Estimating the Boundaries of Plant Stage Classes Using the Vandermeer-Moloney Algorithm

Abstract

We demonstrate the application of the Vandermeer-Moloney algorithm to assign discrete stage classes to a continuous variable (e.g. age or density), that does not always have natural divisions. The algorithm provides a numerical approach to assign individuals to classes. This is done by minimising two possible sources of error. If the stage classes are too wide, much information will be lost because individuals will be growing within each stage class and secondly if the classes are too narrow then this can lead to problems with parameter estimation, since each new class requires a new set of parameters to specify its mortality, fecundity and state transition rates. We obtain not only a stage distribution, but since our data set contains values over a number of years, we have also estimated transition probabilities from stage to stage. The task presented in this paper is to implement a methodology for taking this raw data (in particular, the canopy size) and determining class boundaries in terms of age from this physical data.