Community adaptation to temperature explains abrupt soil bacterial community shift along a geothermal gradient on Iceland. (February 2023)

• Record Type: Journal Article
• Authors: Weedon, James T.; Bååth, Erland; Rijkers, Ruud; Reischke, Stephanie; Sigurdsson, Bjarni D.; Oddsdottir, Edda; van Hal, Jurgen; Aerts, Rien; Janssens, Ivan A.; van Bodegom, Peter M.
• Is Part Of: Soil biology and biochemistry. Volume 177(2023)
• Publication Date: 2023-02
• Subjects: Geothermic gradient -- Soil bacterial community -- Bacterial growth -- Temperature adaptation -- Threshold; Soil biochemistry -- Periodicals; Soil biology -- Periodicals; Sols -- Biochimie -- Périodiques; Sols -- Biologie -- Périodiques; Sols -- Microbiologie -- Périodiques; Bodembiologie; Biochemie; 631.46
• DOI: 10.1016/j.soilbio.2022.108914
• Languages: English
• ISSNs: 0038-0717

Abstract

Abstract: Understanding how and why soil microbial communities respond to temperature changes is important for understanding the drivers of microbial distribution and abundance. Studying soil microbe responses to warming is often made difficult by concurrent warming effects on soil and vegetation and by a limited number of warming levels preventing the detection of non-linear effects. A unique area in Iceland, where soil temperatures have recently increased due to geothermic activity, created a stable warming gradient in both grassland (dominated by Agrostis capillaris ) and forest ( Picea sitchensis ) vegetation. By sampling soils which had been subjected to four years of temperature elevation (ambient (MAT 5.2 °C) to +40 °C), we investigated the shape of the response of soil bacterial communities to warming, and their associated community temperature adaptation. We used 16S rRNA amplicon sequencing to profile bacterial communities, and bacterial growth-based assays ( 3 H-Leu incorporation) to characterize community adaptation using a temperature sensitivity index (SI, log (growth at 40 °C/4 °C)). Despite highly dissimilar bacterial community composition between the grassland and forest, they adapted similarly to warming. SI was 0.6 (equivalent to a minimum temperature for growth of between −6 and −7 °C) in both control plots. Both diversity and community composition, as well as SI, showed similar threshold dynamics along the soil temperature gradient. There were no significant changes up to soil warming of 6–9 °C above ambient, beyond which all indices shifted in parallel, with SI increasing from 0.6 to 1.5. The consistency of these responses provide evidence for an important role for temperature as a direct driver of bacterial community shifts along soil temperature gradients. Highlights: A geothermic gradient allowed evaluation of direct temperature effects on bacteria. The 4-years old gradient spanned temperatures from ambient to +40 °C. Under both forest and grassland, effects were observed in soils warmed >6–9 °C. Soil bacterial community composition and temperature adaptation changed similarly. This correlation suggests an important role for direct temperature effects.