. The soil organic carbon content of Cinnamomum camphora was the highest in summer. The soil organic carbon content of Metasequoia glyptostroboides, Cryptomeria fortunei Hooibrenk and orchard was the highest in autumn. The soil organic carbon content of mixed forest was the highest in spring. The soil organic carbon content of orchard and farmland had no obvious seasonal variation because of strong interference of human factors.(4) The active carbon component of different vegetation types showed a different seasonal variations. The amount of WSOC was high in autumn and spring, and was low in winter and summer. The amount of SMBC was high in autumn and summer, and was low in spring and winter. POC, ROC, LFOC did not show significant seasonal variation characteristics.(5) The results of correlation analysis between soil organic carbon and its components and soil ecological factors showed that SOC and its active carbon components and soil moisture content was a significant positive correlation. OC and its active carbon components and soil pH value was negatively correlated. Soil organic carbon and its components and soil bulk density was negatively correlated.