Initial Establishment of Saxicolous Lichens Following Recent Glacial Recession in Sverdrup Pass, Ellesmere Island, Canada

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Abstract
In the recently deglaciated zone of a valley glacier in Central Ellesmere Island the mean period of time before the onset of colonization on bare rock surfaces was estimated to be about 80 years. The first species to establish was Xanthoria elegans, followed by Lecanora crenulata and Umbilicaria virginis approximately 20 years later. Summer temperature appeared to be one factor which affected lichen establishment in recently deglaciated bare areas in the High Arctic. Warmer microsites were identified as preferred locations for thallus establishment; these, therefore, constitute ideal sites for studies of thallus initiation under natural conditions. Following the retreat of a glacier from its most advanced Little Ice Age position, 16 species of saxicolous lichens have become established on bare rock debris in the icefree zone, but in nine transects only five species had a constancy of 80% or more. Lichen diversity in this successional photocommunity was comparable to that in a nearby pre-Little Ice Age landscape with more varied substrata.