Woody Species Diversity and Structure of Parkia biglobosa Jacq. Dong Parklands in the Sudanian Zone of Togo (West Africa)

Abstract

Aims: This study aims at assessing the impact of land use on woody species diversity and the structure of Parkia biglobosa parklands in the Sudanian zone of Togo. Place and Duration of Study: Fieldworks were carried out in April 2013 and data analysis were realized in August 2014. Methodology: Data were collected within four type of P. biglobosa parklands: young fields (one to three years), old fields (aged more than three years), young fallows (one to three years), and old fallows (aged more than three years). In each type of parkland, the total height and girth of all woody species with diameter at breast height (dbh) ≥ 10 cm were measured within twenty sample plots of 2500 m² (50 m x 50 m).Furthermore, P. biglobosa individual with dbh < 10 cm considered as potential regeneration were counted in the same plots. Results: Thirty eight (38) woody species belonging to 34 genera and 18 families were identified. The most representative families were Fabaceae (8 species), Malvaceae (6 species), Moraceae (5 species), and Anacardiaceae (4 species). The highest species richness was recorded in old fallows (27 species), followed by young fallows (18 species) and young fields (17 species). The species Important Value Index (IVI) showed that the most important species apart from P. biglobosa was Vitellaria paradoxa. Added to V. paradoxa, the most represented species were Diospyros mespiliformis, Blighia sapida, Adansonia digitata and Vitex doniana respectively in young fields, old fields, young fallows and old fallows. The diameter structure of P. biglobosa showed a left dissymmetric bell-shape curve with Weibull distribution shape parameter c, 1 <c<3 indicating a predominance of small diameter individuals within the overall stands. However, the overall rate of regeneration was weak with a nearest absence in old fields. Fisher test showed a significant difference between all dendrometric parameters. The species richness and density decline from young fields to old fields, and increase from young fallows to old fallows. Conclusion: In spite of the predominance of young individuals, the weak regeneration of P. biglobosa will threaten its population in the future and consequently lowering its productivity. The introduction of juvenile individuals into farmlands may be needed to ensure its conservation in agroforestry systems.