Soil geochemistry confines microbial abundances across an arctic landscape; implications for net carbon exchange with the atmosphere

Abstract

A large portion of the World's terrestrial organic carbon is stored in Arctic permafrost soils. However, due to permafrost warming and increased in situ microbial mineralisation of released carbon, greenhouse gas releases from Arctic soils are increasing, including methane (CH 4(g) ). To identify environmental controls on such releases, we characterised soil geochemistry and microbial community conditions in 13 near-surface Arctic soils collected across Kongsfjorden, Svalbard. Statistically significant correlations were found between proxies for carbonate mineral content (i.e. Ca and Mg) and soil pH (Spearman rho = 0.87, p \ 0.001). In turn, pH significantly inversely correlated with bacterial and Type I methanotroph gene abundances across the soils (r = -0.71, p = 0.01 and r = -0.74, p = 0.006, respectively), which also co-varied with soil phosphorous (P) level (r = 0.79, p = 0.01 and r = 0.63, p = 0.02, respectively). These results suggest that soil P supply, which is controlled by pH and other factors, significantly influences in situ microbial abundances in these Arctic soils. Overall, we conclude microbial responses to increasing 'old carbon' releases in this Arctic region are constrained by nutrient-deficiency in surface soils, with consequential impacts on the flux and composition of carbon gasses released to the atmosphere.

Distinct summer and winter bacterial communities in the active layer of Svalbard permafrost revealed by DNA- and RNA-based analyses

“…The dominance by Proteobacteria, Actinobacteria, Verrucomicrobia, Acidobacteria , and Gemmatimonadetes (Figure 2A ) is in accordance with other studies of Arctic soils (Chu et al, 2010 ; Yergeau et al, 2010 ; Mackelprang et al, 2011 ; Tveit et al, 2013 ), except that the relative abundance of Verrucomicrobia in our samples (20 ± 6%) was about twice as large as in other Arctic soils. Also, the correlation between pH and the bacterial community structure (Figure 5 ) is in agreement with other studies from similar environments, including Arctic soil (Lauber et al, 2009 ; Gray et al, 2014 ; Kim et al, 2014 ; Siciliano et al, 2014 ). However, in contrast to a number of other studies we found no correlation between relative abundance of Acidobacteria and pH, and in contrast to Chu et al ( 2010 ), we found that the relative abundance of Actinobacteria was negatively correlated with pH.…”

Origin and temporal variability of unusually low δ13C‐DOC values in two High Arctic catchments

“…Microbial sequencing is increasingly being used to gain insight into biogeochemical cycling [e.g., Skidmore et al , ; Boyd et al , ]. The widespread occurrence of methane cycling in northern latitude systems is supported by the detection of methanogens and methanotrophs both in unglaciated permafrost areas [e.g., Høj et al , ; Barbier et al , ; Gray et al , ] and in subglacial environments [ Boyd et al , ; Hamilton et al , ; Dieser et al , ]. In this study, neither archaeal 16S rRNA amplicons nor mcrA (alpha subunit of the methyl coenzyme M reductase), a gene required for methanogenesis [ Luton et al , ], were detected in any of the four sediment samples, suggesting the apparent absence of methanogens.…”

Unexpected stimulation of soil methane uptake as emergent property of agricultural soils following bio‐based residue application

“…It is thought that methanotrophs in agricultural soils are nitrogen limited due to strong competition for nutrients by plants, but upon relief of nitrogen limitation, the methanotrophs responded immediately to the available nitrogen, suggesting a yet unknown mechanism regulating nitrogen metabolism (Bodelier et al, 2000;Bodelier, 2011). Besides nitrogen, methanotroph abundance may be restricted by PO 3À 4 , as observed in an Arctic soil (Gray et al, 2014). However, the effects of PO 3À 4 on the methanotrophic activity and composition are less well known (Veraart et al, 2015).…”