Alpine life is shaped by topography

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Abstract
Aspect and steepness with ridges and depressions of different spatial extent, hence, the topography of high-elevation terrain affects the incidence angle of sun rays, the influence of wind, the redistribution of snow and the sorting action of gravity for water, nutrients, diaspores and sediments. These factors jointly shape life in the treeless alpine world, beyond the influences related to the strong vertical profile of the air temperature with a mean lapse rate of 0.55 K 100 m −1 . On top of diverse soil types, the resulting thermal habitat conditions within a given elevation belt substantially exceed the current (+2.9 K) and future (+4 K) climatic warming in the European Alps. To account for the full spectrum of life conditions, the spatial scale of analysis is essential. We show that pronounced topography effects on microclimate on nunatak-type cliffs above the trimline of glacial ice shields could most likely not fully counteract the then lower and hostile temperatures. Life conditions across snowbeds exemplify the effect of season length on alpine plant’s phenology and growth over short distances, with halved aboveground biomass production for a shortening of the season by two to three weeks. Furthermore, we highlight potential pitfalls in microclimate assessments of topography effects in open terrain, but also explain how to improve such measurements. Throughout this review, we emphasize the interactive effect of plant canopy structure (height, density) with topography, mutually creating life conditions not predictable from standard meteorological sources, but responsible for the over-proportional plant species richness of the alpine flora globally.
Funding Information
  • Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung

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