Effect of clearing invasive woody species on plant species diversity in a tropical rangeland ecosystem in Ghana

Herbaceous species used by ruminant livestock are competing with invasive woody species, including Prosopis juliflora (Sw.) DC, Jatropha curcas L, and Azadirachta indica A. Juss. (neem), in the Coastal Savannah rangelands of Ghana. It is, therefore essential to evaluate the impact of woody species encroachment on plant species diversity. This study evaluated the effect of the three invasive species, Prosopis juliflora, Jatropha curcas, and Azadirachta indica on plant species diversity, with special reference to herbaceous species. An area of 95 m x 20 m was divided into two equal parts: the Cleared and the Uncleared areas. The cleared area had all woody species removed but not in the Uncleared area. Plant species were inventoried to determine species richness and grazing value. A qualitative assessment was conducted using the Braun-Blanquet scale and other descriptive analyses. 16 different plant species belonging to the Amaranthaceae, Euphorbiaceae, Fabaceae, Malvaceae, Meliaceae, Mimosaceae, and Poaceae families were identified. Clearing led to a significant difference (p < 0.05) in the number of individual plant species between the two treatments. There was no significant difference (p < 0.05) in the number of species types between the two treatments. Range cover, species abundance, plant families and habits did not differ. There was no marked difference in plant diversity between the two treatments. This study provides a location-based and species-specific novelty on the synergistic effects of the three invasive woody species on herbaceous plant species diversity in the Coastal Savannah rangelands of Ghana. The study results will provide baseline information for policy decisions related to invasive species management and ecosystem conservation in the Coastal Savannah rangelands of Ghana. It is recommended that this study be conducted over a longer period to elicit the long-term effects of these encroaching species on herbaceous plant species diversity.