Plant belowground trait and vegetation survey data from the Stordalen mire 2023

Description This data package contains three datasets related to plant root and rhizome traits and vegetation composition across a permafrost thaw gradient (from intact permafrost to partly and fully thawed permafrost) at the Stordalen mire, northern Sweden (68°20’N, 19°03’E) in 2023. The data were used in the manuscript "Määttä, T., et al.: Plant belowground traits reflect increased plant-mediated methane transport along a peatland permafrost thaw gradient" (in prep. as of 2026-01-12), in association with automated chamber methane (CH4) flux and porewater gas concentration data (CH4 flux and pore water gas concentration and isotope data will be published at the EMERGE database in due course at https://emerge-db.asc.ohio-state.edu/). The datasets contain vegetation data at the plot (belowground traits and vegetation survey datasets) and depth scales (only belowground traits), separated into plant functional types (PFTs) and species (latter only for vegetation survey datasets). Belowground trait data include root and rhizome biomass, surface area, average diameter, and tissue density, as well as total root length and specific root length along with edaphic variables. Vegetation survey files include data of vegetation (per species and PFT, alive and dead), litter, and water cover (%), as well as vascular plant green area (per species and PFT) and edaphic variables. The belowground traits were obtained from peat cores separate from automated chamber plots. The vegetation survey datasets include data from both belowground trait and automated chamber plots. Datasets belowground_traits.csv: Root and rhizome traits (roots and rhizomes: biomass, surface area, diameter, and tissue density; roots only: total length and specific length) at plot and depth (in 10 cm increments down to 30 cm depth) scales and separated into PFTs (herbaceous and shrub). The dataset also includes edaphic variables measured at each plot (soil/porewater pH, gravimetric water content, and active layer depth). plot_veg_survey.csv: Plot (belowground trait and automated CH4 flux chamber measurement plots) vegetation composition (per PFT, where PFTs include herbaceous, shrub, aerenchymatous and nonaerenchymatous, as well as vascular plants and mosses), land cover (litter, dead vegetation, and water) and vascular plant green area (per PFT, where PFTs include herbaceous, shrub, aerenchymatous and nonaerenchymatous). The dataset also includes edaphic variables measured at each plot (mean and standard deviation of soil temperature, soil/porewater pH, gravimetric water content, and active layer depth). species_veg_survey.csv: Plot (belowground trait and automated CH4 flux chamber measurement plots) vegetation composition and vascular plant green area per species. The dataset also includes edaphic variables measured at each plot (soil/porewater pH, gravimetric water content, and active layer depth). Please see the README.txt file for details. Contact For questions, please contact Tiia Määttä ([e-mail]). Acknowledgements We thank Melina Bucher, Charmaine Bassfeld, Yves Brügger, and Thomas Keller for help in the field and laboratory. We also thank Dr. Martina Peter, Felix Zimmermann, and Mara Wieser for facilitating laboratory work at the Swiss Federal Institute for Forest, Snow and Landscape Research WSL. We thank the EMERGE team, Prof. Dr. Ruth Varner and Prof. em. Patrick Crill for help in facilitating the field work in Stordalen. We acknowledge funding from the Swiss Polar Institute Polar Access Grant (PAF‐2023‐001) awarded to TM, Universität Zürich Stiftung für Wissenschaftliche Forschung (STWF-22-028) and the Swiss National Science Foundation (project 200021_215214) awarded to AM.We thank Alisa Heuchel, the Swedish Polar Research Secretariat and SITES for the support of the work done at the Abisko Scientific Research Station. SITES is supported by the Swedish Research Council.