20世纪下半叶干旱对新疆农业的影响及灾害链效应

Influences of drought on agriculture and disaster-chain effect during the second half of the 20^(th) century in Xinjiang

利用历史灾害数据对20世纪下半叶新疆农业的干旱影响及灾害链效应进行了评价。同时对干旱灾害的时间特征也做了分析。结果表明,1950-2001年的52年里,新疆年平均农田旱灾成灾面积为109.25×103hm2,其中.2000年最高达312.0×103hm2,1950年最低仅为2.01×103hm2。1950-1997年48年年平均受灾人口与减产粮食分别为285.63×103人和174.85×103t。从1950-2001年,新疆农田成灾面积大致上呈上升趋势,虽然其间也有暂时的下降时段,即20世纪70年代早期和90年代早期。1950-1997年受旱人口和减产粮食也存在大致的上升趋势。有两个时期(20世纪60年代和80年代到90年代早期)干旱灾害相对较严重。另外,还发现干旱灾害与沙尘天气和草原蝗灾有明显的相关性,表现出了明显的干旱灾害链性。本评价的结果暗示干旱及其相关灾害的增多可能意味着天气和气候极端事件的增多;20世纪80年代中期以来,尽管区域年降水和径流量的增多对减轻干旱及其灾害具有很大的正效应,但由于降水和径流的年内分布不均匀性,加上耕地向易旱区的扩张,区域干旱灾害还是比较严重,并表现出了与降水和径流增加不一致的趋势。

Effects of drought were assessed using historical data on the damaged cropland areas, the affected population and the reduced grain production, and the other disasters, such as the sandstorm and floating dust days and the diseases and pests associating with the drought during the second half of the 20th century in an arid province, Xinjiang, China. The 52-year average annual damaged area was 109.25 ×10^3hm^2 with a 1-year maximum of 312.0 ×10^3hm^2 in 2000 and a minimum of 2.01 ×10^3hm^2 in 1950. The 48-year average annual affected people and reduced grain output amounted to 285.63 ×10^3 persons and 174.85×10^3 ton, respectively. The temporal behaviors of these effects were also assessed. There was a general increase trend in drought damaged cropland area in Xinjiang from 1950-2001, thought there was temporary decrease times, i.e. the early-1970s and the early 1990s. Trends were upward for drought disasters during 1950-1991 including affected population amount, and reduced grain output. There were two higher disaster periods; 1960s, and 1980s-the early 1990s. In addition, other drought-related disasters, such as floating dust and sandstorm, and burst of grasshopper were associated with the drought disaster. The main revelations revealed by this assessment lie in the following aspects- firstly, increase in drought and drought-related events may imply that there was increase trend in weather and climatic event; and secondly, though recent increases in precipitation and surface runoff have contributed much to the positive effects on decrease in drought, sandstorm and their disasters, but the drought disaster, sandstorm and outbreak of grasshopper have increased owing to uneven distribution of the precipitation and the surface runoff, and the expansion of cropland to drought-prone areas.