This volume contains a selection of scientific papers which were presented at an international workshop on the impacts of climatic variability held in Wengen, Switzerland, September 1997. For the first time, an assessment is made of the interactions between physical and biological elements of the Earth System on the basis of shifts in extreme climatic conditions, rather than simply changes in mean atmospheric conditions which research has tended to focus on until recently. Natural ecosystems and forests are typical examples of systems which, while constrained within certain ranges of mean climate, can undergo rapid and often irreversible damage in the face of short-lived but intense extreme events.

interactions between physical and biological elements of the Earth System - integration of numerical modeling, statistical analysis and palaeoenvironmental approaches

The impact of climatic extremes on forests: An introduction.- Meteorological extremes and their impacts on forests in the czech republic.- Changes in temperature variability in relation to shifts in mean temperatures in the swiss alpine region this century.- Evaluation of the 2xCO2 impact on european climate variability with a variable resolution GCM.- Precipitation and snow cover variability in the french alps.- Influence of forest cover in the eastern united states on regional climate.- Extremes of moisture availability reconstructed from tree rings for recent millennia in the great basin of western north America.- Predictive models of tree-growth: preliminary results in the French Alps.- Documenting the effects of recent climate change at treeline in the canadian rockies.- Annual- versus decadal-scale climatic influences on tree establishment and mortality in northern Patagonia.- High-altitude forest sensitivity to global warming: results from long-term and short-term analyses in the eastern italian alps.- Climate, limiting factors and environmental change in high-altitude forests of Western North America.- Managing swiss forests: when climate intervenes.- Worldwide positions of alpine treelines and their causes.- Vascular plant species richness in relation to altitudinal and slope gradients in mountain landscapes of central norway.- Environmental information from stable isotopes in tree rings of Fagus sylvatica.- Simulated impacts of mean vs. intra-snnual climate changes on forests.- Sensitivity analysis of a forest gap model concerning current and future climate variability.- Simulated effects of bark beetle infestations on stand dynamics in Picea abies stands: coupling a patch model and a stand risk model.- Impacts of climatic variability and extreme on forests: synthesis.