https://doi.org/10.5194/bg-2020-420 Preprint. Discussion started: 2 December 2020 c Author(s) 2020. CC BY 4.0 License. Multi-year CO2 budgets in South African semi-arid Karoo ecosystems under different grazing intensities Oksana Rybchak1, Justin du Toit2, Jean-Pierre Delorme1, Jens-Kristian Jüdt1, Kanisios Mukwashi1, Christian Thau3, Gregor Feig4,5, Mari Bieri1, Christian Brümmer1 5 1Thünen Institute of Climate-Smart Agriculture, Braunschweig, 38116, Germany 2Grootfontein Agricultural Development Institute, Middelburg, 5900, South Africa 3Department of Earth Observation, Friedrich-Schiller University Jena, Grietgasse 6, 07743 Jena, Germany 4South African Environmental Observation Network, Colbyn, Pretoria, 0083, South Africa 5Department of Geography, Geoinformatics and Meteorology, University of Pretoria, Pretoria, 0002, South Africa 10 Correspondence to: Oksana Rybchak (
[email protected]), Christian Brümmer (
[email protected]) Abstract. Climatic and land management factors, such as water availability and grazing intensity, play an important role in seasonal and annual variability of the ecosystem–atmosphere exchange of CO2 in semi-arid ecosystems. However, the semi- arid South African ecosystems have been poorly studied. Four years of measurements (November 2015–October 2019) were 15 collected and analysed from two eddy covariance towers near Middelburg in the Karoo, Eastern Cape, South Africa. We studied the impact of grazing intensity on the CO2 exchange by comparing seasonal and interannual CO2 fluxes for two sites with almost identical climatic conditions but different intensity of current and historical livestock grazing. The first site represents lenient grazing (LG) and the vegetation comprises a diverse balance of dwarf shrubs and grasses, while the second site has been degraded through heavy grazing (HG) in the past but then rested for the past 10 years and mainly consists of 20 unpalatable grasses and ephemeral species.