塔里木河下游近50a来沙质荒漠化演变规律

荒漠化是人为强烈活动与脆弱生态环境相互作用的产物,是人地关系矛盾的结果。我国最长的内陆河-塔里木河下游卡拉的来水量,由50年代的14.80亿m³减少到90年代的2.38亿m³,造成地下水位下降,植被衰败。同时,受过度放牧、开垦、樵采等原因的影响,下游地区土地沙质荒漠化十分严峻,宏观格局上表现为绿色走廊由上段至下段,由中间至两侧沙漠化程度趋于加强。通过1959、1983、1992及1996年遥感信息制图定量研究表明,50年代至90年代沙漠化年均增长率达0.24%,其面积扩大的同时,程度也在加剧,自然景观也发生了一系列变化。应用GM(1,1)模型、非线性回归模型及多元线性回归模型趋势分析表明,以土地沙质荒漠化为主的环境问题仍十分突出。科学规划,整治上、中游河道,合理利用水资源,以解决下游生态及生产、生活用水。应用RS、GIS监测沙漠化变化,通过增加生态用水,恢复铁干里克-阿拉干段的天然植被,遏制沙漠化扩展,同时利用工程措施,保护阿拉干以下绿洲走廊及218国道安全畅道,防止脆弱生态环境继续恶化。

Evolution Patterns of Sandy Desertification in the Lower Reaches of Tarim River Basin in Recent 5 Decades

Desertification is the result of interaction between human being and fragile eco-environment.It is also the consequence of the contradiction between human being and land.The water amount in Qiala station at the lower reaches of Tarim River is reduced from 14.80×10⁸ m³ in 1950s to 2.38×10⁸m³ in 1990s,which causes the reduction of underground water table and the degradation of vegetation.Meanwhile,under the influences of extreme raising living stock,reclaiming wasteland and cutting off firewood,sandy desertification developes seriously in the lower reaches area,whose degree is becoming strongly and strongly from upper section to lower section and from the middle to both sides of the Green Corridor on macro pattern.Mapping with remote sensing information of 1959,1983,1992 and 1996,the result shows that the annual mean growth rate of sandy desertification area is 0.24 percent from 1950s to 1990s.With area increasing the degree is strengthened.At the same time,a series of changes in natural landscape have occurred.The result of trend analyses with models of GM(1,1),non linear regression and multi-factor regression reveals that environment problems predominated by land desertification are quite out-standing.In order to solve the problem of water resources in ecology,production and life in the lower reaches area,it should be available to plan scientifically,use water resources rationally and control river courses in the upper and middle reaches of Tarim River.In addition to recover natural vegetation and prevent sandy desertification from expanding between Qieganlike and Alagan,monitoring sandy desertification changes by RS and GIS as well as increasing ecological water amount are very important.Meanwhile,in order to protect the Green Corridor and safeguard the No.218 national highway in the lower reaches of Tarim River area,some engineering measurements should be adopted.