Horizontal growth in arctic-alpine clonal plants is not affected by climatic variability among regions

Background: Many arctic and alpine plant species from cold environments reproduce mainly vegetatively and can be extremely long-lived. To understand the life history and population dynamics of such species, careful in-situ measurements of growth are essential, but reports of such measurements are still scarce. Aims: Our objectives were to compare annual horizontal growth in populations of five clonal arctic-alpine species in different geographic regions, successional stages and years, and to test how much their mean annual growth is affected by season length. Methods: We performed replicated measurements of annual size increments in 36 populations of Carex curvula, Dryas octopetala, Salix herbacea, Vaccinium uliginosum and Empetrum nigrum in three arctic-alpine regions of Europe for 2 years (2008–2010). Results: The mean annual horizontal growth was different among the species and between early and late successional stages in both years. In late successional populations, the mean growth over both years wa...