Foliage-sapwood area equations for balsam fir require local validation

Abstract

The foliage-sapwood area relationship (AL/AS) for balsam fir has been described in three separate studies with no less than four regression model forms. While there are clear differences in predicted A L values between the studies, it is not apparent if these differences are an artifact of the regression model form used or caused by regional differ-ences in the AL/AS relationship. We extracted published AL and AS values from the literature to statistically determine the best model form to describe the AL/A S relationship. Using this model form, we then explicitly tested for regional differences in the AL/AS relationship. We found that a linear model using natural logarithmic transformations best satisfied the assumptions of least squares regression in describing the AL/A S relationship. Based on the published data, there may be regional differences in the AL/AS relationship for balsam fir.