Through scales: carbon cycling and microbial fitness under exacerbating freeze-thaw cycles in arctic biological soil crusts

Arctic ecosystems have been experiencing faster and more intense warming compared to anywhere else in the world, strongly affecting their structure and function. For instance, it has been shown that increasing temperatures may accelerate microbial decomposition in soil and biological soil crusts (BSCs) and enhance depletion of carbon stocks. The microbial communities are further disturbed by changes in frequency and intensity of freeze-thaw cycles (FTCs), but it is largely unknown how this will affect the related carbon fluxes to the atmosphere. The aim of this study is to determine the effects of exacerbated intensity and frequency of FTCs on the carbon cycling in arctic BSCs with particular focus on microbial fitness, recovery and related physiological traits at the organism scale. We combine microscale measurements using soil chips, optical microscopy observations and Raman microspectroscopy with bulk analyses of microbial respiration to identify parameters connecting single-cell level processes with macroscale responses, such as pulses of CO2 after thawing. These parameters related to microbial functional traits can be implemented in the future modifications of the CoupModel and improve its prediction capacity for ecosystem scale effects of climate change, which is essential for finding strategies for climate mitigation and adaptation.