Preferential substrate use decreases priming effects in contrasting treeline soils

Abstract Climate change currently manifests in upward and northward shifting treelines, which encompasses changes to the carbon (C) nitrogen (N) composition of organic inputs soils. Whether these changed will increase or decrease microbial mineralisation native soil matter remains unknown, making it difficult estimate how treeline shifts affect C balance. Aiming improve mechanistic understanding cycling regions experiencing shifts, we quantified priming effects soils high altitudes (Peruvian Andes) latitudes (subarctic Sweden), differentiating landcover types (boreal forest, tropical tundra heath, Puna grassland) horizons (organic, mineral). In a controlled laboratory incubation, were amended with substrates different C:N, composed an source at constant ratio 30% substrate-C biomass C, combined levels nutrient solution neutral pH. Substrate additions elicited both positive negative ecosystems, independent from substrate C:N. Positive prevailed above mineral latitudes, where consequently climate change-induced deeper rooting plants may enhance SOM-mineralisation emissions. However, such loss be compensated by priming, dominated other was larger magnitude than priming. line studies, results indicate consistent mechanism linking decreased (negative priming) increased utilisation, suggesting preferential use as potential tool support storage. Graphical abstract