格尔木河中游地区植被覆盖与地下水埋深关系研究

在干旱区内陆盆地,地下水对植被的分布有很大的影响。在格尔木河中游地区,同样发现植被依赖地下水分布的特征。通过归一化植被指数(NDVI)的遥感影像数据与地下水埋深的实地观测数据来研究分析植被覆盖对地下水埋深的关系。研究结果表明:当地下水埋深小于4m时,NDVI均值与标准差均随着地下水埋深的增加而减小。当地下水埋深大于4m但小于8m时,植被生长开始逐渐受到影响,对地下水的敏感性开始减弱。当地下水埋深超过8m时,植被覆盖严重下降,并且对地下水埋深变化表现的愈加不敏感。8m被认为是影响研究区植被覆盖的地下水埋深上限,超过该上限,地区生态环境会受到严重影响;不同植被类型受地下水的影响也不同:水柏枝的生长与地下水关系较密切,芦苇盐生草甸与膜果麻黄可能受土壤盐渍化的影响其生长状况与地下水的关系较复杂。对比不同研究区研究成果,由于降雨、蒸散发等气象要素、水文地质条件、人类活动等多方面因素的不同,植被覆盖与地下水的相关性有明显差异。

Study on the relationship between vegetation cover and groundwater depth in the middle reaches of Golmud River

In the arid inland basin, groundwater has a great influence on the distribution of vegetation. In the middle reaches of the Golmud River, the distribution of vegetation is also groundwater-dependent. We used the normalized difference vegetation index (NDVI) and field observation data of groundwater depth to study the relationship between vegetation distribution and groundwat erdepth. The results showed that when the groundwater depth was less than 4m, the mean NDVI would decrease with the increase of groundwater depth. When the groundwater depth was greater than 4m but less than 8m, the growth of vegetation was affected and became less sensitive to groundwater. When the groundwater depth was more than 8m, the vegetation cover declined seriously, and was not sensitive to the change of groundwater depth. We consider 8m to be the upper limit of groundwater depth that affects vegetation cover in the study area. The regional ecological environment will be severely affected when the groundwater depth is beyond this limit. Different vegetation types were differently influenced by groundwater: The growth of Myricaria was closely associated with groundwater. For salt meadow reed and Ephedra przewalskii, the relationship between their growth and groundwater was complex probably because of soil salinization. A comparison of the research results of different research areas revealed that due to rainfall, evapotranspiration, hydrogeological conditions, human activities, and other factors, the correlation between vegetation and groundwater varied significantly.