Modeling Caribbean Tree Stem Diameters from Tree Height and Crown Width Measurements

Regression models to predict diameter at breast height (DBH) as a function of tree height and maximum crown radius were developed for Caribbean forests based on data collected by the U.S. Forest Service in the Commonwealth of Puerto Rico and Territory of the U.S. Virgin Islands. The model predicting DBH from tree height fit reasonably well (R2 = 0.7110), with strongest in subtropical moist and wet forest. The model predicting DBH from crown radius fit the data poorly (R2 = 0.2876), but improvements were made when the model was fit by forest life zone and crown radius measurement protocol. Models fit with both maximum crown radius and tree height had R-square values that ranged from 0.1803 for the subtropical dry forest to 0.8018 for the subtropical moist forest life zone where crown radius was measured with urban forest inventory protocols. Tree heights had stronger correlations with DBH than did crown radius, perhaps due to difficulties in measuring tree crown width or natural variability in this hurricane-disturbed environment. Models that use tree height have some potential for predicting DBH for use in Caribbean forest biomass and carbon estimation models, but the potential for error propagation by using DBH predicted from crown radius is too great to earn our recommendation for such applications.