Plant community and diversity change due to localized permafrost dynamics in bogs of western Canada

Abstract

Localized permafrost formation and melt at the southern limit of permafrost has a large effect on boreal bog plant community structure and diversity in continental western Canada (Alberta, Saskatchewan, and Manitoba). Non-metric multidimensional scaling ordinations show that non-permafrost-affected bogs, areas currently underlain by permafrost (frost mounds), and areas of permafrost degradation (internal lawns) have distinct plant communities. Bryophytes respond more strongly than vascular plants to lengthened environmental gradients in the bogs studied. Seventy-two vascular plant and bryophyte species were found, with mean alpha diversity (species richness) similar in bogs and internal lawns (22.6 and 22.1) and lowest on frost mounds (15.6). Beta diversity (species turnover between landforms) is greater for bryophytes (4.22) than vascular plants (2.54). Comparisons within internal lawns show highly variable height above water table, community composition, and species diversity in wet communities and reduced variability as peat accumulates and converges on dry surfaces dominated by Sphagnum fuscum (Schimp.) Klinggr. Overall, localized permafrost dynamics increase bog plant diversity by 47% by introduction of unique dry, shaded (frost mound) and wet, open (internal lawn) conditions absent from non-permafrost-affected bogs, making localized permafrost bogs one of the most bryologically diverse peatland types in western Canada.Key words: peatlands, bryophytes, plant communities, non-metric multidimensional scaling ordination, permafrost, climate change.