Prolonged exposure does not increase soil microbial community response to warming along geothermal gradients

Abstract

Predicting effects of climate change on ecosystem functioning requires knowledge of soil microbial community responses to warming. We used natural geothermal gradients (from +1{degrees}C to +19{degrees}C above ambient) in two subarctic grasslands to test the hypothesis that long-term exposure (>50 years) intensifies microbial community responses to warming compared to short-term exposure (5-7 years). Community profiles from amplicon sequencing of bacterial and fungal rRNA genes did not support this hypothesis: significant changes relative to ambient were observed from +9{degrees}C and upwards in the long-term and from 7{degrees}C to 11{degrees}C / +3{degrees}C to +5{degrees}C and upwards in the short-term, for bacteria and fungi, respectively. Our results suggest that bacterial communities in high-latitude grasslands will not undergo lasting shifts in community composition under the warming predicted for the coming 100 years. Fungal communities do appear to be temperature sensitive to the warming within this range, but only for short-term exposures.