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In mountainous regions, climate warming is expected to shift species' ranges to higher altitudes. Evidence for such shifts is still mostly from revisitations of historical sites. We present recent (2001 to 2008) changes in vascular plant species richness observed in a standardized monitoring network across Europe's major mountain ranges. Species have moved upslope on average. However, these shifts had opposite effects on the summit floras' spedes richness in boreal-temperate mountain regions (+3.9 species on average) and Mediterranean mountain regions (-1.4 species), probably because recent climatic trends have decreased the availability of water in the European south. Because Mediterranean mountains are particularly rich in endemic species, a continuation of these trends might shrink the European mountain flora, despite an average increase in summit species richness across the region.

Focusing on mountain plant communities across Europe, a study shows that ongoing climate change causes a gradual decline in cold-adapted species and a corresponding increase in warm-adapted species, which could be an early sign that mountain plant diversity is at risk. Climate impact studies have indicated ecological fingerprints of recent global warming across a wide range of habitats 1 , 2 . Although these studies have shown responses from various local case studies, a coherent large-scale account on temperature-driven changes of biotic communities has been lacking 3 , 4 . Here we use 867 vegetation samples above the treeline from 60 summit sites in all major European mountain systems to show that ongoing climate change gradually transforms mountain plant communities. We provide evidence that the more cold-adapted species decline and the more warm-adapted species increase, a process described here as thermophilization. At the scale of individual mountains this general trend may not be apparent, but at the larger, continental scale we observed a significantly higher abundance of thermophilic species in 2008, compared with 2001. Thermophilization of mountain plant communities mirrors the degree of recent warming and is more pronounced in areas where the temperature increase has been higher. In view of the projected climate change 5 , 6 the observed transformation suggests a progressive decline of cold mountain habitats and their biota.

1. High alpine plants endure a cold climate with short growing seasons entailing severe consequences of an improper timing of development. Hence, their flowering phenology is expected to be rigorously controlled by climatic factors. 2. We studied ten alpine plant species from habitats with early and late melting snow cover for 2 years and compared the synchronizing effect of temperature sums (TS), time of snowmelt (SM) and photoperiod (PH) on their flowering phenology. Intraseasonal and habitat-specific variation in the impact of these factors was analysed by comparing predictions of time-to-event models using linear mixed-effects models. 3. Temperature was the overwhelming trigger of flowering phenology for all species. Its synchronizing effect was strongest at or shortly after flowering indicating the particular importance of phenological control of pollination. To some extent, this pattern masks the common trend of decreasing phenological responses to climatic changes from the beginning to the end of the growing season for lowland species. No carry-over effects were detected. 4. As expected, the impact of photoperiod was weaker for snowbed species than for species inhabiting sites with early melting snow cover, while for temperature the reverse pattern was observed. 5. Our findings provide strong evidence that alpine plants will respond quickly and directly to increasing temperature without considerable compensation due to photoperiodic control of phenology.

Aim Assessing potential response of alpine plant species distribution to different future climatic and land-use scenarios. Location Four mountain ranges totalling 150 km2in the north-eastern Calcareous Alps of Austria. Methods Ordinal regression models of eighty-five alpine plant species based on environmental constraints and land use determining their abundance. Site conditions are simulated spatially using a GIS, a Digital Terrain Model, meteorological station data and existing maps. Additionally, historical records were investigated to derive data on time spans since pastures were abandoned. This was then used to assess land-use impacts on vegetation patterns in combination with climatic changes. Results A regionalized GCM scenario for 2050 (+ 0.65 ° C, -30 mm August precipitation) will only lead to local loss of potential habitat for alpine plant species. More profound changes (+ 2 ° C, -30 mm August precipitation; + 2 ° C, -60 mm August precipitation) however, will bring about a severe contraction of the alpine, non-forest zone, because of range expansion of the treeline conifer Pinus mugo Turra and many alpine species will loose major parts of their habitat. Precipitation change significantly influences predicted future habitat patterns, mostly by enhancing the general trend. Maintenance of summer pastures facilitates the persistence of alpine plant species by providing refuges, but existing pastures are too small in the area to effectively prevent the regional extinction risk of alpine plant species. Main conclusions The results support earlier hypotheses that alpine plant species on mountain ranges with restricted habitat availability above the treeline will experience severe fragmentation and habitat loss, but only if the mean annual temperature increases by 2 ° C or more. Even in temperate alpine regions it is important to consider precipitation in addition to temperature when climate impacts are to be assessed. The maintenance of large summer farms may contribute to preventing the expected loss of non-forest habitats for alpine plant species. Conceptual and technical shortcomings of static equilibrium modelling limit the mechanistic understanding of the processes involved.

Areas of 2,800-3,000 m a.s.l. represent the alpine-nival ecotone in the Alps. This transition zone connecting the closed swards of the alpine belt and the scattered vegetation of the nival belt may show particularly strong climate warming driven fluctuations in plant species richness compared to the nival belt. To test this hypothesis, 12 summits within this range were investigated in the canton of Grisons, Switzerland in 2004. Complete lists of vascular plant species consisting of 5-70 species were collected on each summit and the elevation of the uppermost occurrence of each species was recorded. These data were compared to historical records over 120 years in age. Within this time, vascular plant species richness increased by 11% per decade on summits in the alpine-nival ecotone. Despite this considerable change, a comparison with nival summits did not support the hypothesis that species richness increase at the alpine-nival ecotone is higher than in the nival belt. A general trend of upward migration in the range of several metres per decade could be observed. Anemochorous species were more often found to be migrating than zoochorous or autochorous species and migration was higher on calcareous than on siliceous bedrock. A comparison between the summits with the adjacent slopes in our study revealed that changes in species number could be used as an indicator for climate-induced changes--if at all--only for the narrow summit areas.

Aim To test predictions of different large-scale biodiversity hypotheses by analysing species richness patterns of vascular plants in the Austrian Alps. Location The Austrian part of the Alps (c. 53,500 km2). Methods Within the floristic inventory of Central Europe the Austrian part of the Alps were systematically mapped for vascular plants. Data collection was based on a rectangular grid of 5 x 3 arc minutes (34-35 km2). Emerging species richness patterns were correlated with several environmental factors using generalized linear models. Primary environmental variables like temperature, precipitation and evapotranspiration were used to test climate-related hypotheses of species richness. Additionally, spatial and temporal variations in climatic conditions were considered. Bedrock geology, particularly the amount of calcareous substrates, the proximity to rivers and lakes and secondary variables like topographic, edaphic and land-use heterogeneity were used as additional predictors. Model results were evaluated by correlating modelled and observed species numbers. Results Our final multiple regression model explains c. 50% of the variance in species richness patterns. Model evaluation results in a correlation coefficient of 0.64 between modelled and observed species numbers in an independent test data set. Climatic variables like temperature and potential evapotranspiration (PET) proved to be by far the most important predictors. In general, variables indicating climatic favourableness like the maxima of temperature and PET performed better than those indicating stress, like the respective minima. Bedrock mineralogy, especially the amount of calcareous substrate, had some additional explanatory power but was less influential than suggested by comparable studies. The amount of precipitation does not have any effect on species richness regionally. Among the descriptors of heterogeneity, edaphic and land-use heterogeneity are more closely correlated with species numbers than topographic heterogeneity. Main conclusions The results support energy-driven processes as primary determinants of vascular plant species richness in temperate mountains. Stressful conditions obviously decrease species numbers, but presence of favourable habitats has higher predictive power in the context of species richness modelling. The importance of precipitation for driving global species diversity patterns is not necessarily reflected regionally. Annual range of temperature, an indicator of shortterm climatic stability, proved to be of minor importance for the determination of regional species richness patterns. In general, our study suggests environmental heterogeneity to be of rather low predictive value for species richness patterns regionally. However, it may gain importance at more local scales.

Background For assessing the risk of escape of transgenes from cultivation, the persistence of feral populations of crop plants is an important aspect. Feral populations of oilseed rape, Brassica napus , are well known, but only scarce information is available on their population dynamics, particularly in Central Europe. To investigate genetic diversity, origin and persistence of feral oilseed rape in Austria, we compared variation at nine polymorphic microsatellite loci in eight feral populations with 19 commercial varieties. Results Overall, commercial varieties and feral populations showed a similar pattern of genetic variation and a similar level of observed heterozygosity. The two groups, however, shared less than 50% of the alleles and no multilocus genotype. A significant among-group (commercial varieties versus feral populations) component of genetic variation was observed (AMOVA: F CT = 0.132). Pairwise comparisons between varieties and feral populations showed moderate to very high genetic differentiation ( F ST = 0.209 - 0.900). The software STRUCTURE also demonstrated a clear separation between commercial varieties and feral samples: out of 17 identified genetic clusters, only one comprised plants from both a commercial variety and feral sites. Conclusions The results suggest that feral oilseed rape is able to maintain persistent populations. The feral populations may have derived from older cultivars that were not included in our analyses or perhaps have already hybridised with related crops or wild relatives. Feral populations therefore have to be considered in ecological risk assessment and future coexistence measures as a potential hybridisation partner of transgenic oilseed rape.

Low temperatures and the short growing season in high altitude snow patches in temperate mountains constrain life cycles and reproduction of snowbed species. This leads to a highly adapted timing of sexual reproduction. Winter precipitation and temperature, the main factors determining growing season length, are predicted to change with global warming. To understand their impacts on plant phenology, we studied the responses of seven alpine vascular plant species during 2001. Temperature had a clear impact on phenological patterns. The start of the reproductive development was not directly linked with the date of snowmelt, but rather with the cumulative energy input. In addition, photoperiodism may also contribute to the control of plant development through an increasing temporal adjustment of phenology until flowering.