“亚洲水塔”变化对青藏高原生态系统的影响

Effects of Changed Asian Water Tower on Tibetan Plateau Ecosystem: A Review

        底阳平(中国科学院地理科学与资源研究所 生态系统网络观测与模拟重点实验室 北京 100101;北京大学深圳研究生院 深圳 518055)
        张扬建(中国科学院地理科学与资源研究所 生态系统网络观测与模拟重点实验室 北京 100101;中国科学院青藏高原地球科学卓越创新中心 北京 100101;中国科学院大学 资源与环境学院 北京 100190)
        曾辉(北京大学深圳研究生院 深圳 518055;北京大学 城市与环境学院 北京 100871)
        唐泽(中国科学院地理科学与资源研究所 生态系统网络观测与模拟重点实验室 北京 100101;中国科学院大学 资源与环境学院 北京 100190)

         气候变化;降水;青藏高原;物候;群落组成;水分条件

        climate change;precipitation;Tibetan Plateau;phenology;community composition;water

        青藏高原及周边地区作为"亚洲水塔"，拥有广大的冰川、冻土和湖泊，是重要的储水区域，为陆地生态系统提供了最基本的水分资源。生态系统赖以生存的水分资源主要来自自然降水，同时温度的改变会通过调节蒸发散而影响土壤湿度，从而影响生态系统过程。文章从生态系统群落组成和结构，植被物候、覆盖度和生产力，以及生态系统水源涵养功能等多个角度，综述近年来水资源变化给青藏高原生态系统带来的影响，旨在深入了解内部机制，为理论研究和环境治理提供参考。在群落组成和结构方面，水分条件改变引起群落盖度和多样性改变，影响草地群落物种的比例及其相对重要性，进而驱动群落演替。在物候方面，增加季前降水使春季物候提前，生长季降水的增加使秋季物候推迟，季前降水同时调节了物候对温度的响应。植被覆盖度和生产力总体态势为变好，但局部变化存在差异，增温和降水的非协调性变化对植被造成复杂的影响，体现在不同地区的生态控制因子存在差异。水源涵养功能是土壤-植被-大气系统相互作用的结果，受到气候、植被、土壤和人类活动等多种因素影响。在未来需要用系统的思想和方式，关注气候要素和植被覆盖变化对水源涵养量的耦合作用，探究各组分的作用效果和强度。

        As the "water tower" of Asia, the Tibetan Plateau provides basic water resources for the regional ecosystems. Among the variety of water resources, natural precipitation is most relevant to ecosystems, and temperature also affects soil moisture availability by regulating evapotranspiration, thus affecting ecosystem process. From the aspects of community composition and structure, vegetation phenology, coverage and productivity, and water conservation function by ecosystems, this paper reviewed the series of impacts caused by changed water resources on the Tibetan Plateau ecosystems in recent years, and the underlying mechanism was further revealed. The shifted water conditions led to changes in community coverage, species diversity, and relative importance of each species, thereby driving community succession. The strengthened preseason precipitation advanced spring phenology, and postponed autumn phenology. The preseason precipitation also adjusted the responses of vegetation phenology to temperature. Under global changes, the vegetation coverage increased and ecosystem productivity strengthened on the Tibetan Plateau, but with high spatial heterogeneities. The incongruous changes of temperature and precipitation complicated their effects on vegetation, as exhibited by their distinct relative determination effects in different areas. Water conservation by ecosystems stems from interactions among soil-vegetation-atmosphere, which is influenced by climate, vegetation, soil, human activities, etc. The future studies need to pay mounting attentions to the coupling effects of climates and vegetation cover on water conservation of ecosystems, and also attribute the separate contribution from each factor.