Phenology and distribution strategy of key plant species within the subalpine-alpine ecocline in the Valaisan Alps (Switzerland)

Sexual reproduction of the high mountain plant Saxifraga moschata Wulfen at varying lengths of the growing season

“…Phases of linear growth such as shoot elongation, leaf expansion, and enlargement of seeds during histogenesis are especially closely related to temperature (Larcher, 1996;Sofield et al, 1977;Wagner and Mitterhofer, 1998). Cumulative degree-days can be a useful tool to model precisely the role of temperature (Granier and Tardieu, 1998), and it can also be a measure for total heat accumulation during phenological phases or the entire growing season (Grulke and Bliss, 1985;Molau, 1996a;Theurillat and Schlu¨ssel, 2000). However, for S. moschata on early-and latethawing sites, no clear relationship could be found between temperature and the length for any phase, either for main phenological phases or for phases of seed development.…”

Climate continentality and treeline species distribution in the Alps

“…This species is considered the best adapted to colonize the upper subalpine, and even the lower alpine, belt given its decreasing need for summer heat with increasing altitude, and its frost resistance. Its request for summer heat and its sensitiveness to summer drought make it less adapted to oceanic conditions (Theurillat & Schlü ssel, 2000) as well as to extremely continental ones (Tinner & Kaltenrieder, 2005). Picea abies and Larix decidua, less conditioned by the continentality values, showed a less contrasting distribution between Laghi Gemelli and Valfurva.…”

A comparison between different treeline types shows contrasting responses to climate fluctuations

“…In our case, a lack of recruitment seems to be important, which can be due to high seedling mortality, low germination rates or to a less effective dispersal strategy of Larix decidua compared with zoochorous Pinus cembra (Holtmeier & Broll 2007;Lingua et al 2008). Species composition seems to be determining for treeline behaviour, and is probably linked to climatic continentality, Pinus cembra being less adapted to relatively oceanic climates (Theurillat & Schlüssel 2000;Caccianiga et al 2008). The overall low density of the population may also play a role.…”