Examining the natural nitrogen biogeochemical cycling and impacts across South African ecosystems

Abstract

The biogeochemical nitrogen (N) cycle in South Africa is influenced by, and in turn influences a number of crucially important global change processes. However, the natural N cycling in South Africa is not well-understood. The “Emissions, deposition, impacts - Interdisciplinary study of N biogeochemical cycling (EDI-SA)” project is working to improve our baseline understanding of the natural biogeochemical cycling of N in non-industrialized ecosystems across South Africa. This includes quantifying N fluxes from emissions through to deposition, identifying linkages between N cycling and related species such as sulphur (S) and ozone, and evaluating ecosystem impacts. Previous work has focused on the impact of atmospheric deposition of N and S species on ecosystems at sites almost exclusively on the industrialized Highveld. This has left large gaps of knowledge in the biogeochemical cycling and ecosystem impacts, particularly within the diverse natural ecosystems found across South Africa. In order to address this gap, EDI-SA is applying a more holistic approach using measurements (from two South African Research Infrastructures; EFTEON and BIOGRIP) and modelling to investigate multiple linkages within the biogeochemical cycling of N with a focus on improving the understanding of the natural cycling. The project is applying a variable resolution sampling approach to investigate processes which occur at multiple spatial scales, and applying multiple measurement techniques including atmospheric measurements, stable isotope analysis of aerosol particles, rainwater and soil, and analysis of soil chemistry and biology. This contribution will detail the approach of this interdisciplinary project, highlight results from the first soil and air sampling campaigns, as well as the atmospheric composition modelling that assesses the relative importance and impacts of N emissions from soil across South Africa. This baseline understanding will allow future research to assess the potential changes to N biogeochemical cycling into the future in a changing climate.