Vegetation re-establishment in polar "lichen-kill" landscapes: a case study of the Little Ice Age impact

It has been accepted that the extremely sparse vegetation currently observe d in Canadian polar deserts is due to prevailing unfavourable climatic cond itions, inhibiting plant establishment, growth and survival. Less considere d in the literature is the additional antagonistic factor of episodic adver se climatic anomalies. Such was the most recent Little Ice Age (LIA) coolin g which caused a setback to, or even large scale extinction of, high Arctic plant communities that had taken centuries to develop. The LIA brought abo ut 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 literatu re referred to as "lichen-kill zones." In these zones the current plant div ersity and abundance are exceedingly low and the plants are all relatively young and even-aged, factors which all point to their recent origin. Here w e maintain that this vegetation has not yet reached equilibrium with the pr esent prevailing climate and that it is still in an initial stage of succes sion. We present results of eight upland sites sampled in the vicinity of A lexandra Fiord Lowland, Ellesmere Island, Canada, to demonstrate the slow r ecolonization process that has been occurring within the last 100-150 years after the LIA termination. The widespread presence of the "lichen-kill" zo nes throughout the Canadian polar regions reflects the extent and destructi ve nature of even minor climatic cooling on vulnerable polar ecosystems.