Change of Soil Fertility in Pinus sylvestris var. mongolica Natural Forest in Sandy Land

The characteristics of change of soil fertility in Pinus sylvestris var.mongolica natural forest in Hulunbeier sandy land has been studied at some aspects such as soil nutrients content,particle composition and humus feature.The results showed: with the increase of age of Pinus sylvestris var.mongolica natural forest,soil organic matter content,total nitrogen content,total phosphate content and available phosphate content have increased,but soil available nitrogen content has decreased,and the soil pH value has decreased.Soil particle composition has mainly gathered from 20 nm to 200 nm,with average content at 63.04%～93.49%.During growth,Pinus sylvestris var.mongolica natural forest in Hulunbeier sandy land can obviously influence the soil humus composition,and with the increase of forest age,it's favorable to form good soil humus structure and improve the soil nutrient preserving capacity.