Ecological risk assessment of the Gannan Plateau,northeastern Tibetan Plateau

Desertification, soil salinization and grassland degradation are the major environmental hazards faced by the Gannan Plateau, northeastern Tibetan Plateau. Ecological risk assessment plays an important role in formulating environmental management strategies yet little attention to this region. In this study, we established an ecological risk assessment index system based on 30 evaluation indices in the categories of hydrometeorology, ecological environment, ground surface disturbance, and society and economy for the Gannan Plateau. An entropy method was used to calculate an index weight,and subsequently the matter-element method was used together with extension theory to establish a matter-element extension model of ecological risk. We assessed the ecological risk in this region by calculating the degree of association between index layer, system layer and target layer, and the cumulative ecological risk index. The degrees of ecological risk for the counties of the region were determined by using Arc GIS which would represent a spatial heterogeneity of the risk grade in production. Our results showed that the areas of high ecological risk were in Zhouqu County and Zhuoni County, and others were of low risk(Hezuo City, Diebu County, Xiahe County and Lintan County) or intermediate risk(Maqu County). The results of the assessment were in accord with the actual observed situation. Thus, our ecological risk assessment index system is appropriate for this region and suggests that high risk counties need a priori ecological protection. Such research could provide a technological support which would potentially prevent or reduce disasters by establishing an ecological barrier to promote the sustainable development of Gannan Plateau.

基于GeoWEPP模型的桥子沟流域土壤侵蚀对比研究

为探讨人类活动对黄土丘陵区土壤侵蚀时空格局的影响,选取黄土高原丘陵区典型小流域桥子沟(包括桥子东沟和桥子西沟两个对照小流域)为研究对象,利用GeoWEPP模型对不同时段内两个子流域土壤侵蚀时空格局进行了定量模拟,并开展了1988-2000年水土保持治理效应对比分析,探讨了土地利用变化对流域产流和产沙的影响.结果表明,模拟获得的两子个流域各阶段径流深及输沙模数与实测数的相对误差均小于15%,说明GeoWEPP模型适用于桥子沟;在阶段1(1988-1990年)、阶段2(1991-1995年)和阶段3(1998-2000年)三个阶段,桥子沟土壤侵蚀状况均有好转.对比发现,在实施了土地利用整改措施的阶段1-阶段2时期,两个子流域土壤侵蚀均得到改善,而在阶段2-阶段3时期,实施水土保持措施的桥子东沟土壤侵蚀改善效益明显高于未实施措施的桥子西沟,表明水土保持措施在水土流失治理中发挥了积极的作用;不同时期流域的土地利用与土壤侵蚀强度的时空变化关系密切,说明合理的土地利用变化改变了该流域下垫面条件,能有效地减缓流域土壤侵蚀,是流域土壤侵蚀格局变化的主要驱动力.研究结果可为黄土高原有效实施水土保持治理措施,开展土壤侵蚀监测、防治和小流域管理提供依据.

基于地理探测器的干旱区内陆河流域产水量驱动力分析——以疏勒河流域为例

明确干旱区产水量的驱动因素,能为区域水资源优化和可持续发展提供科学依据。基于MODIS植被指数、HWSD的土壤数据集以及气象要素数据,采用InVEST模型和地理探测器探究疏勒河流域多年平均产水量的空间分布,揭示不同空间尺度上产水量的单因子及双因子交互驱动机制。结果表明:疏勒河流域多年平均产水量呈现南部>北部>中部。流域尺度上,产水量空间格局的主导驱动力为降水,坡度与降水交互驱动作用最为显著。区域尺度上,南部山区、北部马鬃山地区和中部平原区的主导驱动力各不相同,分别为日照时数、人为干扰强度、降水,双因子交互作用显示人为干扰强度与其它因子的交互最为显著。不同土地利用类型中,耕地产水量的主导驱动力为坡度,而其它地类产水量的主要影响因子为降水。各地类中降水与其他因子的交互均大大增强了单因子驱动力。因此,干旱区产水量多尺度驱动机制研究对区域水资源可持续管理至关重要。

疏勒河流域土壤含水率反演

土壤含水率是影响干旱区植物生长的重要因素,获取区域尺度土壤含水率数据,能够为干旱半干旱区生态恢复和脆弱生态系统保护提供科学依据。结合MODIS地表温度和反射率数据及全球陆面数据同化系统（GLDAS）土壤含水率数据,利用表观热惯量法和统计降尺度方法反演疏勒河流域土壤含水率,研究其时空变化及其与植被的相关性,得到以下结论：2016年整个疏勒河流域年均土壤含水率偏低,且季节变化显著,其均值、离散程度存在7月〉 10月〉 4月〉 12月的趋势;流域东部土壤含水率整体高于西部;流域土壤含水率空间分布的季节变化显著,其变异系数的空间分布与年均土壤含水率相似;土壤含水率与归一化植被指数NDVI正相关,但不同区域两者相关程度不同,灌区土壤含水率与植被的相关性最高。