Replication Data and Analyses for: E. Ingvarsson, C. Gudasz, M.B. Siewert. Continental to meter scale climatic, topographic and geomorphological gradients control soil organic carbon distribution in complex Arctic terrain.

This dataset corresponds to the forthcoming manuscript: "Elis Ingvarsson, Cristian Gudasz, Matthias B. Siewert. Continental to meter scale climatic, topographic and geomorphological gradients control soil organic carbon distribution in complex Arctic terrain." Author Affiliations Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden Climate Impacts Research Centre (CIRC), Department of Ecology, Environment and Geoscience, Umeå University, Umeå, Sweden Paper Abstract Arctic soils store large amounts of soil organic carbon (SOC), but landscape-scale variation remains poorly understood, especially in complex mountainous regions. Understanding climate change impacts on Arctic carbon dynamics requires in-depth knowledge on the controls of SOC due to multiple drivers and potential responses. We map and quantify SOC stocks at meter scale in a large-scale catchment in the Swedish Arctic, and evaluate environmental controls of SOC distribution along a climate continentality gradient and complex mountain topography. A total of 310 georeferenced soil profiles were compiled. SOC stocks were modeled using machine learning trained on 14 environmental predictors. We observed a large variation of predicted SOC values, ranging from 0 to 145.1 kg C m-² and a catchment mean of 4.8 ± 7.0 kg C m-². Organic layers including deep peat deposits contributed approximately 48% of total SOC. Two dominant gradients structured SOC distribution: (1) a climate-enabled peatland gradient, where flat, winter cold, and dry eastern areas support extensive peat accumulation and high SOC stocks, and (2) a topographic and geomorphological gradient, where valley bottoms and depositional slopes stored more SOC than uplands. Geomorphological features furthermore led to substantial variation at meter scale. We show that SOC variability in Arctic-mountainous regions is strongly controlled by the interplay between climate, topography, and fine-scale geomorphology. Revealing these interactions at high spatial resolution highlights the need for landscape studies across environmental gradients to determine the sensitivity of Arctic SOC stocks to climate change.