Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100081, China; Key Laboratory of Crop Physiology and Ecology, Ministry of Agriculture and Rural Affairs, Beijing 100081, China.
Sci Total Environ. 2020 Jun 20;722:137677. doi: 10.1016/j.scitotenv.2020.137677. Epub 2020 Mar 4.
Degraded ecosystems refer to systems that deviate from their natural state as a result of natural or anthropogenic disturbances. Alpine swamp meadows on the eastern edge of the Tibetan Plateau have dramatically degraded owing to climate change, overgrazing, and rodents. Understanding the influence of meadow degradation on soil water availability is essential for the development of hydrological models and alpine swamp meadows restoration, which has been poorly explored in the eastern Tibetan Plateau. In this study, we analyzed how degradation affects variation in soil water availability with a series of parameters derived from soil moisture content and soil water retention curves. Our results showed that (1) soil moisture content consistently decreased with degradation and increased with soil depth; (2) soil water retention curves decreased with increasing degradation due to coarser soils and organic matter loss. Field water capacity and the permanent wilting point decreased, whereas the air entry value increased with the severity of degradation; and (3) soil water availability, as represented by soil water potential, available soil water content and fraction was less responsive to degradation than individual soil moisture content or soil water retention curves, which showed similar decreasing trends. However, soil water potential, available soil water content and fraction under moderate and severe degradation were relatively lower than those under light degradation, especially in deep soil layers (>20 cm). Thus, swamp meadow degradation negatively influences soil water availability, which might impede water absorption by deeply rooted species, thereby inducing soil-water stress and possibly increasing drought vulnerability.
退化生态系统是指由于自然或人为干扰而偏离其自然状态的系统。由于气候变化、过度放牧和啮齿动物的影响，青藏高原东缘的高山沼泽草甸已经严重退化。了解草地退化对土壤水分供应的影响对于水文模型的发展和高山沼泽草甸的恢复至关重要，而在青藏高原东部，这方面的研究还很缺乏。在本研究中，我们分析了退化如何通过一系列由土壤水分含量和土壤水分保持曲线得出的参数来影响土壤水分供应的变化。研究结果表明：（1）土壤水分含量随着退化程度的增加而持续下降，随着土壤深度的增加而增加；（2）由于土壤质地变粗和有机质损失，土壤水分保持曲线随着退化程度的增加而降低。田间持水量和永久萎蔫点下降，而进气值随退化程度的加重而增加；（3）土壤水分有效性（以土壤水势、有效土壤含水量和分数表示）对退化的响应不如单个土壤水分含量或土壤水分保持曲线敏感，后者表现出相似的下降趋势。然而，在中重度退化和重度退化下的土壤水势、有效土壤含水量和分数相对较低，尤其是在较深的土层（>20 cm）。因此，沼泽草甸退化会对土壤水分供应产生负面影响，这可能会阻碍深根物种的吸水能力，从而导致土壤-水分胁迫，并可能增加干旱脆弱性。
