汾河源头地区土壤侵蚀时空变化及其空间自相关分析

目的]汾河源头地区是山西省重要的水源涵养地和供水区,土壤流失严重。研究该区域土壤侵蚀时空变化的目的在于为该流域的水土保持工作提出科学依据。方法]采用2004和2009年9月的SPOT影像作为数据源,将GIS和USLE结合对汾河源头地区土壤侵蚀的时空变化进行研究,并借助GeoDa软件分析了研究区2009年土壤侵蚀的空间自相关性。结果](1)从时间变化来看,2009年汾河源头地区土壤侵蚀模数较2004年有所增加,中度以上侵蚀的面积占总侵蚀面积的比例也相应增大,且以极强度侵蚀和剧烈侵蚀增加为主;(2)从空间上看,土壤侵蚀程度高的区域分布在流域的东南部,土壤侵蚀程度低的区域分布在流域的西北部;(3)降雨和植被覆盖是影响汾河源头地区土壤侵蚀的2个主要因子;(4)除了微度侵蚀和剧烈侵蚀外,其他侵蚀强度类型向更高程度的侵蚀强度类型转移的面积都远大于向低程度的侵蚀强度类型转移的面积;(5)空间自相关分析表明,研究区土壤侵蚀存在一定的正相关和空间集聚,主要表现为高值与高值集聚,低值与低值集聚。结论]研究区内土壤侵蚀现象不断加剧,应加强土壤侵蚀治理力度。

Spatio-temporal Variations of Soil Erosion and Its Spatial Autocorrelation Analysis in Source Area of Fenhe River

Objective] The source area of Fenhe river is one of the most important water source area in Shanxi Province, but soil erosion in this area is severe. The objective of this study is to investigate the spatio-temporal variations of soil erosion in order to provide basis for soil and water conservation in this region. Methods] We used the SPOT images(September in 2004 and 2009) as data sources, explored the spatio-temporal variations of soil erosion in the source area of Fenhe river based on GIS and USLE. The spatial autocorrelation of soil erosion in 2009 was analyzed by using GeoDa software. Results] (1) The modulus of soil erosion showed an increasing trend from 2004 to 2009 in the source area of Fenhe river. The eroded land above moderate erosion increased as well, especially, the strong erosion and the severe erosion; (2) Spatially, severe soil erosion distributed in the southeast of the area, while slight soil erosion distributed in the northwest of the area; (3) Rainfall and vegetation cover were the most important factors that influence soil erosion in the area; (4) Except for the slight and severe erosion, the area transformed from the low to high level soil erosion was much larger than the area transformed from the high to low level soil erosion; (5) Spatial autocorrelation analysis revealed that soil erosion in the study area was spatially positive autocorrelated and spatial concentrated. Conclusion] Soil erosion intensified continuously in the source area of Fenhe river, and soil erosion regulation should be strengthened.