Look North for a deeper picture of decomposition The soil in northern ecosystems may freeze in Winter, yet recent research shows that decompositional processes can still continue during the colder months. Researchers in the FluxWIN project are taking gas flux measurements throughout the year, aiming to gain deeper insights into the processes behind Winter emissions of greenhouse gases, as Dr Claire Treat explains. A lot of
studies on the carbon cycle and greenhouse gas emissions have been conducted during the growing season in Summer when plants are active, yet less attention has been paid to the Winter months. Extrapolations to the cold season have been based on our understanding of these growing season processes, yet earth system models of carbon emissions tend to break down over the Winter months, for reasons that are not fully understood. “We don’t really understand why the models don’t work, whether it’s something to do with the physical soil properties for example, or representations of the soil dynamics,” says Dr Claire Treat, a researcher at the Alfred Wegener Institute in Germany. As the head of the ERC-funded FluxWIN project, Dr Treat is looking at greenhouse gas emissions both in the growing season and also outside it, reflecting a recent shift in perspective. “Over the past 15 years or so it’s been found that soil microbes can be active at colder temperatures than modellers - who parameterise soil decomposition processes had previously realised,” explains Dr Treat.
Greenhouse gas budgets The nature of soil thermodynamics means that the surface of the soil can freeze before the layer underneath, so decompositional processes can in fact continue into the Winter. This may then affect the greenhouse gas budget, a topic that Dr Treat and her colleagues in the project are investigating. “One of the questions we’re looking at is whether the freezing of
unaffected by human activity. “They haven’t been used for agriculture, and they haven’t been logged recently,” continues Dr Treat. “We plan to conduct several campaigns over the Winter and Spring, and take measurements over some longer periods over the course of a year. We’re very interested in the transition between Spring and Summer when plants are starting to come out.”
This high-frequency greenhouse gas analyser lets us measure pretty small fluxes of both methane and nitrous oxide. Our focus really is on carbon dioxide and methane, and also on this nitrous oxide component. the soil surface is enough to impede oxygen diffusion into the soil and make it anaerobic, and then turn a site that wouldn’t normally produce methane into a site where oxygen is sufficiently depleted that it does,” she outlines. Researchers are taking measurements at several ecosystems on the Siikenava II site in Finland, a location which has been relatively
This research involves using automated chambers to take the measurements throughout a whole year, without the need for a researcher to be physically present. Measurements are collected throughout the day at 6 hour intervals, providing researchers with a wealth of data. “These chambers are essentially like a gas sampling mechanism. They are highly portable,
The FluxWIN project investigates how greenhouse gas emissions and soil processes change throughout the year. In summer, warm soil temperatures and plant activity stimulate the production of methane (CH4) and net uptake of carbon dioxide (CO2). In the fall and spring, larger than expected emissions of CO2 and CH4 have been observed despite cooler soil temperatures and lack of plant activity. These periods are a focus of the project.
34
EU Research
