13CPLFA Analysis of the Microbial Community Composition within Peat Depth Profiles in Response to Seasonal Changes and Warming.

Peatlands represent a critical and unique natural resource, especially in their role as carbon sinks. As much of the world’s peatlands are located in Northern ecosystems where the climate is changing at a rapid pace, there is great interest and concern with how the changing climate will influence them. Although studies regarding the response of peatlands to climate change have emerged, the microbial dynamics of these systems are still less well understood. This is in spite of the fact that the microbial community is a crucial aspect of the peatland ecosystem; both in terms of mediating biogeochemical cycling, as well as in its ability to provide information about the resource availability of the peatland.

In this study, ¹³CPLFA analysis was used to characterize the microbial community along peat depth profiles taken from the SPRUCE Project, as well as to provide isotopic information about the carbon being used by the microbes. The SPRUCE Project is an extensive study of the response of peatlands to climatic manipulation in the Marcell Experimental Forest in northern Minnesota. Heating rods were installed in peatland plots where peat is being warmed to temperatures ranging from ambient to +9 degrees Celsius, to a depth of 1 meter. The effects of natural environmental fluctuation over time to the microbial community will be evaluated based on peat samples taken from ambient plots from June 2014, September of 2014, and June of 2015, throughout the depth profile. The effects of warming on the microbial community composition and their use of ¹³C will be evaluated based on peat samples from September 2014 and June 2015.

This study will result in useful information about the influence of environmental fluctuation over time and different depths on the microbial community composition within the peatland. This study will also provide insight into the influence of warming on the microbial community composition and on how the microbes are using the carbon present at these different levels of warming.

Preliminary isotopic data at both sampling dates appears to show that microbial biomass has a higher d¹³C lower in the peat profile, indicating as expected that microbes at depth utilize older carbon or carbon more enriched in ¹³C. The increase over depth in the δ¹³C coefficient may also reflect the increasing dominance of pre-industrial carbon which is more enriched in ¹³C.