塔河胡杨蒸腾与土壤水-地下水间的水力联系识别与分割

Freshwater fluxes via plant transpiration, streamflow and groundwater recharge are central components of terrestrial hydrosphere. Understanding the sources of water and process that govern each component is important for predicting the effects of climate change on water security and ecosystem services. Compartmentalization of a poorly mobile plant transpiration water pool versus a highly mobile stream/ groundwater pool, if widespread, would challenge existing land surface model parameterizations that assume that plants and streams draw from a single, well mixes subsurface water reservoir. So one of current hot questions of Eco-hydrology is how to quantify water-cycle components and the linkages between plant ecology and physical hydrology by stable-isotope tracing. In order to trace the water sources of plant transpiration and quantify the contribution of each component to Populus euphratica transpiration base on the Lysimeter platform and river-basin scale monitoring system, our objectives are to (1) analyze the 18O and 2H content of each water sources; (2) separate the component, distribution and contribution for Populus euphratica transpiration and soil evaporation; (3) distinguish the hydraulic relationship and the space heterogeneity of heat and water process linked between Populus euphratica transpiration, soil water ,groundwater and streamflow; (4) develop a well physically numerical model framework for simulating the coupled soil water, groundwater and Populus euphratica root water process; (5) prove the mechanism of interaction among surface water, soil water, groundwater and ecological water in Tarim River Basin. Finally, to improve understanding of the effects of climate change on water security and ecosystem services and the response to anthropogenic and natural disturbances and management or restoration in Tarim River.

如何基于区域蒸散发的同位素水文分割，探明地表水热耦合过程的空间异质性成因及水力联系，实现陆面模型植物生理过程和径流过程的参数化已经成为当前生态水文学的难点和热点问题。本项研究旨在利用多学科交叉，借助大型Lysimeter与流域监测平台，开展区域蒸散发的地面观测与同位素示踪试验，研究土壤水和胡杨蒸腾水的多源性水文分割，识别地表蒸散发与土壤水-地下水互为激励-响应的水力联系，阐明胡杨蒸腾水分来源及流域水热耦合过程的空间异质性成因，量化不同水源对胡杨生长的贡献率，构建基于多元信息校正的胡杨蒸腾与土壤水-地下水相互转化的耦合模型，揭示气候变化和人类活动双重驱动下胡杨蒸腾与土壤水-地下水的相互转化机制，为塔河实现水资源优化配置和生态建设提供依据，完善和发展流域生态水文学理论和方法。

如何基于同位素水文分割，探明地表水热耦合过程的空间异质性成因及水力联系是现代生态水文学的难点。项目基于大型Lysimeter，开展了区域蒸散发的地面观测与同位素示踪试验，研究了胡杨蒸腾水的水文分割，识别了地表蒸散发与土壤水-地下水互为激励-响应的水力联系，阐明了胡杨蒸腾水分来源及流域水热耦合过程的空间异质性成因，量化了不同水源对胡杨生长的贡献率，构建了基于多元信息校正的胡杨蒸腾与土壤水-地下水相互转化的耦合模型，揭示了气候变化和人类活动影响下胡杨蒸腾与土壤水-地下水的相互转化机制，为区域水资源优化配置和生态建设提供了依据，发展了流域生态水文学理论和方法。运用水文界面互补相关理论，探明了塔河近40年不同下垫面水热通量变化特征及分异规律，潜在蒸发量平均每10年潜在蒸发下降约9.7mm。探明了塔河降水、河水、土壤水、地下水、胡杨木质部水的稳定同位素含量及空间分布特征，不同林龄胡杨和柽柳的土壤水δ2H和δ18O值均随土壤深度增加呈现出下降趋势，不同林龄胡杨和柽柳的吸水层位随林龄增加而加深，胡杨幼苗和成熟木主要利用0-60cm浅层土壤水且利用比例达到53.4%。中国北方沙区大气降水与土壤水、植物茎干水和地下水中的δ2H和δ18O值呈线性关系，自东向西随着降水量的减少，植物对土壤水分的利用逐渐趋于深层土壤，不同固沙植物（樟子松、油蒿、柠条、柽柳、梭梭、胡杨）土壤水的δ18O值均随土层深度的增加呈现下降趋势。诠释了地下水波动对土壤蒸发、植被蒸腾和低层大气感热和潜热通量的分配的影响，提出了不同生境植物群落演替适宜生态地下水位，＜4 m以乔灌草结构为主，4～5.5 m以乔灌结构为主，＞5.5 m以灌木柽柳为主的单优群落，揭示了胡杨蒸腾与土壤水-地下水相互转化机制以及胡杨生长的响应机理。定量识别了不同下垫面地下水流场分布特征、含水层的赋水条件及水文地质参数，建立了分布式胡杨耗水与地表水-地下水耦合数值模型，探明了不同植物水分利用策略，为人工固沙植被生态修复提供了范式。