Patterns of boreal permafrost peatland vegetation across environmental gradients sensitive to climate warming

Abstract

This study documents changes in community and functional group across environmental gradients sensitive to climate warming in boreal permafrost peatlands and describes how future changes in temperature and precipitation may lead to changes in species composition and ecosystem properties. At the landscape scale, the presence of permafrost strongly influenced species composition. The position of permafrost thaw affected surface water pH and species composition. At local scales, a combination of water table depth and vegetation structure strongly controlled community composition. Permafrost plateau plots with high Picea mariana basal area were characterized by darker and drier understorey conditions, low cover of Sphagnum fuscum, Ledum groenlandicum, and lichen, and high cover of feather mosses. Aquatic collapse scar plots were dominated by aquatic Sphagnum and Carex, whereas more xeric plots were dominated by hummock Sphagnum and ericaceous shrubs. Functional group responses indicated that changing environmental conditions with climate warming may have significant impacts on community composition and ecosystem processes. A decomposition example is presented to show how changes in species and functional group composition could have important implications for ecosystem-level processes like peat accumulation during climate warming.Key words: bogs, fens, boreal, permafrost, vegetation, ordination