塔克拉玛干沙漠南缘地下水在脆弱生态环境中的作用

The Role of Groundwater in the Fragile Ecology in the South of Taklimakan Desert

塔克拉玛干沙漠南缘属典型的干旱区内陆盆地生态环境脆弱带 ,在绿洲与沙漠相互交错分布的干旱生态系统中 ,地下水显示出重要的生态调控作用 .土壤环境 (水分、土壤含盐量 )受地下水环境状况 (地下水位、水质 )的制约 ,从而决定了植被的生长情况 .地下水埋深小于 4 m时 ,土壤含水量一般在 11.7%～ 33.9%之间变化 ,荒漠河岸林、柽柳灌丛和多数草本植物均能正常生长 .当地下水位埋深大于 4 m时 ,天然植物生长明显受到制约 .土壤含盐量与潜水位埋深成反比 ,与潜水矿化度呈线性关系 ,3m为土壤盐渍化临界水位 .另一方面 ,地下水矿化度小于 3g/ L时植物生长良好 ,高于 5～ 10 g/ L生长受到抑制 .因此荒漠植被生长的最佳水文地质环境应是地下水位埋深在 3～ 4 m;地下水矿化度小于 3g/

It is characteristic of crisscross distribution between oasis and desert,which are two confronting aspects of arid eco system in the south of Taklimakan Desert.Correspondingly,desertification and oasification will happen and exist simultaneously, but they depend on the water condition.Groundwater is an organic part of hydrological cycle and water resources.It actively participates in the movement and transformation of matter and energy in nature.The regulating and controlling role of ecology of groundwater is very outstanding in the arid land,especially in the fragili ecology in the south of Taklimakan Desert.The soil environment(moisture,salinity)is controlled by groundwater level and quality, so is the plant growth.If groundwater level is higher than the depth of 4 m, the soil moisture content ranges from 11.7% to 33.9% with an overall mean of 21.1%,which is well satisfied with desert plant growth such as Populus diverrifolia Tugayi, Tamarix shrub and the majority of herbs. If deeper than 4 m of groundwater,the plant growth is affected seriously.The soil salinity is inversely proportional to groundwater depth,and directly proportional to groundwater quality.However,the soil salinity increases dramatically as groundwater salinity increases when groundwater is shallower than 3 m,but it has almost no effect if otherwise.On the other hand,when groundwater quality has values lower than 3 g/L salinity,the plant grows well.The groundwater suitable for desert plant growth is at the depth of 3 to 4 m with a salinity lower than 3 g/l; if it is higher,the salinization will rise,and if lower than that,the plant degradation and land desertification must result.