The Changing Alpine Treeline

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.

This book delivers current state-of-the-science knowledge of tree ecophysiology, with particular emphasis on adaptation to a novel future physical and chemical environment. Unlike the focus of most books on the topic, this considers air chemistry changes (O3, NOx, and N deposition) in addition to elevated CO2 effects and its secondary effects of elevated temperature. The authors have addressed two systems essential for plant life: water handling capacity from the perspective of water transport; the coupling of xylem and phloem water potential and flow; water and nutrition uptake via likely changes in mycorrhizal relationships; control of water loss via stomata and its retention via cellular regulation; and within plant carbon dynamics from the perspective of environmental limitations to growth, allocation to defences, and changes in partitioning to respiration. The authors offer expert knowledge and insight to develop likely outcomes within the context of many unknowns. We offer this comprehensive analysis of tree responses and their capacity to respond to environmental changes to provide a better insight in understanding likelihood for survival, as well as planning for the future with long-lived, stationary organisms adapted to the past: trees.

This book brings together comprehensive multi-disciplinary knowledge on diverse aspects of the Himalayan treeline ecotone which is considered one of the most sensitive ecosystems to climate change. The contents of this book are based on the results of extensive research and provide a holistic understanding of the treeline ecotone in Himalaya. The book will serve as an important reference manual and a textbook on treeline ecology. The book is unique in the sense that it provides an engaging account of almost all the aspects of the treeline ecotone, such as taxonomic, functional and phylogenetic species diversity, temperature lapse rates, tree phenology, water relations, and stress physiology, tree ring width chronology, and climate relationships and the role of treeline ecotone in human sustenance in the Indian Himalayan region The treelines in the Himalaya, being the highest in the Northern Hemisphere (up to 4900 m), are among the least investigated systems and hence this book is timely and fills all-important knowledge gaps vis-à-vis treeline shifts, physiognomic, structural, and functional changes in mountain landscapes and ecosystems, particularly under the changing climate This book, for the first time, summarizes evidence-based knowledge about various aspects of treeline ecotone in Himalaya that was largely generated through a well-coordinated a team science approach. The book will be of interest to ecologists, climatologists, dendrochronologists, foresters, plant physiologists and resource managers and policy planners for a better understanding of the organization and dynamics of this fragile ecosystem in relation to climate change and other anthropogenic stresses that are rampant in the Himalaya. The book lays a solid foundation for further investigation of the ecology and dynamics of the treeline ecotone in the Himalayas and provides a rationale for pursuing a team science approach for macroecological investigations.

This book gives an overview of the state of research in fields pertaining to the detection, understanding and prediction of global change impacts in mountain regions. More than sixty contributions from paleoclimatology, cryospheric research, hydrology, ecology, and development studies are compiled in this volume, each with an outlook on future research directions. The book will interest meteorologists, geologists, botanists and climatologists.

Climate change is thought to be especially relevant to ecosystems in the cold biomes. Observed warming has been higher in cold climates through various positive feedbacks, especially declining snow and ice cover, and climate projections indicate further rapid warming in the decades to come. Temperature change can have profound impacts in cold biome ecosystems, either directly in terms of impacts on physiology or growing season length, or indirectly via changes in nutrient cycling. The regions focused on here are the (sub)arctic and the (sub)alpine areas, both characterized by short growing seasons and low annual temperatures, but with different radiation environments depending on latitude. Climate change can have impacts in all seasons. Increased spring temperatures can accelerate snowmelt, leading to an earlier onset of the growing season, while warmer summers may stimulate primary productivity through temperatures closer to metabolic optima and/or increased mineralization rates. Winter warming can lead to the vegetation being damaged because of exposure to harsh frost without insulating snow cover. In all of this, concurrent changes in precipitation also play an important role: increased snowfall can buffer warming-induced advances in snowmelt, a higher ratio of rain to snow can greatly accelerate snowmelt in winter and spring, and summer drought may reverse growth-stimulation by warming directly (drought stress) or indirectly (e.g. impaired nutrient uptake). Micro-climate is crucial in these systems and requires particular attention as it can vary widely across the landscape, creating different growing environments in the space of a few meters or even less. Interest in cold region responses to climate change does not only arise from the fact that they harbor unique ecosystems that may be endangered, but also because they store large amounts of carbon that may be released under climate change. However, research is challenging because of the remoteness of many of these areas and the harsh conditions during much of the year. In spite of this, some studies have been carried out over an extensive period, spanning decades and yielding information on for example plant community reorganization (including invasions), and changes in phenology above- and/or belowground. Other studies focus on shorter term effects, such as impacts of heat waves, late frosts or other anomalous weather, including longer term (after-) effects that may differ drastically from other regions because of the short growing season in cold climates. Ultimately, models are used to predict future changes in vegetation along latitudinal or elevational gradients, although phenology and microclimatic variation may pose particular challenges. Contributions to this Research Topic focus on climate change, encompassing both changes in the mean (gradual warming) and variability (heat waves, altered precipitation distribution) in cold biomes. The Topic contains reports on observed changes or events, but also research making use of experimentally imposed environmental changes. The focus is varied, including phenology, physiology, soil and vegetation science and biogeochemistry, with the aim of providing a comprehensive overview of observed and expected responses to climate change in cold biome ecosystems.

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.