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Introduction

Global warming can trigger enormous releases of carbon (C) from soils, with positive feedbacks to climate change. Northern high latitude soils can constitute a major contributor to this positive feedback loop. Climate change predictions are however still largely uncertain, partly due the lack of accurate representation of vegetation and soil microbial feedbacks and C and nitrogen (N) interactions.

Warming enhances microbial mineralization of soil organic matter –i.e. soil C outputs– to a higher degree than vegetation productivity –i.e. soil C inputs–, resulting in large C losses from northern soils. Pioneer results point to proportional N losses in response to warming, which may be the key to this phenomenon.

This project will combine the expertise of a multidisciplinary group of researchers on ecosystem stoichiometry, stable N isotopic methods and applied biotechnology with the existence of unique and established research sites in geothermal systems in Iceland to reveal the fate of N lost in response to warming, and uncover the mechanisms behind observed soil C losses. StoiCa will elucidate, for first time, three key knowledge gaps: (1) the rates, forms and mechanisms of N losses from arctic soils under warming; (2) the transient- and persistent responses and the warming-induced transitions from a closed to a leaky, open N cycle; and (3) the shifts towards a more symbiotic N cycle and role of thermo-adapted mycorrhiza in stimulating plant growth.