Precipitation Change & Aridity Index in Zhanggutai Sandy Area

Meteorological data of Zhanggutai region from 1983 to 2010 were analyzed.The average annual rainfall is 469.4 mm,the maximum value is 689.2 mm and the minimum is 285.9 mm,furthermore rainfall mainly concentrated in June,July August;July is the highest.Precipitation is not only the main factor which affects the water table,but also the main limiting factor of local vegetation.In recent 28 years,de Martonne dryness index of Zhanggutai region ranges between 16.7 and 43.1,average value being 28.2;Kira dryness index ranges from 2.8 to 7.1,mean value being 4.6,and that Rhythm dryness index ranges from 0.8 to 2.1,average value being 1.3;de Martonne dryness index and Kira dryness index tend to decrease;rhythm dryness index tends to increase;local climate becomes dry and severe.According to three dryness indices,Zhanggutai is a typical sub-humid arid area;semimoist composition is more than semiarid ingredients.Consequently,meadow steppe,forest steppe,woodland and grassland should be the major trends of local vegetation and ecological restoration.