Vegetation re-establishment in polar “lichen-kill” landscapes: a case study of the Little Ice Age impact
AbstractIt has been accepted that the extremely sparse vegetation currently observed in Canadian polar deserts is due to prevailing unfavourable climatic conditions, inhibiting plant establishment, growth and survival. Less considered in the literature is the additional antagonistic factor of episodic adverse climatic anomalies. Such was the most recent Little Ice Age (LIA) cooling which caused a setback to, or even largescale extinction of, high Arctic plant communities that had taken centuries to develop. The LIA brought about new glacial advances, expansion of permanent snow banks and formation of ice crusts over entire landscapes. The newly formed ice (and snow) killed the underlying vegetation, thus creating what is in the geological literature referred to as “lichen-kill zones.” In these zones the current plant diversity and abundance are exceedingly low and the plants are all relatively young and even-aged, factors which all point to their recent origin. Here we maintain that this vegetation has not yet reached equilibrium with the present prevailing climate and that it is still in an initial stage of succession. We present results of eight upland sites sampled in the vicinity of Alexandra Fiord Lowland, Ellesmere Island, Canada, to demonstrate the slow recolonization process that has been occurring within the last 100–150 years after the LIA termination. The widespread presence of the “lichen-kill” zones throughout the Canadian polar regions reflects the extent and destructive nature of even minor climatic cooling on vulnerable polar ecosystems.
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