Effect of grazing intensity on understory vegetation in a Village Land Forest Reserve in Northern Tanzania

In Tanzania, grazing in Village Land Forest Reserves is prohibited in some villages but is allowed and practiced in other villages. This study investigated the composition of forest understory vegetation in terms of number of species, abundance, and height and their response to livestock grazing intensities in a grazed Village Land Forest Reserve in Tanzania. A 12-month grazing experiment with five grazing cycles was conducted within four blocks of 4 ha each, with 0, 8, 12, and 18 adult cows/ha for control, low, moderate, and high grazing intensities, respectively. A total of 178 plant species belonging to 146 genera and 43 families were recorded. These were classified into nine growth forms; annual climber, annual forb, annual grass, perennial climber, perennial forb, perennial grass, sedge, shrub, and tree seedling, with dominant and co-dominant species found among the annual forbs and tree seedlings, respectively. Low and moderate intensity treatments showed no significant reduction in the number, abundance, and stem height of plant species, while the high intensity treatment showed a significant reduction in abundance and stem height, but not in number of species relative to the control. We conclude that, within the duration of the study, the grazing intensities applied did not affect the number of plant species, whereas both abundance and height were affected significantly. The study indicates that reducing grazing to low or moderate intensities with resting periods can enable the community to benefit from forage production without affecting the vegetation composition of the study forest.