Through gathering massive soil samples and determining the moisture content in the lab.

the author had research on the moisture content and the moisture restore in the depth of 0 ~ 6 m in the different vegetation around extreme precipitation in Xi'an area.The research indicates that in Xi'an area in the poplar woods

the plane tree forest and the Chinese parasol tree forest the moisture content in the depth of 1.5 ~ 4 m separately is 9.3%

9.0% and 9.7%

the soil dryer has existed

and the thickness is approximately 2.5 m.In the wheat and lawn field the soil dryer does not appear in the depth of 0 ~ 6 m.In abundant water year after extreme precipitation the soil dryer vanishes

the soil moisture restores well

and the moisture content in the original dryer is obviously higher than the upside and lower part.That the weak-growth dryer does not affect the normal growth of the planted forest indicates in Xi'an area or in other area of loess plateau with similar rainfall amount to the Xi'an area planting big tree forests is feasible

but should avoid a more serious soil dryer appearing.