Differences in stem taper of loblolly pine (Pinus taeda) grown in Coastal Plains and Southern Appalachians regions of the United States

Taper equations are useful to forest managers as they allow the prediction of diameter at any height or height to any diameter along the stem and facilitate the estimation of total or merchantable volume. These equations are typically species-specific and fit with data from a small geographic area. Even when the models are developed with regional datasets, most taper equations overlook the difference in tree shape across geographic regions and how the errors propagate when models fit to one region is applied to another region. This study aimed to find the difference in stem taper and volume of loblolly pine ( Pinus taeda) across two ecological regions and the associated environmental factors in the southern United States. Results showed considerable differences in the taper and volume of trees between the regions. Prediction errors increased when models trained on one region were applied to the other region compared to region-specific validation. Errors were largest when the model was developed using data from the Coastal Plains and applied to trees in the Southern Appalachians. This suggests that forest managers should consider the source of model fitting data when selecting taper models to accurately estimate the total or sectional volumes.