基于防风蚀效应下的绿洲-荒漠交错带上灌草植被生态需水量的研究

Oasis-desert ecotone is the important barrier which protect oasis in arid region. A large number of shrub grass vegetation on the ecotone mainly depends on the water. The shrub grass vegetation consume water to realize their growth and resistant wind erosion by their ground biomass at the same time, therefore, the shrub grass vegetation ecological water requirement is based on water-growth and shrub grass vegetation attain to resistant wind erosion. This issue includes three aspects: (1) the relationship between the vegetation water consumption and the growth of shrub grass vegetation (function of growth to vegetation water requirement). (2) the relationship between the growth of shrub grass vegetation and the effect of the resistant wind erosion of shrub grass vegetation. (3) the relationship between water consumption and the effect of the resistant to wind erosion. Based on the above research, the concrete meaning of shrub grass vegetation ecological water requirement is clarified, a quantitative standard is provided for shrub grass vegetation ecological water requirement, and it is also helpful for the reasonable distribution of water resources in the arid zone.

绿洲—荒漠交错带是维护干旱绿洲区稳定的重要屏障，交错带上广泛分布着以水为主导因子的灌草植被生态系统。灌草植被消耗水分用于生存、生长的同时，主要利用地上部分实现防风蚀效应。因此，植被生态需水是在植被耗水生长的基础上，以植被达到一定防风蚀效应为目标的需水量。本项目在已有研究成果的基础上，重点对三个方面进行了试验研究。（1）灌草植被耗水量与生长量之间的关系（即水分生长函数）。（2）灌草植被生长量与防风蚀效应之间的关系。（3）灌草植被需水量与防风蚀效应之间的关系。通过对以上问题的研究，阐明了植被生态需水的具体内涵，为灌草植被生态需水量提供了一个可量化标准，并为干旱区水资源的合理配置提供了帮助。

项目研究了不同水分条件下，典型灌木梭梭的耗水规律、生长规律及其水分生长函数，并在此基础上探寻出不同水分条件下的梭梭的耗水量及其相应的生态效应。试验中发现，不同水分条件下，梭梭的耗水量与生长量不同。梭梭新生枝条的生长速率随着梭梭的耗水量的增加呈现快-慢-快的趋势。当受到水分胁迫时，梭梭减少水分消耗以维持自身的生存，并尽量维持新生枝条的生长，但同期的株高增长速率缓慢；当耗水量继续增加时，新生枝条的生长速率随着耗水量增加开始变缓；当耗水量超过一定范围时，梭梭的新生枝条生长速率又开始加快。冠幅的增长速率随耗水量的变化趋势与新生枝条随耗水率变化趋势稍有不同，当梭梭耗水量超过一定范围后，冠幅的增长速率随着耗水量的增加的变化趋势明显。结合梭梭的新生枝条及冠幅的耗水规律和生长规律推导出梭梭水分生长函数。此外，项目通过对不同水分条件下、不同植被覆盖度下梭梭防风阻沙效应进行观测和研究发现，随着植被覆盖度的增加，下垫面的粗糙度也随着增大，梭梭灌丛减弱风速和阻沙的效果也就越明显。中等植被覆盖度下，下垫面粗糙度随着植被覆盖度的增加而增加的趋势不显著，这与梭梭水分生长函数的变化趋势一致。由此可知，中等覆盖度下的植被可以同时满足水资源的高效利用与防风蚀效应的实现这两方面的要求。. 以上的研究成果对荒漠植被覆盖的有限恢复及植被生态需水量的确定提供了依据，并对于干旱区绿洲生态系统的稳定和水资源的科学合理配置具有重要意义。