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Forest production on drained peat release greenhouse gases

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Forests have long been seen as a sink for greenhouse gases. Research conducted by scientists from University of Gothenburg has shown that over a forest rotation of 80 years, forest production on drained peat soil is a large source of greenhouse gases to the atmosphere.

Spruce forest on drained peat soil and drainage ditch.

Skogaryd research site spruce forest on drained peat soil and drainage ditch.

“Growing forests are commonly seen as taking up atmospheric carbon dioxide (CO2) thus an important climate change mitigation measure. However, if draining fertile wetland for forestry use, the old peat will decompose emitting greenhouse gases back to the atmosphere. In Sweden, forests on drained wetlands cover about 1.7 Mha and according to the Swedish national inventory report, these lands emit 11 Mtonnes CO2equivalent annually, almost equal to the traffic sector emitting 18 Mtonnes CO2equ. Therefore understanding the greenhouse gas balance for such lands is urgently needed for mitigation actions.” says Dr. Hongxing He at the Department of Earth Sciences, University of Gothenburg.

DitchSo far the emission estimates are based on rough emission factors not designed for mitigation but simple enough for national greenhouse gas (GHG) reporting. A research group led by Dr. Åsa Kasimir with close collaboration with Gothenburg University Laboratory for Dendrochronology studied the greenhouse gas balance for a spruce forest on drained wetland, from planting in 1951 until a final harvest in 2031. The entire GHG balance over the 80 year forest rotation was simulated by using a detailed process model (CoupModel) by Dr. Hongxing He and his colleagues. The study used data collected from the Skogaryd research site in-between Uddevalla and Vänersborg.

TPortrait of Hongxing Hehe study was recently published in the journal ‘Biogeosciences’ and the results show that at a forest age of 80 years, the spruce carbon storage have not been able to catch up with the GHG release from disappearing soil and forest thinning of short-lived products.
“Similar high fertile drained peat soil as in Skogaryd covers 0.4 Mha in Sweden. Up-scaling our results these areas would emit 7 Mtonnes CO2equ annually, which is equivalent to 12 % of the emissions coming from all other sectors in Sweden. From a climate change perspective, forests on drained wetland should be highlighted for actions, making the soil wet again. However, measures need support from policy makers since landowners often only recognize Portrait of Åsa Kasimirrevenues from forest production, not the cost of greenhouse gas emissions causing climate change.” Hongxing said, “Therefore a more wise use of the now drained wetland is urgently needed.”

More about the study here:
He, H., Jansson, P.-E., Svensson, M., Björklund, J., Tarvainen, L., Klemedtsson, L., and Kasimir, Å.: Forests on drained agricultural peatland are potentially large sources of greenhouse gases – insights from a full rotation period simulation, Biogeosciences, 13, 2305-2318, doi:10.5194/bg-13-2305-2016, 2016.

For more information, contact:
Hongxing He, PhD in the Department of Earth Sciences, University of Gothenburg
Tel: +46 (0)31 786 2811, hongxing.he@gvc.gu.se.
Åsa Kasimir, Department of Earth Sciences, University of Gothenburg
Tel: +46 (0)31 786 1960, asa.kasimir@gu.se

Photos:
Skogaryd research site spruce forest on drained peat soil and drainage ditch.
Photos by Åsa Kasimir