A regression application for comparing growth potential of environmental at different points in the growth cycle

Regression techniques are used to quantify a procedure for indexing the productive capacity of forested sites. The regression model parameters theta' = (gamma*, beta 1, beta 2,..., beta m) are defined in such a way that the value of the indexing parameter gamma* identifies individual growth-over-time response curves from a family of curves that have the parameters beta 1, beta 2,..., beta m in common. The beta terms are estimated from historical cumulative growth data, while gamma* is estimated from these historical data together with r values of the response characteristic observed at a single point in the growth cycle of each new environment to which the prediction equations are to be applied. The formulation allows comparison of growth potential of environments containing equal-aged groups of experimental units that are at different points in the growth cycle, by means of an index defined as projects growth at a preselected common age.