Modeling Ecosystem Processes and Peat Accumulation in Boreal Peatlands

Northern peatlands have accumulated up to about 450 Gt of carbon, mostly during the Holocene (the last 12,000 years) after the last glaciation (Gorham 1991; Clymo et al. 1998). Although northern peatlands have a relatively low average net accumulation rate (e.g., 19.4 g C m–2 year–1 in western interior Canada; Vitt et al. 2000), their extent, high-latitude location, and the large size of their carbon pool raise concerns that northern peatlands may become significant sources for atmospheric carbon under a changing climate. However, significant uncertainties exist in addressing peatland carbon responses to climate change. The credible assessment of carbon sink–source relationships in peatlands must be based on the understanding of processes responsible for carbon-accumulation patterns over short and long terms. Peatland dynamics are a function of the balance of photosynthetic production of living plants atop the acrotelm (surface and upper oxic layer) and decomposition of litter and peat in both the acrotelm and the catotelm (underlying anoxic layer) (Ingram 1978; Clymo 1984). Owing to the complex interactions involved in peatland dynamics, a model is often used to facilitate understanding of processes and to make projections. Because peatlands are ecosystems bordering between upland and aquatic ecosystems, they have some unique features that cannot be easily accommodated in standard ways as for other ecosystems. The objective of this chapter is to review some existing models that have been used to simulate peatland carbon dynamics.