Peatlands and the carbon cycle: from local processes to global implications – a synthesis
- 1Nature Conservation and Plant Ecology Group, Wageningen University, Wageningen, The Netherlands
- 2Limnological Research Station and Department of Hydrology, University of Bayreuth, 95440 Bayreuth, Germany
- 3Global Carbon Project, CSIRO Marine and Atmospheric Research, GPO Box 3023, Canberra, ACT 2601, Australia
- 4School of Biological Sciences, Bangor University, Wales, LL57 2UW, UK
- 5School of Geography, University of Leeds, Leeds, LS2 9JT, UK
- 6Department of Geography, McGill University, 805, Sherbrooke Street West, Montréal, Québec, H3A 2K6, Canada
- 7Department of Plant Ecology, Evolutionary Biology Centre, Uppsala University, Villavägen 14, 752 36 Uppsala, Sweden
Abstract. Peatlands cover only 3% of the Earth's land surface but boreal and subarctic peatlands store about 15–30% of the world's soil carbon (C) as peat. Despite their potential for large positive feedbacks to the climate system through sequestration and emission of greenhouse gases, peatlands are not explicitly included in global climate models and therefore in predictions of future climate change. In April 2007 a symposium was held in Wageningen, the Netherlands, to advance our understanding of peatland C cycling. This paper synthesizes the main findings of the symposium, focusing on (i) small-scale processes, (ii) C fluxes at the landscape scale, and (iii) peatlands in the context of climate change.
The main drivers controlling C fluxes are largely scale dependent and most are related to some aspects of hydrology. Despite high spatial and annual variability in Net Ecosystem Exchange (NEE), the differences in cumulative annual NEE are more a function of broad scale geographic location and physical setting than internal factors, suggesting the existence of strong feedbacks. In contrast, trace gas emissions seem mainly controlled by local factors.
Key uncertainties remain concerning the existence of perturbation thresholds, the relative strengths of the CO2 and CH4 feedback, the links among peatland surface climate, hydrology, ecosystem structure and function, and trace gas biogeochemistry as well as the similarity of process rates across peatland types and climatic zones. Progress on these research areas can only be realized by stronger co-operation between disciplines that address different spatial and temporal scales.