Species-Independent Height-Age Models for British Columbia

Abstract

Abstract Species-specific height-age models abound in the scientific literature. Some researchers have used Zeide's two-point system to reduce the number of models in service. However, this system requires two height-age pairs which are not always available. The purpose of this research is to develop a height-age model for British Columbia, Canada, that is independent of species. From a large database of stem analysis data, 15 plots from three coastal and seven interior species were chosen to uniformly cover the range of site index for each species. After converting the stem analysis data into height-age data, a model based on the logistic function was fit to each plot. A preliminary analysis showed that site index, geographic region (coast, interior), and shade tolerance (tolerant, intolerant) are potentially good predictors of height. These variables, along with breast height age, were incorporated into a species-independent height-age model based on the log-logistic function. An additional ten plots per species were chosen to test the model. The testing showed that the species-independent model had approximately the same accuracy as the species-specific models. Future endeavors can be directed at improving the model by incorporating more species into the analysis and including other important climatic and ecological variables. FOR. SCI. 47(2):150–157.