Estimating impact of leaf harvest on diameter growth and survival of fodder trees in West African Savannah

Understanding how the growth and survival of tropical savannah trees respond to anthropogenic pressures, particularly leaf harvesting, is essential for the successful restoration of degraded forests. Leaf harvesting of fodder trees poses a chronic threat to the population dynamics of Afzelia africana , Khaya senegalensis , and Pterocarpus erinaceus , whose leaves are intensively harvested during the dry season. The objective of this study was to estimate the diameter growth rate and survival rate of fodder species in order to identify leaf harvesting intensities that support high growth potential and contribute to savannah restoration. Data were collected through an inventory based on systematic sampling of 1,040 individuals of Afzelia africana , Khaya senegalensis , and Pterocarpus erinaceus . These individuals were obtained from one-hectare plots distributed across nine populations located in two ecological zones of Benin (Sudanian and Sudanian-Guinean). The study was conducted over three consecutive years (2021, 2022, and 2023). The trees were classified according to four levels of leaf harvesting intensity: unharvested, moderately harvested, heavily harvested, and fully harvested. The effects of leaf harvesting intensity on tree diameter growth and survival were assessed using linear and exponential statistical models, selected according to the Akaike Information Criterion (AIC), and the Kaplan–Meier method for survival analysis. The ecological zone and harvesting intensity were significantly associated (p < 0.05) with tree diameter growth and survival across the three species. Results showed that diameter growth rate of trees decreased with tree size. For the majority of species, the diameter growth rate of trees decreased with leaf harvesting intensities. This study indicates that total leaf harvesting strongly compromises tree viability, while zero or moderate harvesting maintains better survival in the medium term. These results suggest the need to set an acceptable harvest intensity threshold (50%) to guarantee the sustainability of fodder species in areas subject to anthropogenic pressure. • Fodder seedlings and young trees have a higher growth rate than larger fodder trees. • The growth rate of fodder trees decreases as leaf harvesting intensity increases. • The basal area of fodder trees changes little as leaf harvesting intensity increases. • The survival probability of fodder trees decreases when leaf harvesting intensity is greater than 50%. • Larger fodder trees are more resistant to high leaf harvesting intensity.