Effect Of Land Use Change Of The Agriculture And Forestry On Soil Organic Carbon Storage Of Soil In A Hilly Landscape Of The Red Earth Region

In order to understand the influence of land use change on the soil organic carbon storage in the landscape scale in the red earth region of subtropical China, land use changes from1933to2005and soil organic carbon content under different land uses were analyzed using technologies of remote sensing (RS), geographic information system (GIS) and field survey of1264surface (0-20cm) sample sites and35profile (0～100cm) sample sites. Paddy soil transformed mutually to woodland and tea plantation with a main transition form of woodland to paddy soil in that3period. From1990turn out tea plantation, areas have a tendency of reducing. Land use changes mainly occurred at the elevation of50～150m.Topsoil organic carbon contain in the red earth region of subtropical China occurred from7.8to20.0g·kg-1, the average contents of soil organic carbon were13.4g·kg-1.Peddy soil (87.6%) organic carbon occurred from10.0to20.0g·kg-1; woodland (84.7%) organic carbon occurred from1.4to20.0g·kg-1; while tea plantation (87.7%) organic carbon occurred in<15.0g·kg-1. Among the various land uses, paddy soil exerted the organic carbon content of14.3g·kg-1, which is significantly higher than those in woodland (13.0g·kg-1) and tea plantation (9.5g·kg-1)(p<0.01). In addition, the variation coefficient of organic carbon in paddy soil was26.0%, obviously lower than woodland (355.5%) and tea plantation (50.9%). Bulk density of tea plantation (1.27g/cm) were highest, significantly much higher than woodland (1.22g/cm3) and paddy soil (1.19g/cm3). Topsoil organic carbon were remarkably different from land use changes, paddy topsoil organic carbon density (36.4t/hm2) were highest, followed by woodland (33.4t/hm2), the density of soil organic carbon of tea plantation (24.8t/hm) was the lowest. Land use changes significantly affect spatial distribution of topsoil organic carbon density (p<0.01).Soil organic carbon stock were increased from1933to2005and1955～2005, acted obviously as a carbon sink. From1990to2005, a reduced soil organic carbon stock occurred due to area of woodland transformed to paddy soil were reduced. Woodland and tea plantation transformed to paddy soil increased soil organic carbon stock, with a main increment from woodland transformed to paddy soil. Paddy soil transformed to woodland and tea plantation soil reduced soil organic carbon stock, with a main decrement from paddy soil transformed to woodland.On the whole, soil organic carbon stock in the paddy soil were increased from1933to2005and acted as a carbon sink. The effect of land use changes on soil organic carbon stock mainly occurred in the elevation of50-150m. Thus, the protection and increase of the rice fields in the elevation of50-150m is of importance to advance the soil carbon sequestration potential in the red earth region of subtropical China.