Low winter temperatures and divergent freezing resistance set the cold range limit of widespread alpine graminoids

Aim: “Where and why does a species exist” is a fundamental question in ecology. However, the actual range limits of alpine plant species are largely unexplored and unexplained. We aim at identifying the low temperature range limits of the two most abundant alpine graminoid species on acidic soils that intermingle in mosaics of high-elevation habitats across the European Alps.
Location: Alpine grasslands in the Swiss Alps.
Taxon: Carex curvula (Cyperaceae) and Nardus stricta (Poaceae), named by the genus name hereafter.
Results: Carex and Nardus clearly segregated across different microsites. Season length, growing degree hours and soil chemistry (pH, C/N-ratio, phosphorus) did not demarcate the two species’ ranges, while their distribution was strongly affected by soil minimum temperature in winter. Carex occurred at sites with and without protecting snow cover and resisted low soil temperatures (-13 °C). Nardus was absent at microsites with snow cover duration less than 5 months and so...