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This special issue of the journal Alpine Botany brings together syntheses, macroecological and taxon-specific studies of patterns and processes of plant evolution in major mountain ranges across Europe, Africa, the Americas and Asia. Apart from reflecting current conceptual and methodological perspectives in the field, it contributes to our understanding of the interplay between factors determining the evolution and distribution of plant variation across topographically complex areas, and will help to identify the components necessary for building an integrative model of the origin and distribution of diversity in mountain areas. [ABSTRACT FROM AUTHOR]

Abandonment of pastures and successional shrub expansion are widespread in European mountain regions. Moderate shrub encroachment is perceived beneficial for plant diversity by adding new species without outcompeting existing ones, yet systematic evidence is missing. We surveyed vegetation along 24 transects from open pasture into shrubland across the Swiss Alps using a new protocol distinguishing different spatial scales, shrub cover of each plot (2 × 2 m) and larger-scale zonal cover along the transect. Data were analysed using generalized linear models of shrub cover, shrub species and environmental conditions, such as geology, aspect or soil. Most shrub communities were dominated by Alnus viridis (62% of transects) and Pinus mugo (25%), and the rest by other shrub species (13%). These dominant shrub species explained vegetation response to shrub cover well, without need of environmental variables in the model. Compared to open pasture, A. viridis resulted in an immediate linear decline in plant species richness and a marginal increase in beta-diversity (maximally + 10% at 35% cover). Dense A. viridis hosted 62% less species than open pasture. In P. mugo, species richness remained stable until 40% shrub cover and dropped thereafter; beta-diversity peaked at 35% cover. Hence, scattered P. mugo increases beta-diversity without impairing species richness. In transects dominated by other shrubs, species richness and beta-diversity peaked at 40–60% shrub cover (+ 23% both). A. viridis reduced species richness in a larger area around the shrubs than P. mugo. Therefore, effects of shrub encroachment on plant diversity cannot be generalized and depend on dominant shrub species. [ABSTRACT FROM AUTHOR]

The largest alpine–nival vegetation permanent plot site in the Alps, the GLORIA mastersite Schrankogel (Tirol, Austria), provided evidence of warming-driven vegetation changes already 10 years after its establishment in 1994. Another decade later, in 2014, substantial compositional changes with increasing ratios of warmth-demanding to cold-adapted species have been found. The current study deals with species-specific responses involved in an ongoing vegetation transformation across the alpine–nival ecotone on Schrankogel by using presence/absence as well as cover data from permanent plots, situated between 2900 and 3400 masl. The number of occupied plots per species remained constant or even increased during the first decade, whereas disappearance events became more frequent during the second one, especially for cold-adapted specialists (subnival–nival species). Remarkably, the latter was accompanied by continued strong losses in cover of all subnival–nival species. These losses were more frequent in plots with a more thermophilous species composition, suggesting an increasing maladaptation of subnival–nival species to warmer habitat conditions and a successive trailing-edge decline. Several species with a distribution centre at lower elevations (alpine–subnival) markedly increased in cover, comparatively more so in colder plots, indicating a leading-edge expansion. Moreover, our findings show an increase in occupied plots and cover of almost all snowbed species, suggesting that areas previously with a too long snowpack period are now becoming suitable snowbed habitats. Vegetation gaps arising from population dieback of cold-adapted species, however, could only be partly filled by advancing species, indicating that species declines have occurred already before the onset of strong competition pressure. [ABSTRACT FROM AUTHOR]

Mountains are hotspots of biodiversity. Yet, evaluating their importance in global biodiversity inventories requires the adoption of a pertinent definition of mountains. Here, we first compare the well-established WCMC and GMBA definitions, which both use geographical information systems. We show that the WCMC approach arrives at twice the global mountain area and much higher human population numbers than the GMBA one, which is explained by the inclusion of (mostly) low latitude hill country below 600 m elevation. We then present an inventory of the world's mountains based on the GMBA definition. In this inventory, each of the 1003 entries corresponds to a polygon drawn around a mountain or a mountain range and includes the name of the delineated object, the area of mountainous terrain it covers stratified into different bioclimatic belts (all at 2.5′ resolution), and demographic information. Taken together, the 1003 polygons cover 13.8 Mio km of mountain terrain, of which 3.3 Mio km are in the alpine and nival belts. This corresponds to 83.7% of the global mountain area sensu GMBA, and 94% of the alpine/nival area. The 386 Mio people inhabiting mountainous terrain within polygons represent 75% of the people globally inhabiting mountains sensu GMBA. This inventory offers a robust framework for the integration of mountain biota in regional and larger scale biodiversity assessments, for biogeography, bioclimatology, macroecology, and conservation research, and for the exploration of a multitude of socio-ecological and climate change-related research questions in mountain biota, including the potential pressure on alpine ecosystems. [ABSTRACT FROM AUTHOR]

Stable carbon and nitrogen isotopes provide time-integrated signals of plant carbon and nitrogen relations. We assessed an entire alpine flora in the Swiss Alps at ca. 2400 m elevation, using year 2007 herbarium samples of 245 species, 141 genera and 42 families to explore functional trait diversity. Despite overall similar macro-environmental conditions (moisture, soils, elevation), signal variation covered the full spectrum known for C plants. Variation among means for plant families for both δC and δN was smaller than variation among species within families. Species identity was of far greater importance than family affiliation. Similarly, tissue nitrogen and carbon concentrations varied in a rather species-specific manner, not permitting any a priori plant functional group definition based on such traits. The study also yielded tissue-type specificity of isotope signals. The elevation signal in δC (known to be less negative at high elevation) was much less pronounced than observed previously in con-generic comparisons. Thus, elevational δC trends are hard to distinguish from species effects in mixed populations over narrow ranges of elevation. δN data offer more space for ecological interpretation and show family specificity of signals in few cases. Cyperaceae, the most prominent family in this region, show no discrimination against N (like Fabaceae) and must have access to N sources different from most other families. This deserves experimental clarification, given the significance of Cyperaceae in cold environments. Overall, our study evidenced very high functional diversity among alpine plant species, as captured by these isotope signals. [ABSTRACT FROM AUTHOR]