Study on Growth and Transpiration of Pinus Sylvestris var.Mongolica,Pinus Tabulaeformis and Populus Simonii in North Shanxi Province

Pinus sylvestris var.mongolica,Pinus tabulaeformis and populus simonii are main tree species to defend wind and sand in north Shanxi province.The paper studied the growing indices and the transpiration rate of these three kinds of trees.The results show that Pinus sylvestris var.mongolica is growing and developing regularly in north Shanxi province and is better than Pinus tabulaeformis and Populus simonii,and its transpiration rate is weak,its drought-resistance is strong.so it is one of the best tree species in north Shanxi province.Pinus tabulaeformis has the characteristic of broad accommodation、stronger resistance、weaker transpiration rate、stronger drought-resistance,it is also one of the important tree species of north Shanxi province.Poplus simonii is a tree species which likes sunlight and humid climate,it is hard to adapt to bad environment of north Shanxi province,so its value is very low and named small old tree.Because of the obvious difference of these three kinds of trees,they have very big differences in defending wind and sand and in improving the environment.so it is very important to study the characteristics of these three kinds of trees,this will contribute to selecting trees species according to the living conditions and improving the ecological environment completely in North Shanxi Province.