灌区农业-生态水文过程对土地利用和种植结构调整的响应机制研究

Land use and plant cover is a dominant factor in hydrological processes. With the development of productivity, large-scale cultivation is an inevitable trend of agricultural development in china. In addition, plant structure is also changing significantly due to the fluctuation of agricultural product prices. Land use and plant cover changes would affect the current hydrological processes and related ecosystems. However, the response mechanism of agro-eco-hydrological processes to land use and plant cover changes has not been fully elucidated. The general objectives of the proposed research are, therefore, to (1) characterize the hydrological processes in irrigated agro-ecosystems with fragmented land cover types and shallow groundwater; (2) set up an agro-eco-hydrological model that can fully take account of the hydrological processes in both crop fields and the natural lands; and (3) quantify the hydrological effects caused by land use and plant cover changes. The Hetao Irrigation District located in Inner Mongolia Autonomous Region is selected as a case study region. Land use and crop distribution maps of the last twenty years are derived from high resolution satellite images of QuickBird or Worldview (about 0.5 m resolution). Field experiments, process model, GIS and RS techniques are to be integrated to build a distributed agro-eco-hydrological model. Then, the current hydrological processes including soil water and salt dynamics, plant transpiration and soil evaporation, groundwater and salt exchange between different land cover types are to be simulated and analyzed using the model. Based on this, a twenty-year model simulation is to be conducted to reveal the influence mechanism of multi-year land use/plant cover changes on agro-eco-hydrological processes. In addition, several large-scale cultivation scenarios are also to be simulated, thus to clarify their hydrological effects. At last, suitable plant cover and land use pattern will be proposed for the study area. It is expected that this research will shed new light on the nature of hydrology in arid irrigated agro-ecosystems and provide a promising tool to describe the hydrological processes. Thus, the proposed research has both scientific and practical merit for modern agriculture.

土地利用和土地覆被对水文过程有显著的影响。伴随着生产力的发展，规模化种植是我国农业发展的必然趋势；同时，受农产品价格的影响，种植结构也在发生着深刻的变化。土地利用和种植结构的调整将会打破农业生态系统现有的水文过程与水资源转化关系，继而影响到其所支撑的生态环境。然而，关于干旱灌区农业-生态水文过程对土地利用和种植结构调整的响应机制研究尚待深入。本研究以此为研究背景，选择内蒙河套灌区为典型研究区，通过集成田间观测、过程模型、GIS和遥感反演，构建灌区农业与生态水文过程耦合模型，对灌区现状条件下的水盐动态及植被耗水过程进行模拟研究；继而根据所构建的模型和高分辨率遥感影像反演的种植结构信息，对近20年来种植结构演变对农业-生态水文过程的影响机制进行分析研究；并通过设置不同的规模化种植格局，预测未来规模化农业生产条件下的生态水文效应；最后根据研究结果提出研究区适宜的种植结构和土地利用格局。

本研究围绕我国农业水资源高效利用与生态环境保护的重大需求，以我国耕地景观单元破碎为背景，选取内蒙古河套灌区典型灌域为研究对象，通过开展系统的野外观测及长序列数据资料搜集，研究了灌区不同景观单元的水盐迁移转化规律，诠释了灌区水转化与生态环境的耦合作用机理；通过集成田间观测、过程模型、GIS和遥感反演，构建了能够同时考虑农田不同作物与天然植被的灌区农业与生态水文过程耦合模型，实现了不同土地利用/种植结构下的水盐动态模拟，分析了现状条件下不同土地利用/种植结构的水文过程及其影响因素；并进一步基于构建的灌区农业与生态水文过程模型，开展了灌区不同土地利用/种植结构地下水位控制和灌溉策略的模拟优化，揭示了灌区水分生产力的尺度效应，提出了能够提高灌区水生产力和生态健康的种植结构及土地利用格局。. 研究结果表明：（1）研究区多年平均ET为628mm，其中耕地737mm，荒地525mm，生长季ET约为全年的74%；研究区总供水量（包括灌溉和降雨）的36%首先储存在地下水系统，通过重分布，总引水量的63%被耕地消耗，20%被荒地消耗，总引入盐分的67%积累在了荒地。（2）灌区现状灌溉渗漏量占到了模拟时段总施加水量的40%，同时耕地地下水毛管上升量占到了总腾发量的23%-53%，天然荒地的占到了75-82%；耕地为地下水补给区，以净地下水盐流出为主，荒地为地下水消耗区，以净地下水盐流入为主；总引水量的21% 通过地下水迁移到了荒地，同时总引入盐量的57-79%的盐分积累在了荒地。（3）耕地的最优地下水埋深区间为1.7-2.3m，天然荒地的最优区间为1.4-2.0m；在最优地下水埋深情景下，生长季有15-30%的节水潜力；对瓜菜和荒地的补充灌溉推荐深度分别为100mm和250mm；水分生产力的尺度效应主要来自灌溉水的再利用及土地利用分布格局；研究区采用较大的种植规模（20 hm2）更有利于灌区节水、排盐。该研究成果可为农业节水、生态保护和土地利用/种植结构调整提供科学依据。