Seasonal in situ estimation of soil methane uptake
in a dry Arctic tundra

by Ludovica D´Imperio

In Northern latitudes climatic changes are predicted to be most pronounced resulting in variations in growing season length, soil active layer depth and nutrient cycling. As a consequence of raises in temperature, large stocks of Carbon stored in the permafrost would become available for soil microbial transformations and this will potentially lead to changes in greenhouse gas (GHG) emissions with positive climatic feedback.

Methane (CH4), the third most important GHG in the atmosphere, can be removed by photochemical reactions in the troposphere or by microbial oxidations under aerobic conditions. In dry soils, like the Arctic tundra, the direct uptake of atmospheric CH4 by bacterial populations represents an important sink of this GHG which risks to be altered as a consequence of climatic changes.

The field work for this project was carried out in a dry Arctic tundra in Disko Island, Western Greenland, during summer 2013. The chosen experimental set-up makes use of snow fences installed in 2012 which allow investigating the emissions of GHGs from soil under increased winter snow deposition and ambient field conditions. Three treatments and one control have been included: increased summer temperatures (Plexiglas open-top chambers), scrub removal and a combination of both. CH4 and CO2 fluxes have been measured in situ using dark and transparent chambers connected to a Methane Flux Measurer and a LI-COR instrument.

Aim of the study

We will test the soil responses to seasonal and inter-annual variations in snow cover (duration/depth) and temperature in order to verify two main scenarios:

  1. Enhanced winter precipitation will delay the snow melt leading to wet and cold soil during summer time, potentially reducing the soil capacity to uptake CH4 while
  2. enhanced summer temperature, hence drier soil, will promote soil CH4 oxidation.

Further on, we will link the measured fluxes to seasonal variations in the abundance and activity of the functional microbial guilds (e.g. methanotrophs and methanogens) responsible of CH4 production/consumption.

If you want to know more, please contact Ludovia D´Imperio.