高寒草地斑块破碎化格局形成及侵蚀响应

With the influence of global climate change and human activities, the fragmentation pattern of patch reduced the vegetation coverage and exposed soil surface during alpine grassland degradation. The exposed soil surface is easy to generate serious soil and water loss due to it suffering intense ultraviolet radiation and the combined action of water erosion, wind erosion and freezing-thawing. Severe soil and water loss caused serious impact on the restoration and sustainable development of regional ecosystems. This project focuses on the formation of patch pattern, and the erosion process under frozen and thawed conditions in alpine grassland. Effects of patch pattern on water transportation were studied by field in situ monitoring. Artificial simulation of melting water erosion was established to explore the mechanism of erosion response under frozen and thawed conditions in patch pattern of alpine grassland. The findings of this project could provide scientific basis for vegetation restoration and soil and water conservation in the Qinghai-Tibet Plateau.

在全球气候变化和人类活动影响下高寒草地退化形成斑块破碎化格局，植被覆盖度降低，地表裸露。裸露地表受高原强烈的紫外线辐射，极易在水蚀和冻融等多源驱动力的综合作用下产生严重水土流失，对区域生态系统恢复与可持续发展产生严重影响。本研究围绕高寒草地斑块破碎化格局的水土流失过程，采用野外原位监测方法探究草地斑块破碎化格局在冻融条件下的水分再分配及坡面产流产沙过程；结合人工模拟融水试验，深入分析草地斑块破碎化格局在冻结及解冻条件下侵蚀发生、发展及演变过程，揭示高寒草地斑块破碎化格局在冻融条件下的侵蚀响应机制，为青藏高原高寒草地区域植被恢复与水土保持提供科学依据。

在全球气候变化和人类活动影响下高寒草地退化形成斑块破碎化格局，地表裸露，发生严重水土流失，对区域生态系统恢复与可持续发展产生严重影响。为了明确草地斑块格局的形成对土壤侵蚀过程的影响，本项目以典型退化高寒草地为研究对象，采用野外原位监测与人工模拟的方法，研究了高寒草地斑块格局的水土流失过程。结果明确了草地斑块破碎化格局形成的地上-地下驱动过程，由于过度放牧以及鼠害破坏，打破了原有植被演替的平衡和规律，加之气候变暖，使得高寒草地植被及其土壤结构被严重破坏，导致土壤水源涵养功能急剧降低。通过天然和人工模拟降雨的结合，阐明了草地斑块破碎化格局的水分入渗、地表径流的降雨再分配及水土流失过程，即当草甸斑块覆盖度从90%降低到30%时，土壤侵蚀量增加了3.4倍，同时也降低36.8%的径流量和对下游河流的补给量。降雨强度和斑块盖度决定了斑块格局的水土流失过程，高寒草地浅而密的植物根系和较高的植被盖度，使其在保持地表径流的同时存储足够多的雨水以满足不同物种的生长需要，既保持了地表径流，又控制了水土流失，有利于该地区的土壤侵蚀调控和水资源的可持续发展。提出了退化高寒草地人工生态恢复中的水土流失防治策略，其中根茎型和密丛型结合的混播模式可保持141.5%-275.9%的地表径流，降低51.2%-58.8%的侵蚀产沙，是防治极度退化高寒草地水土流失的有效途径。研究结果为青藏高原区高寒草地植被恢复与水土保持研究提供科学依据。