Influences of land use patterns on spatial-temporal distribution of soil organic carbon in Southeast Chongqing karst mountain

Organic carbon content is an important index for measurement of land quality. Its change has direct effects on land fertility and growth status of vegetation. The organic carbon spatial-temporal patterns in Xiushan, Qianjiang and Youyang areas is analyzed in four different land use patterns, dry land, paddy field, vegetable garden and orchard, with geostatistical approach through field work, sampling and analysis in the paper. The result suggests that the contents of SOC in the cultivation horizon and subsoil horizon in vegetable garden is the highest, while that in dry land is the lowest, and the differences between them are remarkable. The contents of SOC in the ground layer in orchard are the highest, while that in the paddy land is the lowest, and the differences between them are unremarkable. Different land use patterns has the same effects on SOC of soil section, descending from upper to lower layers, that is contents of SOC in cultivated horizon is the highest, while that in subsoil is the lowest, and decreasing amplitude is largest in paddy field and least in dry land with remarkble differences. Compared with the second soil survey conductedin1984,the content of SOC in the cultivation horizon(0~20 cm in thickness)has been increasing for20 years except dry land; the increasing range of SOC in vegetable garden is the biggest and in the paddy field the smallest. But on the whole, the content of organic in soil in the study area is relatively low, so approaches of enhancing the ability of carbon storage of the soil should be developed and introduced new farming technology such as no-tillage and straw returning in order to improve the content of organic of the land.