Study on the characteristics of precipitation resources and the afforestation suitability in the Loess Plateau.

Located in the arid and semi-arid regions,the Loess Plateau is a fragile region with low precipitation and intensive evaporation.Therefore,water is the most important limiting factor,and how to restore suitable vegetation in different regions based on the precipitation is a foundation to the ecological conservation and regeneration in the plateau.Based on the 40-year(1961-2000) climate data observed by 68 meteorological stations in the Loess Plateau,the precipitation characteristics in the plateau are analyzed.The results show that precipitation is distinctly different from the different areas,the average annual precipitation decreases from 600 mm in the south to 200 mm in the north of the plateau;80% annual precipitation occurs in plant growing season,so it is drought in spring and autumn but rainy in summer.According to the water balance of the forest ecosystem in growing season,the afforestation suitability is calculated using precipitation and ecological water requirement of woodlands.On which four different regions for afforestation are divided by regarding the counties in the Loess Plateau as the units.The results reveal that the area suitable to plant trees is about one quarter of the whole plateau,and another one quarter of the plateau are suitable to plant shrubs.