Water contents of sandy soil and loess in Jingbian County

Shaanxi Province are studied through the field investigations and measurements. Experimental results show that water content of sandy soil is less than 3% and water content of loess under poplar trees

about 7%. Severe dried layer occurs in sandy soil and moderate dried layer under poplar trees

in loess. All the dried layers are above 6m in depth. The degree and depth of dried layer indicate that natural arid climate is a dominant factor causing dried layers in the area

with the tree species being an important factor. During ecological and environmental construction

different types of vegetation should be recovered in view of the different levels of dried layer development. Grass and bush should be planted in the sandy soil area and grass and drought tolerant bush with trees should be plan-ted in the loess soil area. Where dried layers develop severely

afforestation is unsuitable because it can not bring environmental and economical benefits

but can cause excessive consumption of deep soil moisture and underground water.