Swiss Federal Institute for Forest, Snow and Landscape Research WSL

Rationale Determining several isotope ratios in one analysis multiplies the information that can be retrieved from a sample in a cost‐efficient way. The stable isotope ratios of hydrogen (δ ² H), carbon (δ ¹³ C), and oxygen (δ ¹⁸ O) in organic compounds are highly relevant due to their complimentary hydroclimatic and physiological signals. Different types of organic material reflect different processes and integration times, like short term in leaf sugars and long term in tree ring cellulose, but currently, no simple method exists for their triple isotope analysis. Methods Here, we present a method that enables the isotopic analyses of the three elements H, C, and O in one run and is applicable to different types of carbohydrates and bulk organic matter. We discuss all steps required from water vapor equilibration necessary for obtaining reliable δ ² H values of carbon‐bound H to high‐temperature conversion (HTC) of the sample to CO and H 2 and to the mass‐spectrometric isotope‐ratio analysis. Results We show that reliable triple isotope analysis is possible for a large range of samples, although it results in some reduction of precision compared to individual isotope analysis. Important considerations are the equilibration procedure, the type of autosampler, selection of HTC reactor, the influence of nitrogen in the sample, the verification of δ ¹³ C values obtained by HTC versus combustion, and the selection of reference materials. Conclusions By presenting a relatively simple triple‐isotope method, we promote the use of multi‐isotope studies in environmental sciences, which helps in addressing many important climate and ecological research challenges that we face today.

Aims Mixed cropping systems such as intercropping and crop rotation have been proven to be sustainable agronomic tools that provide agro-ecological services and improve crop yield through soil physical, chemical and biological changes in the soil. In this study, we aimed to assess the impact of different mixed cropping systems on a crop well-adapted to high temperatures and low precipitation, like purslane (Portulaca oleracea L.) and to study the underlying microbial mechanisms involved. Methods A field experiment in a semiarid region of southern Spain was conducted to study the short-term effects of crop rotation (R) and intercropping (I) with peas or cowpeas, as well as a combination of both (IR) on purslane yield and soil quality parameters such as microbial enzymatic activity, bacterial diversity, microbial composition and functionality. Results All the tested treatments increased purslane yield without significant differences among each other, but only the R and IR treatments affected the rhizospheric soil properties, through the increase of the enzymatic activities and the modification of the bacterial composition and functionality, and promoted organic matter degrading bacteria such as Bacillaceae, Myxococcaceae, and Planococcaceae and nitrogen-fixing bacteria, mainly Rhizobiaceae and Beijerinckiaceae. Conclusion This study demonstrates how sustainable cropping practices may improve the yield of a low maintenance crop like purslane under low-maintenance conditions by improving soil fertility in semiarid areas and also provides insights into the biological mechanisms responsible for the recorded effects.

Phytophthora species are a cause for concern due to their invasive potential and the damage they can cause in agriculture, forestry, and natural ecosystems worldwide. Since water plays a crucial role in their dispersal, stream and river baiting is commonly used to survey risk areas for the presence of quarantine Phytophthora species. However, our understanding of the distribution and diversity of Phytophthora species in European watercourses remains incomplete. This study investigated the presence and diversity of Phytophthora species in Swiss watercourses, with a focus on the highly urbanized Swiss Plateau. Over the period 2012–2016, we sampled 32 watercourses, including major rivers and smaller streams. We isolated Phytophthora on selective media and sequenced the internal transcribed spacer region to identify the species. We recovered 241 Phytophthora isolates, representing 11 species from five major clades. Phytophthora clade 6 prevailed, with P. lacustris being the most common, found in 94.7% of the watercourses. The number of Phytophthora species per watercourse ranged from one to five, with no correlation to watercourse complexity. Our study reveals the presence of six previously unreported species in Switzerland, while known invasive species were not found. Watercourses appear less suited to detect invasive pathogenic Phytophthora species with a still limited distribution in the environment.

Understanding the concurrent responses of aboveground and belowground biota compartments to global changes is crucial for the maintenance of ecosystem functions and biodiversity conservation. We conduct a comprehensive analysis synthesizing data from 13,209 single observations and 3223 pairwise observations from 1166 publications across the world terrestrial ecosystems to examine the responses of plants and soil organisms and their synchronization. We find that global change factors (GCFs) generally promote plant biomass but decreased plant species diversity. In comparison, the responses of belowground soil biota to GCFs are more variable and harder to predict. The analysis of the paired aboveground and belowground observations demonstrate that responses of plants and soil organisms to GCFs are decoupled among diverse groups of soil organisms for different biomes. Our study highlights the importance of integrative research on the aboveground-belowground system for improving predictions regarding the consequences of global environmental change.

Tree-microbe interactions are essential for forest ecosystem functioning. Most plant–microbe research has focused on the rhizosphere, while composition of microbial communities in the phyllosphere remains underexplored. Here, we use 16S rRNA gene sequencing to explore differences between beech and Scots pine phyllospheric microbiomes at the European continental scale, map their functional profiles, and elucidate the role of host trees, forest features, and environmental factors such as climate and atmospheric deposition in phyllosphere microbiota assembly. We identified tree species and the associated foliar trait (specifically carbon:nitrogen ratio) as primary drivers of the bacterial communities. We characterized taxonomical and functional composition of epiphytic bacteria in the phyllosphere of beech and Scots pine across an environmental gradient from Fennoscandia to the Mediterranean area, with major changes in temperature and nitrogen deposition. We also showed that temperature and nitrogen deposition played a crucial role in affecting their assembly for both tree species. This study contributes to advancing our understanding on factors shaping phyllosphere microbial communities in beech and Scots pine at the European continental scale, highlighting the need of broad-scale comparative studies (covering a wide range of foliar traits and environmental conditions) to elucidate how phyllosphere microbiota mediates ecosystem responses to global change.

Human pressures, particularly urbanisation and agricultural expansion, profoundly affect biodiversity by reshaping species and functional trait distributions, with critical consequences for ecosystem resilience and multifunctionality. Yet, the extent and strength of these impacts across diverse taxa and ecosystems remain poorly understood. Here, we analyse 160 spatial datasets, encompassing over 13,000 local communities and nine major taxa in freshwater and terrestrial ecosystems worldwide. Our results reveal that human pressure is the dominant driver of species and trait replacement, consistently outweighing the effects of climate and spatial distance. Despite observing a prevalence of biotic differentiation across landscapes, we reveal that the occurrence of biotic homogenisation is consistently linked to the dominant effects of human pressure. These homogenising effects are particularly pronounced in the trait composition of terrestrial communities and the species composition of freshwater communities, suggesting distinct mechanisms across realms. We find that rates of species and trait replacement increase rapidly along the human pressure gradient, especially between low and medium pressure, before they stabilise. Importantly, an exception occurs in urban landscapes, where species replacement increases exponentially. Although ecological communities generally exhibit species turnover along the human pressure gradient, we find that they are disproportionately homogenised in traits. While this provides resilience to environmental changes, it can delay the recognition of species collapse until key functional traits are lost, risking sudden ecosystem breakdown. Our findings underscore the urgent need for conservation strategies that prioritise the preservation of minimally impacted habitats to sustain ecosystem resilience and multifunctionality.

Patchy global data on belowground litter decomposition dynamics limit our capacity to discern the drivers of carbon preservation and storage across inland and coastal wetlands. We performed a global, multiyear study in over 180 wetlands across 28 countries and 8 macroclimates using standardized litter as measures of “recalcitrant” (rooibos tea) and “labile” (green tea) organic matter (OM) decomposition. Freshwater wetlands and tidal marshes had the highest tea mass remaining, indicating a greater potential for carbon preservation in these ecosystems. Recalcitrant OM decomposition increased with elevated temperatures throughout the decay period, e.g., increase from 10 to 20 °C corresponded to a 1.46-fold increase in the recalcitrant OM decay rate constant. The effect of elevated temperature on labile OM breakdown was ecosystem-dependent, with tidally influenced wetlands showing limited effects of temperature compared with freshwater wetlands. Based on climatic projections, by 2050 wetland decay constants will increase by 1.8% for labile and 3.1% for recalcitrant OM. Our study highlights the potential for reduction in belowground OM in coastal and inland wetlands under increased warming, but the extent and direction of this effect at a large scale is dependent on ecosystem and OM characteristics. Understanding local versus global drivers is necessary to resolve ecosystem influences on carbon preservation in wetlands.

Clarifying the controlling factors of annual variations in evapotranspiration (ET) and its components (transpiration (T) and evaporation (E)) over alpine grasslands of high‐cold regions is vital to understanding the hydrological processes of the terrestrial ecosystem. Therefore, this study investigated the variability of ET and its components over the alpine grasslands of the Tibetan Plateau (TP) and the driving factors underlying these changes during 1961–2013. The results showed that the annual ET over alpine grasslands was 339 mm, of which 59% and 41% were contributed by E and T, respectively. Annual ET, E, and T over the TP grasslands changed insignificantly before 1995, whereas increased dramatically during 1995–2013. Regarding different alpine grassland types, annual ET and its components in seasonal frost regions (SAG) were larger than in permafrost regions (PAG). The increase of ET and its components in PAG was profoundly larger than that in the SAG region during 1995–2013. Water and energy factors controlled the ET of approximately 65% and 31% area of the TP grasslands, respectively. Leaf area index was the major cause of T variability throughout 64% area of TP grasslands, while regions where energy factors were the major force of T change were mainly located in the eastern SAG region. Variability of E on entire TP grasslands (81%) was mainly regulated by available water supply. Our results indicate that as permafrost degradation has the potential to amplify climate warming and precipitation increase, ET over the PAG region was expected to continue increasing faster than the SAG region.

Purpose of Review To synthesize new information regarding the environmental sensitivity and impact of climate change on leaf-, wood-, phloem- and root phenology of deciduous forests of the temperate (and boreal) zone, comprising overstory and understory, and both woody and herbaceous species. Recent Findings The environmental sensitivity and impact of climate change on spring leaf phenology are relatively well understood, with ongoing efforts focusing on the spatial and temporal variability in both overstory and understory. Autumn leaf phenology and cambial phenology have received increasing attention in recent years. The drivers of senescence progression are well understood (current temperature), while the drivers of the onset of senescence are still uncertain but likely relate to spring temperature, water availability and light conditions. Studies on cambial phenology of angiosperm trees have focused on the variability across populations and years, while studies on phloem remain scarce and synthesis studies are unavailable. For fine root phenology, asynchronicity with leaf phenology and high variability among species have been demonstrated, but large uncertainty remains regarding the drivers of the onset and cessation of their growth. Studies on woody and herbaceous understory highlight the importance of microclimate differences within the stand. Summary Future phenology research should focus on (i) onset of leaf senescence, (ii) fine roots, (iii) the relationships between overstory and understory species not only regarding leaves, but also wood and fine roots, (iv) variability across multiples scales (e.g. individuals, stands), and (v) interannual legacy effects and connections among phenophases of different organs and forest compartments.

In the context of the ongoing biodiversity crisis, understanding forest ecosystems, their tree species composition, and especially the successional stages of their development is crucial. They collectively shape the biodiversity within forests and thereby influence the ecosystem services that forests provide, yet this information is not readily available on a large scale. Remote sensing techniques offer promising solutions for obtaining area-wide information on tree species composition and their successional stages. While optical data are often freely available in appropriate quality over large scales, obtaining light detection and ranging (LiDAR) data, which provide valuable information about forest structure, is more challenging. LiDAR data are mostly acquired by public authorities across several years and therefore heterogeneous in quality. This study aims to assess if heterogeneous LiDAR data can support area-wide modeling of forest successional stages at the tree species group level. Different combinations of spectral satellite data (Sentinel-2) and heterogeneous airborne LiDAR data, collected by the federal government of Rhineland-Palatinate, Germany, were utilized to model up to three different successional stages of seven tree species groups. When incorporating heterogeneous LiDAR data into random forest models with spatial variable selection and spatial cross-validation, significant accuracy improvements of up to 0.23 were observed. This study shows the potential of not dismissing initially seemingly unusable heterogeneous LiDAR data for ecological studies. We advocate for a thorough examination to determine its usefulness for model enhancement. A practical application of this approach is demonstrated, in the context of mapping successional stages of tree species groups at a regional level.

The increasing online availability of biodiversity data and advances in ecological modeling have led to a proliferation of open‐source modeling tools. In particular, R packages for species distribution modeling continue to multiply without guidance on how they can be employed together, resulting in high fidelity of researchers to one or several packages. Here, we assess the wide variety of software for species distribution models (SDMs) and highlight how packages can work together to diversify and expand analyses in each step of a modeling workflow. We also introduce the new R package ‘sdmverse' to catalog metadata for packages, cluster them based on their methodological functions, and visualize their relationships. To demonstrate how pluralism of software use helps improve SDM workflows, we provide three extensive and fully documented analyses that utilize tools for modeling and visualization from multiple packages, then score these tutorials according to recent methodological standards. We end by identifying gaps in the capabilities of current tools and highlighting outstanding challenges in the development of software for SDMs.

In the context of rapidly growing African cities, a thorough understanding of the complexities of urban food systems is essential for addressing the challenges of food insecurity and undernourishment for city dwellers. Particularly in South Africa, where pre-existing inequalities drive disparities in food access and diet-related health outcomes, a comprehensive perspective including the spatial distribution of malnutrition in urban environments is required to develop effective interventions. The present study examines the essential elements of an urban food system by employing a Bayesian network as a causal framework. By integrating survey data from households and food outlets with spatial information, a food systems model was created to test policy interventions. The study demonstrates the challenges of intervening in complex urban food systems, where dietary choices are shaped by various factors, often in a spatially heterogeneous manner. Interventions do not always benefit the targeted groups and are sometimes ineffective as result of system interactions. Our study shows that Bayesian network models provide a powerful tool to effectively analyse the complex interactions within such systems, thereby enabling the identification of optimal combinations of multifactor interventions. In our case study for Worcester, South Africa, the results reveal that the largest potential for improvement of food and nutrition security lies in the informal food sector, and support for affordable and local fresh produce is a viable measure for enhancing local nutrition, though the extent of impact varies across the city.

We investigate the impact of a 20‐yr irrigation on root water uptake (RWU) and drought stress release in a naturally dry Scots pine forest. We use a combination of electrical resistivity tomography to image RWU, drone flights to image the crown stress and sensors to monitor soil water content. Our findings suggest that increased water availability enhances root growth and resource use efficiency, potentially increasing trees' resistance to future drought conditions by enabling water uptake from deeper soil layers. This research highlights the significant role of ecological memory and legacy effects in determining tree responses to environmental changes.

The Pleidae, or pygmy backswimmers, is a family of aquatic bugs (Hemiptera, Heteroptera, Nepomorpha) containing four genera. Here, we describe Plea cryptica sp. nov. and redescribe its sister species, Plea minutissima Leach, 1817. Whereas the morphological distinction of these closely related species is only possible for males, molecular data clearly separate them. As part of our taxonomic study, we provide comprehensive molecular data including more than 200 DNA barcodes from all over Europe, complete nuclear ribosomal DNA, full mitochondrial genome data, and 3D scans for both species. Furthermore, the same molecular markers are also presented for Neoplea striola (Fieber, 1844). We used Maximum Likelihood (ML) analyses to reconstruct the phylogeny of the Pleidae and Notonectoidea based on available mitogenomic data. Our study represents a successful implementation of the proposed concept of taxonomics, using data from high-throughput sequencing technologies for integrative taxonomic studies, and allowing high confidence for both biodiversity and ecological research. Supplementary Information The online version contains supplementary material available at 10.1038/s41598-024-78224-6.

Estimating flow velocities is key to assessing hazards associated with debris flows. One approach to post‐event velocity estimation is the superelevation method, which uses debris‐flow mudlines to measure the cross‐channel surface inclination, or superelevation, produced by centripetal forces acting on the flow in a bend. Flow velocities are then calculated using a subjective parameterization of the forced vortex equation modified to include a debris‐flow specific correction factor. Subjective parameterization of this equation leads to substantial variability and uncertainty in the resulting flow velocities. We present an analysis of the reliability of the superelevation method using a large UAV‐based data set of 14 debris flows with front velocities of ∼0.8–6.5 m s⁻¹ and cross‐channel surface inclinations of ∼0.6–8.5°, as well as a validation for a single debris flow measured using high‐resolution, high‐frequency 3D lidar data fused to video imagery. The validation event indicates that when the flow surface inclination can be measured directly, the forced vortex equation produces excellent results without needing a correction factor for Froude numbers ranging from 0.7 to 1.5. This finding indicates that the main challenge with the superelevation method lies in obtaining accurate measurements of superelevation from the mudlines, and that a correction factor may serve to compensate for measurement difficulties rather than variable flow properties. For very small and highly subcritical flows, the superelevation method may generate a large overestimation of flow velocities.