Aggregating tree species to develop diameter increment equations for tropical rainforests

Vanclay, J.K., 1991. Aggregating tree species to develop diameter increment equations for tropical rainforests. For. Ecol. Manage., 42: 143-168. Pairwise F-tests provided an efficient approach for aggregating large numbers of species into a manageable number of groups for developing diameter increment functions. The first stage of the two-stage procedure identified the number of groups required and the species defining these groups; the second stage aggregated all the remaining species into the most appropriate group. Although there is no guarantee that this leads to an optimal solution, empirical results suggest that the outcome is near optimal. This approach is readily automated and computationally efficient. An analysis of diameter increments of 237 species from the rainforests of north Queensland indicated 41 species groups, each with increment functions significantly different at P<0.01. These provided a substantially better model than the previous model based on subjectively formed groups.