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在黄土塬区无灌溉条件下衣－林－路复合生态系统中，林路与衣作物界面附近（１Ｈ内）土壤水分低于一般农田，其中垂直方向６０～１００ｃｍ受林木的强烈影响，水平方向距林缘０．２～０．７Ｈ范围内林农水分竞争剧烈，水分亏缺严重。应用灰色关联分析结果表明，土壤水分亏缺是系统各组分综合影响的结果，其中林分影响程度占总影响程度的５２％，其次是道路状况和有无小沟措施；影响的主要因素依次是林带平均高度、平均冠高、平均胸径、林分密度、道路纵向坡度、树种组成、有无小沟、平均冠幅、道路类型、农田田面宽度、道路走向等因素。所以，在该区旱作且森林覆被率较高的地区，道路衣田防护林树种选择上应抛弃传统的以杨树为主等高大乔木的作法，选择树高适中的经济林树种。
Under the condition of no irrigation in the Loess Plateau, the soil moisture in the vicinity of the forest road and the clothing crop interface (1H) was lower than that in the general farmland, in which the vertical direction of 60-100 cm was strongly influenced by the forest and the horizontal direction Forest far from the edge of 0.2 ~ 0.7H water fierce competition, water deficit serious. The results of gray correlation analysis show that the soil water deficit is the result of the comprehensive influence of all components of the system, of which the influence degree of forest stand is 52% of the total impact degree, followed by the road conditions and the presence or absence of small ditches; the main factors affecting Is the average height of forest belt, average crown height, average breast diameter, stand density, vertical gradient of the road, tree species composition, with or without small ditches, average crown, road type, farmland width, road direction and other factors. Therefore, in the area with dry cultivation and high forest cover rate, the selection of the suitable high poplar-tree species should be abandoned on the selection of tree-type shelterbelts in the road.