Windthrow disturbance is an important driver of arthropod diversity in forests. In the past, studies have mainly focused on the first years after disturbance, and there are hardly any data on arthropod trajectories in windthrows and on salvage logging effects over decades. We sampled arthropods of different functional groups on 16 permanent plots following two windstorms (Vivian and Lothar) in coniferous and broadleaf forests at different elevations in Central Europe over two decades. Flight interception and pitfall traps were operated during the entire growing seasons in three habitat types per site: unsalvaged windthrow, salvaged windthrow and control forest. In total, 524,115 individuals from 1666 arthropod species were identified, of which more than 90% occurred in windthrows, including 40%-53% species exclusively found in windthros. Over the two decades, saproxylics, herbivores, pollinators, predators and endangered species showed significantly higher species numbers and abundances in windthrows than in control forests, where only 6% exclusive species occurred. Arthropod communities in windthrows showed distinct dynamics during the two decades. Their species numbers and abundances peaked in the first 3 years, coined by saproxylic species, such as bark beetles, and by pollinating hoverflies. While abundances declined rapidly, species numbers remained elevated for two decades. Arthropod similarity between windthrows and forests (indicating resilience) increased with time but depended on elevation and forest type. After 20 years, it reached an average of 50% in lowland broadleaf forests, but only 30% in high-elevation spruce forests, indicating lower resilience. Salvage logging had no significant effect on overall species numbers but altered species composition. More than 10% exclusive species were found in salvaged and up to 20% in unsalvaged windthrows, with the latter supporting more endangered species, particularly towards the second decade. Synthesis and applications. Our study shows that windthrow causes an initial boost of arthropod diversity. While abundances thereafter rapidly decline, species numbers remain at relatively high levels during at least two decades. Unsalvaged windthrows are an indispensable resource for endangered species, particularly in later wood decay stages. St & uuml;rme sind wichtige Faktoren f & uuml;r die Erhaltung der Arthropodenvielfalt in W & auml;ldern. Bisherige Untersuchungen bezogen sich haupts & auml;chlich auf die ersten Jahre nach der St & ouml;rung, und es gibt kaum Angaben zur l & auml;ngerfristigen Entwicklung von Arthropoden in Windw & uuml;rfen und zu den Auswirkungen einer Holzr & auml;umung. Wir beprobten verschiedene funktionelle Gruppen von Arthropoden auf 16 Dauerbeobachtungsfl & auml;chen nach zwei St & uuml;rmen (Vivian, Lothar) in Nadel- und Laubw & auml;ldern unterschiedlicher H & ouml;henlagen in Mitteleuropa & uuml;ber zwei Jahrzehnte. W & auml;hrend der gesamten Vegetationsperiode wurden Flug- und Bodenfallen in drei Lebensraumtypen betrieben: unger & auml;umter Windwurf, ger & auml;umter Windwurf und intakter Kontrollwald. Insgesamt wurden 524 ' 115 Individuen von 1 ' 666 Arthropodenarten bestimmt. Mehr als 90% der Arten kamen in den Windw & uuml;rfen vor, 40%-53% sogar ausschlie ss lich dort. In dieser Periode von 20 Jahren wiesen Windw & uuml;rfe deutlich h & ouml;here Artenzahlen und Abundanzen an Xylobionten, Herbivoren, Best & auml;ubern, R & auml;ubern und gef & auml;hrdeten Arten auf als intakte W & auml;lder. Nur 6% der Arten kamen ausschliesslich im Kontrollwald vor. Die Artengemeinschaften in Windw & uuml;rfen zeigten eine deutliche Dynamik in diesen zwei Jahrzehnten. Ihre Artenzahlen und Abundanzen erreichten in den ersten drei Jahren ihr Maximum. Diese Phase war von xylobionten Arten wie Borkenk & auml;fern und Bl & uuml;tenbesuchern wie Schwebfliegen gepr & auml;gt. W & auml;hrend die Abundanzen rasch zur & uuml;ckgingen, blieb die Artenzahl zwei Jahrzehnte lang auf einem hohen Niveau. Die & Auml;hnlichkeit (Similarity) der Arthropoden zwischen Windw & uuml;rfen und W & auml;ldern nahm mit der Zeit zu (Resilienz), hing jedoch von H & ouml;henlage und Waldtyp ab. Nach 20 Jahren erreichte sie in den Laubw & auml;ldern des Tieflandes durchschnittlich 50%, in hochgelegenen Fichtenw & auml;ldern jedoch nur 30%, was eine geringere Resilienz bedeutet. Die Sturmholzr & auml;umung hatte keine signifikanten Auswirkungen auf die Gesamtartenzahl, ver & auml;nderte aber die Artenzusammensetzung. Mehr als 10% exklusive Arten wurden in ger & auml;umten und bis zu 20% in unger & auml;umten Windw & uuml;rfen gefunden, wobei letztere mehr gef & auml;hrdete Arten aufwiesen, insbesondere in der zweiten Dekade. Synthese und Anwendungen: Unsere Studie zeigt, dass ein Windwurf zu einer markanten Zunahme der Arthropodenvielfalt f & uuml;hrt. W & auml;hrend die Abundanzen schnell wieder abnehmen, bleiben die Artenzahlen & uuml;ber mindestens 20 Jahre auf relativ hohem Niveau. Unger & auml;umte Sturmfl & auml;chen sind eine herausragende Ressource f & uuml;r gef & auml;hrdete Arten, insbesondere in sp & auml;teren Zerfallsstadien.

AbstractUnderstanding natural disturbance regimes and their impacts is crucial in designing ecosystem management strategies. However, disturbances do not always occur in isolation; the occurrence of one disturbance influences the likelihood or the effect of another. In this chapter, we illustrate the importance of disturbance interactions by focusing on a subset of interactions present in different parts of the boreal forest. The selected interactions include insects and wind, insects and fire, and wind and fire. The potential consequences of climate change on these interactions are also discussed.

Street lights are important light sources that contribute to artificial light at night (ALAN). To date, ecological impacts of individual LED properties (color temperature, dimmability) have been studied, while interactions between light properties or aspects of luminaire design have not been addressed. However, the design of luminaires can influence ALAN impacts as the shape determines the spatial distribution of light and its visibility in the environment. This may cause amplifying or mitigating effects. We assessed the relative individual and interacting effects of two LED luminaire designs and three LED color temperatures (1750 K, 3000 K, 4000 K) on nocturnal insect abundance, bat foraging and feeding activity. We considered a standard LED luminaire shape with focused light emission and a luminaire shape with a diffusor to scatter the light spatially, leading to increased visibility of the light in the environment. During 104 nights, we trapped 51263 nocturnal insects of which 97% were caught at lights and 3% at dark sites. For bats, up to 44.8% fewer acoustic signals were recorded at dark sites. We caught 31% insects at LEDs with1750 K, 34% and 35% at 3000 K and 4000 K, respectively. Thus, color temperatures of 1750 K proved less detrimental than 3000/4000 K. Effects of luminaire shape led to an increase (16%) of trapped insects for luminaires with diffusors compared to the standard shape. In addition, luminaires with diffusors amplified the effects of LED color (+12% insects at 1750 K/3000 K; +25.6% at 4000 K). In contrast, bat foraging activity was independent of the light treatments while bat feeding activity was increased by 21.5% at standard luminaire shapes. Likely, intense straylight at diffused lights negatively affects the target-focused echolocation by deterring the bats. We concluded that ecological impacts of luminaire shape are an important, yet underestimated variable in light-pollution impact research.

Der Eichenprozessionsspinner ist ein in Europa heimischer Schmetterling, der sich hauptsächlich auf Eichen entwickelt. In der Schweiz konzentriert sich seine Verbreitung auf Regionen in der West- und Nordwestschweiz sowie auf die Alpensüdseite. Nach dem Schlupf ernähren sich seine in geselligen Verbänden lebenden Raupen von Eichenblättern und können bei grossen Populationsdichten zur völligen Entlaubung der befallenen Bäume führen. Besondere Aufmerksamkeit wird dem Eichenprozessionsspinner zuteil, weil die Brennhaare seiner Raupen bei Menschen und Tieren allergische Reaktionen auslösen können.

The oak processionary moth is a moth native to Europe that develops mainly on oak trees. In Switzerland, it is mainly found in western and north-western regions, and on the southern side of the Alps. After hatching, its caterpillars feed in gregarious clusters on the leaves of oak trees, and large populations can lead to the complete defoliation of infested trees. The oak processionary moth attracts particular attention because the urticating (stinging) hairs of its caterpillars can cause allergic reactions in humans and animals.

Climate change exposes ecosystems to strong and rapid changes in their environmental boundary conditions mainly due to the altered temperature and precipitation patterns. It is still poorly understood how fast interlinked ecosystem processes respond to altered environmental conditions, if these responses occur gradually or suddenly when thresholds are exceeded, and if the patterns of the responses will reach a stable state. We conducted an irrigation experiment in the Pfynwald, Switzerland from 2003-2018. A naturally dry Scots pine (Pinus sylvestris L.) forest was irrigated with amounts that doubled natural precipitation, thus releasing the forest stand from water limitation. The aim of this study was to provide a quantitative understanding on how different traits and functions of individual trees and the whole ecosystem responded to increased water availability, and how the patterns and magnitudes of these responses developed over time. We found that the response magnitude, the temporal trajectory of responses, and the length of initial lag period prior to significant response largely varied across traits. We detected rapid and stronger responses from above-ground tree traits (e.g., tree-ring width, needle length, and crown transparency) compared to below-ground tree traits (e.g., fine root biomass). The altered above-ground traits during the initial years of irrigation increased the water demand and trees adjusted by increasing root biomass during the later years of irrigation, resulting in an increased survival rate of Scots pine trees in irrigated plots. The irrigation also stimulated ecosystem-level foliar decomposition rate, fungal fruit body biomass, and regeneration abundances of broadleaved tree species. However, irrigation did not promote the regeneration of Scots pine trees which are reported to be vulnerable to extreme droughts. Our results provide extensive evidence that treeand ecosystem-level responses were pervasive across a number of traits on long-term temporal scales. However, after reaching a peak, the magnitude of these responses either decreased or reached a new stable state, providing important insights into how resource alterations could change the system functioning and its boundary conditions.

La processionnaire du chêne est un papillon européen qui se développe principalement sur les chênes. En Suisse, son aire de répartition comprend essentiellement les régions de Suisse occidentale et du Nord-Ouest ainsi que le Sud des Alpes. Après leur éclosion, les chenilles sociales vivent en groupes, se nourrissent de feuilles de chênes et peuvent causer des défoliations totales lorsque leurs populations se densifient. La processionnaire du chêne retient particulièrement l’attention, car les poils urticants de la chenille peuvent provoquer des réactions allergiques chez l’homme et l’animal.

ABSTRACTDisturbances alter biodiversity via their specific characteristics, including severity and extent in the landscape, which act at different temporal and spatial scales. Biodiversity response to disturbance also depends on the community characteristics and habitat requirements of species. Untangling the mechanistic interplay of these factors has guided disturbance ecology for decades, generating mixed scientific evidence of biodiversity responses to disturbance. Understanding the impact of natural disturbances on biodiversity is increasingly important due to human‐induced changes in natural disturbance regimes. In many areas, major natural forest disturbances, such as wildfires, windstorms, and insect outbreaks, are becoming more frequent, intense, severe, and widespread due to climate change and land‐use change. Conversely, the suppression of natural disturbances threatens disturbance‐dependent biota. Using a meta‐analytic approach, we analysed a global data set (with most sampling concentrated in temperate and boreal secondary forests) of species assemblages of 26 taxonomic groups, including plants, animals, and fungi collected from forests affected by wildfires, windstorms, and insect outbreaks. The overall effect of natural disturbances on α‐diversity did not differ significantly from zero, but some taxonomic groups responded positively to disturbance, while others tended to respond negatively. Disturbance was beneficial for taxonomic groups preferring conditions associated with open canopies (e.g. hymenopterans and hoverflies), whereas ground‐dwelling groups and/or groups typically associated with shady conditions (e.g. epigeic lichens and mycorrhizal fungi) were more likely to be negatively impacted by disturbance. Across all taxonomic groups, the highest α‐diversity in disturbed forest patches occurred under moderate disturbance severity, i.e. with approximately 55% of trees killed by disturbance. We further extended our meta‐analysis by applying a unified diversity concept based on Hill numbers to estimate α‐diversity changes in different taxonomic groups across a gradient of disturbance severity measured at the stand scale and incorporating other disturbance features. We found that disturbance severity negatively affected diversity for Hill number q = 0 but not for q = 1 and q = 2, indicating that diversity–disturbance relationships are shaped by species relative abundances. Our synthesis of α‐diversity was extended by a synthesis of disturbance‐induced change in species assemblages, and revealed that disturbance changes the β‐diversity of multiple taxonomic groups, including some groups that were not affected at the α‐diversity level (birds and woody plants). Finally, we used mixed rarefaction/extrapolation to estimate biodiversity change as a function of the proportion of forests that were disturbed, i.e. the disturbance extent measured at the landscape scale. The comparison of intact and naturally disturbed forests revealed that both types of forests provide habitat for unique species assemblages, whereas species diversity in the mixture of disturbed and undisturbed forests peaked at intermediate values of disturbance extent in the simulated landscape. Hence, the relationship between α‐diversity and disturbance severity in disturbed forest stands was strikingly similar to the relationship between species richness and disturbance extent in a landscape consisting of both disturbed and undisturbed forest habitats. This result suggests that both moderate disturbance severity and moderate disturbance extent support the highest levels of biodiversity in contemporary forest landscapes.

Droughts and other rapid changes in abiotic environmental conditions can predispose trees to damage by pest insects and pathogens. For survival of coniferous trees, functional resin-based defences are essential, and it is important to know how they react to changes in environmental conditions at various time scales. We studied the effects of differing water availabilities on resin-based defences in mature Scots pine (Pinus sylvestris) trees in a naturally drought-prone forest within a long-term irrigation experiment. Our objectives were to understand the effects of long-term drought on carbon allocation to resin production and to analyse its influence on resin flow and pressure in comparison to the shorter-term effects of seasonal drought. We tracked carbon allocation to resin after C-13-pulse labelling experiment in late summer 2017 and compared the observed resin dynamics between drought-exposed control trees and irrigated trees from June to August during the dry hot summer of 2018. Dry control trees showed higher allocation of labelled carbon to resin than irrigated trees. Resin pressure was higher in dry control than in irrigated trees with similar water potentials, and resin flow in June was higher in dry control than in irrigated trees with similar crown transparency. Yet, resin pressures of dry control trees in particular decreased with decreasing water availability from June to August. Resin flow was little affected by short-term changes in water availability and mostly associated with crown transparency. We suggest that because of differing timescales of direct drought effects and changes in allocation patterns, dry conditions may support resin-based defences in the long term, but a drought period decreases resin pressure in the short term.

Aim: Red wood ants (Formica rufa group) mitigate invertebrate pest outbreaks, alter invertebrate communities, and contribute to nutrient cycling. The IUCN lists these insects as near threatened. We investigated whether disturbances of Red Wood Ant (RWA) forest habitats related to recreation, infrastructure, and forest management were associated with RWA occurrence. We also investigated the habitat associations of this group. Location: Switzerland. Methods: We trained random forest models to predict RWA occurrence using data from 6,341 plots distributed throughout Swiss forests. Our explanatory variables included descriptions of vegetation, terrain, climate and human disturbance of the forest. A model trained using all of these variables (Model 1) was compared to another trained using all of these variables except those describing human disturbance (Model 2). We compared the abilities of these models to differentiate between RWA presences and absences using areas under receiver operator curves (AUC). The nature of the associations between the probability of RWA occurrence predicted by Model 1 and the explanatory variables that made the greatest contributions to the AUC of this model were investigated using individual conditional expectation plots. Results: No significant difference in AUC was detected between Models 1 and 2. RWA occurrence was positively associated with elevation, conifers, canopy gaps, ground cover vegetation and solar insolation while negatively associated with air temperature and a soil wetness index. Main conclusions: The distribution of RWA within Swiss forests appeared unassociated with the human disturbances we investigated. To conserve RWA in Switzerland, we recommend the conservation of forests with high proportions of conifers, particularly those at high elevations. We also recommend forest management that promotes ground cover vegetation and open canopy structures. The negative associations between RWA occurrence and temperatures raise concerns for the prospects of RWA in the context of predicted climate warming.

Increased tree mortality has become a widespread phenomenon and is largely attributed to climate change. Little field research has addressed the complex interactions between trees, herbivores, and their natural enemies as affected by temperature. We recorded the densities of bark insects and their natural enemies emerging from felled trees in Scots pine forests at 17 study sites along 6 elevation gradients encompassing different temperature ranges in 3 regions in Switzerland and Italy. We additionally measured tree resin defense at different elevations. The density of aggressive bark beetles decreased with increasing temperatures while that of non-aggressive species did not respond to temperature. Contrasting patterns were also found for natural enemies, with the densities of most predatory taxa decreasing with increasing temperature whereas densities of parasitoids increased. Consequently, bark beetle mortality by predators decreased and that by parasitoids increased with temperature. Exudation of resin increased with temperature. As the number of resin ducts did not change with temperature, this is assumed a physical effect of reduced viscosity. Despite lower densities of aggressive bark beetles and improved tree resin flow under higher temperatures, the currently experienced drought-induced reduction in tree vigor is likely to increase tree mortality under the ongoing climate warming.