近50a以来塔里木河下游土地沙漠化影响因子分析

Analysis on Impact Factors of Land Desertification in Lower Reaches of Tarim River in Past 50 Years

塔里木河下游地区是干旱区中沙漠化进程最显著的地区之一,一直深受社会各界关注,尤其是它的成因。由于近50 a来人类不合理的水土资源和生物资源的开发利用,导致塔里木河下游大西海子水库以下363 km河道断流近30 a,地下水位由20世纪50年代的3～5 m逐年下降至2000年的8～12 m,由此而引起下游天然植被面积逐年减少。由于天然植被严重衰败,固定和半固定沙地面积也以百分之几至百分之几十的速率减小,林间沙地活化,沙漠化面积逐年增加,沙漠化程度也在不断增强,塔里木河下游地区1958年沙漠化面积仅占土地总面积的12%,到2000年沙漠化土地面积超过90%,使本来就处于干旱环境中的塔里木河下游朝着更加干旱的方向急剧发展。在塔里木河下游这一特定区域,从近50 a来研究区域平均气温和降水资料来看,降水和气温有波动性变化,但毕竟较小;现代气候条件和变化的幅度不足以造成环境大的改变,不足以造成沙漠的大幅度扩张或收缩,大范围的活化或固定;而同期人口急剧增加造成的压力和经济活动对环境的强烈干扰,才是造成大范围生态环境恶化和沙漠化发生发展的主要原因。

The quick process of desertification in the lower reaches of the Tarim River is obvious in the arid regions of the world, where all social sectors have pay more attention to, especially to its causes. Because of the irrational water-land resources use and biological resources exploitation in the past 50 years, the lower reaches of near 363 km from the DaXiHaiZi reservoir had been dry for 30 years, the groundwater level in these areas decreased from 3-5 m in 1950 to 8-12 m in 2000, resulting in the reduction of natural vegetation area year by year. Consequently the desertification area increased year after year, increasing from 12 % in 1958 to over 90% of the total land area. The aridity degree of environment in the lower reaches of the Tarim River was strengthened. In the past 50 years, the regional precipitation and temperature wavely changed, not too strong to bring about great environmental change. The anthropogenic causes superimposed on climatic ones are the key reasons for eco-environment degrading and desertification developing in study region.