Organic matter accumulation, peat chemistry, and permafrost melting in peatlands of boreal Alberta

Abstract

In the discontinuous permafrost zone of boreal western continental Canada, permafrost is limited almost exclusively to ombrotrophic peatlands. Permafrost in peatlands recently has been degrading and continues to degrade at its southern limit across western Canada, with no evidence of regeneration. The melting of permafrost could have dramatic effects on organic matter accumulation, organochemical properties, and nutrient status in peatlands. Our objectives are to quantify differences in peat chemistry (i.e., concentrations of organic fractions, N, P, and S) and rates of organic matter accumulation over the past 200 years between a site with permafrost, a site with degraded permafrost (internal lawn), and three sites with no evidence of permafrost since the last glaciation (continental peatlands: two bogs and one poor fen). Results indicate that peat chemistry may differ according to the presence, absence, or degradation of permafrost. Recent rates of organic matter accumulation follow similar trends over the past 100-200 years in the permafrost and continental bogs; however, net rates of organic matter accumulation are accelerated by 60% in the internal lawn. As decomposition in peatlands is influenced by nutrient limitations and organic matter quality, peat chemistry is likely to be a critical factor in the carbon balance response of boreal peatlands to climate change.