中国东部典型沙地植被稳定性与水资源关系特征

Vegetation sustainability in relation to water resources in typical sandy areas of eastern China

在恢复或重建干旱地区的沙地植被时,降水和浅层地下水是决定植被稳定性的关键因素。只有在植被需水量、降水量和地下水补充量达到平衡状态时,植被才能维持稳定,其防风固沙功能才具有可持续性。选择毛乌素沙地和科尔沁沙地,利用具有连续时相的植被覆盖度、气象和地下水观测数据,研究了沙地水分动态变化、植被需水与水分供给的平衡关系。结果表明:(1)毛乌素沙地和科尔沁沙地生长季植被覆盖度分别与前一年、当年的降水量相关性最高,各栅格缓冲区对地下水的响应也多存在一年的滞后性,不同类型植被对降水量和地下水变化发生响应的滞后时间不同。(2)两个沙地的植被生长季各月植被需水量和月平均植被需水量均呈现上升趋势,空间变化差异显著。(3)毛乌素沙地和科尔沁沙地植被需水的主要来源均为地下水,地下水位下降可能导致植被不可持续;由于自然地理差异,毛乌素沙地更依赖降水,科尔沁沙地对地下水更敏感。(4)植被稳定性具有周期性,周期为2~24年。

When restoring or rebuilding sandy vegetation in arid areas,precipitation and shallow groundwater are two key factors in determining vegetation stability,because vegetation can only be stable and sustainable in its windbreak and sand fixation function when the water demand of vegetation,precipitation and groundwater replenishment are in balance.In this paper,Mu Us Sandy Land and Horqin Sandy Land,which are typical sandy lands in eastern deserts of China,were selected,and vegetation coverage data,meteorological station data,groundwater data and field survey data with continuous time phases were used,the dynamic changes of sandy moisture and the balance between vegetation water demand and water supply were calculated.The results showed:(1) Mu Us Sandy Land and Horqin Sandy Land had the highest correlation between VC during the growth season and P in the previous year and the current year,separately.The response of each grid buffer zone to groundwater is also abundant in a one-year lag and different vegetation types have different lag times in responding to changes in P and groundwater.(2) The monthly vegetation water demand and average monthly W of vegetation in these two sandy areas showed an increasing trend in each growing season,with significant spatial variation;(3) The main source of water demand for vegetation in the Mu Us Sandy Land and Horqin Sandy Land is groundwater,and declining groundwater levels may causes unsustainable vegetation;the Mu Us Sandy Land is more dependent on precipitation and the Horqin Sandy Land is more sensitive to groundwaterfor natural geographic differences.(4)The vegetation stability of two sandy areas is cyclical,varying from 2-24 years depending on local ground conditions.