Abstract
Abstract. Dynamic global vegetation models (DGVMs) are designed for the study of past, present and future vegetation patterns together with associated biogeochemical cycles and climate feedbacks. However, most DGVMs do not yet have detailed representations of permafrost and non-permafrost peatlands, which are an important store of carbon, particularly at high latitudes. We demonstrate a new implementation of peatland dynamics in a customized Arctic version of the LPJ-GUESS DGVM, simulating the long-term evolution of selected northern peatland ecosystems and assessing the effect of changing climate on peatland carbon balance. Our approach employs a dynamic multi-layer soil with representation of freeze–thaw processes and litter inputs from a dynamically varying mixture of the main peatland plant functional types: mosses, shrubs and graminoids. The model was calibrated and tested for a sub-Arctic mire in Stordalen, Sweden, and validated at a temperate bog site in Mer Bleue, Canada. A regional evaluation of simulated carbon fluxes, hydrology and vegetation dynamics encompassed additional locations spread across Scandinavia. Simulated peat accumulation was found to be generally consistent with published data and the model was able to capture reported long-term vegetation dynamics, water table position and carbon fluxes. A series of sensitivity experiments were carried out to investigate the vulnerability of high-latitude peatlands to climate change. We found that the Stordalen mire may be expected to sequester more carbon in the first half of the 21st century due to milder and wetter climate conditions, a longer growing season, and the CO2 fertilization effect, turning into a carbon source after mid-century because of higher decomposition rates in response to warming soils.
Highlights
Peatlands are a conspicuous feature of northern latitude landscapes (Yu et al, 2010), of key importance for regional and global carbon balance and potential responses to global climate change
We demonstrate a new implementation of peatland dynamics in the LPJ-GUESS Dynamic global vegetation models (DGVMs), aiming to emulate the long-term dynamics of northern peatland ecosystems and to assess the effect of changing climate on peatland carbon balance at the regional scale and across climatic gradients
In the standard (STD) experiment, a total of 94.6 kg C m−2 (91.4–98.9 kg C m−2) of peat was accumulated over 4700 years, leading to a cumulative peat depth profile of 2.1 m (1.9–2.2 m) predicted for the present day (Fig. 4), comparable to the observed peat depth of 2.06 m reported by Kokfelt et al (2010)
Summary
Peatlands are a conspicuous feature of northern latitude landscapes (Yu et al, 2010), of key importance for regional and global carbon balance and potential responses to global climate change. In the past 10 000 years (10 kyr) they have sequestered 550 ± 100 PgC across an area of approximately 3.5 million km (Gorham, 1991; Turunen et al, 2002; Yu, 2012). Around 19 % (3556 × 103 km2) of the soil area of the northern peatlands coincides with low altitude permafrost (Tarnocai et al, 2009; Wania et al, 2009a). Permafrost changes the peat accumulation process by altering plant productivity and decomposition, affecting the carbon sequestration rate (Robinson and Moore, 2000). Thawing of permafrost exposes the organic carbon stored in the frozen soil which becomes available for decomposition by soil microbes (Zimov et al, 2006)
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