Soil Organic Carbon Pools At Different Land Uses In A Reclaiming Land Area From Taihu Lake

Reclaiming land from a lake area is a kind of human disturbance that has emerged in large numbers since the late 1950s in China. In order to understand the characteristics of soil organic carbon pools in the reclaiming land from lake under different land uses in the Xiaodian Lake area, the concentrations and seasonal fluctuation of soil labile organic carbon in the 0~40 cm soil layer and soil respiration at the surface were analyzed. The results showed that:The proportions of soil water soluble organic carbon (WSOC)(1.22%~3.03%) and readily oxidizable carbon (ROC)(10.56%~30.64%) were higher than those in highland forests of the same climate zone, while the proportions of soil particulate organic carbon (POC)(3.43%~17.28%) were lower. That implied that the stability of soil organic carbon was poor in impoldering land. Compared with the remnant stream sediment in the research region, soil total organic carbon (TOC) under the forests and the cropland significantly increased.Seasonal dynamics of soil microbial biomass carbon (MBC) under each land use were significantly. MBC concentrations under the forests in summer and autumn were higher than those in winter and spring. Under the cropland the seasonal changes of MBC from autumn to spring were slight, and significantly increased in summer. The concentrations of MBC under each land use decreased sharply with increasing soil depth. MBC concentrations under the cropland were higher than those in the forests, and the concentrations under coniferous forest were lower than those in broadleaf forest.Seasonal dynamics of WSOC under different land uses were significantly. The concentrations of WSOC in autumn and winter were higher than those in spring and summer, generally. WSOC concentrations under forests decreased sharply with increasing soil depth. The vertical change of WSOC concentrations in the cropland soil was different from the forests: the highest concentrations were at 10~20 cm depth while the lowest were at 0~10 cm depth. The concentrations of WSOC under the cropland were lower than those in the forests at 0~10 cm deep of soil layer, and the concentrations under coniferous forest were higher than those in broadleaf forest. At 10~20 cm and 20~40 cm deep of soil layer WSOC concentrations under the cropland were higher than those in the forests, and the concentrations under coniferous forest were lower than those in broadleaf forest.ROC concentrations under Cinnamomum camphora and Phyllostachys heterocycla in spring and summer were higher than those in winter, while under Metasequoia glyptostroboides and the cropland the seasonal changes were relatively slight. The concentrations of ROC declined with increasing depths. ROC concentrations under the cropland were lower than those in the forests.There were significant seasonal variation of soil respiration under each land use, showing that the highest value was in summer while the lowest value was in winter. Soil temperature was the main factor controlling the seasonal fluctuation of soil respiration. The soil respiration and the Q10 value were higher in the impoldering land relative to the upland of the same climate zone.