The Research on the Dried Layer and the Moisture Restoration of the Soils in the Planted Forests in Xi''an Area
西安地区人工林土壤干层与水分恢复研究

For making sure the dried layers of the soils and the moisture restoration after the high flow year in Xi'an area,using drying method the research has been carried out on the moisture content of the soils in the planted forests such as poplar,chinese parasol and chinar.The results indicate that the moisture content of the soils in the poplar,chinese parasol and chinar forestlands at a depth ranging from 1.5 to 4 m are separately 9.3%,9.0%,9.7% and 9.1% before extreme precipitation in the high flow year in Xi'an area.They are all lower than 12%,indicating that the dried soil layer exists under the condition of normal precipitation in Xi'an area.The dried layers develop widely with a thickness of about 2.5m.The soil moisture content from 0 to 6 m in the four planted forests has restored well after extreme precipitation in high flow year and the dried layer from 1.5 to 4 m have disappeared completely.Through about one year infiltration,the depth of the moisture restoration may reach to about 6m.After two years of extreme precipitation,the soil dried layers in the four planted forests still do not appear.According to the consumption of the soil moisture after high flow year,it is preliminarily determined that the dried layers in the planted forests will appear again after three or four years of high flow in Xi'an area on the basis that there is normal precipitation after the high flow year.In Xi'an area the soil dried layers in the four planted forests develop weakly.The weakly-developed dried layers do not affect the normal growth of the planted forest and the four planted forests such as poplar,chinese parasol and chinar grow well in Xi'an area,indicating that in Xi'an area or in other areas of the Loess Plateau with similar precipitation to Xi'an area planting arbor forests is feasible.