Vessel characterization and ring-width of a multipurpose agroforestry tree species (Garcinia kola.(Heckel)) and its relationship with climate in Nigeria

Tropical agroforestry species are characterized by irregular growth and fruiting pattern, this is because of seasonal differences in the region and unanticipated environmental changes. Tree-ring width features and vessel variables could have a direct relationship with environmental conditions and factors such as precipitation and temperature could impact the growth of the species. This is because, during stressful environmental conditions, tree species record environmental changes through their physiological adjustment. Therefore, wood anatomical and tree-ring width time series was developed for Garcinia kola, a multipurpose tropical species, from a humid forest zone and derived savannah, along two vegetation zones in Nigeria. The species forms rings characterized by marginal parenchyma. The mean tree-ring width (TRW) ranges from 2.63 and 2.30 mm in the humid forest zone and derived savannah, respectively while the vessel number (VN) and vessel density (VD) are 95, 93, and 9.46, and 10.28 N/mm² respectively. The results revealed that the radial growth of G. kola showed a positive relationship with the precipitation and the minimum temperature during the peak of the rainy season in derived savannah areas. The VN, RW, and TVA show a significant relationship with the mean annual maximum temperature in the Rainforest and derived savannah area. The vessels are more abundant in samples from the rainforest area than in the derived savannah area, the results revealed that the wood anatomical variables and TRW were sensitive to climatic variables. Hence, they could be good indicators for evaluating tropical tree responses to environmental changes in tropical agroforestry species.