Individual tree volume and stand yield prediction for Eucalyptus in Kenya

Abstract

Individual tree volume data obtained from 365 trees collected from five forest regions in Uasin Gishu district of Kenya were used to derive regressIon equations for estimating total and merchantable tree volume and in comparing the forest regions. The predictor variables were diameter at breast height outside bark and total tree height. The techniques used in comparing the various methods included regressIon analysis, analysis of variance and multiple comparison analysis. The best equation for total tree volume was a nonlinear standard volume function, while merchantable volume was appropriately estimated' by a ratio function. All the equations tested for the two estimations gave closely similar results within the range of the data. Forest region comparisons revealed some differences between one region and the others, but the real cause for this difference could not be evaluated with the data available in this study. Yield estimation variables included number of trees, average top height, basal area and age of plantations. Equations based on age only gave poor estimation compared to equations derived from field measurements of both basal area and average top height in a nonlinear equation. The poor relation is probably due to the excessive variation in number of trees. However, equations based on age are cheaper to use since no field measurement is required.