Effect of Warming on Arctic Tundra Microbes

One the biggest challenges today is the environmental disruption caused by climate change. Climate change is particularly important in arctic environments which are warming faster than the global average. This can result in a thicker and warmer active layer of the tundra soil and increased microbial activity, resulting in the release of vast quantities of stored carbon and nitrogen in form of greenhouse gases into the atmosphere, depending on mainly water content. Despite its importance, we currently have a limited understanding of how warming can affect arctic microbes and only a few studies that have examined fungi and bacteria at the same time or compared the total and active communities.

We show the effect, after one year, of simulated warming using open-top chambers and snow fences on a soil microbial community in Greenland, using a multifactorial study design that considers bacteria and fungi, the total (DNA-based) and active (RNA-based) community and changes over the course of a growing season. We observed a significant increase in soil temperature at the treated sites as well as changes in the environmental variables of carbon:nitrogen, total organic carbon, microbial carbon, microbial nitrogen, microbial carbon:nitrogen and loss on ignition.

The microbial communities of both bacteria and fungi were highly variable across replicates with sampling site accounting for the majority of variation explained in community composition for both bacteria (16.9%) and fungi (27.5%). While warming had an effect on the communities, it accounted for only a small proportion of variation (2.6% for bacteria, 4.9% for fungi) and few specific taxa were identified as differentially abundant. The bacterial community showed a clear split between the total and active community that accounted for 10.5% of the total variation, however there was no difference in the fungal community. We also observed changes in the community throughout the season but these differences were small and accounted for a similar amount of variation as the treatment (4.2% for bacteria, 3.6% for fungi). The majority of fungi (65%) could not be assigned to a guild, however, we found that the abundance of saprotrophs increased in response to warming.

Our results show only minor changes to the composition of an arctic soil microbial community in response to climate manipulation. This suggests that climate change will primarily influence the activity of microbes rather than the community composition.