华北土石山区变化环境下的流域径流响应规律及其尺度变异

Over the past 40 years, water yield, from the mountains areas of Northern China, showed a sharp reduction. Water shortage has become increasingly prominent. Under the influence of both warming and drying climate and high intensity of human activities, analysis of the impact of large-scale afforestation on runoff has become a hotspot in ecohydrology at present. However, the current reseach lacks of multi-scale studies, and the results of different studies vary greatly. In addition, previous studies rarely consider the effect of change in forest structure and landscape on runoff, which limits the fully understanding of the mechanism of the runoff evolution at different scales and its driving factors caused by forest change. It also limits the sustainable development of water, soil and vegetation. Hence, multiscale typical forest watershed, located in Mountain Area of Northern China, will be selected as our study objects. Firstly, the characteristics and the dynamics evolution of climatic factors, land cover, runoff and its components will be analyzed. Secondly, the respective contribution of changes in climate, forest and other environmental factors to runoff will be evoluted. Thirdly, the drive mechanism of hydrological processes in forest watersheds will be distinguished, and the relationship between forest and water at different spatial and temporal scales will be identified. This study will enhance our understanding of the transfer mechanism of the relationship between forest and water at watershed scale. Meanwhile, this project will promote the integrated management of water, soil and vegetation in North China.

近40年华北土石山区上游来水量急剧减少，水资源短缺问题日益凸显。在气候暖干化和高强度人类活动耦合影响下，大规模森林植被建设对流域产水量有何影响成为流域生态水文学研究的热点。目前相关研究缺乏尺度关联，不同研究结果差别较大，且多围绕森林数量变化对流域径流的影响展开，缺乏森林格局与质量变化对流域径流影响的研究，导致不同尺度流域径流变化机理及其驱动机制认识不清，限制了区域水-土-植被资源的可持续发展。为此，本研究拟以华北土石山区多尺度典型森林流域为研究对象，分析流域气候与土地覆被时空动态变化特征，探究环境变化下多尺度流域径流及其组分演变规律，量化评估气候、森林数量与质量等环境要素变化对流域径流量的影响，辨析森林流域水文过程变化驱动机制，初步探讨流域林水关系在不同空间和时间尺度上的变异规律。该研究利于增进对森林植被在流域尺度调水机理的认识，对推动华北地区水-土-植被资源综合管理具有重要意义。

摘要：近40年华北土石山区上游来水量急剧减少，水资源短缺问题日益凸显。在气候暖干化和高强度人类活动耦合影响下，大规模森林植被建设对流域产水量有何影响引发社会关注。目前相关研究缺乏尺度关联，且多围绕森林数量变化对流域径流影响展开，缺乏森林质量变化对流域径流影响的研究。为此，本项目以大规模生态建设背景下的华北土石山区典型多尺度流域为研究对象，以区域上游来水量急剧减少为背景，采用数理统计、经验模型以及分布式水文模型等方法探讨了变化环境下的华北土石山区典型多尺度流域径流变化规律及其主要驱动因素，深入分析了森林植被数量与质量变化对流域径流及其组分的影响机制和流域林水关系尺度依存特征。研究结果表明：（1）近40年华北土石山区潮白河流域年降水量下降趋势不显著，但年均气温呈显著上升趋势，不同尺度典型流域年均径流量呈现出不同程度的下降趋势；（2）基于多个流域计算分析结果，较森林植被建设而言，气候变化对流域径流变化影响更大，是华北土石山区径流减少的主要驱动因素。（3）流域降水每增加1%，流域径流平均增加0.25%；潜在蒸散发每增加1%，流域径流平均减少0.07%；森林单位面积生物量每增加1%，流域年径流深减少0.06%，其中，壤中流比例减少0.028%。（4）流域森林植被与年径流率之间存在尺度效应。即：在中小尺度流域（<1000km2），每1km2森林覆被减少径流1.23mm；在中大尺度流域上（1000-15000 km2），每1km2森林覆被减少径流0.02mm，森林对流域径流影响不大。