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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.

The reasons why some species occur widespread, while related species have restricted geographical ranges have been attributed to habitat specialization or ecological niche breadth. For species in the genus Saxifraga , habitat specialization alone cannot explain the distributional differences observed. We hypothesize that recruitment traits (i.e., germination, emergence, and survival) may account for differences in geographical ranges and that early life stages correlate to survival. We studied recruitment responses in 13 widespread and 12 narrow-ranged Saxifraga species in the laboratory and common garden experiments using seeds collected from 79 populations in the European Alps. We found that in the laboratory cold temperature led to higher germination percentages compared with warm temperature for both distribution groups. This represents an exception to the general assumption that alpine species require warm cues for germination. In warm laboratory temperatures, widespread species germinated better than narrow-ranged species, indicating a greater tolerance of warm temperatures for the former. Subsequent to germination, recruitment traits between the two distribution groups were lower or null in the common garden, suggesting that the impact of recruitment on species’ geographical ranges occurs at the earliest life stage. Mean time to emergence of narrow-ranged species showed lower variability than that of widespread species. Consistently, intraspecific variation of mean annual temperatures between seed collection sites was lower for narrow-ranged species, indicating a close relationship between home sites and emergence time. Emergence percentage was a strong predictor of survival only for widespread species, underlining that seed and seedling functional traits differ between distribution groups, which require further research. Our results support the view that early life stages are critical to population dynamics and thus can influence species’ geographical ranges. The wider responses to climatic conditions in widespread species may have facilitated their spread across the Alps. Our results also suggest that all Saxifraga species face a considerable threat from climate warming due to their overall cold-adapted recruitment niche.

Satellite-based long-term observations of vegetation cover development in combination with recent in-situ observations provide a basis to better understand the spatio-temporal changes of vegetation patterns, their sensitivity to climate drivers and thus climatic impact on proglacial landscape development. In this study we combined field investigations in the glacier forelands of Fürkele-, Zufall- and Langenferner (Ortles-Cevedale group/Eastern Italian Alps) with four different Vegetation Indices (VI) from Landsat scenes in order to test the suitability for modelling an area-wide vegetation cover map by using a Bayesian beta regression model (RStan). Since the model with the Normalized Difference Vegetation Index (NDVI) as predictor showed the best results, it was used to calculate a vegetation cover time series (1986–2019). The alteration of the proglacial areas since the end of the Little Ice Age (LIA) was analyzed from digital elevation models based on Airborne Laser Scanning (ALS) data and areal images, orthophotos, historical maps and field mapping campaigns. Our results show that a massive glacier retreat with an area loss of 8.1 km2 (56.9%; LIA–2019) resulted in a constant enlargement of the glacier forelands, which has a statistically significant impact on the degree of vegetation cover. The area covered by vegetation increased from 0.25 km2 (5.6%) in 1986 to 0.90 km2 (11.2%) in 2019 with a significant acceleration of the mean annual changing rate. As patterns of both densification processes and plant colonization at higher elevations can be reflected by the model results, we consider in-situ observations combined with NDVI time series to be powerful tools for monitoring vegetation cover changes in alpine proglacial areas.

Questions: What are the colonization trends in vegetated vs. bare-ground plots over a 10-year period in a central Alpine glacier foreland? What are the long-term effects of artificial seed addition to these plots? Location: Glacier foreland of the Rotmoosferner in the Central Alps, Obergurgl, Tyrol, Austria, 2380 – 2400 m a.s.l. Methods: A total of 40 permanent plots were established on moraines ice-free for 35 and 50 years on vegetated and bare-ground areas. Half of them were treated with a seed mixture in 1996 and 1997. Number and cover of the species were recorded in 1996 and from 2002/2003 to 2006. Results: Species richness doubled in the control plots and tripled in seeded plots on the 35-year-ice-free moraine. On the 50-year-ice-free moraine the increase in species number was more modest. Significant site, seeding and time effects were found. Seed addition had no effects in the bare-ground plots on the older moraine and low effects in those on the younger moraine. All plots showed significant changes in cover of single species. The pioneer species decreased significantly in both moraines, in the control as well as in the seeded plots. A disappearance during the next years is predicted. Conclusions: Colonization in bare-ground plots is limited by a lack of safe sites, whereas vegetated plots facilitate recruitment and establishment. Colonization on the glacier foreland is also dispersal limited. Seed addition enhanced the presence of already established species, and late successional species were newly introduced. Nomenclature: Fischer et al. (2005).

Temperature and drought effects on germination were explored by comparing species from above and below the treeline of the Central Alps. This study should enhance the understanding of species recruitment under changing environmental conditions. The timing of germination, final germination percentage, and optimum temperature of 14 congeneric species pairs were investigated. We hypothesized that (i) temperature will affect the timing of germination, with species above the treeline having a more rapid germination time; (ii) final germination percentage (FGP) will be generally enhanced by higher temperatures; (iii) species below the treeline will have wider temperature ranges and will be more adapted to drought; (iv) species above the treeline will have higher optimum temperatures of germination, and (v) seed mass will affect the germination rates. Germination experiments were carried out using alternating temperature regimes (25°/10 °C, 20°/10 °C, 15°/5 °C) and decreasing water potentials (–0.3, –0.6, –0.9 MPa), generated using polyethylene glycol. Temperature significantly affected the timing and FGP; species above the treeline exhibited a delayed timing at lower temperatures and a generally lower FGP at all temperature regimes in contrast to their congeners below the treeline. The optimum germination temperatures were significantly higher for species above the treeline. Five of 28 species did not germinate at all. Drought generally affected all species; however, the negative response of the species above the treeline was more pronounced. The seed mass did not affect the FGP. We conclude that the germination traits of the species above the treeline may have major disadvantages in a changing climate, resulting in a weaker performance and delayed growth, whereas the species below the treeline may be considered pre-adapted for potential migration to higher altitudes.

Safeguarding plants as seeds in ex situ collections is a cost effective element in an integrated plant conservation approach. The European Alps are a regional centre of plant diversity. Six institutions have established a regional network covering the European Alps which will conserve at least 500 priority plant species and which will improve the conservation status of plant species in grassland communities in the subalpine, alpine and nival altitudinal belts. Targeted research will expand the knowledge of the ecology of target speeies. Public engagement activities will raise the awareness for the importance of specific conservation actions in the European Alps.

Globally accelerating trends in societal development and human environmental impacts since the mid-twentieth century 1 – 7 are known as the Great Acceleration and have been discussed as a key indicator of the onset of the Anthropocene epoch 6 . While reports on ecological responses (for example, changes in species range or local extinctions) to the Great Acceleration are multiplying 8 , 9 , it is unknown whether such biotic responses are undergoing a similar acceleration over time. This knowledge gap stems from the limited availability of time series data on biodiversity changes across large temporal and geographical extents. Here we use a dataset of repeated plant surveys from 302 mountain summits across Europe, spanning 145 years of observation, to assess the temporal trajectory of mountain biodiversity changes as a globally coherent imprint of the Anthropocene. We find a continent-wide acceleration in the rate of increase in plant species richness, with five times as much species enrichment between 2007 and 2016 as fifty years ago, between 1957 and 1966. This acceleration is strikingly synchronized with accelerated global warming and is not linked to alternative global change drivers. The accelerating increases in species richness on mountain summits across this broad spatial extent demonstrate that acceleration in climate-induced biotic change is occurring even in remote places on Earth, with potentially far-ranging consequences not only for biodiversity, but also for ecosystem functioning and services. Analysis of changes in plant species richness on mountain summits over the past 145 years suggests that increased climatic warming has led to an acceleration in species richness increase.

Storing seeds in seed banks is an effective way to preserve plant diversity and conserve species. An essential step towards a valuable conservation is the validation of germination. This study presents a germination screening of seeds from 255 species of the European Eastern Alps, which were to be stored at the Millennium Seed Bank (Kew, UK). The final germination percentage (FGP) was determined using a standard protocol in the laboratory. Species were classified according to species rarity, plant community, occurrence at elevation belts, bedrock types, as well as CSR strategies, and further, seed mass was examined. We could not find statistically significant differences of FGP within these classes, but 74.9% of all tested species germinated using the standard protocol, and half of them had FGP ≥ 20.1–100%. A treatment with gibberellic acid enhanced the germination in half of the species to which this treatment was applied. Common families in alpine regions, i.e. Asteraceae, Poaceae and Saxifragaceae were highlighted in terms of their germination behaviour. The results provide an evaluation of the application of standard protocols to a broad Alpine species pool on the one hand, and on the other hand, provide ecological insights of the species tested. Germination is not only one of the most important events of the reproductive cycle of plants but could also be a key feature in species’ responses to changing environmental conditions.

On a glacier foreland of the Central Austrian Alps, a permanent plot study was performed to investigate the successional pathway on two moraines. We expected that the pioneer stage deglaciated for 25 years will converge to an early successional stage after another 25 years and the early stage deglaciated for 40 years will show trends toward a late successional stage. Different dynamics of species occurrence such as colonization/persistence and cover increase/decrease, were anticipated. Twenty plots of 25 × 25 cm were established in 1996 on each successional stage by selecting vegetated and bare ground plots to account for impacts of facilitation on seedling recruitment. We expected seed and establishment limitations, therefore, also effects of sowing were studied on sown and control plots. Species enrichment occurred on all control and sown plots of both stages. However, the pioneer stage did not converge to an early successional stage as it was expected. On the early successional stage, only on sown plots a development toward a late successional stage was found. Bryophyta were the most efficient colonizers on all plots together with the lichen Stereocaulon alpinum at the pioneer stage and the sown species Anthyllis vulneraria ssp. alpicola at the early successional stage. The pioneer species Saxifraga oppositifolia was still present after 25 years on the pioneer and early successional stages, although its cover significantly decreased. We conclude that seed and establishment limitations, drought, facilitation deficits, and ageing of individuals are the essential drivers on the studied glacier foreland, creating ‘quasi-stationary’ communities.