Since density dependent mortality is caused by the increase of tree size,it is more natural to choose an indicator of the size to express the relationship between the number of trees and the size.We chose the total stand basal area as the indicator of the size,and established an equation relating the number of trees to the total basal area of even aged pure plantations of Pinus sylvestris var. mongolica on sandy soil during their self thinning.We reviewed the -3/2 power law of plant self thinnin...