Abstract
Rising temperatures in the Arctic and the expansion of plants to higher latitudes will significantly alter belowground microbial communities and their activity. Given that microbial communities are major producers of greenhouse gases, understanding the magnitude of microbial responses to warming and increased carbon input to Arctic soils is necessary to improve global climate change models. In this study, active layer and permafrost soils from northern Greenland (81° N) were subjected to increased carbon input, in the form of plant litter, and temperature increase, using a combined field and laboratory approach. In the field experiment, unamended or litter-amended soils were transplanted from the permafrost layer to the top soil layer and incubated for one year, whereas in the laboratory experiment active layer and permafrost soils with or without litter amendment were incubated at 4 °C or 15 °C for six weeks. Soil microbial communities were evaluated using bacterial 16S and fungal ITS amplicon sequencing and respiration was used as a measure of microbial activity. Litter amendment resulted in similar changes in microbial abundances, diversities and structure of microbial communities, in the field and lab experiments. These changes in microbial communities were likely due to a strong increase in fast-growing bacterial copiotrophic taxa and basidiomycete yeasts. Furthermore, respiration was significantly higher with litter input for both active layer and permafrost soil and with both approaches. Temperature alone had only a small effect on microbial communities, with the exception of the field-incubated permafrost soils, where we observed a shift towards oligotrophic taxa, specifically for bacteria. These results demonstrate that alterations in High Arctic mineral soils may result in predictable shifts in the soil microbiome.
Highlights
The Arctic is changing rapidly with climate warming at a rate of more than twice the global average (IPCC, 2019), resulting in the retreat of glaciers and ice sheets, as well as the accelerated thawing of perma frost (Camill, 2005; Jorgenson et al, 2010)
Respiration rates of active layer and permafrost soils incubated at 4 ◦C were initially close to zero, rose quickly within the first 8 days
Respiration rates of active layer and permafrost soils incubated in the field for one year with or without litter input showed a significant increase in respired CO2 in litteramended soils (Fig. S2)
Summary
The Arctic is changing rapidly with climate warming at a rate of more than twice the global average (IPCC, 2019), resulting in the retreat of glaciers and ice sheets, as well as the accelerated thawing of perma frost (Camill, 2005; Jorgenson et al, 2010). Permafrost is covered by an active layer, soil that undergoes seasonal freeze-thaw cycles. The depth of this active layer has increased in many locations over the last few decades, at the expense of the underlying permafrost (Gruber and Haeberli, 2009). More liquid water becomes available and microbial activity increases. This can result in increased decomposition of previously frozen soil organic matter and in turn can increase the production of greenhouse gases such as CO2, CH4 and N2O (Knoblauch et al, 2013; Schuur et al, 2015)
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