The Responses of Herbaceous Plant Species of Miombo Woodlands to Different Grazing Intensities in Tanzania

The scarcity of grazing resources has forced pastoralists to relocate to the miombo woodland in Tanzania. Although pastoralism has coexisted with miombo for centuries, an increased number of pastoralists in miombo woodlands may lead to a loss of miombo resources. This study evaluated the effect of grazing intensity on herbaceous plant species composition, in terms of richness, diversity, and evenness to propose the optimal grazing that will ensure the existence of miombo and livestock. Data were collected from Kilosa, Kilombero, and Handeni districts in wet and dry seasons. In each district, three villages were selected based on the presence of miombo and livestock. Four grazing intensities were established using livestock grazing signs and the extent of grazed vegetation. There were 108 herbaceous plant species identified in the study area: 45 forbs, 17 grasses, 44 shrubs, and 2 sedges. An increase in grazing intensity from light to medium grazing intensity improved the availability of forage species, but availability decreased beyond this level, favoring undesirable species. The medium grazing intensities had more species (richness), higher diversity, and more evenness, followed by light, zero, and heavy grazing intensities. Light and medium grazing improved the species composition indices; however, heavy grazing negatively affected the herbaceous layer by reducing species richness, diversity, and evenness. This study suggests that controlled grazing improved the herbaceous species composition, regarding richness, diversity, and evenness compared to un-grazed land and high grazing intensity.