红壤丘陵景观土地利用变化对稻田土壤有机碳储量的影响

为研究区域景观尺度土地利用方式变化对稻田土壤有机碳储量的影响,利用野外实地采样中1264个土壤样点有机碳含量的调查,采用遥感和GIS手段,分析红壤丘陵景观1933-2005年的土地利用变化引起的稻田表层土壤有机碳储量的动态变化。结果表明:研究区稻田与林地、茶园呈双向演替机制,以林地转变为稻田为最主要的土地利用变化方式,集中在高程50m-150 m内。稻田表层土壤有机碳含量为14.3 g/kg,显著大于林地(13.0 g/kg)和茶园(9.5 g/kg)(p<0.01);且稻田土壤有机碳的变异系数仅为26.0%,明显低于林地(55.5%)和茶园(50.9%)。1933-2005年间,由稻田转变为其他利用方式(主要为林地和茶园)的面积为1233.53 hm2,共损失碳10015 t,而由其他利用方式转变为稻田的面积为1598.90 hm2,共增加碳15372 t。总体而言,1933-2005年间稻田土壤表层碳库呈增加的趋势,表现为碳增汇;土壤有机碳储量在高程50m-150 m内受土地利用变化影响的方向和程度最为显著。因此,保护和增加50m-150 m高程内的稻田面积对于提升亚热带红壤丘陵区的固碳潜力具有重要的意义。

Effect of Land Use Change on Topsoil Organic Carbon Storage of Paddy Soil in a Hilly Landscape of Red Earth Region

In order to understand the influence of land use change on the topsoil organic carbon storage of paddy soil in the landscape scale in the red earth region of subtropical China,land use changes from 1933 to 2005 and topsoil organic carbon content under different land uses were analyzed using technologies of remote sensing(RS),geographic information system(GIS) and field survey of 1264 sites.Paddy soil transformed mutually to woodland and tea plantation with a main transition form of woodland to paddy soil.Land use changes mainly occurred at the elevation of 50 m-150 m.Among the various land uses,paddy soil exerted the organic carbon content of 14.3 g/kg,which is significantly higher than those in woodland(13.0 g/kg) and tea plantation(9.5 g/kg)(p<0.01).In addition,the variation coefficient of organic carbon in paddy soil was 26.01%,obviously lower than woodland(55.5%) and tea plantation(50.9%).From 1933 to 2005,a reduced topsoil organic carbon stock(10015 t C) occurred due to paddy soil transformed to woodland and tea plantation(1233.53 hm2),while an increased topsoil organic carbon stock(15372 t) occurred due to woodland and tea plantation transformed to paddy soil(1598.90 hm2).On the whole,top soil organic carbon stock in the paddy soil were increased from 1933 to 2005 and acted as a carbon sink.The effect of land use changes on soil organic carbon stock mainly occurred in the elevation of 50 m-150 m.Thus,the protection and increase of the rice fields in the elevation of 50m-150 m is importance to advance the soil carbon sequestration potential in the red earth region of subtropical China.