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The water level of Lake Neuchâtel (Switzerland) was lowered 150 years ago, initiating soil formation and colonization by riparian forests of the previously submerged areas. Although the soils of the whole area are young and have probably quite similar parent material (lacustrine sediments and moraine), the present soils show a large diversity of horizon structures and contents. The aim of this study is to describe the respective processes of accumulation, integration, and stabilization of organic matter and assess the soil variables influenced by these processes in the various types of riparian forests with different moisture levels. The investigation employed a semi-quantitative, holistic approach that combined field observations, laboratory analyses, and micromorphological examination of soil thin sections. The results indicate that the accumulation and stabilization of organic matter are primarily governed by physicochemical factors associated with the parent material, particularly soil texture and calcium cation saturation. Soil moisture and groundwater elevation were found to mainly influence biological activity and vegetation types. Additionally, the incorporation of organic matter is affected by both soil texture and bioturbation processes. Overall, this study underscores the complexity of the mechanisms regulating organic matter dynamics in young soils.

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.

While the upward shift of plant species has been observed on many alpine and nival summits, the reaction of the subalpine and lower alpine plant communities to the current warming and lower snow precipitation has been little investigated so far. To this aim, 63 old, exhaustive plant inventories, distributed along a subalpine–alpine elevation gradient of the Swiss Alps and covering different plant community types (acidic and calcareous grasslands; windy ridges; snowbeds), were revisited after 25–50 years. Old and recent inventories were compared in terms of species diversity with Simpson diversity and Bray–Curtis dissimilarity indices, and in terms of community composition with principal component analysis. Changes in ecological conditions were inferred from the ecological indicator values. The alpha‐diversity increased in every plant community, likely because of the arrival of new species. As observed on mountain summits, the new species led to a homogenization of community compositions. The grasslands were quite stable in terms of species composition, whatever the bedrock type. Indeed, the newly arrived species were part of the typical species pool of the colonized community. In contrast, snowbed communities showed pronounced vegetation changes and a clear shift toward dryer conditions and shorter snow cover, evidenced by their colonization by species from surrounding grasslands. Longer growing seasons allow alpine grassland species, which are taller and hence more competitive, to colonize the snowbeds. This study showed that subalpine–alpine plant communities reacted differently to the ongoing climate changes. Lower snow/rain ratio and longer growing seasons seem to have a higher impact than warming, at least on plant communities dependent on long snow cover. Consequently, they are the most vulnerable to climate change and their persistence in the near future is seriously threatened. Subalpine and alpine grasslands are more stable, and, until now, they do not seem to be affected by a warmer climate. Mountain regions are warming rapidly, and the upward shift of plant species has been observed on many alpine and nival summits. In this study, we address the following question: Are there observable changes also at lower elevations in the subalpine–alpine vegetation? Revisiting 67 old, exhaustive plant inventories in the Swiss Alps after 25–50 years, we show that the magnitude and direction of changes varied across the different plant communities: grasslands were quite stable in terms of plant community composition while snowbeds showed pronounced vegetation changes corresponding to the colonisation of species from surrounding grasslands.

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.

Since the late 1990s, Nature’s Contributions to People (NCPs; i.e. ecosystem services) were used as a putative leverage for fostering nature preservation. NCPs have largely been defined and mapped at the landscape level using land use and cover classifications. However, NCP mapping attempts based directly on individual species are still uncommon. Given that species shape ecosystems and ultimately deliver NCPs, mapping NCPs based on species distribution data should deliver highly meaningful results. This requires first establishing a census of the species-to-NCP relationships. However, datasets quantifying these relationships across several species and NCPs are rare. Here, we fill this gap by compiling literature and expert knowledge to establish the relationships of 1816 tracheophyte and 250 vertebrate species with 17 NCPs in the Swiss Alps. We illustrated the 31,098 identified species-NCP relationships for the two lineages and discuss why such a table is a key initial step in building spatial predictions of NCPs directly from species data, e.g. to ultimately complement spatial conservation planning.

Ecological gradients shape the evolution of plant functional traits through variation in climate, abiotic factors, and biological processes. While recent observations highlight elevation clines in functional trait variation, several traits vary independently of others and vary in species-specific manner, thereby hindering community-level generalization. In this study, we examined whether whole plant communities at different elevations independently converge to elevation-specific trait values. Using a combination of field-derived trait quantification and a literature survey, we analyzed eight functional traits relating to plant palatability [specific leaf area (SLA), leaf dry matter content, carbon-to-nitrogen ratio], and defenses (spines, trichomes, silica, and the relative importance of phenolic- or non-phenolic-based chemical defenses in plants) of plants growing along several mountain transects in Switzerland, and computed community-level means for each trait. We observed a general decline of most defense traits in communities at high elevations. The individual traits' patterns underlined a concerted decline of the physico-chemical defense syndrome at high elevation, and low SLA values at high elevation also indicate investment in the production of leaves with slow turnover rates. In addition, we found that high-elevation plant trait values tend to converge, while at low elevation, to diverge within communities. Our data suggest that community-level defense syndromes along elevation gradients are influenced by ecological filtering. Lower herbivore pressures select for reduced plant defenses, while harsh environmental conditions select for investment in tolerance-related traits. Secondly, since species are highly variable in their functional trait space within communities, niche-partitioning theory might explain which variabilities of the defense functional space are selected within communities, particularly at low elevation.

Using information on current species distributions and dispersal traits, this study forecasts climate-driven range dynamics of plant species across the European Alps. Simulations predict moderate range contractions over the twenty-first century; however, more severe effects of climate warming on mountain plant diversity are expected in the longer term. Quantitative estimates of the range loss of mountain plants under climate change have so far mostly relied on static geographical projections of species’ habitat shifts 1 , 2 , 3 . Here, we use a hybrid model 4 that combines such projections with simulations of demography and seed dispersal to forecast the climate-driven spatio-temporal dynamics of 150 high-mountain plant species across the European Alps. This model predicts average range size reductions of 44–50% by the end of the twenty-first century, which is similar to projections from the most ‘optimistic’ static model (49%). However, the hybrid model also indicates that population dynamics will lag behind climatic trends and that an average of 40% of the range still occupied at the end of the twenty-first century will have become climatically unsuitable for the respective species, creating an extinction debt 5 , 6 . Alarmingly, species endemic to the Alps seem to face the highest range losses. These results caution against optimistic conclusions from moderate range size reductions observed during the twenty-first century as they are likely to belie more severe longer-term effects of climate warming on mountain plants.

The relationship between species’ niche breadth (i.e. the range of environmental conditions under which a species can persist) and range size (i.e. the extent of its spatial distribution) has mostly been tested within geographically restricted areas but rarely at the global extent. Here, we not only tested the relationship between range size (derived from species’ distribution data) and niche breadth (derived from species’ distribution and co‐occurrence data) of 1255 plant species at the regional extent of the European Alps, but also at the global extent and across both spatial scales for a subset of 180 species. Using correlation analyses, linear models and variation partitioning, we found that species’ realized niche breadth estimated at the regional level is a weak predictor of species’ global niche breadth and range size. Against our expectations, distribution‐derived niche breadth was a better predictor for species’ range size than the co‐occurrence‐based estimate, which should, theoretically, account for more than the climatically determined niche dimensions. Our findings highlight that studies focusing on the niche breadth vs range size relationship must explicitly consider spatial mismatches that might have confounded and diminished previously reported relationships.

Upward migration of plant species due to climate change has become evident in several European mountain ranges. It is still, however, unclear whether certain plant traits increase the probability that a species will colonize mountain summits or vanish, and whether these traits differ with elevation. Here, we used data from a repeat survey of the occurrence of plant species on 120 summits, ranging from 2449 to 3418 m asl, in south-eastern Switzerland to identify plant traits that increase the probability of colonization or extinction in the 20th century. Species numbers increased across all plant traits considered. With some traits, however, numbers increased proportionally more. The most successful colonizers seemed to prefer warmer temperatures and well-developed soils. They produced achene fruits and/or seeds with pappus appendages. Conversely, cushion plants and species with capsule fruits were less efficient as colonizers. Observed changes in traits along the elevation gradient mainly corresponded to the natural distribution of traits. Extinctions did not seem to be clearly related to any trait. Our study showed that plant traits varied along both temporal and elevational gradients. While seeds with pappus seemed to be advantageous for colonization, most of the trait changes also mirrored previous gradients of traits along elevation and hence illustrated the general upward migration of plant species. An understanding of the trait characteristics of colonizing species is crucial for predicting future changes in mountain vegetation under climate change.