Peatland CO2 Exchange More Strongly Influenced by Drying than Warming, Finds Study

Around one-third of soil carbon of the world, which is nearly 500 gigatons, is stored by Northern Peatlands. Since the peatland carbon cycling is mostly regulated by partially anaerobic soil conditions, the carbon stored in these soils is highly susceptible to climate warming that is likely to decrease soil moisture and thus increase soil aeration.

Gaining insights into the interactions between soil moisture and warming is mainly essential in peatland types found in boreal and arctic regions that are likely to experience high rates of climate warming. This area is the central region for northern peatlands, and thus, increased mineralization could have high potential to further speed up climate change.

New research headed by scientists from the University of Eastern Finland and Natural Resources Institute Finland proposes that drying has a more powerful impact on peatland CO₂ exchange than warming as such, and also that soil moisture may be vital to determining if fen ecosystems can adapt to a varying climate. The research was recently reported in Global Change Biology, a top journal in environmental science.

The study is on the basis of a four-year field experiment in two Finnish fenlands exposed to warming and water level drawdown. The authors analyzed respiration, photosynthesis, and net CO₂ exchange during the third and fourth experimental growing seasons. Although warming had a slight impact on any gas flux component, dryer conditions were linked to increased photosynthesis and respiration, and warming increased the effects of drying so that CO₂ uptake in one region reduced. On the basis of these outcomes, in northern fens, the water table plays a crucial role in regulating the extent to which the increased temperature influences the CO₂ exchange.

The Academy of Finland (projects 138041, 287039, 140863) funded the study.