森林植被生态需水量的确定和计算——以泾河流域为例

Calculation of Ecological Water Requirement of Forests in Jinghe Watershed

森林植被的生态需水可以理解为林地的蒸散耗水量,与土壤含水量关系密切。根据土壤水分有效性的划分,林木暂时凋萎含水量和生长阻滞含水量分别是能保证林木基本生存和正常生长时土壤含水量的下限,因此,相应的林地耗水量分别为林地的最小生态需水定额和适宜生态需水定额,其数值通过计算林地的潜在蒸散并利用土壤水分修正系数和林木系数进行订正获得。根据最新遥感图像资料,在GIS支持下,计算了泾河流域现有林地生长季的最小生态需水量和适宜生态需水量,分别为203960×104m3和340330×104m3。

The ecological water requirement of forests means the water resources used to maintain and improve the natural balance of forest ecosystem which can be expressed by the evapotranspiration of trees in growing season. The relationship of evapotranspiration and soil moisture of forestland to growing activity of trees showed that, if the soil moisture was above temporary-wilt or growth-retard, the growth of trees can be basically or normally sustained respectively. Therefore, they can be taken as the minimum ecological water requirement and suitable ecological water requirement of the forest respectively. And, they can be estimated by introducing the soil factor (K_s) and tree species factor (K_t) to potential evapotranspiration with Penman formula. With GIS, the ecological water requirement for forests in Jinghe watershed was estimated, and by the water balance of the forest ecosystem in their growing season, the ecological water shortage was calculated. The results revealed that the minimum and suitable ecological water requirement of the forests in Jinghe water wereapproximately 2 039.6×10~6 m^3 and (3 403.3)×10~6 m^3 respectively.