【摘要】 本文旨在将毛乌素沙地植被建设的水分平衡与半固定沙丘持续发展原则应用于治沙造林的实践中。毛乌素沙地是一个灌木“王国”，然而沙地灌丛植被的发育常常受到水分亏缺的严重制约。为此，根据水分平衡的原则与方法确立适宜的植物种植密度，对沙地植被的经营管理具有重要的指导意义。在水分平衡研究中，蒸散是最难估计的一项。本文提供了一种根据叶面积指数的季节变化与蒸腾速率的观测资料计算蒸腾耗水量的方法，并根据沙地水分平衡的要求估算了几种优势灌木的适宜种植密度。结果表明，毛乌素沙地灌丛生态系统的蒸发散主要来自植物蒸腾作用；在所研究的植物当中，除沙地柏（Ｓａｂｉｎａｖｕｌｇａｒｉｓ）可以形成很大的密度外（因其强的蒸腾控制能力），其它灌木的适宜种植密度应控制在使沙丘处于半固定状态的水平上。更多还原

【Abstract】 This paper aims at applying the principles of water balance and the semifixed dunes for the establishment of the productprotective systems in Maowusu Sandland(Zhang Xinshi,1994;1996)to the practices of afforestation and control of desertification.As water serves as a limiting factor for the shrubs ecosystems in China’s Maowusu Sandland,one of the shrubs ‘kingdoms’ in the temperate arid zones of the world,it is very important to estimate the appropriate planting densities with the aid of the principles and methodologies of water balance for the rational management and sustainable development for the area’s vegetation.In this,evapotranspiration(ET) is the most difficult to be determined accurately.This paper proposes a method for the estimation of seasonal transpiration water loss based on field measured data of transpiration rate,considering the typical pattern of change of aboveground green biomass during the typical growing seasons from midApril to midOctober.The evaporation from sand surface during the growing seasons is estimated by using a semiempirical model and taking the monthly mean temperatures at sand surface as the input.Finally,the appropriate planting densities for the major shrubs are discussed as constrained by the water balance equation.According to the results obtained,the evapotranspiration of the shrubs ecosystems of Maowusu Sandland comes mainly from plants rather than the soil.As a result,the appropriate planting densities for the dominant shrubs ought to be controlled at such a level that the dunes are semifixed by the plants,with the exception of Sabina vulgaris stands having a high density owing to its powerful capability of transpiration control.更多还原