ANALYSIS OF GROWTH EQUATIONS

Growth of plants results from two opposing factors: the intrinsic tend ency toward unlimited increase (biotic potential) and restraints impos ed by environmental resistance and aging. The expansion tendency preva ils in the beginning of a tree's life, while growth decline becomes pr ominent toward the end. The existing growth equations can be transform ed (by differentiation, decomposition into the division components, an d taking logarithms) so that the components that correspond to these t wo factors are exposed. This transformation reveals two basic forms in trinsic in most of the analyzed equations. Their common feature is tha t growth expansion is proportional to current tree size. Growth declin e of individual trees appears to be more variable and can be rendered with equal accuracy by a variety of expressions. This may reflect that a greater number of factors hinder growth: scarcity of resources, com petition, reproduction, diseases, herbivory, disturbances, etc. Conseq uently, the growth path is inherently imprecise and can be viewed as a wide valley rather than a single line. This analysis laid groundwork for the classification of known equations and made possible the discov ery of a promising new equation form.