微咸水灌溉和干热风交互作用下华北冬小麦蒸腾的响应机理和地面遥感诊断研究

Both water resource crisis and climate risk become more remarkable in the North China Plain, a major grain-producing area in China. Brackish water irrigation may be an alternative way to relieve water resource shortage and climate risk in the North China Plain in the near future. Existing brackish water utilization and extreme climate researches have not addressed response mechanism of crops affected by both brackish water and extreme climate events, and remote sensing diagnosis on the affected crops. Taking irrigation-dependent winter wheat in the North China Plain as a research object, this proposal designs scenarios of brackish water irrigation and dry-hot wind, a typical extreme climate event during the growth period of winter wheat. We will (1) deploy the cross experiments of brackish water irrigation and dry-hot wind in the Yucheng Experimental Station; (2) measure winter wheat physiological and ecological parameters, spectra and thermal infrared temperature, and then (3) explore the response mechanism of winter wheat transpiration to brackish water irrigation and dry-hot wind. Also, we will (4) improve a remote sensing model to diagnose winter wheat health affected by brackish water irrigation and dry-hot wind through transpiration estimation. This proposal is expected to fill gaps in understanding the response and adaptation of farmland ecosystems to extreme climate, and also to improve managements of agricultural resources in the North China Plain, especially in deep groundwater mining-limited areas.

作为中国粮食主产区的华北平原，水资源危机和气候风险的矛盾尤为突出。华北平原微咸水资源可能是未来应对淡水资源不足和气候风险的重要途径。已有的微咸水利用和极端气候研究还没有报道其交互作用下作物响应机理及遥感诊断方法。本项目以华北平原主要灌溉作物冬小麦为研究对象，设定微咸水灌溉场景和典型极端气候事件（干热风）场景，拟在禹城综合试验站设置微咸水灌溉和干热风交互试验，观测冬小麦生理生态响应特征以及光谱和热红外温度响应特征，揭示冬小麦蒸腾对微咸水灌溉和干热风响应的机理过程；同时改进遥感模型，提高作物蒸腾估算精度，研发冬小麦蒸腾对微咸水灌溉和干热风响应的遥感诊断方法。本项目研究结果有望丰富农田生态系统响应和适应极端气候的基础理论，也为华北平原农业资源合理配置，特别是深层地下水限采区农业重新布局提供科学依据。

华北平原淡水资源日趋紧张，但是地下浅层微咸水资源较为丰富，可作为华北主要耗水作物冬小麦补充灌溉的重要水源。该地区冬小麦种植经常受到干热风的危害，随着气候变化的影响，作为极端气候事件的重要形式之一，干热风的危害将日趋严重。微咸水灌溉对冬小麦会形成轻微盐分胁迫，而这种胁迫可能提升冬小麦的抗干热风能力。为了验证该科学假设，在中科院禹城综合试验站设置微咸水灌溉田间控制和干热风模拟发生试验，并利用高光谱成像仪和红外热成像仪对作物冠层进行遥感试验观测。经过4年（2016-2019年）试验和观测，基本验证了以上科学假设。研究发现：1）微咸水灌溉对叶片光合蒸腾和气孔行为的生理胁迫作用与干热风的生理胁迫作用有相似性；2）0.3%矿化度微咸水灌溉比淡水提高了叶片对干热风的生理适应能力，体现了微咸水灌溉对冬小麦抗干热风生理适应的驯化作用；3）由蓝光和红边/近红外光谱波段组成的植被指数有助于土壤盐分的遥感反演；4）基于遥感的冠层阻抗估算模型能够较好的反演微咸水灌溉处理与干热风处理下的冬小麦气孔行为，为作物胁迫遥感诊断提供了有力工具。通过本研究初步明确了冬小麦光合、蒸腾、气孔与微咸水灌溉及干热风之间的关系；初步掌握了冬小麦微咸水灌溉–干热风–气孔–蒸腾的响应机理；改进了Sim-ReSET模型，提高了模型在胁迫环境下估算冬小麦蒸腾的精度。这为微咸水资源科学合理利用和作物的极端气候适应性技术开发提供了理论支撑和模型工具。