【摘要】 本文根据“三北”防护林体系建设中的理论研究和实践经验得出:①我国“三北”防护林体系荒漠半荒漠区无灌溉条件下造林的降水极限,在大陆性季风气候区为150—200mm。在地中海气候区,为100—150mm。②最大根幅区的降水收入与水分支出平衡时的降水量,就是理论上无灌溉条件下造林的降水极限。③水平根系越发达,无灌溉、无地下补给条件下植物的抗旱性越强。较小的造林密度有利于脆弱的水分平衡。④耐旱乔木造林的地下水埋深极限为4—6米;耐旱灌木(小乔木)为5—10m。耐盐乔木的矿化度极限为3g/l;耐盐灌木为3—8g/t。更多还原

【Abstract】 In arid and semi aird region of China,precipitation between irrigation plantation region and non -irrigation plantation region is 150-200mm in the monsoon climatic region and 100-150mm in the Mediterranean climatic region. In the area where precipiation is less than their limit precipitation, non —irrigation plantation should be carried out;where the groundwater table is lower than 4-6m it suits to plant trees and lower than 5-10m for xeric shrubs (dwarf trees). Mineral content of groundwater is less than 3g/l. for salt-avoiding trees and 3-8g/l. for salt-avoiding shrubs.更多还原