Bryophyte colonisation on recently deglaciated lands in the European Alps

Introduction: There is an increasingly urgent need for knowledge of primary succession along glacier forelands in order to improve our understanding of biodiversity changes at high elevations. Bryophytes play a key ecological role in primary succession, especially in the early stages, but bryophyte colonisation on alpine glacier forelands is still poorly studied. We investigated the first stages of bryophyte primary succession along a chronosequence on a glacier foreland in the European Alps. Methods: Bryophytes on the Sforzellina glacier (Central Italian Alps) were sampled during the summer of 2022 in areas where the glacial front occurred in 1989, 2003, 2015 and 2019. At each site, six plots of 1 m × 1 m (5 m apart from each other) were sampled. For the most frequent species, plant and shoot size were measured to analyse growth trends throughout the succession. Key results and discussion: In total, 13 moss species and two liverwort species were found. The mean number of species increased with the number of years since deglaciation, following an ‘addition and persistence’ model. The first pioneer species, Pohlia filum (Schimp.) Mårtensson and Ptychostomum sp., were present only 3 years after deglaciation; the occurrence of bulbils may help the former colonise bare ground quickly. Sporophytes had appeared 7 years after deglaciation. In P. filum, both shoot and plant size increased during the first stages of succession but had decreased on 33-year-old substrates. This pattern could be related to the fact that this species usually occurs on soils with very low organic matter content.