我国北方地区苹果干旱时空分布特征

以我国北方苹果主产省为研究区域，基于研究区域内1981—2016年144个气象站点逐日气象数据，结合苹果生育期数据，以干旱指数作为苹果农业干旱指标，明确了研究区域内苹果干旱的空间分布特征及时间变化趋势，结合小波分析方法，揭示了北方苹果干旱发生的周期性规律。结果表明:苹果各生育阶段降水量整体呈由西北向东南增加的趋势，干旱指数空间分布特征呈由西北向东南降低的趋势，苹果花芽萌动-盛花生育阶段干旱程度最大。干旱指数近36年果树萌动-花芽萌动生育阶段呈上升趋势，平均为3.90/（10 a），花芽萌动-盛花、盛花-成熟以及成熟-落叶生育阶段均呈下降趋势，平均值分别为-3.14/（10 a），-0.01/（10 a）和-1.65/（10 a）。苹果不同生育阶段干旱存在3种不同尺度的变化周期，其中花芽萌动-盛花生育阶段发生干旱的周期最短，最小周期为2年。

Spatial and Temporal Distributions of Apple Drought in Northern China

Clarifying the spatial-temporal distribution and the periodic law of drought during different growth stages of apple in northern China can provide a scientific basis for disaster prevention and mitigation and high yield and quality. Based on daily meteorological data of 144 meteorological stations in north of China from 1981 to 2016, precipitation, water requirement, continuous no-precipitation days and the drought index during different growth stages of apple are calculated. Spatial distribution characteristics and temporal trends of apple drought in the study area are clarified. Finally, the periodic law of drought during different growth stages of apple in northern China is revealed with wavelet analysis. Results show that the spatial distribution of precipitation during different growth stages of apple is consistent with the spatial distribution of drought index. The precipitation exhibits an increasing trend from northwest to southeast during different growth stages. The precipitation during fruit tree sprouts to flower buds and flowering to maturity show a decreasing trend and the precipitation in stages from flower buds sprout to flower full bloom and from mature to fallen leaves exhibit an increasing trend from 1981 to 2016. The apple water requirement during stages from fruit tree sprouts to flower buds and from flower bud sprout to flower full bloom exhibit an increasing trend, while the other growing stages exhibit a decreasing trend from 1981 to 2016. High values for drought index are mainly distributed in Gansu, Ningxia, Hebei and Beijing. The drought index during the stage from fruit tree sprouts to flower buds shows an increasing trend, while during the other growth stages the drought index shows a decreasing trend from 1981 to 2016. There are three different scales of periodic variation for apple drought during different growth stages.Above all, areas with the most serious drought are mainly concentrated in Gansu, Ningxia, Hebei and Beijing. The drought is the most serious during the stage from flower bud sprout to flower full bloom, and the drought index during the growth stage from fruit tree sprouts to flower buds shows an increasing trend.