气候变化背景下黄土高原土地利用影响径流的空间尺度效应

The runoff from rivers of the Loess Plateau has been reduced in recent decades so strong that the water supply security of this region is threatened. The climate change with a dry-warm trend contributed to this runoff reduction at a certain extent, but the key reason was the land use change as large-scaled vegetation restoration and terrace building for controlling soil erosion. Therefore, it is very necessary to have a rational and integrated management of the natural resuources of water, soil and vegetation in watersheds, in order to maintain the regional sustainable development and safe water supply. The precondition for this is to fully understand and exactly quantify the land use impact on runoff and its spatio-temporal variation. However, the current studies were mostly scale-independent and the individual results were obviously diffrerent from each other. The mechanism of the environment change impact on runoff is still not fully understood, which limits the integrated management of water, soil and vegetaion. In this project, it is planed to implement a multi-scaled (from plot to large watershed) eco-hydrological study in the representative watersheds of the Loess Plateau, such as the Jinghe River. Firstly, the spatio-temporal distribution and dynamics of hydrological environment including land cover, will be investigated; secondly, the environment change impact on hydrological processes and runoff will be identified; thirdly, the dominant processes controlling runoff and its variation with environement and spatial scale will be distinguished; fourthly, the scale effect of environment impact on runoff will be quantitatively expressed with some parameters. Based on the new progresses mentioned above, the distributed eco-hydrological watershed model will be improved, and then the runoff response in multiple scales to the land use change (such as afforestation, vegetation restoration and terrace building) under climate change will be simulated. This project will promote the further development of eco-hydrology and the integrated management of water, soil and vegetation in the Loess Plateau.

黄土高原的河川径流近几十年间大幅减少，严重威胁区域水安全，这与气候干热化有一定关系，但土地利用变化特别是为控制侵蚀的大规模植被恢复和梯田修建是主要原因。因此，要维持区域协调发展和供水安全，就要合理调控水-土-植被资源的利用，其前提是准确辨识土地利用的径流影响及其时空差异。然而，目前的研究缺乏尺度关联，不同研究结果间差别较大，对环境影响径流的尺度效应机理认识不清，不能满足水土资源综合管理的科技需求。本项目拟主要在黄土高原泾河流域，从样地到流域的多个空间尺度上，研究土地覆被等水文要素的时空动态特征，辨识其对水文过程和径流数量的影响，揭示影响径流的主导过程随环境条件和尺度大小的变化规律并进行参数化定量表达，在理解尺度效应形成机理的基础上改进现有的分布式流域生态水文模型，多尺度模拟分析气候变化背景下造林种草和修建梯田等土地利用变化的径流影响，推动生态水文学发展和黄土高原水-土-植被资源的综合管理。

黄土高原河川径流近几十年大幅减少，严重威胁到区域供水安全和协调发展，主要驱动因素已从水土保持措施转为退耕还林导致的森林植被大规模恢复。因此，需准确评价和调节植被的径流影响，关键是要深入认识径流影响的空间尺度效应并寻找尺度转换技术，使小尺度观测结果能上推应用到大尺度。为此，在黄土高原典型流域和区域，分析了气候和植被的变化趋势及退耕还林驱动作用和其导致的土壤变化，发现增加森林植被导致的径流减少存在空间差异；在样地尺度研究了林、灌、草的植被结构及水文作用，对比了主要植被类型的水文影响；尤其在六盘山区典型坡面上研究了植被与土壤水文特征的坡位变化和水文影响及其尺度效应，确定了主要影响因素；在样地、坡面、小流域、流域（区域）尺度分析了森林减少径流作用；建立了森林蒸散及组分响应潜在蒸散、土壤湿度、叶面积指数的耦合模型；改进了Budyko模型以能同时反映流域气候和土地利用的径流影响；发现了流域年蒸散及其受森林影响随流域面积增加而增大的黄土区特有规律并建立了数量关系；提出了考虑优势度影响的从样树到样地的蒸腾估计和考虑水文要素空间差异的从样地到坡面的水文影响尺度上推技术，以及将样地的植被水文影响上推应用到坡面和流域的技术途径；确立了考虑径流影响的森林多功能管理途径和决策步骤。培养博、硕士12、25名并在读4、5名，发表论文113篇和专著2章，2人获省部级荣誉，4人获省部级科技奖励。广泛开展了学术交流，组织学术会议3次，接待国外专家22人次，参加国际会议24人次，大会发言3人次，参与了FAO的森林与水行动计划，2人学术任职国际林联；多家媒体多次报道研究成果，参加了中国科学院生态水文学科发展咨询项目，参与了中央财经领导小组重大课题《我国水安全战略》和《生态文明建设》调研报告，得到国家领导人批示，促进完善了我国旱区林业政策，推动发展了旱区生态水文学及水-土-植被综合管理，产生了积极的学术和社会影响。