一、前言水是构成植物的必要成份,又是植物赖以生存的必不可少的生活条件。因此,如何满足植物的水分需要,始终是农、林业生产中的一个重要课题。黄土高原地貌类型复杂,在不同地形部位上承受降水量的不同、土壤渗透及保墒能力以及径流损失的不同,就造成土壤实际保蓄水分出现明显的差异,这种差异基本反映了黄土高原不同立地条件宜林性质的差别。因此,在进行黄土高原造林立地条件类型划 I. Introduction Water is an essential ingredient in the composition of plants and an indispensable living condition on which plants depend for survival. Therefore, how to meet the water needs of plants has always been an important issue in agriculture and forestry production. The complex types of topography on the Loess Plateau, the difference in precipitation, the ability of soil infiltration, the ability of preserving soil moisture and the loss of runoff on different topographical sites resulted in obvious differences in the actual holding moisture of the soil, which basically reflects the differences in the Loess Plateau Site conditions should be the difference between the nature of forest. Therefore, in the Loess Plateau afforestation site conditions type planning