Soil biogeochemical data from acidic tundra soils throughout a twenty freeze-thaw cycle incubation (2023)

The motivation of this study was to characterize how Arctic tundra soil biogeochemical properties responded to freeze-thaw cycles. Soil were cored in 2022 from an acidic tundra hillslope near Toolik Lake and incubated in 2023 in a BMT Friocell freeze-thaw incubator at the University of Tennessee Knoxville. Soils were subsampled by depth into organic surface, upper mineral, and lower mineral, with lower mineral being very ice rich and possibly including some upper permafrost soil. The tundra hillslope had three sites delineated across soil moisture conditions (upland, midslope, and lowland), with three replicate 5 x 5 meter (m) plots at each site. Soil cores to 80 centimeter (cm) were collected via SIPRE corer at every site but only the wet soils underwent the freeze-thaw incubation. Soil cores were collected to approximately 20 cm depth in each site periodically throughout the 2021 thaw season. Iron fractionations were conducted by scientists in the Plant-Soil Interactions Group at Oak Ridge National Laboratory. Total carbon and nitrogen bulk soil analysis, X-ray diffraction spectroscopy, Mössbauer spectroscopy, and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry were conducted by scientists at the Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory through EMSL user proposal #60557. Soil moisture (gravimetric moisture) was determined along with other soil properties (determined by University of Georgia Agricultural; Environmental Services Laboratories), including soil pH, Carbon (C) and Nitrogen (N) content, and Mehlich-I nutrients.