Page 31 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

as the “Arctic amplification”, accelerates these local changes (ACIA 2005; Tenenbaum 2005; Graversen et al. 2008).
The effects of environmental changes on CH4 emissions were, for example, observed in warming permafrost, where differences in soil substrate availability resulted in taxonomic shifts in methanogen communities (Tveit et al. 2015). Similar effects have also been observed in marine environments in which vegetation changes induced shifts in both methanogen community and activity (Yuan et al. 2014).
Effects of environmental parameters, such as temperature and water activity on the community composition, and activity of methanotrophs, have been reported in several studies on soil ecosystems (King 1997; Horz et al. 2005; Knoblauch et al. 2008). These taxonomic shifts will, in turn, lead to community changes of metabolic partners, which could potentially cause a cascade effect through the whole microbial community. These changes can strongly alter CH4 dynamics (Høj, Olsen and Torsvik 2008; Bridgham et al. 2013; Blake et al. 2015). The interactions of CH4 cycling microorganisms and vegetation can also strongly influence CH4 fluxes. In terrestrial zones, elevated atmospheric CO2 levels can increase primary production and organic C transfer to the rhizosphere (the soil zone influenced by microbial and plant root dynamics), increasing resource availability for methanogenesis (Nazaries et al. 2013). Methanotrophy in these zones is thought to be less influenced by temperature and more by soil moisture, which controls oxygen availability (Nazaries et al. 2013).
In wetlands, the co-occurrence of mosses and CH4-oxidizing bacteria forms an important CH4 filter. In Siberian polygonal tundra, CH4 oxidation associated with submerged brown mosses reduces methane emissions by at least 5% (Liebner et al. 2011). On a global scale, Sphagnum mosses comprise an important CH4 filter in peat bogs (Kip et al. 2010; van Winden et al. 2012; Kox et al. 2019). Temperature-dependent incubation studies have shown that this process is more efficient at lower temperatures, with an up to 98% removal rate of CH4 at 5°C (van Winden et al. 2012).
1.3 Important carbon pools and their link with the methane cycle
Natural systems function as important carbon reservoirs in the global carbon cycle. Terrestrial and marine ecosystems, including soils, vegetation, and permafrost, store considerable amounts
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