Background

A history of many centuries of seasonal livestock grazing of alpine pastures has significantly depressed the treeline in many European mountain ranges. Therefore, observations of treeline patterns are more likely to be obscured by historical land use than in regions with less human influence and might not provide relevant information about environmental factors that influence mortality and growth patterns at the natural high-elevation limit of tree existence. To overcome this, we used a large afforestation experiment in the Swiss Alps, "Stillberg", to address the following questions:

Can trees survive above the current treeline in the European Alps? Are environmental factors that influence spatial patterns of mortality the same as those that influence height growth? Does the relative importance of these environmental variables change over the first 40 years after planting as seedlings?

Dataset

The 5 ha Stillberg long-term afforestation research area is located near Davos (Central Alps, Switzerland). The bottom of the afforestation is approximately at the current treeline and it covers an altitudinal gradient of more than 150 m (2075 to 2230 m a.s.l.; see picture above). Approximately 92'000 seedlings of three treeline species (Larix decidua, Pinus mugo ssp. uncinata and Pinus cembra) were systematically planted in 1975, and mortality and height growth were closely monitored during the following 40 years.

Publications Barbeito, I., Dawes, M. A., Rixen, C., Senn, J. and Bebi, P. (2012), Factors driving mortality and growth at treeline: a 30-year experiment of 92 000 conifers. Ecology, 93: 389–401. http://dx.doi.org/10.1890/11-0384.1