基于“源”“汇”景观指数的定西关川河流域土壤水蚀研究

基于“源-汇”理论,利用“源”“汇”景观指数分析方法,计算甘肃定西关川河流域1995年、2000年、2005年和2010年的“源”“汇”景观指数(LWLI,Location-weighted landscape index),对比分析“源”“汇”景观空间格局变化与土壤水蚀的关系.结果表明:(1)关川河流域从1995年到2010年的LWLIelevation、LWLIdistance和LWLIslope指数呈降低的趋势.在高海拔和距流域出水口较远的区域,“源”景观的贡献逐渐小于“汇”景观的贡献.林地主要分布在坡度较小的地区,而草地主要分布在坡度较大地区.(2)“源”“汇”景观综合指数LWLI从1995年到2005年持续下降,但2010年的LWLI值比2005年又有所提高,说明由于地区人口的扩大和自然资源的限制,某些地区农地扩张的压力依然很大.(3)20年间流域大气降水没有发生显著变化,但河川径流量、径流系数和土壤侵蚀模数逐年减少.LWLI与土壤侵蚀模数(P＜0.05)具有显著正相关关系.LWLI能够较好地反映流域土壤水蚀规律,可作为流域水土流失评价的有效方法.对深入探讨黄土高原“退耕还林还草”工程与流域水文过程的关系,有效控制水土流失,优化黄土高原的治理,具有重要的理论和实践意义.

Research on soil erosion based on Location-weighted landscape undex(LWLI) in Guanchuanhe River basin, Dingxi, Gansu Province

Based on source-sink landscape theory, the relationship between spatial pattern changes and soil erosion from 1995 to 2010 was studied using method of Location-Weighted Landscape Index (LWLI) in Guanchuanhe River basin, Dingxi, Gansu Province. Following results were captured. First, it showed that the values of LWLI_elevation,LWLI_distance and LWLI_slope decreased gradually from 1995 to 2010. In the areas with high altitude or with long distance from basin outlet, source landscape contributed less than sink landscape. Forestland was mainly distributed in low gradient region, while grassland was mainly distributed in the areas with steep slope. Second, LWLI declined continuously from 1995 to 2005, and there was a slight increase from 2005 to 2010, which indicated that the pressure of farmland expansion was still high because of population expansion and natural resource limitation. Third, in the past two decades, no significant change was detected for precipitation in this region, while river runoff, runoff coefficient and soil erosion modulus all decreased in Guanchuanhe River basin. Soil erosion modulus has a positive correlation with LWLI (P<0.05). Therefore, it was considered that LWLI can correctly reflect the effect of source and sink landscape on soil erosion, and LWLI can be used as a valid tool to evaluate the potential risk of soil erosion. Our study would provide scientific basis for better understanding the relationships between "Grain for Green" project and its hydrological effects in the basin, helping to control severe soil-water loss and achieving wise ecosystem management on the Loess Plateau.