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Abstract
The development of vegetation in Arctic glacier forelands has been described as unidirectional, non-replacement succession characterized by the gradual establishment of species typical for mature tundra with no species turnover. Our study focused on two early colonizers of High Arctic glacier forelands: Saxifraga oppositifolia (Saxifragaceae) and Braya purpurascens (Brassicaceae). While the first species is a common generalist also found in mature old growth tundra communities, the second specializes on disturbed substrate. The demographic population structures of the two study species were investigated along four glacier forelands in Petuniabukta, north Billefjorden, in central Spitsbergen, Svalbard. Young plants of both species occurred exclusively on young substrate, implying that soil conditions are favourable for establishment only before soil crusts develop. We show that while S. oppositifolia persists from pioneer successional stages and is characterized by increased size and flowering, B. purpurascens specializes on disturbed young substrate and does not follow the typical unidirectional, non-replacement succession pattern. Plants at two of the forelands were examined for the presence of root-associated fungi. Fungal genus Olpidium (Fungus incertae sedis) was found along a whole successional gradient in one of the forelands.
Acknowledgements
We are grateful to M. Šmilauerová, P. Šmilauer, M. Kavková, K. Picard and A. Jumpponen for help with root staining and endophyte determination, Grzegorz Rachlewicz for determining the age since deglaciation of our sampling sites, and two anonymous referees for their helpful comments. The study was supported by the Ministry of Education, Youth and Sports of the Czech Republic through funding for CzechPolar—Czech polar stations: construction and logistic expenses (LM2010009).