基于水分盈亏指数的四川省玉米生育期干旱时空变化特征分析

四川省地形地貌复杂多样,常年多旱灾,玉米是该省主要粮食作物之一,在粮食生产中占有重要地位,但干旱一直是制约四川省玉米生长发育和产量形成的重要因素,常年春、夏、伏旱频发重发,造成玉米年际间产量不稳定。评估四川省玉米生育期干旱状况,分析其时空变化特征,可为相关部门制定农业生产计划、防灾减灾措施以及保险部门确定保费率提供科学依据。本文利用四川省144个玉米种植区气象台站1970—2010年逐日气象数据,以水分盈亏指数作为干旱指标,分析四川省6大玉米种植区域(盆南丘陵区、盆中浅丘区、盆西平丘区、盆周边缘山地区、盆东平行岭谷区和川西南山地区)玉米生育期内干旱频率的时空变化特征及干旱发生风险度的空间分布。结果表明:从时间变化看,各区域干旱频率变化趋势不同,但大部区域从20世纪90年代后期开始明显增加,其中拔节—乳熟期干旱站均次数变化趋势除盆东平行岭谷区随年代呈下降趋势,其余各区都呈上升趋势,乳熟—成熟期干旱站均次数变化趋势盆南丘陵区、盆西平丘区及盆周边缘山地区呈明显上升趋势;从空间分布看,盆南丘陵区轻旱发生次数最高,盆中浅丘区中旱发生次数最高,盆西平丘区及盆东平行岭谷区发生干旱次数相对较低;干旱发生风险度空间分布为:全生育期干旱风险重度区主要集中在盆中浅丘区、盆东平行岭谷区大部及盆南丘陵区部分区域,拔节—乳熟期重度风险区主要集中在盆地北部及盆中浅丘区大部,乳熟—成熟期重度干旱区域分布在盆北、盆东南及盆中浅丘区部分区域。

Spatio-temporal characteristics of drought at different maize growth stages in Sichuan Province as determined by water budget index

Maize, as a major grain crop in Sichuan, has contributed significantly to total grain production in the province. Sichuan Province has a complex topography and various landforms where droughts have posed serious threat to crop production. Drought is therefore a critical factor that has limited the development, growth and yield formation of maize in Sichuan. It has frequently occurred with an increasing severity in the spring and summer, and has caused the unstable yearly maize production. This paper analyzed spatio-temporal distribution of drought at different maize growth stages in order to lay the scientific basis for relevant departmental development of agricultural production programs and disaster prevention and mitigation strategies which would guide insurance agencies in formulating agricultural insurance premium rates. Daily meteorological data, collected from 144 stations in main corn production regions in Sichuan during 1970-2010, were used to calculate water budget index as an indicator for drought during corn growth season. Spatio-temporal variations in drought frequency and drought risk distribution were analyzed for each corn growth stage in 6 six main production regions (hilly area of southern basin, hilly area of central basin, plain and hill areas of western basin, mountain area around basin, equal ridge-valley region of eastern basin and mountain area of southwest Sichuan) of Sichuan Province. The results showed that since the late 1990s, drought frequency had increased in most corn production regions. The changes in drought frequency with time, however, varied from region to region. With the exception of the eastern basin, station-based mean drought frequency during maize jointing to milk-ripening stage increased across the regions. Also station-based mean drought frequency during maize milk-ripening to maturity stage increased in the southern and western basins and the basin edge. For the entire maize cultivation region in Sichuan, mild to strong drought was more prevalent than severe drought. While mild drought was most common in the hilly area of the southern basin, strong drought was prevalent in the shallow hilly area of the central basin. More severe droughts were less frequent in the low hilly areas of the western basin and in the paralleled ridge valley areas of the eastern basin. Severe drought was most frequent in the hilly areas of the southern basin of Sichuan. The risk of drought was high in the central basin and across most of the eastern basin and parts of the southern basin during corn growth season. Between jointing and milking stage, the risk of drought was high in the northern basin and across most of the central basin. From milk to maturity, there was high risk of drought during corn growth season in the north and southeast of the basin and parts of the central basin.