Plant ecology at high elevations

Abstract

Plants respond to the harsh alpine environment with a high degree of specialization, the structural and functional aspects of which this book aims to explore. Palaeorecords suggest that life on land started out in sheltered, warm and moist environments, and gradually expanded into more demanding habitats where water is rare, thermal energy is either low or overabundant or where mechanical disturbance is high. More than 100 million years ago, when the large, hot deserts of the Cretaceous period where formed, coping with drought became a matter of survival in higher plants. Why is this of relevance here? Because survival of both drought and freezing temperatures requires cell membranes which can tolerate dehydration. When plant tissues freeze, ice is first formed in gaps between cells, which draws water from protoplasts (see Chap. 8). A link between the ultrastructural and molecular basis for freezing tolerance and the evolution of dehydration tolerance of biomembranes has therefore been suggested (Larcher 1981). Plant survival in cold as well as hot “deserts” — the two thermal extremes on the globe — thus may have common evolutionary roots, although life under such contrasting thermal conditions requires many additional, rather different metabolic and developmental adaptations. The ability to survive low temperature extremes opened the highlands of the earth to plants. The Tertiary (and still ongoing) uplift of mountain ranges strongly accelerated the evolution of alpine taxa (Billings 1974;Agakhanyantz and Breckle 1995). Embedded in different floras of the world, high mountains became both highly fragmented refugia and corridors of cross-continental migration, and often bear plant diversities richer than those in their surrounding lowlands (Körner 1995a; Barthlott et al. 1996; Chap. 2 and color Plates 1–3 at the end of the book).