Can successional species groups be discriminated based on their life history traits? A study from a glacier foreland in the Central Alps

Abstract

Background: Retreating glaciers expose mineral substratum for colonisation and, as such, offer unique opportunities to study primary succession processes and life history traits of the colonisers. Aims: Results of published and unpublished case studies in a central Alpine glacier foreland were used to clarify if the species groups involved in primary succession could be discriminated by their life history traits. Methods: The case studies were carried out in the glacier foreland of the Rotmoosferner, Obergurgl site (Ötztal, Tyrol, Austria) using standard methods for life history trait determination and population analyses. Results: Pioneer species could be discriminated by their low seed masses and their high seed numbers from all other successional stage species. On the moraine exposed in 1971, seed rain and seed bank composition was consistent with that of the standing vegetation. Divergent dynamics were detected on the moraines of 1923 and of 1858. The highest seedling mortality rates were recorded for the pioneer Saxifraga aizoides (86–94%); the other species studied showed survival rates of 40–76%. Conclusions: Life history traits such as seed mass, number, dispersal, persistence, and seedling recruitment govern the colonisation process and the progress of plant succession. However, seed availability appears to be the bottleneck. Succession success therefore highly depends on input of diaspores in the form of plant fragment from adjacent slopes.