孤山川流域近30年土壤侵蚀时空动态特征分析

目的 针对区域水土保持效益评价、土壤流失治理的需求,选择黄土高原土壤侵蚀较为严重的孤山川流域为研究区,定量研究了孤山川流域近30a的土壤侵蚀时空变异特征。结果表明,1975～2006年间,研究区土壤侵蚀的变化分两个阶段。第一阶段为1975～1986年,土壤侵蚀强度加剧,侵蚀面积增加了138.13km2,流域东南部增加最多;第二阶段为1986～2006年,全流域土壤侵蚀强度减弱,侵蚀面积减少了163.09km2,1986年和1997年,东部地区减弱趋势更明显。中度以上的土壤侵蚀主要发生在高程1 070～1 300m处,都对应于18°～35°的陡坡地;1975年和2006年,中度以上侵蚀分别集中在900～1 150和1 300～1 800,单位为 MJ·mm·hm-2·h-1。流域土壤侵蚀主要发生在耕地和林地。1975～2006年,耕地面积减少,林草地面积增加,土地利用向良性循环发展。可为认识黄土丘陵沟壑区I副区土壤侵蚀规律和该区土壤侵蚀防治宏观决策提供科学支撑。

Spatial-Temporal Dynamic Features in Soil Erosion of theGushanchuan Basin in the Past Three Decades

Objective The Gushanchuan basin was chosen as a study area which is prone to serious soil erosion inthe Loess Plateau to investigate the requirements of soil and water conservation benefit assessment andsoil loss control.We quantitatively studied the spatial-temporal dynamic features of the soil erosion ofthe area over the past three decades by applying soil science,remote sensing(RS)and geographic in-formation systems(GIS).We obtained three main results.Firstly,variations of the soil erosion in thestudy area in the past three decades(1975to 2006)were divided into two stages.The first stage wasbetween 1975and 1986,when soil erosion intensified and eroded area increased by 138.13km2,par-ticularly in the southeast part of the basin.The second stage was between 1986and 2006,when soil e-rosion weakened.The eroded area decreased by 163.09km2,and soil erosion decreased in the entirebasin,particularly in the east.Secondly,soil erosion above the medium degree mainly occurred in theelevation ranging from 1 070mto 1 300m,with the slope ranging from 18°to 35°correspondingly.The precipitation in 1975and 2006was scanty,and the erosion above the medium degree have a rain-fall erosivity ranging from 900MJ·mm·hm-2·h-1 to 1 150MJ·mm·hm-2·h-1.The erosion a-bove the medium degree in 1986and 1997have a rainfall erosivity ranging from 1 300MJ·mm·hm-2·h-1 and 1 800MJ·mm·hm-2·h-1.The area with serious soil erosion corresponded to the areadistributed with high rainfall erosivity.Thirdly,the soil erosion in the basin predominantly occurredin farmlands and woodlands.During the period between 1975and 2006,the farmland area decreased,and the woodland and pasture areas increased,and the soil erosion weakened as a whole.The develop-ment of the land use of the basin was in a positive way,and soil erosion showed an obvious weakeningtrend.These results would provide references for understanding soil erosion and macro decision -making for controlling soil erosion in the first Loess Hill and Gully area sub-region.