The Ecological Water Demand of Different Vegetation Types in the Bashang Area, Northwest Hebei Province

Abstract

In order to construct stable vegetation for reducing wind and sand disasters and soil erosion in the Bashang Area of Northwest Hebei Province in China, it is very important to understand the ecological water demand of different vegetation types in this area. Based on observed data and the Irmak-Allen formula, we investigated the ecological water demand and ecological water shortage of arbor, shrub and grassland in Bashang Area of northwestern Hebei province. The results showed that the actual evapotranspiration values of the three vegetation types in the growing seasons in the study area from high to low were arbor forest (401.81 mm), shrub (358.78 mm) and grassland (346.02 mm). The minimum ecological water requirements of arbor forest, shrub and grassland in the growing season were 243.96 mm, 218.35 mm and 211.36 mm, respectively, and the optimal ecological water requirements were 472.99 mm, 423.34 mm and 409.77 mm, respectively. In addition, the optimal ecological water shortage values were 198.56 mm for arbor forest, 148.91 mm for shrub and 135.34 mm for grassland. The ecological water shortage of vegetation has obvious seasonality, with the largest water shortage in May and June, and a lower and steady water surplus in July to October. Therefore, an artificial water supplementation in May and June would alleviate the drought stress of the vegetation. The rainfall in Bashang Area of Northwest Hebei Province can meet the requirements of minimum ecological water demand for arbor forest, but the gap between the rainfall and the optimal ecological water requirement is too large to support good growth of an arbor forest, which could explain why the degradation of poplar protective forests has occurred in Bashang Area.