Soil water balance of the artificial forestland planted with locust treeshas been studied quantitatively for years on the water balance plots setsin Ansai soil conservatin station of loess hilly region in northern Shaanxi

based on the soil water balance equetion for the soil of artificial forestland.The analyse result shows that the soil is becoming dry because ofintense evapotransporation and the watersucking effect due to the development of the root system in deep layer if the artificial forest is madeon the loess hilly region with semiarid climate.The providing functionof the water stored in deep layer to adjust the need of water from treeswill be vanished

thus

only could the trees grow depending on the precipitation in current year.From this point of view

it is thought that the artificial forests deteriorate their own soil water condition constantly

whichmakes the trees grow slowly and limits the growth amount with water.