近55a来河西走廊荒漠绿洲区季节变化特征及其对胡杨年生长期的影响

利用河西走廊荒漠绿洲胡杨林集中分布区的4个气象站点1955-2009年日平均气温资料,采用5d滑动平均、气候倾向率、Mann-Kendall和滑动t检验等方法,分析其四季开始日与长度的变化特征及其对胡杨年生长期的影响。结果表明:近55a来,河西走廊荒漠绿洲区四季开始日主要表现为春、夏和秋季提早,冬季推迟的变化趋势,并以夏季提早最显著,且以21世纪初更突出。研究区平均四季长短变化特征为:冬季>夏季>春季>秋季。胡杨年生长期有开始日提早、终止日推后的趋势,且推迟趋势更明显;胡杨年生长期天数具有延长趋势。突变分析表明:春季开始日在1969年和2001年发生突变,夏、秋开始日则分别在1998年、 1985年和1997年发生突变,而冬季开始日发生突变的时间早于其它3季,为1985年;胡杨年生长期开始日具有多个突变,分别在1961年、1973年和1997年发生突变。显然,研究区胡杨对气候变化的响应更敏感。

Climate characteristic of seasonal variation and its influence on annual growth period of populus euphratica Oliv in Hexi Corridor in recent 55 years

In the last 100 years, especially in the last 50 years, the earth is getting warmer and warmer in the most parts of the world and China, which leads climatic belts moving northward and higher altitude region and the change of the phenological period and growing season. The climatic change of seasons is also observed in some parts of China. Based on the daily average temperature data of the 4 weather stations of Dunhuang, Jinta, Guazhou and Minqin in Hexi Corridor during the period from 1955 to 2009, using the methods of climate trending rate, 5 days running mean temperature and Mann-Kendall abrupt change test and slide T detected method, the average beginning dates, length of four seasons and the annual growth period of populus euphratica were analyzed. The results showed that: (1) The beginning dates of the spring, summer and autumn come earlier in the study area in recent 55 years, especially in summer, but winter comes later. It is more obvious at the beginning of the 21st century. The average beginning dates in spring, summer, autumn and winter are Apr.11, Jun.13, Aug.25, and Oct.13 respectively, and their average length were 62d, 73d, 50d and 180d, respectively. The average length of four seasons change as follow: winter> summer > spring> autumn. (2) In last 55 years, the average beginning dates of spring, summer and autumn were advanced for 2.6d, 7d and 0.7d respectively, but winter was delayed for 0.6d, and only that of the summer was changing significantly. The earliest 6.0d advanced for spring was in Guazhou County, 14.3d advanced for summer in Minqin County, Minqin County and Dunhuang City ware delayed for autumn and winter in last 55 years. The average length of spring and winter was shortened for 4.9d and 0.7d respectively, those of summer and autumn were prolonged for 6.8d and 0.4d, respectively, and those of autumn and winter vary little. That means the change in spring and summer was more than that in autumn and winter in the study area in recent 55 years. (3) It is a trend that the beginning dates of annual growth of populus euphratica was becoming earlier and its the ending dates was becoming later, and the delaying trend is more clear. The beginning dates and ending dates of annual growth of populus euphratica were Mar.20, and Oct.28 respectively and the average length of annual growth was 224d. The annual growth period of populus euphratica is becoming longer. The average beginning dates of the annual growth of populus euphratica was advanced for 1d, the average ending dates was delayed for 4.2d and the average length was prolonged for 5.2d in last 55years. (4) The abrupt change analysis results showed that there was abrupt change in 1969 and 2001 in the beginning dates of spring, summer in 1998, autumn in 1985 or 1997 and winter in 1985. The beginning dates of populus euphratica annual growth period had several obvious abrupt change, such as in 1961, 1973 and 1997.There is an obvious response to the climatic change of the seasons and populus euphratica is an indicator of climate in the study area.