Effectiveness of inventory plot patterns and spatial distribution of trees and recruits in West African forest estimates: Recent findings and perspectives

Forest inventories constitute an important tool in decision-making by assessing quantitative and qualitative pattern of plant material and its evolution over time. Inventory techniques used in different countries in West Africa are numerous and diversified. This situation does not allow comparison of forest inventory results between different countries and decision making at regional level. Many studies have attempted to determine optimal inventory plot (shape and size) for different vegetations types. However, most of these studies have been undertaken outside Africa and did not take into account most common vegetation types of Africa. Recent studies in West Africa have focused on the comparison of inventory plot sizes and shapes and spatial pattern of trees and recruits on the floristic and dendrometric analysis of dense forest and woodland. From these studies, the direction and shape of inventory plots do not influence the precision of the quantitative analysis of vegetation. However, square plots were suitable in practice. On the contrary, plot size is significantly correlated with the precision of floristic analysis and estimation efficiency. Where trees tended to be aggregated, estimation error increases with degree of aggregation, and rectangular plots of 0.24 ha resulted in more precision. In terms of regeneration, shape and size of subplots highly influence the estimation of the density of recruits and rectangular subplots were most efficient for the estimation of the density of recruits in dense forest. As for stem diameter distribution of regeneration, only the plot size had a significant effect on the mean absolute error of the stem diameter structure. Further studies are required in order to cover all the vegetation types met in Africa.