四川水稻不同生育阶段的干旱风险评估

水稻是四川最主要的粮食作物,而干旱是制约水稻生产的主要因素,四川省春旱、夏旱和伏旱灾害频发,常导致水稻减产。本研究基于气象资料、水稻灾情史料和生育期资料,选取湿润指数距平率作为水稻干旱指标,构建了四川水稻干旱等级,并利用灾情样本进行了验证。在此基础上,分析了1961-2015年四川水稻不同种植区不同生育阶段的干旱时空变化特征及风险分布状况。结果表明:从时间变化看,近55年来,水稻移栽～孕穗期干旱总站数平均每10年增多0.56个,其中轻旱和重旱平均每10年分别增多0.20个和0.41个,而中旱基本不变;孕穗～开花期干旱总站数平均每10年减少0.49个,其中中旱和重旱平均每10年均减少0.22个,而轻旱基本不变;开花～成熟期干旱总站数平均每10年增多0.54个,其中轻旱和重旱平均每10年分别增多0.23个和0.55个,而中旱基本不变。干旱频率的分布特征为:移栽～孕穗期的干旱频率呈现中部高、西南部和东北部低的特征,高发区主要分布在北部的绵阳-南部的宜宾一线(36%～58.2%);孕穗～开花期的干旱频率由西向东递增,高发区主要分布在盆地北部和东北部(36%～61.9%);开花～成熟期的干旱频率呈由西向东递增的趋势,高发区主要分布在盆地东北部和盆南的局部地区(30%～47.3%)。水稻干旱风险分布为:移栽～孕穗期较高风险区和高风险区主要集中在德阳、资阳和宜宾等地;孕穗～开花期较高风险区和高风险区主要在盆地中部和东北部;开花～成熟期较高风险区和高风险区主要在盆地东北部和盆南的局部地区。

Risk assessment of drought on rice at different growth stages in Sichuan Province

Rice is the most important crop in Sichuan Province, however, drought is a major limiting factor for the rice production in the region. The frequent droughts in spring,summer,and late-summer have been significantly impacting rice yield in Sichuan. We collected daily meteorological data from 84 meteorological stations and corresponding historical disaster and phenology data of rice of 1961 to 2015 in Sichuan and used the wetness index anomaly rate as rice drought index, the spatial and temporary changes and risk of rice growth were evaluated at different development stages. The results showed that during the stage of transplanting to booting, the number of stations showing drought increased in a rate of 0.56 sites·(10a)^-1in the studied period(55 years).Among them, the number of stations with mild and severe droughts showed an increased trend of 0.20 sites·(10a)^-1and 0.41 sites·(10a)^-1, respectively,but no significant changes for moderate drought situations. During the stage from booting to flowering, the number of stations with drought decreased in a rate of -0.49 sites·(10a)^-1. The number of stations with moderate and severe droughts decreased in a rate of -0.22 sites·(10a)^-1, but no significant change for mild drought. In the stage of flowering to maturity, the number of stations with drought increased at a rate of 0.54 sites·(10a)^-1. Among them, the number of stations showing mild and severe droughts increased in a trend of 0.23 sites·(10a)^-1and 0.55 sites·(10a)^-1, respectively, but, no significant changes for moderate drought.From transplanting to booting, the highest values of rice drought frequency appeared in the central part of study area (36%~58.2%), but the lowest values appeared in the southwestern and northeastern parts of study area. From booting to flowering,spatial distribution of drought frequency showed a band shape, gradually increasing from the western to eastern parts of study area, and the highest frequency appeared in the northern basin and northeastern basin (36%~61.9%). From flowering to maturity,spatial distribution of drought frequency also showed a band shape, gradually increasing from the western to the eastern, and the highest frequency appeared in the southern basin and northeastern basin (30%~47.3%).During the stage of transplanting to booting, high-risk areas and sub-high risk areas of drought mainly concentrated in Deyang, Ziyang and Yibin. From booting to flowering, high-risk areas and sub-high risk areas distributed in central basin and northeastern basin. During the next stage,flowering to maturity, high-risk areas and sub-high risk areas appeared in the southern basin and northeastern basin.