Forest fragmentation modulates effects of tree species richness and composition on ecosystem multifunctionality.

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.

Skin mucosome activity as an indicator of Batrachochytrium salamandrivorans susceptibility in salamanders.

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.