Phenology, growth, and fecundity of eight subarctic tundra species in response to snowmelt manipulations

The snow cover extent is an important factor for the structure and composition of arctic and alpine tundra communities. Over the last few decades, snowmelt in many arctic and alpine regions has advanced, causing the growing season to start earlier and last longer. In a field experiment in subarctic tundra in Interior Alaska, I manipulated the timing of snowmelt and measured the response in mortality, phenology, growth, and reproduction of the eight dominant plant species. I then tested whether the phenological development of these species was controlled by snowmelt date or by temperature (in particular growing degree days, GDD). In order to expand our understanding of plant sensitivity to snowmelt timing, I explored whether the response patterns can be generalized with regard to the temporal niche of each species. Differences in the phenology between treatments were only found for the first stages of the phenological development (=phenophases). The earlier the temporal niche (i.e., the sooner after snowmelt a species develops) the more its phenology was sensitive to snowmelt. Later phenophases were mostly controlled by GDD, especially in late-developing species. In no species did an earlier snowmelt and a longer growing season directly enhance plant fitness or fecundity, in spite of the changes in the timing of plant development. In conclusion, the temporal niche of a species' phenological development could be a predictor of its response to snowmelt timing. However, only the first phenophases were susceptible to changes in snowmelt, and no short-term effects on plant fitness were foun

Winter climate change in alpine tundra: plant responses to changes in snow depth and snowmelt timing

Snow is an important environmental factor in alpine ecosystems, which influences plant phenology, growth and species composition in various ways. With current climate warming, the snow-to-rain ratio is decreasing, and the timing of snowmelt advancing. In a 2-year field experiment above treeline in the Swiss Alps, we investigated how a substantial decrease in snow depth and an earlier snowmelt affect plant phenology, growth, and reproduction of the four most abundant dwarf-shrub species in an alpine tundra community. By advancing the timing when plants started their growing season and thus lost their winter frost hardiness, earlier snowmelt also changed the number of low-temperature events they experienced while frost sensitive. This seemed to outweigh the positive effects of a longer growing season and hence, aboveground growth was reduced after advanced snowmelt in three of the four species studied. Only Loiseleuria procumbens, a specialist of wind exposed sites with little snow, benefited from an advanced snowmelt. We conclude that changes in the snow cover can have a wide range of species-specific effects on alpine tundra plants. Thus, changes in winter climate and snow cover characteristics should be taken into account when predicting climate change effects on alpine ecosystem

Resampling alpine herbarium records reveals changes in plant traits over space and time

Acknowledgements This project would not have been possible without the support and enthusiasm of the staff at herbaria around Switzerland (herbaria of University and ETH Zurich, Universities of Basel and Neuchatel, and Museum of Natural History Chur), in particular Hugo Berger, for which we would like to say thanks. We would also like to thank Rachel Imboden, Samuel Stolz, Aino Kulonen, Adrien Gaudard, Louis Quéno, Amy MacFarlane, Ueli Schmid, Lorna Holl and Pirmin Ebner for their invaluable help in the field and in the labPeer reviewedPublisher PD

Dimension and impact of biases in funding for species and habitat conservation

Taxonomic and aesthetic biases permeate biodiversity conservation. We used the LIFE program-the European Union's funding scheme for the environment-to explore the economic dimension of biases in species-and habitat-level conservation. Between 1992 and 2020, animal species received three times more funding than plants. Within plants, species at northern latitudes, with broader ranges, and with blue/purple flowers received more funds regardless of their extinction risk. Conversely, species online popularity was only weakly positively associated with conservation expenditure. At the habitat-level, we found no relationship between expenditure and conservation status of the habitat. Our results can inform ways forward to achieve conservation goals that are comprehensive, sustainable, and cost-effective.Peer reviewe

Boost in Visitor Numbers Post COVID-19 Shutdown: Consequences for an Alpine National Park

The coronavirus disease 2019 (COVID-19) pandemic changed recreation patterns worldwide. Increases in protected areas' visitor numbers were reported along with associated challenges. Changes in visitor numbers, composition, and motivation remain mostly unrecorded due to a lack of baseline records for comparison. We aimed to fill this gap with a study in the Swiss National Park (SNP), an International Union for Conservation of Nature (IUCN) strict nature reserve in the European Alps, where visitor numbers strongly increased in 2020 and 2021 compared to previous years. In summer 2020, we repeated a visitor survey previously conducted in 2006 and 2012, complemented by assessments of COVID-19-related motivations. To deepen our understanding of the COVID-19 context, we conducted semistructured interviews with SNP visitors. In general, COVID-19-related factors were a strong driver of increased visitor numbers. A fifth of survey respondents indicated that they would not have visited the SNP but for the pandemic, with most of them being first-time or infrequent visitors. Furthermore, our data showed that more young, domestic, and less experienced visitors came to the park. We discuss impacts and implications for practitioners and researchers (ie the need to better sensitize newcomers to environmental issues) and argue that our study holds insights for park managers worldwide

Short-term responses of ecosystem carbon fluxes to experimental soil warming at the Swiss alpine treeline

Climatic warming will probably have particularly large impacts on carbon fluxes in high altitude and latitude ecosystems due to their great stocks of labile soil C and high temperature sensitivity. At the alpine treeline, we experimentally warmed undisturbed soils by 4K for one growing season with heating cables at the soil surface and measured the response of net C uptake by plants, of soil respiration, and of leaching of dissolved organic carbon (DOC). Soil warming increased soil CO2 effluxes instantaneously and throughout the whole vegetation period (+45%; +120gCmy−1). In contrast, DOC leaching showed a negligible response of a 5% increase (NS). Annual C uptake of new shoots was not significantly affected by elevated soil temperatures, with a 17, 12, and 14% increase for larch, pine, and dwarf shrubs, respectively, resulting in an overall increase in net C uptake by plants of 20-40gCm−2y−1. The Q 10 of 3.0 measured for soil respiration did not change compared to a 3-year period before the warming treatment started, suggesting little impact of warming-induced lower soil moisture (−15% relative decrease) or increased soil C losses. The fraction of recent plant-derived C in soil respired CO2 from warmed soils was smaller than that from control soils (25 vs. 40% of total C respired), which implies that the warming-induced increase in soil CO2 efflux resulted mainly from mineralization of older SOM rather than from stimulated root respiration. In summary, one season of 4K soil warming, representative of hot years, led to C losses from the studied alpine treeline ecosystem by increasing SOM decomposition more than C gains through plant growt

Climate change affects vegetation differently on siliceous and calcareous summits of the European Alps

The alpine life zone is expected to undergo major changes with ongoing climate change. While an increase of plant species richness on mountain summits has generally been found, competitive displacement may result in the long term. Here, we explore how species richness and surface cover types (vascular plants, litter, bare ground, scree and rock) changed over time on different bedrocks on summits of the European Alps. We focus on how species richness and turnover (new and lost species) depended on the density of existing vegetation, namely vascular plant cover. We analyzed permanent plots (1 x 1 m) in each cardinal direction on 24 summits (24 x 4 x 4), with always four summits distributed along elevation gradients in each of six regions (three siliceous, three calcareous) across the European Alps. Mean summer temperatures derived from downscaled climate data increased synchronously over the past 30 years in all six regions. During the investigated 14 years, vascular plant cover decreased on siliceous bedrock, coupled with an increase in litter, and it marginally increased on higher calcareous summits. Species richness showed a unimodal relationship with vascular plant cover. Richness increased over time on siliceous bedrock but slightly decreased on calcareous bedrock due to losses in plots with high plant cover. Our analyses suggest contrasting and complex processes on siliceous versus calcareous summits in the European Alps. The unimodal richness-cover relationship and species losses at high plant cover suggest competition as a driver for vegetation change on alpine summits