气候变化背景下东北三省大豆干旱时空特征

利用1961—2010年东北三省大豆种植区71个气象站点地面气象观测资料,基于农业干旱指标作物水分亏缺指数(CWDI)及干旱等级,分析了气候变化背景下近50年来我国东北地区大豆干旱发生频率演变趋势及干旱程度演变特征,研究结果表明:东北三省大豆干旱频率空间差异较大,呈明显的西高东低的经向带状分布特征;大豆全生育期干旱频率以轻旱最高,中旱次之,重旱和特严重干旱频率最低;轻旱及以上干旱频率以播种到分枝阶段最高,分枝到开花阶段次之,开花到成熟阶段最低;作物水分亏缺指数年际变化趋势各地不同,总体而言以播种到分枝期干旱为主向开花到成熟期干旱转变的特点;大豆全生育干旱等级存在明显的年代际变化,20世纪80年代干旱范围最小、程度最轻,2000年以后重旱及中旱范围增加明显,干旱趋于严重。

Spatio-temporal characteristics of drought for soybean under climate change in the three provinces of Northeast China

Climate data from seventy-one meteorological stations in the soybean planting areas in three provinces of Northeast China (NEC) during 1961 to 2010 were used to calculate the reference crop evapotranspiration using the Penman-Monteith formula. Then combined with the revised crop coefficient, soybean water requirement can be obtained during each growth stage. Finally, we calculated the Crop Water Deficit Index (CWDI) by considering cumulative effects of moisture surplus condition during the soybean growing season. and obtained the degree of drought Based on this index and the degree of drought, the characteristics of spatio-temporal variation for occurrence frequency and degree of soybean drought in NEC during the study period were analyzed. Result shows that there is a significant spatial variation in the occurrence frequency of soybean drought, which was increased from east to west. Light drought is the most frequent drought, followed by the middle drought and heavy drought during the whole soybean growing season. There could be relatively higher frequency of light drought in the western regions of Heilongjiang Province and the western and southern regions of Liaoning Province. In the western regions of Jilin Province, there is relatively less frequency of light drought, but the frequencies of middle drought and heavy drought are higher. We also found the basic vegetative phase (sowing to branching) experienced the most severe drought and the frequency of drought exceed 50% (once every 2 years) at the 56% of the selected sites in the study areas, the frequency of drought exceed 80% (four every 5 years) at the 31% of the selected sites in the study areas. The drought during the panical formation phase (branching to flowering) is lighter, drought frequency was lower than 80% in most regions in the study area except Qian''an and Tongyu of Jilin Province, and drought frequency was higher than 50% (once every 2 years) at the 48% of the selected sites in the study area. The drought during the reproductive phase (flowering to maturity) is lightest, but there could be still high drought frequency (50%-80%) in the southwest regions of Heilongjiang Province, northern of Sanjiang Plain, western of Jilin Province, and western and southern of Liaoning Province. Interannual variability in CWDI differs from regions. The CWDI showed a downward trend during the sowing to branching stage in all three representatives sites. We can find a maximum inter-annual fluctuation during the branching to flowering stage, it showed a downward trend in Liaoning Chaoyang and Heilongjiang Suihua during this stage, and a upward trend in Jilin Tonghua. There is least value of CWDI during the flowering to maturity stage, and showed an upward trend in Liaoning Chaoyang and Heilongjiang Suihua during this stage; interannual variability is not significant in Jilin Tonghua. In other words, generally the drought threat is progressively more severe during reproductive phase. There is also obvious decadal variability of drought degrees during whole growing period. In 1980s, either drought degree and range were the smallest, from 2000 years, the range of medium drought and heavy drought increased significantly.