全球变化背景下玉米干旱发生发展过程及其致灾临界气象条件研究

According to the key scientific problems of the crop drought occurrence and development and disaster-induced thresholds of meteorological conditions, the drought occurrence and development processes of maize (Spring maize and Summer maize) ecosystems and disaster-induced thresholds of meteorological conditions under global change would be studies in this project, in terms of long-term observation data including eddy covariance data from the Jinzhou (Spring maize) and Gucheng (Summer maize) agrometeorological experimental stations, together with the data from the simulating experiments of the responses of maize (Spring maize and Summer maize) to different water gradients. The research activities include the drought occurrence and development processes of maize agroecosystems and the responding mechanisms of ecophysiological, morphological and functional characteristics of maize, drought sensitive indices of maize growth, disaster-induced thresholds of meteorological conditions in the leaf and canopy scales, and the developments of crop water deficit index (CWDI) and CWDI simulation model driven by remote sensing and meteorological data based on the breakthrough point of maize leaf/canopy water content change, in order to emphasize the comprehensive interactions of atmospheric dryness, water supply capacity of soil and crop drought tolerance and to realize accurately the monitoring and evaluation of long-term and large scale drought occurrence and development processes of maize ecosystems based on remote sense and meteorological data. Further, the disaster-induced thresholds of meteorological conditions under global change and the drought grade division would be verified and improved in terms of nearly 50 years’ observation data from China's maize agricultural meteorological observation stations. The evolution of spatiotemporal patterns of maize drought in China would be evaluated during recent 50 years and future climate scenarios (RCPs). The counter-measures of maize production would be discussed in the project in order to cope with the negative effects of drought.

围绕作物干旱发生发展过程与致灾临界气象条件这一关键科学问题，以玉米为研究对象，基于春玉米(锦州)和夏玉米(固城)农业气象试验站的长期定位观测和涡相关观测资料及玉米对不同水分胁迫响应的模拟试验，研究玉米作物干旱发生与发展过程及其生理生态、形态与功能变化机制；分析玉米生长对干旱响应的敏感性指标；明确玉米叶片/冠层干旱致灾临界气象条件；以玉米叶片/冠层含水量变化为切入点，发展反映大气干燥程度、土壤供水能力和作物耐旱能力综合作用的作物水分亏缺指数及其模拟模型，实现基于遥感信息和气象观测资料的长时期、大范围作物干旱发生发展动态监测和作物受旱程度准确评估。结合近50年我国玉米农业气象观测站的长期观测资料，验证与完善玉米干旱致灾临界气象条件与干旱等级划分。评估近50年及未来气候变化情景(RCPs)下我国玉米干旱时空格局演变趋势，探讨玉米生产应对干旱对策措施，为确保玉米生产安全提供依据。

旱灾是我国农业面临的最主要灾害。项目围绕玉米干旱发生发展过程与致灾临界气象条件这一关键科学问题，重点开展了5方面的研究，即玉米干旱发生发展过程及影响分析，玉米生长对干旱响应的敏感指标分析，玉米干旱的致灾临界气象条件研究，玉米干旱的发生发展模拟模型研究和玉米干旱的时空格局及其演变趋势。通过项目实施，阐明了玉米干旱发生发展过程及其影响，给出了玉米干旱发生发展过程在茎含水率、叶含水率、叶片光合作用、叶面积扩张、叶面积变化和干物质积累变化的影响传递过程，指出初始土壤水分越低影响越显著，且玉米叶片水分利用效率具有空间稳定性与年龄的保守性。给出了玉米对干旱响应的敏感指标，指出光合生理指标较植株水分对干旱敏感程度大，玉米植株水分状况、光合生理指标主要受当前土壤水分状况影响，而形态结构和生物量指标与累积水分变化量的关系更加密切。提出了基于统计容忍区间的玉米干旱致灾临界气象条件确定方法，给出了不同叶位叶片的最大含水率约为83.7%（82.6%-85.1%），叶片光合作用为零的叶片含水量约为72.0%（70.1%-74.0%），且叶片光合作用限制因素由气孔限制向非气孔限制转换时叶片含水率约为75.5%（73.0%-77.4%）。发展了玉米干旱发生发展模拟模型，包括反映干旱强度与持续时间的干旱程度模拟模型与等级划分以及遥感信息驱动的作物干旱监测模型，即基于NDVI与环境湿度的作物水分亏缺指数（WDI）模拟模型、基于NDVI与气温的作物土壤水分模拟模型以及基于高光谱遥感的作物冠层含水量模拟模型。阐明了玉米干旱的时空格局及其演变趋势，确定了玉米趋势产量最优拟合方法为Logistic曲线拟合方法和基于实际灾害的干旱灾害强度等级划分。未来气候情景下，春玉米各生育期干旱发生概率总体上均小于夏玉米。研究结果为提高未来气候变化背景下玉米生产防旱抗旱能力，客观辨识、监测玉米干旱发生发展提供了科技支撑。