Variations Of SOC At Four Different Land Use Types In A Coastal Areas In Northern Jiangsu

The change of land use may dramatically affect the organic carbon composition andstructure, which affects the features of soil carbon exchanges between atmospheric and soil. Tounderstand the characteristics of soil organic carbon pools under four different land uses in acoastal areas in northern Jiangsu, the concentrations and seasonal fluctuation of soil labileorganic carbon in the0~40cm soil layer and the correlations among soil WSOC, ROC and TOC,some other soil factors were analyzed. The results are showed below:(1) The results revealed that WSOC and ROC positively correlated with TOC, TN andnegative correlated with C/N, pH, soil bulk density at the four different land use types. It showedthat the change of land use pattern would lead to the change of the soil physical and chemicalproperties,which would significantly affect the soil actived carbon.(2) The proportions of soil actived organic carbon showed that comparing with0~10cmdeep of soil layers, the proportions of WSOC in cropland was descended significantly in10~25cm deep of soil layers. The proportion of ROC was higher in forest than that in the other threepatterns. Compared with0~10cm deep of soil layers, the proportion of ROC in cropland andpolars-crops intergrated system was descended significantly in25~40cm deep of soil layers, fell55%and75%respectively. There was no significant difference in the ratio of WSOC/TOC andROC/TOC among of the different soil layers. This result suggested that human farming activitieson farmland and polars-crops might have a significant effect.to the soil structure of the activecarbon distribution(3) The effects of land uses on WSOC concentrations were significant. With the increasingof the soil depth, soil WSOC concentration decreased, which had the same variation trend as soilTOC. The soil organic carbon content in cropland is lower than the forest, for the farmland croprotation system, as well as straw, fertilizer input activities were significantly increased soilmicrobial activities, accelerate the decomposition of soil organic carbon, reduce soil organiccarbon storage, weakened the carbon sequestration function of cropland. There was nosignificant difference among four different land used types in each soil layers. Seasonal dynamicsof WSOC under four land use types were significant. The concentration of WSOC in autumnand winter were higher than those in spring and summer, generally. The concentrations ofWSOC in spring and winter were lower than those in autumn and summer in cropland andpolars-crops intergrated system. The lowest concentration of WSOC in these four different landused types was in summer. (4) To account the four land uses, the seasons and the depths, the concentration of ROC wassignificantly higher in forest than those in cropland and meadows in0~10cm depths. Theproportions of ROC in cropland and meadow was decreased significantly in10~25cm deep ofsoil layers compared with0~10cm in the polars-crops intergrated system,25~40cm comparedwith10~25cm in cropland and forest. The concentration of ROC varied dramatically indifferent seasons. Displaying concentration of ROC in spring and summer were higher thanthose in winter. Under cropland and meadow the seasonal changes were relatively slight.