Estimating Rangeland Grass Productivity under Different Herbivore Pressure and Climate Change Scenarios

Rangelands, which include grasslands with interspersed trees, constitute over 50% of the earth’s land surface, carry most of the world’s livestock, and support a significant human population. The productivity of rangeland ecosystems is affected by many factors, of which rainfall variability and herbivory are particularly important. Water limitation constrains net primary productivity in grasslands in both temperate and tropical regions. Heavy grazing pressure on remaining rangelands due to increasing human populations and, thus, livestock product demands, has exacerbated the downward trend of productivity and has contributed to impoverishment of pastoralists in many marginal regions. Little is known about the effect of increasing grazing pressure and less predictable rainfall availability on grass productivity. Few direct experiments have tackled these two factors and quantified the herbaceous vegetation quantity and quality; and particularly experiments on the combination of these two factors have been scarce in African rangelands. Our study compares the effect of different levels of grazing frequencies and variable rainfall amount.  We quantify above- and belowground biomass, nutrient composition and soil properties in relation to the treatments. Our results will provide insights into rangeland productivity under changing environmental factors. This will help to develop a model which would help decision makers to design policies that would be urgently needed for predictions about responses of rangelands to future climatic scenarios.