Faster, higher, more? Past, present and future dynamics of alpine and arctic flora under climate change

Alpine Botany, Sep 2014

Christian Rixen, Sonja Wipf, Esther Frei, Veronika Stöckli

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Faster, higher, more? Past, present and future dynamics of alpine and arctic flora under climate change

Christian Rixen 0 1 2 Sonja Wipf 0 1 2 Esther Frei 0 1 2 Veronika Stockli 0 1 2 0 Present Address: V. Stockli Bergwelten 21 AG, Bahnhofstrasse 8a, 7260 Davos Dorf, Switzerland 1 Present Address: E. Frei Department of Geography, University of British Columbia , Vancouver Campus, GEOG 127A, Vancouver, Canada 2 C. Rixen S. Wipf (&) E. Frei V. Stockli WSL Institute for Snow and Avalanche Research SLF , Fluelastrasse 11, 7260 Davos Dorf, Switzerland Climate warming affects the biotic environment worldwide, and especially in cold regions such as Arctic and alpine biomes. Enhanced plant growth, shrub encroachment and upward migration of species have been observed as a result (Myers-Smith et al. 2011; Stockli et al. 2011; Pauli et al. 2012). Profound changes in ecosystem functioning and potential losses of high-alpine and Arctic species are expected under climate warming as cold-adapted plants may be outcompeted by taller growing species or lost as their habitats vanish. Due to their endangerment in spatially limited habitats and low abundance, it is important to study the dynamics of plant species in cold environments under climate change. In the International Tundra Experiment ITEX (e.g., Elmendorf et al. 2012a), a scientific network of research teams carried out experiments at more than 40 sites focusing on the impact of climate change on plant species in Arctic and alpine vegetation. Similar, multi-year plant manipulation experiments allow comparing annual variation in plant performance with respect to phenological response to climate conditions. The ITEX research combines long-term and short-term experimentations with monitoring and aims - to understand ecosystem responses and vulnerability to change. Across all study sites, the ITEX network found the vegetation height and abundance of growth forms to have changed. Results of long-term changes in control plots were largely consistent with predictions based on warming experiments (Elmendorf et al. 2012b). Inter-site comparisons indicated that shrubs (particularly deciduous shrubs) were increasing over time primarily in sites that were warming rapidly over the study period, but this pattern was only apparent in locations where temperatures were already quite high. In contrast, the vegetation in the coldest tundra sites was relatively insensitive to climate warming. Many other research projects have addressed changes in species distributions and community composition in cold biomes relative to global change. The focus has recently been on vegetation of mountain regions, where upward migration of plant species can lead to changes in taxonomic and functional species composition. For instance, across European summits evidence for so-called thermophilization was found, i.e., more warm-adapted species increased whereas more cold-adapted species declined (Gottfried et al. 2012). In the short period between 2001 and 2008, this upward migration has caused an increase of local species richness in many boreal-temperate mountain regions, but a decrease in Mediterranean mountain regions (Pauli et al. 2012). Looking at longer time scales, i.e., more than a century, the vegetation change has even accelerated in recent decades, most likely in line with accelerated climate warming (Wipf et al. 2013). To understand changes of Arctic and alpine plants and communities in response to current climatic change, it is helpful to consider the full range of research approaches: experimental manipulations of the tundra environment, studies of long-term vegetation changes, attempts to disentangle different environmental factors like temperature and snow cover, studies of evolutionary changes and plasticity of species, and modeling approaches to predict future vegetation. Such changes in alpine and Arctic flora under climate change were the focus of two conferences in September 2013 in Bergun, Switzerland, with the main aim of presenting the state of the art in this research field. The first conference (co-organized with Robert D. Hollister and Kari Klanderud) focussed on recent work of the ITEX network (see above), while the second conference Faster, Higher, More aimed at presenting current research in climate-driven changes in species distribution in alpine and Arctic environments. Presentations ranged from changes in species distribution to phenotypic plasticity and genetic adaptation as mechanisms of change, and also included projections of climate change effects into the future. This special issue of Alpine Botany presents a selection of papers from both conferences. Climatic warming scenarios, and therefore experimental approaches that simulate it, usually focus on a rise in average temperatures. However, a short-term extreme warming may affect plants differently than a longer-term moderate warming. In an experimental approach comparing the effect of different warming treatments on bryophytes in Northern Sweden (Alatalo et al. 2014, this issue), bryophytes and lichens overall w (...truncated)


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Christian Rixen, Sonja Wipf, Esther Frei, Veronika Stöckli. Faster, higher, more? Past, present and future dynamics of alpine and arctic flora under climate change, Alpine Botany, 2014, pp. 77-79, Volume 124, Issue 2, DOI: 10.1007/s00035-014-0141-z