Spatial Distribution of Pterocarpus erinaceus Poir. (Fabaceae) Natural Stands in the Sudanian and Sudano-Guinean Zones of West Africa: Gradient Distribution and Productivity Variation across the Five Ecological Zones of Togo

Abstract

Aims: This study aims to analyze the structure of some populations and the natural regeneration potentials of Pterocarpus erinaceus Poir. According to the environmental conditions, taking into account the 5 ecological zones of Togo. Especially, it aims to: (i) Describe the geographical distribution of the species in Togo, (ii) Analyze the influence of environmental variables (climates, soils and type of vegetation) on the structural characteristics of natural stands and (iii) Determine the natural regeneration potentialities of the species. Place and Duration of Study: Fieldworks were done from 10 October to 15 December 2013 throughout Togo. Methodology: Forestry inventory was carried out on 200 plots of 1000 m² randomly set up in P. erinaceus natural stands in the 5 ecological zones of Togo. In each plot, total height, the merchantable height and diameter at breast height (DBH) ≥ 10 cm were measured. The regeneration was studied in sub-parcels of 25 m² set up in the previous parcels of 1000 m². In these sub-parcels, the natural seedlings, coppices, sucker which the DBH is less or equal to 10 cm were counted. The geographic coordinates of each tree are registered with the GPS. Results: The results show that P. erinaceus had a wide distribution and tolerance range in Togo. Trees populations' average density is between 57±23 N/Ha and 76.5±42 N/Ha. The average diameter, the average total height, the basal area are significantly different for the stands of the 5 ecological zones (P= 0, 00). Diameter distribution indicates a reversed-J in ecological zones 2, 4 and 5 i.e. dominated by small diameters structure of P. erinaceus (Poir.); and unimodal distribution in zones 1 and 3. The study shows that a seedling which is the main strategy of regeneration is not significantly different between the stands studied. Results also show a good natural regeneration capacity of P. erinaceus by a coppice. Conclusion: This study enables to describe the main characteristics of the natural stands of P. erinaceus in Togo and constitute therefore a useful source of information for the management of natural stands notably that of P. erinaceus.