Due to habitat fragmentation and climate change, many plant populations become smaller and more isolated and thus more prone to local extinction. Whereas it is well established for lowland species that plants of small populations have lower individual fitness, alpine species have not been sufficiently studied in this respect. It is also not clear whether relationships between population size and fitness vary between naturally...

Forests in the upper continental montane zone are important ecotones between lowland and subalpine forest ecosystems. A thorough understanding of the past vegetation dynamics at mid elevation is crucial to assess past and future altitudinal range shifts of tree species in response to climate change. Lake sediments from Lac de Champex (1,467 m a.s.l.), a small lake in the Canton Valais in the Central Swiss Alps were analysed to...