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 Citation: # Studies on the Estimate Method for Average Stem Density

• The model y=bx+e is used to estimate the density of stem,where y is dry weight, x is volume, b is density and e is error.According to the relationship between variance of y and x, there are three methods to estimate b: (1)variance of y is uncorrelated with x ;(2)the relationship between the variance of y and x is a positive correlation,or δyx2=xδ2 ;(3)the relationship between the standard deviation of y and x is a positive correlation, or δyx=xδ.In this paper,the three methods were applied to estimate the average density of stem wood and bark,and the differences of the density in different positions of a tree and in different age class were analyzed with dummy variable method.The results showed:the effect of method (1) is better than the others.The differences of the density in different positions of a tree and in different age class are not significant.Same average density can be used to estimate stem dry weight of the same species of trees.
• • ## Studies on the Estimate Method for Average Stem Density

• 1. The Research Institute of Forest Resource Information Techniques, CAF Beijing 100091
• 2. College of Forest Resources and Environment, BUF

Abstract: The model y=bx+e is used to estimate the density of stem,where y is dry weight, x is volume, b is density and e is error.According to the relationship between variance of y and x, there are three methods to estimate b: (1)variance of y is uncorrelated with x ;(2)the relationship between the variance of y and x is a positive correlation,or δyx2=xδ2 ;(3)the relationship between the standard deviation of y and x is a positive correlation, or δyx=xδ.In this paper,the three methods were applied to estimate the average density of stem wood and bark,and the differences of the density in different positions of a tree and in different age class were analyzed with dummy variable method.The results showed:the effect of method (1) is better than the others.The differences of the density in different positions of a tree and in different age class are not significant.Same average density can be used to estimate stem dry weight of the same species of trees.

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