内陆干旱区非生长季生态输水有效性的同位素示踪研究

Ecological water conveyance is an important means to relieve the uneven distribution of water resources, guarantee ecological water demand and rebuild damaged plant communities in inland river basins in arid areas of China. At present, however, the availability of ecological water conveyance in non-growing season for plants and the mechanism of soil moisture regulation across seasons remain unclear. In this study, the riparian zone of the terminal lake of Shiyang River was taken as the study area. Based on field investigation and monitoring of eco-hydrology, the water absorption horizons of main plants were determined by hydrogen and oxygen isotope tracing method. The contribution ratio of ecological water conveyance and precipitation for plant water utilization in non-growing season was calculated. According to the variation of plant water sources along the vertical lakeshore, the differences of water use efficiency and mode between plants in different habitats during non-growing season were analyzed. Based on the monitoring data of water, temperature and isotope in typical profiles, the transforming relationship between lake water, soil water and groundwater was analyzed, especially the effects of freeze-thaw cycle of frozen soil, fluctuation of groundwater and infiltration of seasonally submerged area on water maintenance of plant water-absorbing horizon, and the mechanism of trans-seasonal storage of ecological water in plant boundary was revealed. The study provides a scientific basis for the protection of ecological environment and the optimal distribution of water resources in Shiyang River Basin, and provides a reference for similar studies in other arid inland river basins.

生态输水是缓解我国干旱区内陆河流域水资源分布不均、保障生态需水和重建受损植物群落的重要手段，目前关于非生长季节生态输水对植物的有效性及土壤跨季节对水分的调控机理尚不明确。本研究以石羊河尾闾湖湖岸带为研究区，基于生态水文野外调查和监测，借助氢氧环境同位素示踪，确定主要植物物种的吸水深度，计算非生长季生态输水和生长季降水对植物水分利用的贡献比例；基于植物水分来源在垂直湖岸的样带上的变化，分析不同生境下植物对非生长季输水利用效率和方式的差异；基于典型剖面上水、温、同位素等监测数据，分析湖水-土壤水-地下水间的转化关系，特别是冻土的冻融循环、地下水的波动、季节性淹没区的入渗对植物吸水层位水分维持的影响，进而揭示生态输水在植物生境中跨季度储存的机制。研究为石羊河流域生态环境的保护和水资源的优化配置提供科学依据，也为其他干旱内陆河流域的同类研究提供借鉴。

本研究以西北干旱区石羊河尾闾——青土湖湿地作为研究区，选取区内分布最广泛的建群物种——芦苇和白刺作为研究对象，构建了垂向空间上自下而上的“地下水（Groundwater）-土壤（Soil）-地表水（Surface water）-植被（Plant）-大气（Atmosphere）连续体（GSSPAC）”的地下水—湿地生态系统多要素一体化动态监测网络，通过调查、监测和稳定同位素示踪等手段，确定了植物吸水层位及各水分来源的贡献比例，探究了植物利用非生长季生态输水的时空异质性，阐明了干旱区非生长季生态输水植物的水分来源和水分利用策略，为我国西部干旱区重要湿地保护、生态环境恢复及地下水科学合理开发利用提供了理论依据和参考借鉴。