Esther R. Frei

WSL Institute for Snow and Avalanche Research SLF

Understanding the dynamics of treeline ecotones under global change requires long-term ecological and environmental data. The Stillberg ecological treeline research site in the Swiss Alps was established in 1975 by planting 92,000 seedlings of Larix decidua, Pinus cembra and Pinus mugo ssp. uncinata, and has been continuously monitored since then....

Europe’s semi-natural grasslands support notably high levels of temperate biodiversity across multiple taxonomic groups. However, these ecosystems face unique conservation challenges. Contemporary agricultural practices have replaced historical traditional low-intensity agriculture in many regions, resulting in a spectrum of management intensities...

A warmer climate with drier summers will affect the suitability of tree species in their current range in most of Europe. To preserve ecosystem services in the future, many European countries are looking for tree species adapted to the expected future climate and are setting up trials to test them in different environments. In collaboration with fo...

Sustainable regeneration of silver fir (Abies alba Mill.) is important for maintaining and improving the future resilience and protective capacity of mountain forests in the southern Swiss Alps. However, increasing densities of wild ungulates, such as red and roe deer, can hamper the regeneration success of silver fir. A comprehensive understanding...

Aim Arctic plants survived the Pleistocene glaciations in unglaciated refugia. The number, ages, and locations of these refugia are often unclear. We use high‐resolution genomic data from present‐day and Little‐Ice‐Age populations of Arctic Bell‐Heather to re‐evaluate the biogeography of this species and determine whether it had multiple independen...

Extreme droughts can have long‐lasting effects on forest community dynamics and species interactions. Yet, our understanding of how drought legacy modulates ecological relationships is just unfolding. We tested the hypothesis that leaf chemistry and herbivory show long‐term responses to premature defoliation caused by an extreme drought event in Eu...

The record-breaking drought in 2018 caused premature leaf discoloration and shedding (early browning) in many beech (Fagus sylvatica L.) dominated forests in Central Europe. However, a high degree of variability in drought response among individual beech trees was observed. While some trees were severely impacted by the prolonged water deficits and...

Aim: Arctic plants survived the Pleistocene glaciations in unglaciated refugia, but the number of these refugia is often unclear. We use high-resolution genomic data from present-day and Little-Ice-Age populations of Arctic White Heather (Cassiope tetragona) to re-evaluate the biogeography of this species and determine whether it had multiple indep...

Climate change is leading to species redistributions. In the tundra biome, shrubs are generally expanding, but not all tundra shrub species will benefit from warming. Winner and loser species, and the characteristics that may determine success or failure, have not yet been fully identified. Here, we investigate whether past abundance changes, curre...

Alpine treeline ecosystems are generally expected to advance with increasing temperatures and after land-use abandonment. Multiple interacting factors modify this trend. Understanding the long-term processes underlying treeline advance is essential to predict future changes in structure and function of mountain ecosystems. In a valley in the Centra...

Climate change is leading to a species redistributions. In the tundra biome, many shrub species are expanding into new areas, a process known as shrubification. However, not all tundra shrub species will benefit from warming. Winner and loser species (those projected to expand and contract their ranges, and/or those that have increased or decreased...

During the particularly severe hot summer drought in 2018, widespread premature leaf senescence was observed in several broadleaved tree species in Central Europe, particularly in European beech ( Fagus sylvatica L.). For beech, it is yet unknown whether the drought evoked a decline towards tree mortality or whether trees can recover in the longer...

Im Rahmen der fortschreitenden Klimaerwärmung verdunsten Pflanzen im Sommer immer mehr Wasser, das sie aus dem Boden saugen. Während extremer Dürreperioden nimmt das pflanzenverfügbare Wasser im Boden stark ab, und je nach Bodenwasserverfügbarkeit können Welkeprozesse einsetzen.

Die extreme Sommerdürre 2018 verursachte bei der Buche in der Nordschweiz verbreitet frühe Blattverfärbungen und vorzeitigen Laubfall. Eine WSL-Studie untersuchte, wie sich der Kronenzustand von rund eintausend betroffenen Bäumen über vier Jahre entwickelte.

La sécheresse extrême de l’été 2018 a provoqué un brunissement et une chute précoce des feuilles du hêtre sur de vastes étendues du nord de la Suisse. Une étude du WSL a analysé l’évolution sur quatre ans de l’état des couronnes d’un millier d’arbres touchés.

Ongoing climate warming is increasing evapotranspiration, a process that reduces plant-available water and aggravates the impact of extreme droughts during the growing season. Such an exceptional hot drought occurred in Central Europe in 2018 and caused widespread defoliation in mid-summer in European beech (Fagus sylvatica L.) forests. Here, we re...

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we...

Snow is an important driver of ecosystem processes in cold biomes. Snow accumulation determines ground temperature, light conditions and moisture availability during winter. It also affects the growing season’s start and end, and plant access to moisture and nutrients. Here, we review the current knowledge of the snow cover’s role for vegetation, p...

Snow is an important driver of ecosystem processes in cold biomes. Snow accumulation determines ground temperature, light conditions, and moisture availability during winter. It also affects the growing season’s start and end, and plant access to moisture and nutrients. Here, we review the current knowledge of the snow cover’s role for vegetation,...

Douglas fir (Pseudotsuga menziesii) has regenerated naturally in European forests since the middle of the 20th century. Some cases of an invasive character of the species have been reported under specific site conditions, but systematic data on the extent of natural regeneration and spread of Douglas fir across different forest communities are larg...

Arctic regions are particularly affected by rapidly rising temperatures and altered snow regimes. Snowmelt timing depends on spring temperatures and winter snow accumulation. Scenarios for the Arctic include both decreases and increases in snow accumulation. Predictions of future snowmelt timing are, thus, difficult and experimental evidence for ec...

The low reproductive success of Arctic plants is predicted to increase as the climate warms. However, climate extremes add complexity to these predictions. In the extremely cold year of 2018, multiple Arctic trophic levels experienced reproductive failure. We analysed a unique long-term record of seed viability from experimentally warmed and ambien...

Observations of changes in phenology have provided some of the strongest signals of the effects of climate change on terrestrial ecosystems. The International Tundra Experiment (ITEX), initiated in the early 1990s, established a common protocol to measure plant phenology in tundra study areas across the globe. Today, this valuable collection of phe...

Research in environmental science relies heavily on global climatic grids derived from estimates of air temperature at around 2 meter above ground1-3. These climatic grids however fail to reflect conditions near and below the soil surface, where critical ecosystem functions such as soil carbon storage are controlled and most biodiversity resides4-8...

Douglasiensämlinge im Wettstreit mit mittel-europäischen Baumarten In der Vergangenheit wurde die Douglasie (Pseudotsuga menziesii) in der Schweiz vorzugsweise auf mässig feuchten, produktiven Waldstandorten angebaut. Im Hinblick auf den Klimawandel dürfte sie als Zukunftsbaumart jedoch vermehrt auch auf trockeneren Standorten gepflanzt werden. Um...

Ausbreitungstendenzen und Konkurrenzkraft der Douglasie in der Schweiz Die Douglasie verjüngt sich in Europa seit Mitte des 20. Jahrhunderts auf natürliche Weise. Würde sie einheimische Arten verdrängen, müsste sie als invasiv bezeichnet und entsprechend behandelt werden. Da empirische Daten über das effektive Ausmass der natürlichen Verjüngung und...

The majority of variation in six traits critical to the growth, survival and reproduction of plant species is thought to be organised along just two dimensions, corresponding to strategies of plant size and resource acquisition. However, it is unknown whether global plant trait rela- tionships extend to climatic extremes, and if these interspecific...

Temperature manipulation experiments are an effective way for testing plant responses to future climate conditions, especially for predicting shifts in plant phenological events. While passive warming techniques are widely used to elevate temperature in low stature plant communities, active warming has been applied less frequently due to the associ...

Current analyses and predictions of spatially‐explicit patterns and processes in ecology most often rely on climate data interpolated from standardized weather stations. This interpolated climate data represents long‐term average thermal conditions at coarse spatial resolutions only. Hence, many climate‐forcing factors that operate at fine spatiote...

The majority of variation in six traits critical to the growth, survival and reproduction of plant species is thought to be organised along just two dimensions, corresponding to strategies of plant size and resource acquisition. However, it is unknown whether global plant trait relationships extend to climatic extremes, and if these interspecific r...

Aim Plant functional groups are widely used in community ecology and earth system modelling to describe trait variation within and across plant communities. However, this approach rests on the assumption that functional groups explain a large proportion of trait variation among species. We test whether four commonly used plant functional groups rep...

Motivation: The Tundra Trait Team (TTT) database includes field‐based measurements of key traits related to plant form and function at multiple sites across the tundra biome. This dataset can be used to address theoretical questions about plant strategy and trade‐offs, trait–environment relationships and environmental filtering, and trait variation...

Höhere Temperaturen und trockenere Sommer führen dazu, dass sich die für die Baumarten geeigneten Standorte in höhere Lagen verschieben. Dabei stellt sich konkret die Frage, welche der Baumarten, die gegen Ende des 21. Jahrhunderts auf einem Standort als geeignet gelten, bereits heute dort gedeihen können. Durch den gemeinsamen Einsatz von kantonal...

The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem...

Treeline responses to climate change ultimately depend on successful seedling recruitment, which requires dispersal of viable seeds and establishment of individual propagules in novel environments. In this study, we evaluated the effects of several abiotic and biotic drivers of early tree seedling recruitment across an alpine treeline ecotone. In t...

Rapidly rising temperatures are expected to cause latitudinal and elevational range shifts as species track their optimal climate north and upward. However, a lack of adaptation to environmental conditions other than climate - for example photoperiod, biotic interactions, or edaphic conditions - might limit the success of immigrants in a new locati...

Mountain plant species with wide elevational ranges are expected to be exposed to different selection pressures at low and high elevation. Estimating the extent of genetic population differentiation contributes to our understanding of selective forces shaping phenotypic variation of plants in response to changing climate conditions. Using a common...

Local persistence of plant species in the face of climate change is largely mediated by genetic adaptation and phenotypic plasticity. In species with a wide altitudinal range, population responses to global warming are likely to differ at contrasting elevations. In controlled climate chambers, we investigated the responses of low and high elevation...

Mountain ecosystems are particularly susceptible to climate change. Characterizing intraspecific variation of alpine plants along elevational gradients is crucial for estimating their vulnerability to predicted changes. Environmental conditions vary with elevation, which might influence plastic responses and affect selection pressures that lead to...

Mountain ecosystems can exert different selection pressures on plant populations over small scales due to steep environmental gradients. Gene flow between lower‐ and higher‐elevation plant populations could lead to the increased integration of potentially adaptive genes and thereby to outbreeding vigour under current rapid climatic changes. Alterna...

Sound absorption of snow was measured for test specimens with porosities in the range from 46% to approximately 90% in an impedance tube at frequencies between 125 Hz and 1.6 kHz. In addition, the geometrical structure of the same samples was determined by X-ray microtomography. This novel experimental combination is to provide a reliable basis for...

Environmental gradients caused by altitudinal gradients may affect genetic variation within and among plant populations and inbreeding within populations. Populations in the upper range periphery of a species may be important source populations for range shifts to higher altitude in response to climate change. In this study we investigate patterns...

PCoA plots of Nei’s Distances among populations in a) Briza media, b) Trifolium montanum and c) Ranunculus bulbosus. Populations within the same location are connected by dashed lines. (TIF)

Estimates of total area [m2] of semi dry grasslands between 100 and 2000 m a.s.l. in Switzerland, based on the Swiss national inventory of dry grasslands (TWW). (TIF)

Isolation by distance relationships between pairwise genetic ( F ST) and geographic distances among populations at the same altitudinal level (red = at 1200 m a.s.l.; blue = at 1800 m a.s.l.) and among different altitudinal levels (green = among 1200 and 1800 m a.s.l.) in A) Briza media , B) Trifolium montanum and C) Ranunculus bulbosus...

AFLP genotyping protocol. (DOCX)

Population abbreviation (Code), number of sampled individuals per population (n), geographic coordinates (WGS84), altitude, area of grassland patch [m2], percentage of polymorphic loci (PPL), expected heterozygosity (He), average pairwise FST per population (FST.overall), average inbreeding coefficient per population (fAFLP), and average relatednes...

Background: Plants occupying wide altitudinal gradients may be adapted to their altitude of origin. Upward expansion of lowland populations in response to climate change might therefore facilitate species persistence at higher elevations by introducing pre-adapted genes.Aim: We compared plant growth and fitness in Scabiosa columbaria originating fr...

Species from many different habitats are responding to recent climate change. Mountainous areas are of particular interest as they provide pronounced gradients and have experienced above-average temperature increases. Data from the beginning of the 20th century of both the upper and lower range limits of plants of the European Alps were updated a c...

Visualization and quantification of snow structures at a scale of a few millimetres is important in understanding the mechanical, thermal and electromagnetic properties of snow. Surface sections and, to an even greater degree, three-dimensional (3-D) reconstructions of cast snow samples are difficult to prepare, and automatic image processing is no...

During the summers of 2004 and 2005, the mountain flora of Piz Languard (3262 m a.s.l.) near Pontresina (Switzerland) was monitored and compared to the inventories from the years 1905, 1907, 1941, 1985 and 2003. The occurrence of flowering plants above 3000 m has been recorded with a standard deviation of ± 10 m. Trends, detected in earlier years,...