The Changing Alpine Treeline

Alpine treelines mark the low-temperature limit of tree growth and occur in mountains world-wide. Presenting a companion to his book Alpine Plant Life, Christian Körner provides a global synthesis of the treeline phenomenon from sub-arctic to equatorial latitudes and a functional explanation based on the biology of trees. The comprehensive text approaches the subject in a multi-disciplinary way by exploring forest patterns at the edge of tree life, tree morphology, anatomy, climatology and, based on this, modelling treeline position, describing reproduction and population processes, development, phenology, evolutionary aspects, as well as summarizing evidence on the physiology of carbon, water and nutrient relations, and stress physiology. It closes with an account on treelines in the past (palaeo-ecology) and a section on global change effects on treelines, now and in the future. With more than 100 illustrations, many of them in colour, the book shows alpine treelines from around the globe and offers a wealth of scientific information in the form of diagrams and tables.

The alpine treeline ecotone (ATE) is an area of transition high on mountains where closed canopy forests from lower elevations give way to the open alpine tundra and rocky expanses above. Alpine tundra is an island biome and its ecotone with forest is subject to change, and like oceanic islands, alpine tundra is subject to invasion – or the upward advance of treeline. The invasion of tundra by trees will have consequences for the tundra biome as invasion does for other island flora and fauna. To examine the invasibility of tundra we take a plant’s-eye-view, wherein the local conditions become extremely important. Among these local conditions, we find geomorphology to be exceptionally important. We concentrate on aspects of microtopography (and microgeomorphology) and microclimate because these are the factors that matter: from the plant’s-eye-view, but we pay attention to multiple scales. At coarse scales, snow avalanches and debris flows are widespread and create “disturbance treelines whose elevation is well below those controlled by climate. At medium scales, turf-banked terraces create tread-and-riser topography that is a difficult landscape for a tree seedling to survive upon because of exposure to wind, dryness, and impenetrable surfaces. At fine scales, turf exfoliation of the fronts of turf-banked risers, and boulders, offer microsites where tree seedlings may find shelter and are able to gain a foothold in the alpine tundra; conversely, however, surfaces of needle-ice pans and frost heaving associated with miniature patterned ground production are associated with sites inimical to seedling establishment or survival. We explicitly consider how local scale processes propagate across scales into landscape patterns. The objective of this book is to examine the controls on change at alpine treeline. All the papers are focused on work done in Glacier National Park, Montana, USA. Although any one place is limiting, we are able to examine the alpine treeline here in some detail – and an advantage is that the treeline ecotone in Glacier National Park is quite variable in itself due to the underlying variability in geomorphology at multiple scales. This book will provide insights into an important ecological phenomenon with a distinctly geomorphic perspective. The editors collectively have over 100 years of experience in working in geomorphology, biogeography, and ecology. They also have each worked on research in Glacier National Park for several decades. The book will be a reference for a variety of professionals and students, both graduate and undergraduate, with interests in Physical Geography, Geomorphology, Ecology, and Environmental Science. Because of the importance of the alpine treeline ecotone for recreation and aesthetic interests in mountain environments, wildland and park managers will also use this book. * Subject matter: geomorphology at alpine treeline * Expertise of contributors: each editor brings over 25 years of experience in studies of ecotones and geomorphology, and collectively over 100 years of experience in Glacier National Park * Changing alpine treeline examines climate change

Concerns have been raised with respect to the state of high-altitude and high-latitude treelines, as they are anticipated to undergo considerable modifications due to global changes, and especially due to climate warming. As high-elevation treelines are temperature-limited vegetation boundaries, they are considered to be sensitive to climate warming. As a consequence, in this future, warmer environment, an upward migration of treelines is expected because low air and root-zone temperatures constrain their regeneration and growth. Despite the ubiquity of climate warming, treeline advancement is not a worldwide phenomenon: some treelines have been advancing rapidly, others have responded sluggishly or have remained stable. This variation in responses is attributed to the potential interaction of a continuum of site-related factors that may lead to the occurrence of locally conditioned temperature patterns. Competition amongst species and below-ground resources have been suggested as additional factors explaining the variability in the movement of treelines. This Special Issue (book) is dedicated to the discussion of treeline responses to changing environmental conditions in different areas around the globe.

Changes within and beyond the alpine treeline ecotone are hypothesized to respond to climatic changes and to be controlled by site-specific conditions. Repeated photographs show significant changes in the alpine treeline ecotone of Goodsir Pass in Kootenay National Park, B.C. over the past century. Field work revealed increases in tree density within the ecotone, and a 150 vertical metre increase in the elevation of the ecotone, at a rateof 2.2 metres/year. Change within the ecotone of Goodsir Pass is more closely related to temporal climatic variability than to site-specific spatial variability. Repeated photographs from three National Parks in the southern Canadian Rocky Mountains show this change to be a typical but dramatic example. Results at several scales indicate that the occurrence, magnitude and type of change in the alpine treeline ecotone and the drivers of that change are most influenced by the regional ecologic and geo-climatic setting or context.

Generations of plant scientists have been fascinated by alpine plant life - with the exposure of organisms to dramatic climatic gradients over a very short distance. This comprehensive text treats a wide range of topics: alpine climate and soils, plant distribution and the treeline phenomenon, physiological ecology of water-, nutritional- and carbon relations of alpine plants, plant stress and plant development, biomass production, and aspects of human impacts on alpine vegetation. Geographically the book covers all parts of the world including the tropics.This second edition of Alpine Plant Life gives new references, new diagrams, and extensively revised chapters.

The United Nations Conference on the Environment and Development (UNCED), held in Rio de Janeiro in 1992, spawned a multitude of pro grammes aimed at assessing, managing and conserving the earth's biological diversity. One important issue addressed at the conference was the mountain environment. A specific feature of high mountains is the so-called alpine zone, i. e. the treeless regions at the uppermost reaches. Though covering only a very small proportion of the land surface, the alpine zone contains a rela tively large number of plants, animals, fungi and microbes which are specifi cally adapted to cold environments. This zone contributes fundamentally to the planet's biodiversity and provides many resources for mountain dwelling as well as lowland people. However, rapid and largely man-made changes are affecting mountain ecosystems, such as soil erosion, losses of habitat and genetic diversity, and climate change, all of which have to be addressed. As stated in the European Community Biodiversity Strategy, "the global scale of biodiversity reduction or losses and the interdependence of different species and ecosystems across national borders demands concerted international action". Managing biodiversity in a rational and sustainable way needs basic knowledge on its qualitative and quantitative aspects at local, regional and global scales. This is particularly true for mountains, which are distributed throughout the world and are indeed hot spots of biodiversity in absolute terms as well as relative to the surrounding lowlands.