Climate impacts of a boreal peatland studied in Finland

The peatland had a warming impact on climate during the first 7000 years since its formation, and the change from a fen to bog type peatland ultimately turned the climate impact from warming to cooling.

The historical development and climate impacts of a boreal peatland located in Southern Finland was studied. FMI has studied together with the University of Helsinki the historical growth and the subsequent climate forcing of a peatland which in its current state is a forestry-drained bog. Several peat cores were analyzed and radiocarbon dated and peatland succession and C dynamics was investigated throughout the Holocene. These data were used to reconstruct the long-term atmospheric radiative forcing, i.e., climate impact of the peatland since initiation. Kalevansuo peat records revealed a general development from fen to bog, typical for the southern boreal zone, but the timing of ombrotrophication varied in different parts of the peatland. Peat accumulation patterns and lateral expansion through paludification were influenced by fires and climate conditions. Long-term C accumulation rates were overall lower than the average values found from literature. We suggest the low accumulation rates are due to repeated burning of the peat surface. Drainage for forestry resulted in a nearly complete replacement of typical bog mosses by forest species within 40 years after drainage. The radiative forcing reconstruction suggested positive values (warming) for the first ~7000 years following initiation. The change from positive to negative forcing was triggered by an expansion of bog vegetation cover and later by drainage. The strong relationship between peatland area and peat type with radiative forcing suggests a possible feedback for future changing climate, as high-latitude peatlands may experience prominent regime shifts, such as fen to bog transitions.

Data on past peatland growth patterns, vegetation development, and carbon (C) dynamics during the various Holocene climate phases may help us to understand possible future climate-peatland feedback mechanisms.

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Researcher Annalea Lohila, tel. +358 50 366 3242, nna alea.lo lih a_ÄΤΤ_fmi f. i 

Mathijssen P. J. H., Kähkölä N., Tuovinen J.-P., Lohila A., Minkkinen K., Laurila T. and Väliranta M., 2017. Lateral expansion and carbon exchange of a boreal peatland in Finland resulting in 7000 years of positive radiative forcing. Journal of Geophysical Research – Biogeosciences, DOI: 10.1002/2016JG003749

Published: 24.4.2017
Categories: Research