BOOK OF ABSTRACTS 69 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Tuesday, 25 August 2026 / Hall B+C Research Frontiers SL28 Microbial Fingerprints in Antarctic Soils: Glomalin and the Hidden Drivers of Soil Carbon Vítězslav Vlček1, David Juřička2, Miroslav Pohanka3 1 Mendel University in Brno, Faculty of AgriSciences, Department of Agrochemistry, Soil Science, Microbiology and Plant Nutrition, Zemědělská 1, 613 00 Brno, Czech Republic, xvlcek1@mendelu.cz 2 Mendel University in Brno, Faculty of Forestry and Wood Technology, Department of Geology and Soil Science, Zemědělská 3, 613 00 Brno, Czech Republic 3 University of Defence, Faculty of Military Health Sciences, Třebešská 1575, 500 01 Hradec Králove, Czech Republic Soil organic carbon (SOC) in Antarctic deglaciated soils challenges common assumptions about climatedriven carbon gradients. Earlier surveys on James Ross Island, spanning elevations from 35 to 375 m a.s.l., showed that oxidisable carbon does not correlate with altitude, despite pronounced environmental gradients. This negative result raises a question: if altitude and temperature are not the primary controls, what drives carbon accumulation in Antarctic soils? Here we address this question by treating Antarctic soils as a simplified natural experiment to isolate key biogeochemical drivers of natural organic matter (NOM) formation. Building on earlier datasets, we investigate soil organic matter interactions along an altitudinal gradient (10–320 m a.s.l.) on James Ross Island, with a focus on glomalinrelated soil protein (GRSP) as an overlooked microbial fingerprint. Soil chemical properties, GRSP fractions, nutrient availability, and organic matter decomposition were analysed across nine sites differing in moisture regime, substrate, and vegetation cover, supported by a standardized tea-bag decomposition experiment and thermogravimetric analysis. SOC showed a strong positive relationship with easily extractable GRSP and soil buffering capacity, while no relationship was found between SOC and available mineral nutrients. Phosphorus availability decreased with altitude, indicating still abiotic control of some nutrient distribution. Decomposition experiments revealed rapid loss of labile organic fractions, declining C:N ratios, and signatures of nitrogenfixing microbial activity during early mineralisation. Together, these results challenge altitude-based interpretations of Antarctic soil carbon and propose that liquid water availability and microbialderived organic residues, rather than climate gradients alone, act as hidden drivers of SOC and NOM formation in polar environments [1–3].
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