Background & aim-In general, biodiversity has positive effects on ecosystem functioning. In forests, understorey vegetation is influenced by both the composition and species richness of the overstorey through species-specific effects on environmental conditions at the forest floor. Forest fragmentation is also known to influence understorey vegetation composition and richness. However, the combined effects of tree species diversity and forest fragmentation have not been studied yet. With the TREEWEB research platform, consisting of 53 forest plots along a tree species diversity and forest fragmentation gradient, we aim to unravel the combined effects of tree species diversity, tree species identity and forest fragmentation on the understorey composition and diversity. Methods-The TREEWEB platform includes forest plots of three tree species richness levels, containing all possible species combinations of Quercus robur, Quercus rubra and Fagus sylvatica. Complete dilution is avoided in the design, allowing separation between tree species identity and diversity effects. Vegetation surveys were conducted in all plots to investigate the species richness, species diversity, compositional turnover and cover of the herb layer as well as the shrub layer cover. Key results-Within the TREEWEB platform, overstorey-understorey diversity relationships were mainly characterised by tree species identity effects. No clear effects of tree species diversity and forest fragmentation on understorey composition and diversity were found. Conclusion-Tree species identity effects were most important in explaining the observed patterns in the understorey vegetation. Further in-depth research will allow us to disentangle which mechanisms underlie these patterns and whether effects of fragmentation are more pronounced at higher trophic levels.

Recently emerged fungal diseases, Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal) are an increasing threat to amphibians worldwide. In Europe, the threat of Bsal to salamander populations is demonstrated by the rapid decline of fire salamander populations in Germany, the Netherlands and Belgium. Although most European urodelans are susceptible to infection in infection trials, recent evidence suggests marked interspecific differences in the course of infection, with potentially far reaching implications for salamander conservation. As a salamander’s skin is the first line of defense against such pathogens, interspecific differences in innate immune function of the skin may explain differential susceptibility. Here we investigate if compounds present on a salamander’s skin can kill Bsal spores and if there is variation among species. We used a non-invasive assay to compare killing ability of salamander mucosomes of four different species (captive and wild Salamandra salamandra and captive Ichtyosaura alpestris, Cynops pyrrhogaster and Lissotriton helveticus) by exposing Bsal zoospores to salamander mucosomes and determining spore survival. In all samples, zoospores were killed when exposed to mucosomes. Moreover, we saw a significant variation in this Bsal killing ability of mucosomes between different salamander host species. Our results indicate that mucosomes of salamanders might provide crucial skin protection against Bsal, and could explain why some species are more susceptible than others. This study represents a step towards better understanding host species variation in innate immune function and disease susceptibility in amphibians.

Forest fragments in highly disturbed landscapes provide important ecosystem services ranging from acting as biodiversity reservoir to providing timber or regulating hydrology. Managing the tree species richness and composition of these fragments to optimize their functioning and the deliverance of multiple ecosystem services is of great practical relevance. However, both the strength and direction of tree species richness and tree species composition effects on forest ecosystem multifunctionality may depend on the landscape context in which these forest remnants are embedded. Taking advantage of an observatory network of 53 temperate forest plots varying in tree species richness, tree species composition, and fragmentation intensity we measured 24 ecosystem functions spanning multiple trophic levels and analyzed how tree species diversity-multifunctionality relationships changed with fragmentation intensity. Our results show that fragmentation generally increases multifunctionality and strengthens its positive relationship with diversity, possibly due to edge effects. In addition, different tree species combinations optimize functioning under different fragmentation levels. We conclude that management and restoration of forest fragments aimed at maximizing ecosystem multifunctionality should be tailored to the specific landscape context. As forest fragmentation will continue, tree diversity will become increasingly important to maintain forest functioning.

Diverse communities of symbiotic microbes inhabit the digestive systems of vertebrates and play a crucial role in animal health, and host diet plays a major role in shaping the composition and diversity of these communities. Here, we characterized diet and gut microbiome of fire salamander populations from three Belgian forests. We carried out DNA metabarcoding on fecal samples, targeting eukaryotic 18S rRNA of potential dietary prey items, and bacterial 16S rRNA of the concomitant gut microbiome. Our results demonstrated an abundance of soft-bodied prey in the diet of fire salamanders, and a significant difference in the diet composition between males and females. This sex-dependent effect on diet was also reflected in the gut microbiome diversity, which is higher in males than female animals. Proximity to human activities was associated with increased intestinal pathogen loads. Collectively, the data supports a relationship between diet, environment and intestinal microbiome in fire salamanders, with potential health implications.

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