塔里木河下游地下水位对植被的影响

对塔里木河下游断流河道2000—2002年9个地下水监测断面和18个植被样地的实地监测资料分析表明，地下水埋深对天然植被的组成、分布及长势有直接关系。地下水位的不断下降和土壤含水率大大丧失是引起塔里木河下游植被退化的主导因子。塔里木河下游的四次输水对其下游地下水位抬升起到了积极作用，河道附近地下水位呈逐级抬升过程，横向影响范围达1000m左右，纵向上，表现为上段地下水抬升幅度较大(达84％)，下段抬升幅度较小（6％)。随着地下水位的抬升，天然植被的响应范围由第一次输水后的200～250m，扩展到第四次输水的800m。

The Influence of Groundwater on Vegetation in the Lower Reaches of Tarim River, China

Results of the analyses of the monitored data of the 4 times of stream water conveyance to the river section where the stream flow was cut-off more than 30 years, of the nine groundwater-monitoring sections and 18 vegetation plots in the lower reaches of the Tarim River from 2000 to 2002, show that the composing and type of vegetation, the distribution and the way vegetation is growing closely related to the depth of groundwater; the continuously decreasing of the groundwater and the loss of soil water are the main factors for the degradation of vegetation in the lower reaches of the Tarim River; the 4 times of stream water conveyance to the dry up of the lower reaches of the river plays an important role in raising the groundwater level, which is close to the watercourse. The groundwater was raised gradually. The transverse response scope of groundwater level was gradually enlarged to about 1,000 m after the fourth conveyance and the lift range of groundwater level is the highest in the upper section (84%), median in the middle section and the lowest in the lower section (6%) longitudinally. The natural vegetation in the lower reaches is saved and restored along with the rise of groundwater level, the response scope of vegetation is gradually enlarged, i.e., from 200-250 m in width after the first conveyance to 800 m after the fourth conveyance.