Abstract
Tree growth, especially diameter growth of tree stems, is an important issue for understanding the productivity and dynamics of forest stands. Metabolic scaling theory predicted that the 2/3 power of stem diameter at a certain time is a linear function of the 2/3 power of the initial diameter and that the diameter growth rate scales to the 1/3 power of the initial diameter. We tested these predictions of the metabolic scaling theory for 11 Japanese secondary forests at various growth stages. The predictions were not supported by the data, especially in younger stands. Alternatively, we proposed a new theoretical model for stem diameter growth on the basis of six assumptions. All these assumptions were supported by the data. The model produced a nearly linear to curvilinear relationship between the 2/3 power of stem diameters at two different times. It also fitted well to the curvilinear relationship between diameter growth rate and the initial diameter. Our model fitted better than the metabolic scaling theory, suggesting the importance of asymmetric competition among trees, which has not been incorporated in the metabolic scaling theory.
Highlights
It is important to understand and predict tree growth because it is related to the productivity and dynamics of forest stands
They started from the assumption that whole plant biomass growth rate is proportional to leaf biomass (LB)
If we approximated by a line, for example in plot 4, the slope was obviously greater than unity and the intercept was negative (DT2/3 = -2.22 + 2.31D02/3; r2 = 0.89)
Summary
It is important to understand and predict tree growth because it is related to the productivity and dynamics of forest stands. Tree growth rate is an important demographic parameter, together with mortality and recruitment rates [1]. Among various measurements of tree growth, diameter of tree stem has been most widely monitored because of the easiness and accuracy of the measurement compared to tree height. There are several theoretical models to express stem diameter growth of individual tree. Enquist et al [2] predicted that stem diameter growth rate scales to the 1/3 power of the diameter. This prediction was deduced from the assumption that growth rate of tree biomass is proportional to its gross
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