青藏高原高寒草地土壤水文过程和储水功能对气候变化的响应

The alpine grassland of the Tibetan Plateau is the source of three rivers and the Asian Water Tower. It is important to understand the ecological and hydrological processes of the alpine grassland and its response to climate change, which can make us better understand the ecosystem services of the alpine grassland. Nowadays, the Tibetan Plateau is experiencing a rapid warming process, which has significant effects on the soil water holding characteristics of the alpine grassland, but the potential risks in the future are still not well understood. In this study, a warming and precipitation manipulation experiment was established in the alpine grassland ecosystem in Haibei, Qinghai. Soil water dynamics, freeze-thaw process, evapotranspiration and leakage were selected to monitor by field observation, lab analysis and model simulation. We also calculated the soil water storage function to study the changes of soil hydrological processes and water storage functions of grassland ecosystems in the Tibetan Plateau under climate change. The details included: 1) Studied the differences of soil water dynamics, freeze-thaw process and vegetation water use efficiency under the conditions of warming and precipitation change; 2) Quantitatived the soil surface evapotranspiration and deep soil leakage to establish the water balance equation in the alpine grassland under the warming and precipitation change conditions; 3) Calculated the soil water storage and soil water holding capacity of the ecosystem, and compared the response of soil water storage function under climate change. This study can provide a scientific basis for predicting the water conservation function and sustainable management of the alpine grassland under climate change.

青藏高原高寒草地是三江之源，亚洲水塔。明确高寒草地土壤生态水文过程及其对气候变化的响应，对深入理解高寒草地的生态系统服务具有重要意义。目前青藏高原经历着快速的温暖化过程，这对高寒草地土壤持水特性有哪些重要影响，未来潜在风险如何，仍然不甚了解。本研究选取在青海海北高寒草地生态系统建立的“增温×降雨控制实验”，采用野外观测、室内测定和模型模拟等方法，监测土壤水分动态、冻融过程、蒸散发和渗漏，并计算土壤储水功能，研究气候变化下青藏高原草地生态系统土壤水文过程和储水功能的变化。具体包括：1）增温和降雨改变条件下土壤水分动态、冻融过程和植被水分利用效率的差异；2）量化增温和降雨改变下高寒草地土壤地表蒸散发和土壤深层渗漏，建立水量平衡方程；3）核算生态系统土壤水分储量及土壤持水性能，比较气候变化下土壤储水功能的响应。本研究可以为预测全球气候变化下高寒草地的水源涵养功能和草地可持续管理提供科学依据。

青藏高原高寒草地是三江之源，亚洲水塔。明确高寒草地土壤生态水文过程及其对气候变化的响应，对深入理解高寒草地的生态系统服务具有重要意义。目前青藏高原经历着快速的温暖化过程，这对高寒草地土壤持水特性有哪些重要影响，未来潜在风险如何，仍然不甚了解。本研究选取在青海海北高寒草地生态系统建立的“增温×降雨控制实验”，采用野外观测、室内测定和模型模拟等方法，监测土壤水分动态、冻融过程、蒸散发和渗漏，并计算土壤储水功能，研究气候变化下青藏高原草地生态系统土壤水文过程和储水功能的变化。本文的主要结论是：1.气候变化对水量平衡的影响：增温降低了土壤水分含量，土壤水分含量随降雨量增加而增加；增温减少了土壤入渗，随着降雨增加，土壤入渗量显著增加；增温通过提高植被冠层蒸发，从而提高了地表蒸散发。总体来说，增温减少了土壤水分含量，而降雨直接对土壤水分有补给作用。2.气候变化对土壤持水性质的影响：增温增加了土壤的吸水能力，但土壤的保水能力降低，即增温条件下土壤会更多地吸收和释放土壤水分，增温后的土壤能吸收更多水分但不能够保持。3.气候变化对生态系统水源涵养功能的影响：增温减少了土壤储水量，而且使土壤更难储存水分；另一方面，增温增加了植被水分消耗（冠层蒸发）和土壤蒸发，从而减少了土壤水分，因此，气候变暖不利于生态系统的水源涵养功能。本研究可以为预测全球气候变化下高寒草地的水源涵养功能和草地可持续管理提供科学依据。