Sustainable management insights from the population ecology and carbon storage of Uapaca kirkiana Müll., Arg. across geographic regions in Malawi (Southern Africa)

Abstract

• Stand structure of U. kirkiana reveals disturbed regeneration. • Floristic diversity is higher in the central and southern regions, with the Fabaceae, Phyllanthaceae, and Combretaceae families dominating. • Maximum carbon biomass (57.80 t CO₂/ha) was recorded in the northern region. • Structural indices (Qs and inter-tree distances) revealed little heterogeneity. • The estimated economic value reaches 1011,997.57 MWK/ha (577.95 USD/ha). • The structural distribution of U. kirkiana was characterized by small diameter classes (10–20 cm). Understanding the ecological dynamics of multipurpose tree species such as Uapaca kirkiana Müll., Arg. is crucial for their sustainable management, particularly under increasing climate change pressures. Using forest inventory data from 149 plots, this study assessed the population ecology parameters (size class distribution, structural diversity, species diversity and stability), regulating ecosystem services (carbon storage potential) and importance value indices of U. kirkiana across three regions and six altitudinal classes in Malawi. An analysis of variance (ANOVA) was performed to compare ecological parameter means across regions and altitudes; correlation among these parameters was tested for their association. Overall, we found 124 species, 89 genera, and 39 botanical families, with Fabaceae, Phyllanthaceae, and Combretaceae being the most dominant. Species richness and Shannon diversity indices were higher in the central and southern regions. Structurally, U. kirkiana populations were dominated by small diameter classes (10-20cm), with few mature individuals (>45cm), indicating regeneration disturbance. Diameter at breast height (DBH) was positively correlated with the structural quotient (Qs) and inter-tree distance, but negatively correlated with diameter differentiation, suggesting low heterogeneity in mature stands. U. kirkiana tolerated mixed-species stands (mingling index: 20-44%), supporting its suitability for agroforestry systems. The Northern region had the highest carbon storage (57.80 tCO₂/ha), significantly higher than the Southern (51.25 tCO₂/ha) and Central (43.80 tCO₂/ha) regions (p < 0.05), because this region is characterized by greater annual rainfall (>1,600mm), which supports better tree growth and biomass accumulation. The estimated economic value of U. kirkiana was 1,011,997.57 MWK (577.95 USD/ha), highlighting its significance for both ecological and livelihood purposes. These findings contribute to a better understanding of the ecological behavior and service provision by U. kirkiana , in Malawi.