The effect of land use changes on soil active organic carbon pool in Miyaluo forest zone of the western Sichuan

To increase the understanding of the impact of land use change on soil active organic carbon pool and provide the scientific data for understanding the mechanism of the impact of land use change on soil organic carbon,soil samples were collected from four land use types at Miyaluo in subalpine area of Western Sichuan,including primitive Abies faxoniana forest(M-Y),45-year-old planted spruce forest(Picea likiangensisi var balfourianan)(M-60),25-year-old planted spruce forest(M-80) and cropland(M-C).In the last century,extensive areas of native vegetation in the Miyaluo forest zone in western Sichuan have been converted to agricultural land,secondary forestry and manual planting forestry in different ages.All the soil sections were divided into five layers according to the soil depth,including the surface layer,1-10cm,10-20cm,20-35cm and 35-50cm,except the cropland site.The soil samples were collected in June,August and October in 2006,respectively.The analysis was conducted by the SPSS software.The section distribution and seasonal changes of microbial biomass carbon,water dissolved organic carbon and labile organic carbon was detected in all these four soil samples.The result showed that land use changes significant impact the component of soil labile organic carbon,The distribution of microbial biomass carbon and water dissolved organic carbon are M-YM-60M-80 M-C,while the labile organic carbon is higher in M-60 than in M-Y.The seasonal change range is less in all active organic carbon components.The content in the surface layer is much higher than in depth soil,and the change of allot ratio is lower than the change of active organic carbon.The correlation analysis found that the significant relationship was observed among soil organic carbon and microbial biomass carbon,water dissolved organic carbon and labile organic carbon.Therefore,the components of active organic carbon are the sensitive index to response the change of the soil organic carbon.