长江流域土壤保持能力时空特征

利用MODIS-NDVI数据、地面气象站数据等,采用通用土壤流失方程计算了长江流域2000~2010年土壤保持量,并基于GIS平台与GeoDa软件,辅以Morans I指数以及一元线性回归系数等方法分析了长江流域土壤保持能力的时空分布特征。结果表明:(1)长江源区以及中下游沿岸至长江入海口地区的土壤保持量最低(≤560t/hm2),土壤保持量高值区(≥2 400t/hm2)主要分布于上游四川盆地周围以及中下游长江以南地区;(2)长江流域土壤保持量在市域单元上存在明显的空间聚集现象,"低—低"聚集区分布在长江源区、武汉西部以及流域入海口,"高—高"聚集区主体分布在流域上游与江西南部;(3)土壤保持量年际变化呈增加趋势的区域占62%,其中呈快速增加趋势(b5)的地区分布在陕西南部、湖南西北部、江西东部以及四川东部,呈减少趋势的区域占38%,主要分布于流域上游以及中下游长江以南部分地区。

SPATIAL-TEMPORAL DISTRIBUTION CHARACTERISTICS OF SOIL CONSERVATION ABILITY IN YANGTZE BASIN

The Yangtze River is one of the most important rivers in china and the annual soil erosion amount is about 2.4 billion tons.The serious erosion caused poor soil in upstream and frequent flood disaster in middle and lower reaches.As the major ecological problem of river basin,the soil erosion has become an important factor which restricts the regional development,and analyzing the soil conservation has become the focus of scholar's study.But a lot of soil conservation researches about the Yangtze Basin involved only the upstream.In this paper,the soil conservation ability of the whole Yangtze Basin was calculated by applying the Universal Soil Loss Equation (USLE) and its spatial-temporal distribution characteristics were analyzed by using Moran's I index and linear regression coefficient method.There are five factors in the USLE:R,K,LS,C,P.The R value was computed by using the daily rainfall data provided by the meteorological station in and around the study area.Among this process,the spatial interpolation had to be done.By access to relevant literature,the parameters in K model were obtained.Then,the K factor value was calculated according to the land use data.In Arcmap spatial analysis tool,gradient and slope length was calculated by computing DEM,and then got LS factor.The C factor value was got by calculating MODIS-NDVI data which download from NASA web site.According to the statistic values of P in different land use,the P factor was determined.Before calculate the soil conservation with GIS,all of these factors in USLE should be converted to the raster data with same projection and resolution.Based on the results of USLE,the spatial analysis with Moran's I index can be achieved by GeoDa and the linear regression coefficient method which was used to demonstrated the temporal dynamics can be carried out on GIS.The results showed that:(1) The amount of soil conservation in the estuary and source area of the Yangtze River was the lowest (≤560 t/hm2),while the high levels of soil conservation (≥ 2 400 t/hm2) area located in the upstream around Sichuan Basin,as well as the south of middle and lower reaches; (2) The inter-city soil conservation amount was highly auto-related.The regions of "L-L" type were found mainly in the source and estuary area of the Yangtze River and west of Wuhan; the cities of "H-H" type were mainly in the upper reaches of the Yangtze River and the south of Jiangxi; (3) The area where soil conservation quantity showed a trend of increase accounted for 62％.And the regions that presented rapidly increasing trend (b＞5) distributed in the southern of Shaanxi,northwestern of Hunan,eastern of Jiangxi and eastern of Sichuan.The falling trend area accounted for 38％,mainly in the upper reaches of the Yangtze and south of middle and lower reaches.