Modeling Height–Diameter Allometric Relationships of Dominant African Oak (Afzelia africana Sm) From West African Dry Savannas

Abstract

Tree height is an important ecological parameter for assessing biomass carbon accumulation rate and understanding the ontogenetic development of vascular plants. Given the lack of height measurement data, height–diameter allometric models are needed to improve carbon stock estimates. In this study, we investigated height–diameter relationships of dominant Afzelia africana Sm in West Africa. Using field measurements of 1483 trees across four forest sites and two climatic zones in Burkina Faso, we (i) compared the performance of 10 theoretical models in predicting height–diameter relationships, (ii) tested for site effects on tree height–diameter allometric relationships, and (iii) evaluated the performance of existing regional height–diameter equation in predicting tree height. We found that the asymptotic Gompertz model better described height–diameter allometric relationships of the studied species in the study area. A significant variation of the Lorey’s mean height and the asymptotic maximum height was observed between forest sites, highlighting the variations of height–diameter allometric relationships with site conditions. Existing height–diameter equation developed for West Africa significantly underestimates tree height of A. africana at between 53.34% and 62.63%. The height–diameter allometric models developed in this study can be applied for carbon stock estimates in the semiarid zones of West Africa. Mixed-species height–diameter models integrating other sites and varying climatic conditions can improve biomass estimates and contribute to a better understanding of the drivers of height–diameter relationships in savannas.