Effects of Broussonetia papyrifera invasion and land use on vegetation characteristics in a tropical forest of Ghana

The purpose of this study was to evaluate the effects of Broussonetia papyrifera (paper mulberry) invasion and land use on the floristic composition of a dry semi-deciduous forest in Ghana. Forty-five plots (25mx25m each), distributed among three land uses-selectively logged (SL); abandoned farmlands (AF); and an undisturbed reference (RF)-were surveyed. Results showed lower tree species richness (S), diversity (H '), evenness (S) and basal area (BA) in the SL (46, 0.78, 0.32 and 269.12m(2)ha(-1), respectively) and AF (40, 0.53, 0.45, and 131.16m(2)ha(-1)) sites compared to the RF site (79, 2.66, 0.87, 963.72m(2)ha(-1)). Similar patterns were found at the shrub layer, but no differences were observed at the herb layer. Non-metric multidimensional scaling ordination revealed distinct species composition among the land uses. The two disturbed habitats, SL and AF, were associated with increased B. papyrifera invasion particularly in the overstory, with importance value index and mean relative density of 45 and 65.03%, and 42 and 53.29%, correspondingly. However, the species was only sparsely represented in the RF site. Tree density of B. papyrifera correlated negatively with H ', S, E, BA, and native tree density and richness. These findings highlight the strong link between human land use (i.e., logging and slash-and-burn farming), invasion, and vegetation characteristics, and suggest the need to limit these disturbances to conserve biodiversity within tropical forest ecosystems.