**A Method for Estimating Crown Weight in Eucalyptus, and Some Implications of Relationships between Crown Weight and Stem Diameter **

P. M. Attiwill

School of Forestry, University of Melbourne, Victoria, Australia

*ABSTRACT*

Equations relating crown weight to diameter at breast height outside bark (dbhob) are developed for approximately 50-year-old, even-aged stands of *Eucalyptus **obliqua* from initial branch weight-branch girth relationships. These equations are used to predict crown weights of individual trees; the predictions for n' trees per unit area have standard errors of 15%/√n' of the summed leaf weights and 17.5%/√n' of the summed branchwood weights. Although stem weight is a function of dbhob^2, considerations both of (crown weight) - dbhob and (crown weight) -(stem diameter at base of crown) relationships show that crown weight is a function of (stem diameter at base of crown)^2 = constant (dbhob)^3, thus accounting for form factor. There is no logical basis, therefore, for selecting a tree of mean dbhob as a unit for estimating (weight of mean tree X number of trees) dry weight per unit area. The bias (in this sense meaning the deviation from the true value) of estimates so obtained are discussed; an index of the error is provided by the distribution of dbhob^3 with respect to dbhob. The error, one of underestimation, is likely to increase with stand age, and this must be an important deficiency in some of the productivity-age sequences which have been developed.