Riparian vegetation dynamics in protected and unprotected areas, Kumawu District—Ashanti Region (Ghana)

Abstract

The aim of the study was to explore the response of plant assemblages to environmental drivers among four riparian zones (Amobia, Ninian, Pame and Owname), in Ashanti Region, Ghana, West Africa. A 120 sample plots of 10 × 10 m2 for trees and shrubs and 0.5 × 2 m2 for grasses and herbs, were randomly laid perpendicular to the environmental gradients, and from both sides of the four classified riparian zones. Number of individuals were counted per plot and percentage cover estimated per species. MacArthur broken stick model (BS), Chao-1 estimates and Hill numbers were calculated to quantify community assemblages, while constrained ordination (CCA) was applied to examine the relationship between species assemblages and the distribution of associated environmental factors. A total of 1589 individuals belonging to 48 families and 141 species were registered. Species from the Fabaceae, were the highest (14.2%). Overall, species abundance, richness and diversity, differed significantly across the four zones. Aspilia africana and Panicum maximum were the single most abundant tree and grass species, respectively. Infrequent species including Bussea occidentalis, Celtis zenkarii constituted 0.4% of the total species sampled. Although Pame was found to be species poor, it tended to be the most diverse, while Ninian was the least diverse. CCA analysis showed that farming, bushfire, erosion and logging, accounted for 43.13% (axis I = 23.24% and axis II = 19.89%) patterns of species variability across sites. Though disturbances tend to promote diversity through the creation of evenness in species distribution and richness, but in severe scenarios, sensitive indigenous species may go extinct, leaving only stress-tolerant alien invasive like Arthraxon hispidus and Chromolaena odorota.