Main content area

Microbial utilization of simple carbon substrates in boreal peat soils at low temperatures

Segura, Javier H., Nilsson, Mats B., Schleucher, Jürgen, Haei, Mahsa, Sparrman, Tobias, Székely, Anna, Bertilsson, Stefan, Öquist, Mats G.
Soil biology & biochemistry 2019 v.135 pp. 438-448
bacterial communities, biochemical pathways, carbon, carbon dioxide, climate change, ecosystems, greenhouse gas emissions, growing season, isotope labeling, latitude, metabolism, metabolites, microorganisms, peat, peat soils, peatlands, phospholipid fatty acids, soil carbon, soil temperature, stable isotopes, winter
Boreal peatlands are key high-latitude ecosystem types and act as a carbon (C) sink storing an estimated 25% of the world's soil C. These environments are currently seeing the most substantial changing climate, especially during the winter. CO2 emissions during the winter can correspond to 80% of the growing season's net CO2 assimilation. Yet, our conceptual understanding of the controls on microbial metabolic activity in peat soils at temperatures ≤0 °C is poor. We used stable isotope probing of peat samples and tracked the fate of 13C-glucose using 13C-NMR. We show that microorganisms in frozen boreal peat soils utilize monomeric C-substrates to sustain both catabolic and anabolic metabolism at temperatures down to −5 °C. The 13C-substrate was transformed into 13C–CO2, different metabolites, and incorporated into membrane phospholipid fatty acids. The 16S rRNA-based community analyses revealed the activity at −3 °C changes the composition of the bacterial community over relevant timescales. Below 0 °C, small temperature changes have strong effects on process rates and small differences in winter soil temperature may affect C dynamics of northern peatlands. Understanding biological processes at low and below zero temperatures are central for the overall functioning of these systems representing one of the world's major soil C pools.