扎龙湿地的形成背景及其生态环境意义

Formation Background of the Zhalong Wetland and its Eco-environmental Significance

扎龙湿地位于黑龙江省西部,为乌裕尔河下游尾闾湖形成的苇草湖沼。作者通过野外调查、表土样品粒度对比和遥感影像分析,探讨了湿地形成演化的地质环境背景,分析了扎龙湿地与嫩江、沙地的成因联系。研究认为齐齐哈尔-大庆沙地由北西走向的纵向沙垄和低洼盐碱带组成,与科尔沁沙地一起构成了一个NE向展布的沙带,可能主要形成于末次冰期时期。其后嫩江进入沙地,对沙地进行改造,在扎龙地区留下众多牛轭湖。后期由于构造抬升嫩江河道西迁,乌裕尔河成为内流河,其尾闾湖最后演化成为现在的扎龙湿地。因此扎龙地区的环境演化过程为:风成沙地形成→嫩江改造、破坏沙地→嫩江西迁、乌裕尔河分流→扎龙尾闾湖形成→扎龙尾闾湖退化、湿地形成。因此扎龙湿地与连环湖是在风成沙丘上形成的沼泽地,是整个嫩江流域生态环境最脆弱的一个关键区。一旦湿地消失,将导致这个地区的盐碱化和沙漠化,对附近的齐齐哈尔和大庆两市的生态环境造成严重影响。

Zhalong wetland locates at the western part of Heilongjiang province and was developed from the terminal lake of the Wuyuer fiver. In this paper, the geological environment of the Zhalong area and the relationships among the Zhalong wetland, the Nenjiang fiver and the Songnen desert were studied by field survey, soil sample analysis and remotely sensed image interpretation. It was found that the desert from Qiqihaer to Daqi consisted of NW-extended dunes and saline, forming a NE-extended dune belt with Keerqin desert together. The desert was mainly developed from the last glacial period. After that, the Nenjiang fiver flowed through the dune area and rebuilt the dunes and a lot of yoke lakes were left in Zhalong area. Because of the crustal tectonic uplift in the Zhalong area, the Nenjiang fiver moved westwards and Wuyuer fiver became an inner fiver which terminal lake evolved and developed as the present Zhalong wetland eventually. So the environmental evolution of the Zhalong area since the last glacial period was concluded as： the wind-blown dune belt formed → the Nenjiang fiver rebuilt the dune belt → the Nenjiang fiver westwardly migrated the terminal lake of the Wuyuer fiver evolved and the Wuyuer fiver became an inner fiver →to the Zhalong wetland. Therefore, the Zhalong wetland and the Lianhuan lake developed on an once-existed desert, suggesting that the ecoenvironment of the area is the frailest in the whole Nenjiang watershed. It means that the salinification and desertation in the area would rapidly develop and severely affect the eco-environment of the Qiqihaer-Daqi area if the Zhalong wetland disappeared.