青藏高原东北部牧区气候暖干化趋势及对环境和牧草生长的影响

<title> Climate tendency of warming and drying and its influence on environment and grass growth in pastoral area of Northeast Qingzang Plateau of China

对20世纪80年代以来青藏高原东北部青南牧区和甘南牧区气候变化的统计分析表明,该地区呈现出气温升高、降水量减少和蒸发量增大的明显趋势。两个牧区年平均气温升高的边际倾向分别为0 3℃/10年和0 5℃/10年,年降水量减少的边际倾向分别为-28 6mm/10年和-23 5mm/10年。90年代该地区主要牧业县多年平均气温普遍比60～70年代升高了0 4℃～0 8℃;多年平均降水量减少的趋势尤以甘南牧区明显,最多可减少87 5mm。同时牧草返青期和枯黄期气温升高,使牧草生长期天数增多。气温升高导致地面蒸发量增多,两个牧区气温升高1℃时,年蒸发量分别增多99mm和114mm。气候变暖干旱,造成天然草地产草量下降。曲麻莱县年降水量减少1mm时,0 0667hm2草地产草量将减少1 6kg;夏河县年平均气温升高1℃时,0 0667hm2草地产草量将减少122 6kg。气候暖干化,已经造成该地区干旱缺水,草地退化、沙化和鼠害猖獗,使草畜矛盾不断加剧,已严重威胁到牧区的生存和发展,也影响到长江、黄河中下游地区的可持续发展,对此应予高度重视。

<Abstrcat>The statistical analysis of climate changes in south Qinghai and Gannan grassland of Qingzang Plateau have shown the apparent tendency of an increase in temperature and a decrease in rainfall during the last two decades in these regions.The marginal propensities of average annual temperature are 0.3℃/10a and 0.5℃/10a,while the marginal propensities of average annual rainfall are -28.6mm/10a and -23.5mm/10a,respectively.In main pasturing regions,average annual temperature has increased by 0.4℃～0.8℃during the period 1990-2000,compared with that of during the period 1960-70,while an apparent decrease in annual rainfall has been found in Gannan grassland ,with maximum decrease of 87.5mm.The climate warming and drying could affect the timing of when grass receives water and therefore could affect their yields.It has been shown that the yield of grass(per 0.0667hm2)decrease by 122.6kg with an increase of 1℃ in average annual temperature in Xiahe county,and 1.6kg with an decrease of 1mm in average annual rainfall in Qumala county.In addition,the increase in temperature could produce a corresponding increase in ground evaporation.It is shown that the ground evaporation increase by 99mm and 114mm in two grasslands with an increase of 1℃ in average annual temperature.As a result of the climate warming and drying,the environment has been deteriorated.the problem of soil drought,grassland degraded and the damage by rats have seriously threatened the survive of grasslands as well as sustainable development in regions of the Yellow River and the Yangtze River.