Zero to moderate methane emissions in a densely rooted, pristine Patagonian bog - biogeochemical controls as revealed from isotopic evidence Wiebke Münchberger1, 2, Klaus-Holger Knorr1, Christian Blodau1, †, Verónica A. Pancotto3, 4, Till 5 Kleinebecker2 1Ecohydrology and Biogeochemistry Research Group, Institute of Landscape Ecology, University of Muenster, Heisenbergstraße 2, 48149 Muenster, Germany 2Biodiversity and Ecosystem Research Group, Institute of Landscape Ecology, University of Muenster, Heisenbergstraße 2, 48149 Muenster, Germany 10 3Centro Austral de Investigaciones Científicas (CADIC-CONICET), B. Houssay 200, 9410 Ushuaia, Tierra del Fuego, Argentina 4Instituto de Ciencias Polares y Ambiente (ICPA-UNTDF), Fuegia Basket, 9410 Ushuaia, Tierra del Fuego, Argentina Correspondence to: Wiebke Münchberger (
[email protected]), Klaus-Holger Knorr (kh.knorr@uni- 15 muenster.de) Abstract. Peatlands are significant global methane (CH4) sources, but processes governing CH4 dynamics have been predominantly studied on the northern hemisphere. Southern hemispheric and tropical bogs can be dominated by cushion- forming vascular plants (e.g. Astelia pumila, Donatia fascicularis). These cushion bogs are found in many (mostly southern) parts of the world but could also serve as extreme examples for densely rooted northern hemispheric bogs dominated by rushes 20 and sedges. We report highly variable summer CH4 emissions from different microforms in a Patagonian cushion bog as determined by chamber measurements. Driving biogeochemical processes were identified from pore water profiles and carbon isotopic signatures. An intensive root activity within a rhizosphere stretching over 2 m depth accompanied by molecular -1 oxygen release created aerobic microsites in water-saturated peat leading to a thorough CH4 oxidation (< 0.003 mmol L pore 13 -2 -1 water CH4, enriched δ C-CH4 by up to 10‰) and negligible emissions (0.09 ± 0.16 mmol CH4 m d ) from Astelia lawns.