Will the temperature sensitivity of Arctic soil bacterial communities alter under warmed soil conditions?

Soil temperatures are rising in the Arctic and will likely increase soil microbial activity. The magnitude of subsequent carbon effluxes is difficult to predict but is critical for evaluating the strength of the soil carbon-climate feedback as climate change intensifies. Soil respiration in the Arctic has a relatively high sensitivity to temperature increases. This is hypothesized to be a consequence of physiological adaptation of soil microbial communities to low temperatures. A variety of experimental and gradient studies have suggested that the growth-temperature relationship of bacterial communities will adapt to soil warming.  It remains an open question whether this is driven by changes in community structure. In order to test this hypothesis, we collected 8 soils from the sub- to High Arctic and exposed them to a 0-30 ⁰C temperature gradient. We determined the temperature relationships and community composition of the resulting bacterial communities. To account for substrate depletion we sampled both after 100 days, as well as after a standardized amount of respiration. Temperature relationships were computed by fitting a square root model to leucine incorporation rates measured from 0-40 ⁰C. We will show the relationship between legacy effects of the soil thermal regime and the degree of temperature adaption and discuss whether the soil bacterial community structure is likely to influence soil respiration in Arctic soils under future climate conditions.