Global Change Research and Monitoring in the Maloti-Drakensberg Mountain System (South Africa-Lesotho)
Stuart Demmer – University of KwaZulu-Natal
Michelle Tedder – University of KwaZulu-Natal
Kevin Kirkman – University of KwaZulu-Natal
Globally grasslands are being impacted by human activities which are having strong impacts on the ability of ecosystems to sustainably provide functions. An important driver of global change in grasslands is anthropogenically mediated nitrogen deposition which disrupts belowground competition, eliminates uncompetitive species and reduces the stabilising effect of species diversity. Whilst there is a substantial body of evidence showing how grassland stability changes in response to anthropogenic activities and changes in diversity, whether particular environmental conditions predispose grassland communities to become destabilised remain poorly understood. We explored how grassland stability over consecutive three year periods responds to nutrient addition in a globally replicated grassland fertilisation experiment. Sixty-two different sites across five continents with variable climatic, management, edaphic and plant structural conditions were considered in this investigation. We found that African and North American grassland stability responded negatively to fertilisation. Nutrient addition increased stability in artificially created grasslands but reduced stability in grasslands with a burning regime. Soil property changes induced by nutrient addition also drove changes in stability with changes in macronutrients but not micronutrients being important predictors of grassland stability change. Regions, where nutrient addition reduced species asynchrony, increased compositional dissimilarity and increased species evenness, were also associated with reduced stability. These results will be useful for informing policy and management decisions and guidelines concerning human activities in grasslands.