Abstract: In the region from loess plateau to North Wei River,20-100cm soil laver is the main laver from which the root system of P.×dakuanensis Hsu absorbs water,and 0-0.1H is the range in which P.× dakua-nensis by the roads strongly affdcts by the roads strongly affects moisture condition of farmland.The annual transpiration consurnption of farmland shelterbelt svstem by the roads is 589.9mm,9.8% of which is consumed bv P.×dakuanensis. In 1988-1989,the average moisture content of 0-350cm soil layer in the system is 1.0% higher than control； Meanwhile,the difference in the aspect of growing seasons of trees and crops reduces the contra-diction between water supply and demand in the affected area.

Key words: Pinus, needle, photosynthetic function, chlorophyll fluorescence.