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Performance of germinating tree seedlings below and above treeline in the Swiss Alps

Zurbriggen, Natalie ; Hättenschwiler, Stephan ; Frei, Eva ; Hagedorn, Frank ; Bebi, Peter

In: Plant Ecology, 2013, vol. 214, no. 3, p. 385-396

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    Titre
    • Performance of germinating tree seedlings below and above treeline in the Swiss Alps
    Auteur
    • Zurbriggen, Natalie. WSL Swiss Federal Institute for Forest, Snow and Landscape Research, Zürcherstrasse 111, 8903, Birmensdorf, Switzerland
    • Hättenschwiler, Stephan. Centre of Functional Ecology and Evolution, CEFE-CNRS, 1919 route de Mende, 34293, Montpellier Cedex 5, France
    • Frei, Eva. Agrofutura, Agronomy, Economy & Ecology, Ackerstrasse, Postfach, 5070, Frick, Switzerland
    • Hagedorn, Frank. WSL Swiss Federal Institute for Forest, Snow and Landscape Research, Zürcherstrasse 111, 8903, Birmensdorf, Switzerland
    • Bebi, Peter. WSL Institute for Snow and Avalanche Research SLF, Flüelastrasse 11, 7260, Davos Dorf, Switzerland
    Type de document
    • Postprint
    Identifiant OAI-PMH
    • oai:doc.rero.ch:314462
    Summary
    The germination and early survival of tree seedlings is a critical process for the understanding of treeline dynamics with ongoing climate change. Here we analyzed the performance of 0-4year-old seedlings of seven tree species at three sites above and below the current altitudinal treeline in the Swiss Central Alps near Davos. Starting from sown seeds, we monitored the seedling performance as proportions of living seedlings, seedling shoot height growth, and biomass allocation over 4years to examine changes along an elevational gradient. We evaluated the relative importance of the environmental factors soil temperature, light conditions, water use efficiency, and nitrogen availability on seedling performance. During the 4years, the proportions of living seedlings differed only slightly along the elevational gradient even in species currently occurring at lower elevations. Microsite-specific soil temperature and light availability had only little effect on the proportion of living seedlings and seedling biomass across the elevational gradient. Conversely, seedling biomass and biomass allocation correlated well with the foliar stable nitrogen isotope abundance (δ 15N) that was used as an indicator for nitrogen availability. Collectively, our results suggested that the early establishment of seedlings of a variety of tree species in the treeline ecotone was not limited by current climatic conditions even beyond the species' actual upper distribution limit. Nitrogen dynamics appeared to be an important environmental co-driver for biomass production and allocation in very young tree seedlings