High latitudes are experiencing intense ecosystem changes with climate warming. The underlying methane (CH4) cycling dynamics remain unresolved, despite its crucial climatic feedback. Atmospheric CH4 emissions are heterogeneous, resulting from local geochemical drivers, global climatic factors, and microbial production/consumption balance. Holistic studies are mandatory to capture CH4 cycling complexity. Here, we report a large set of integrated microbial and biogeochemical data from 396 samples, using a concerted sampling strategy and experimental protocols. The study followed international standards to ensure inter-comparisons of data amongst three high-latitude regions: Alaska, Siberia and Patagonia. The dataset encompasses different representative environmental features (e.g. lake, wetland, tundra, forest soil) of these high-latitude sites and their respective heterogeneity (e.g. characteristic microtopographic patterns). The data included physicochemical parameters, greenhouse gas concentrations and emissions, organic matter characterization, trace elements and nutrients, isotopes, microbial quantification and composition. This dataset addresses the need for a robust physicochemical framework to conduct and contextualize future research on the interactions between climate change, biogeochemical cycles and microbial communities at high-latitudes.

This study focused on three regions located in subantarctic, arctic and subarctic latitudes.  The field campaigns were conducted in 2016, during the respective summer for each region: January-February in Chilean Patagonia, June-July in Alaska and July-August in Siberia. For every site included in the present study, a set of nine qualitative environmental and/or ecological site-scale descriptors was selected and adapted from ENVO Environment Ontology, which included for example permafrost state, biome, environmental feature and vegetation type.  The environmental features that are representative for the three regions were considered: lakes, wetlands, broadleaf/coniferous/mixed forest soils, grassland, tundra and palsa. All the metadata is included in the submitted dataset. A specific sampling strategy was defined for each kind of ecosystem, i.e. lakes, soils and wetlands. 

Details for field sampling, in situ (physiochemical analyses, dissolved CH⁴ and CO² concentrations, atmospheric CH4 and CO2 emission rates, sample processing in the field) and laboratory analyses (moisture and organic matter content, suspended solids, filtration, pore water extraction, total and dissolved organic carbon, anions and cations, trace elements, optical properties, isotopes, DNA extraction, qPCR assays, high-throughput amplicon sequencing) are described in the Scientific Data manuscript. 

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