Ecological Impacts of Pteridium aquililium and Chromolaena odorata Invasions in Rangelands of the Bamenda Highlands

Weeds are a growing threat to livestock rearing in the grazing lands of the Bamenda highlands. The ecology of grazing lands in the Bamenda highlands is in a convergent evolution with increasing weed invasion. The recent dynamics has seen the increasing invasion of two notable weeds notably Pteridium aquililium and Chromolaena odorata in the region with different ecological repercussions. The study set out to study the ecological implications of these two species of weed in the grazing landscape. A total of 64 cross section transects were studied in different topographic units across the region both in high plateau areas and lowland areas. Quadrats of 1x1m were laid in foot hills, slopes and top of hill. Information relating to grass species composition, relative abundance, weed species and ground cover was obtained through this field evaluation. Soil analysis from different samples collected across the area was also performed. Results revealed change in vegetation composition with an increase in weeds in composition, reduction in relative abundance for palatable species and shifts in species. There is a significant reduction in native species in densely infested C. odorata sites in the area. Moreover, most native species are absent where C. odorata is abundant, and species richness declines by nearly 72% from the margin to the center of the infestation. In Bracken infested areas where its canopies are quite closed, other weed are associated to its invasion in the undergrowth notably Emilia pratemisa, Taraxacum sp and Alchemilla Cryptantha. Species reductions in fern infested pastures are not as great as C. odorata stands although Pteridium aquililium creates more continuous extensive patch sizes of monospecific stands than C. odorata discontinuous dense stands. Shifts and species reduction due to invasions reached 61%. Species shifts mostly concern Setaria sp. (S. sphacelata), Loudetia and Panicums on the better soils and with Andropogon, Paspalum and Imperata of medium size on the poorer soils. Fuel loads increase and modify fire regimes creating post fire succession species. Management require concerted actions among actors to curb invasions.