Drought Changes in Southwest China and Its Impacts on Rice Yield of Guizhou Province
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摘要: 近几年,我国西南地区干旱频繁发生,严重影响农业生产。为了探讨干旱和水稻产量之间关系的复杂性,采用中国气象局国家气象信息中心提供的西南地区348个站气象数据,计算了西南地区干旱的变化趋势,并利用2000—2011年贵州省县级水稻产量资料分析了干旱对水稻单产的影响,探讨了干旱、水资源灌溉以及水稻产量之间的关系。结果表明:1951—2012年西南地区降水量平均减少16.9 mm/10 a,特别是8—10月降水量明显减少。同时,西南地区干旱日数呈上升趋势,平均增加3.3 d/10 a。对比水稻产量发现,当累计干旱日数少于40 d时,干旱对水稻产量一般不会造成影响;当累计干旱日数超过86 d时,干旱造成水稻减产20%~73%,这意味着当累计干旱日数超过3个月时,江河塘库蓄水将受到影响,进而影响水稻的灌溉,造成水稻严重减产;当累计干旱日数为40~86 d时,水稻减产一般少于20%,但地区差异较大。Abstract: Extreme weather and climate events have become more frequent and severe in recent years in the context of global warming. These extreme events bring serious impacts on human survival and sustaining development of society. Drought is one of the major types of extreme climatic events in China, which seriously affects agriculture and social-economic development. The domestic extreme drought events in recent years mostly occur in Southwest China, influencing the agriculture severely. Using the high quality observations from 348 weather stations and the agriculture data of county level in Southwest China, the complicated relationship among droughts, water supply, and rice yields is investigated.The precipitation decreases in Southwest China from 1951 to 2012, with an average decadal decrease of 16.9 mm per 10 years. In particular, the precipitation decreases distinctly from August to October, mainly due to the weak South Asian monsoon. Drought days are counted by using the drought index ISWAP, and the result shows that the number of drought days generally increases by 3.3 days per 10 years in the past several decades, especially since 2001 due to the less precipitation. Since rice cultivation is irrigated agriculture, drought won't directly affect rice growth. To further understand the complexity, impacts of various drought events on rice yields are investigated using high quality rice yield data collected in 70 counties of Guizhou Province, and the result indicates that the drought has little adverse but favorable impacts on rice yields when annual accumulated number of drought days is less than 40 days. It is because that this kind of drought won't affect the rice irrigation water supply, and the temperature is usually abnormally high with more bright sunshine days during the period of drought which are actually favorable for rice growth. However, when the number of drought days is more than 86 days, rice yields will reduce by 20%-73% due to the drought and the insufficient irrigation. When the number of drought days is between 49-86 days, rice yields usually reduce by less than 20% but with large differences between different regions. This kind of drought has little impact on rice yields in regions of robust drought tolerance but greatly affects rice yields in regions of weak drought tolerance.
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Key words:
- Southwest China;
- drought index;
- rice yield
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表 1 ISWAP等级划分
Table 1 The classification of ISWAP
等级 类型 ISWAP 1 无旱 -0.5 < ISWAP 2 轻旱 -1.0 < ISWAP≤-0.5 3 中旱 -1.5 < ISWAP≤-1.0 4 重旱 -2.0 < ISWAP≤-1.5 5 特旱 ISWAP≤-2.0 表 2 2011年贵州省部分县水稻产量变化以及降水和干旱日数信息
Table 2 Changes of rice yields, precipitation and the number of drought days for some counties of Guizhou Province in 2011
县名 水稻产量变化幅度/% 4—9月降水量/mm 4—9月降水距平百分率/% 累计干旱日数/d 石阡 -72.9 336.1 -59.2 155 余庆 -67.7 456.8 -42.9 112 正安 -67.6 433.1 -47.4 102 黔西 -63.6 353.1 -53.5 136 水城 -60.4 559.7 -42.5 113 凤冈 -59.9 544.9 -39.9 117 德江 -58.5 597.2 -35.8 99 册亨 -57.1 524.6 -47.9 117 习水 -52.0 392.7 -52.2 140 开阳 -44.8 407.6 -51.6 147 毕节 -43.8 441.4 -37.2 127 金沙 -42.9 422.0 -46.8 115 安龙 -42.2 448.2 -53.7 141 榕江 -41.1 548.1 -37.6 100 锦屏 -39.0 546.2 -38.4 110 关岭 -38.9 712.4 -35.4 76 岑巩 -38.6 616.5 -24.7 92 福泉 -37.6 518.5 -40.7 111 贵定 -35.1 435.2 -49.7 142 独山 -34.5 519.5 -40.9 89 剑河 -31.3 556.8 -35.4 105 从江 -30.4 615.3 -29.8 68 长顺 -26.5 724.5 -33.8 93 赤水 -26.4 522.3 -41.4 107 -
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