THE INTRODUCTION OF TREES AND SHRUBS IN LHASA AND ITS VICINITIES

Formerly there were not many species of indigenous trees and shrubs in Las a(Lhasa) region.For more than one hundred years,the people of Xizang(Tibet) have introduced and tamed.many exotic species to Lasa region.Up to now,there,are more than sixty species of trees and shrubs being cultivated in Lasa,of-which,about 50% are introduced from other provinces,25% from Xizang except Lasa,and the original species of Lasa occupies only 25%.It is suggested that the tree introduction to Lasa must pay attention to the following points.1、The introduced species must come from the regions where the ecological conditions are similar or close to that of Lasa.2.The introduced species must be widely distributing in our country.3.The key to succeeding introduction is climatic conditions,and the limited factors are temperature and humidity.4.Species of positive heliotropism appear more successful in introduction than that of negative heliotropism.