Data from: A tipping-point in carbon storage when forest expands into tundra is related to mycorrhizal recycling of nitrogen

• Main Author: Clemmensen, Karina
• Format: Dataset
• Language: unknown
• Published: 2022
• Subjects: Fungal community; Ectomycorrhizal fungal community; ectomycorrhizal exploration type; soil carbon storage; Climate feedback; ITS2 meta-barcoding; litter bags; litter saprotrophs; C-N dynamics; soil profiles; mycorrhizal type; Ericoid Mycorrhiza; treeline ecotone; Arctic greening; functional genes; quantitative PCR; soil solution; ergosterol; Arctic; Arctic Greening; Northern Sweden; Subarctic; Tundra
• Online Access: https://zenodo.org/record/4958161; https://doi.org/10.5061/dryad.79cnp5htw

Tundra ecosystems are global belowground sinks for atmospheric CO2. Ongoing warming-induced encroachment by shrubs and trees risks turning this sink into a CO2 source, resulting in a positive feedback on climate warming. To advance mechanistic understanding of how shifts in mycorrhizal types affect long-term carbon (C) and nitrogen (N) stocks, we studied small-scale soil depth profiles of fungal communities and C-N dynamics across a subarctic-alpine forest-heath vegetation gradient. Belowground organic stocks decreased abruptly at the transition from heath to forest, linked to the presence of certain ectomycorrhizal fungi that seemingly contribute to decomposition when mining N from organic matter. In contrast, ericoid mycorrhizal plants and fungi were associated with organic matter accumulation and slow decomposition. If climatic controls on arctic-alpine forest lines are relaxed, increased decomposition will likely outbalance increased plant productivity, decreasing the overall C sink capacity of displaced tundra. Soil samples were taken in 24 plots representing four vegetation types along a subarctic-alpine birch forest-heath tundra ecotone in Northern Sweden. Soil cores were split into fine-scaled layers, which were analysed for various biochemical characteristics and for fungal communities based on ITS2 meta-barcoding. Please find all details on sampling and analyses in the associated paper.