Impact of climate, land management and harvesting patterns on the ecological traits and the population structure of Pterocarpus lucens in West African semi-arid areas

Multipurpose woody plant species experience severe pressure owing to human overexploitation, land management and climate change. In response to their inability to cope with environmental disturbances in their natural range, some species such as Pterocarpus lucens migrate to more suitable areas. To better conserve P. lucens, this study examined the impacts of climate, land management and harvesting practices on its natural populations.

This study was conducted in Burkina Faso using a combined gradient approach involving two climatic zones and two land management types. Data on the biological age classes, structural traits and intensities of harvesting were collected on each individual of the species. Linear models were used to assess the effects of the investigated gradients on structural traits of the species. The diameter and height class size distributions were evaluated using the least squares method.

The results showed that the species’ pre-reproductive individuals increased significantly (p < 0.05) with climatic and the protection gradient, resulting in an invasive trend of P. lucens in the Sudano-Sahelian protected areas. The species is overexploited in unprotected areas, with the majority of individuals undergoing all pruning intensities. However, while in the Sahelian climatic zone, decreasing pruning rates were observed according to the severity gradient (low intensity 36.02 %, moderate intensity 27.47 %, and severe intensity 19.73 %), an increasing pruning rate was observed in the Sudan-Sahelian climatic zone (low intensity 16.49 %, moderate intensity 17.38 %, severe intensity 24.48 %, and very severe intensity 35.79 %). Linear regression analysis showed a significant effect (p < 0.05) of climate, land management, pruning, and debarking on the structural traits of the species. The diameter class structure revealed unstable populations of the adult stratum in the Sahelian climatic zone, regardless of the land management types. The juvenile stratum of this species exhibited an unstable structure in unprotected areas, regardless of climatic zone.

This study highlights the urgent need to implement effective management strategies to mitigate the decline of P. lucens populations in the Sahelian climatic zone and in unprotected areas through its integration in reforestation programmes.