Effects of Deferred Grazing Regime on Rangeland Productivity and Health: A Case Study of Simanjiro District in Northern Tanzania

Abstract

Deferred grazing regimes are viewed as a grazing management strategy that can aid in the enhancement of rangeland productivity and health. However, there is limited empirical evidence from drylands of East Africa. This study investigated the effects of deferred grazing regime on rangeland productivity and health in northern Tanzania. Aboveground vegetation biomass, plant species composition and diversity, as well as soil organic carbon (SOC) were assessed in 45 rectangular sample plots (20 × 50 m) which were randomly distributed in a rangeland subjected to deferred grazing for 8 years. For control adjacent rangelands subjected to continuous grazing management were evaluated. Statistical analyses were performed using an independent t-test to discern differences in vegetation biomass, SOC, species abundance and diversity between the two grazing regimes. Additionally, Multivariate General Linear Model (MvGLM) were performed to test if grazing system affected vegetation composition. Results revealed that the herbaceous biomass, SOC, and the richness of shrubs (with a diameter at breast height, or DBH ≥5 cm and <10 cm) and trees (DBH ≥10 cm) were higher in rangeland subjected to deferred grazing, in comparison to the rangeland under continuous grazing regime. Moreover, rangeland under continuous grazing was found to be more heavily invaded by non-native plant species, notably the invasive weeds Prosopis juliflora and Calotropis procera. The findings of this study suggest that rangelands in the study area can be both more productive and healthier when managed under a deferred grazing regime, as compared to continuously grazing rangeland.