Abstract
Abstract. The CoupModel was used to simulate a Norway spruce forest on fertile drained peat over 60 years, from planting in 1951 until 2011, describing abiotic, biotic and greenhouse gas (GHG) emissions (CO2 and N2O). By calibrating the model against tree ring data a “vegetation fitted” model was obtained by which we were able to describe the fluxes and controlling factors over the 60 years. We discuss some conceptual issues relevant to improving the model in order to better understand peat soil simulations. However, the present model was able to describe the most important ecosystem dynamics such as the plant biomass development and GHG emissions. The GHG fluxes are composed of two important quantities, the spruce forest carbon (C) uptake, 413 g C m−2 yr−1 and the decomposition of peat soil, 399 g C m−2 yr−1. N2O emissions contribute to the GHG emissions by up to 0.7 g N m−2 yr−1, corresponding to 76 g C m−2 yr−1. The 60-year old spruce forest has an accumulated biomass of 16.0 kg C m−2 (corresponding to 60 kg CO2 m−2). However, over this period, 26.4 kg C m−2 (97 kg CO2eq m−2) has been added to the atmosphere, as both CO2 and N2O originating from the peat soil and, indirectly, from forest thinning products, which we assume have a short lifetime. We conclude that after harvest at an age of 80 years, most of the stored biomass carbon is liable to be released, the system having captured C only temporarily and with a cost of disappeared peat, adding CO2 to the atmosphere.
Highlights
Peatlands contain around one third of the carbon (C) stored in global soils, which is equivalent to almost half that present in the atmosphere (FAO, 2012; IPCC, 2013)
The spruce trees gradually increased their leaf cover until a closed canopy formed in the 1980s with a maximum leaf area index (LAI) of around 6, which was similar to field measurements (Fig. 2b)
We first discuss the validity of these two variables by comparing our simulated results with values published in the literature
Summary
Peatlands contain around one third of the carbon (C) stored in global soils, which is equivalent to almost half that present in the atmosphere (FAO, 2012; IPCC, 2013). Undisturbed peatlands accumulate C as partially decayed vegetation, and the decay processes emit C in the form of carbon dioxide (CO2) and methane (CH4). When peatlands are drained for intensified land use, i.e. agriculture or forestry, the stored peat starts to decompose aerobically. The accelerated soil decomposition emits large amounts of CO2, in contrast CH4 emissions are greatly reduced, possibly even accounting for a net uptake of atmospheric CH4 (Limpens et al, 2008). Peatlands cover only 3 % of the Earth surface, of which in turn 10–20 % have been drained for agriculture or forestry, mainly in the boreal and Published by Copernicus Publications on behalf of the European Geosciences Union
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