中国西北半干旱区玉米干旱脆弱性特征及调控机制

The semi-arid regions in northwestern China are an important rain-fed agricultural region. Maize is one of the main crops in this area. Drought is one of the most important factors that restrict the growth and yield formation of maize. Through analyzing the temporal and spatial distribution characteristics of maize drought, considering the physiological characteristics, crop cultivation, farming system, the sensitivity of the crop growth period for precipitation, and the impact of climate, social economy and natural environment conditions on drought vulnerability, and starting with environmental adaptive capacity, adaptability, sensitivity and exposure, we construct the evaluation indexes and evaluation model of vulnerability of maize to drought and quantitatively analyze the temporal and spatial distribution characteristics of vulnerability of maize to drought in different growth stages, then explore the influencing factors of vulnerability of maize to drought by mathematical statistics method in different time and region. Choosing the typical drought years and according to the relationship between vulnerability of maize and the yield loss by drought, we establish the curve of “vulnerability - loss”. Quantitative analysis of influence degree on the yield loss of maize by drought from hazard factors in different growth period of water supply, heat condition, etc. and through analyzing the curve of “vulnerability - loss”, the regulation mechanism of vulnerability of maize to drought is revealed. This work is important to enrich basic theory research of vulnerability of maize to drought and provide scientific basis for drought relief management of maize in northwestern China.

中国西北半干旱区是重要的雨养农业区，玉米是该地区主要的粮食作物，干旱是制约其生长发育和产量形成的最主要因素。本项目通过分析玉米干旱时空分布特征，充分考虑玉米自身生理特征、作物栽培、耕作制度、作物生育期对降水的敏感性以及气象、社会经济和自然环境等条件对干旱脆弱性的影响，从环境适应性、自适应性、暴露性和敏感性4方面入手，构建玉米干旱脆弱性评价指标和评价模型，定量分析不同生育期玉米干旱脆弱性的时空分布规律，并运用数理统计方法探讨不同时间和地域的玉米干旱脆弱性影响因素。选择典型干旱年，根据玉米干旱脆弱性强度和干旱灾损指标之间的关系，建立干旱“脆弱性——损失”曲线。定量分析不同生育期水分供应、热量状况等致灾因子对玉米干旱灾损的影响程度，并通过玉米干旱“脆弱性——损失”曲线，揭示玉米干旱脆弱性调控机制。该工作对于丰富玉米干旱脆弱性基础理论研究具有重要价值，为西北半干旱区玉米抗旱减灾工作提供科学依据。

中国西北半干旱区是重要的雨养农业区，玉米种植面积和单位面积产量明显增加，占粮食生产比重明显提高。干旱是制约玉米生长发育和产量形成的最主要因素。本项目揭示了玉米干旱脆弱性分布特征及变化规律；获得了玉米干旱脆弱性分布曲线；探讨了玉米干旱脆弱性调控机制。研究表明，甘肃省玉米相对气象产量概率分布离散性强，受气象条件影响剧烈，陕西、宁夏次之。玉米干旱的高及次高脆弱区主要位于甘肃的临夏、定西、会宁、秦安、平凉东北部和庆阳北部，宁夏的盐池和固原以及陕西榆林的西部和南部、关中的东部和南部地区。采用二维正态信息扩散方法构造了气象干旱程度与相对气象产量的脆弱性关系，得到了中国西北地区东部玉米干旱脆弱性曲线，发现当气象干旱程度较低时，玉米相对气象产量表现为轻度增产，随着气象干旱程度增加，玉米相对气象产量逐渐减产。西北地区东部玉米播种期提前，快速生长期缩短，生长中期延长，全生育期增加。玉米生育期内温度呈增加趋势，有效降水量呈减少趋势，研究区北部太阳辐射呈增加趋势。干旱在玉米生长初期和末期呈增加趋势。将研究区分为高聚类区（产量较高HH）、低聚类区（产量较低LL）和高值主要由低值围绕的异常区（高产量区与低产量区之间的过渡区HL）。玉米生长初期和后期，HH和LL区温度与玉米产量呈正相关；快速生长期，HL区温度升高令玉米增产；LL区温度增加令玉米减产。HH区玉米各生长阶段有效降水量与产量呈负相关；LL区玉米生长中期和后期有效降水与产量分别呈正相关和负相关；HL区有效降水增加对产量具有正效应。HH和HL区太阳辐射在玉米生长初期与产量呈负相关，在玉米生长末期与产量呈正相关；LL区太阳辐射与玉米产量关系不显著。HH区玉米各生育期生长发育过程普遍受干旱影响。HL区干旱主要影响玉米生长初期、快速生长期和生长中期。LL区干旱主要影响玉米的快速生长期。研究结果可以为当地农业干旱灾害风险评估、预警及抗旱减灾适应对策提供依据。