Abstract. Northern soils play an important role in Earth's climate system as they store large amounts of carbon that, if released, could strongly increase greenhouse gas levels in our atmosphere. Most research to date has focused on how the turnover of organic matter in these soils is regulated by abiotic factors and few studies have considered the potential role of biotic regulation. Here, we claim that soil organisms' presence or absence is key to understanding and predicting future climate

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... edbacks from northern soils. We propose that the arrival of soil organisms with currently 'missing traits', i.e., properties that the present community does not have, can alleviate functional limitation and result in greatly enhanced decomposition rates, in parity with effects predicted due to increasing temperatures. We base this argument on a series of emerging evidence suggesting that the dispersal of until-then absent micro-, meso- and macro-organisms (i.e., microbes and invertebrate soil fauna) into new regions and newly-thawed soil layers can drastically affect soil functioning. These new observations make us question the current view that neglects organism driven 'alleviation effects' when predicting the future feedbacks between northern ecosystems and our planets' climate. We therefore advocate for an updated framework in which soil biota and their traits become essential when predicting the fate of soil functions in warming northern ecosystems.