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Kaldhusdal A.,Ludwig Maximilians University of Munich | Brandl R.,University of Marburg | Muller J.,Sachgebiet Forschung und Dokumentation | Muller J.,TU Munich | And 2 more authors.
Methods in Ecology and Evolution | Year: 2015

Summary: Ecologists increasingly consider phylogenetic relatedness in both community composition and spatial arrangements in communities. Here we considered both the phylogenetic correlation between multiple species and the spatial correlation induced by unobserved spatial heterogeneity on multiple plots. For this analysis, we introduced phylogenetic spatial generalised linear mixed models (PSGLMMs), which are an extension of phylogenetic generalised linear mixed models (PGLMMs). We used the framework of generalised linear array models to simultaneously model species and plot dimension. Such models have the potential to explain the correlation of the phylogenetic relationship of the observed species and of the spatial proximity of the plots, or both. We proposed model selection strategies based on proper scores and empirically evaluated them in a case study using bird count data. In our analysis, we focused on two special cases: the community composition model and the environmental sensitivity model. Our simulation study indicated that it might be difficult to correctly identify phylogenetic signals when the phylogenetic correlation is rather low and when studying presence-absence or count data of rare or pervasive species. © 2014 British Ecological Society.

Hothorn T.,Ludwig Maximilians University of Munich | Brandl R.,University of Marburg | Muller J.,Sachgebiet Forschung und Dokumentation | Muller J.,TU Munich
PLoS ONE | Year: 2012

Ungulates, in particular the Central European roe deer Capreolus capreolus and the North American white-tailed deer Odocoileus virginianus, are economically and ecologically important. The two species are risk factors for deer-vehicle collisions and as browsers of palatable trees have implications for forest regeneration. However, no large-scale management systems for ungulates have been implemented, mainly because of the high efforts and costs associated with attempts to estimate population sizes of free-living ungulates living in a complex landscape. Attempts to directly estimate population sizes of deer are problematic owing to poor data quality and lack of spatial representation on larger scales. We used data on >74,000 deer-vehicle collisions observed in 2006 and 2009 in Bavaria, Germany, to model the local risk of deer-vehicle collisions and to investigate the relationship between deer-vehicle collisions and both environmental conditions and browsing intensities. An innovative modelling approach for the number of deer-vehicle collisions, which allows nonlinear environment-deer relationships and assessment of spatial heterogeneity, was the basis for estimating the local risk of collisions for specific road types on the scale of Bavarian municipalities. Based on this risk model, we propose a new "deer-vehicle collision index" for deer management. We show that the risk of deer-vehicle collisions is positively correlated to browsing intensity and to harvest numbers. Overall, our results demonstrate that the number of deer-vehicle collisions can be predicted with high precision on the scale of municipalities. In the densely populated and intensively used landscapes of Central Europe and North America, a model-based risk assessment for deer-vehicle collisions provides a cost-efficient instrument for deer management on the landscape scale. The measures derived from our model provide valuable information for planning road protection and defining hunting quota. Open-source software implementing the model can be used to transfer our modelling approach to wildlife-vehicle collisions elsewhere. © 2012 Hothorn et al.

Thorn S.,Sachgebiet Forschung und Dokumentation | Bassler C.,Sachgebiet Forschung und Dokumentation | Gottschalk T.,Rottenburg College of Forest Sciences | Hothorn T.,University of Zürich | And 4 more authors.
PLoS ONE | Year: 2014

Windstorms, bark beetle outbreaks and fires are important natural disturbances in coniferous forests worldwide. Windthrown trees promote biodiversity and restoration within production forests, but also cause large economic losses due to bark beetle infestation and accelerated fungal decomposition. Such damaged trees are often removed by salvage logging, which leads to decreased biodiversity and thus increasingly evokes discussions between economists and ecologists about appropriate strategies. To reveal the reasons behind species loss after salvage logging, we used a functional approach based on four habitat-related ecological traits and focused on saproxylic beetles. We predicted that salvage logging would decrease functional diversity (measured as effect sizes of mean pairwise distances using null models) as well as mean values of beetle body size, wood diameter niche and canopy cover niche, but would increase decay stage niche. As expected, salvage logging caused a decrease in species richness, but led to an increase in functional diversity by altering the species composition from habitat-filtered assemblages toward random assemblages. Even though salvage logging removes tree trunks, the most negative effects were found for small and heliophilous species and for species specialized on wood of small diameter. Our results suggested that salvage logging disrupts the natural assembly process on windthrown trees and that negative ecological impacts are caused more by microclimate alteration of the dead-wood objects than by loss of resource amount. These insights underline the power of functional approaches to detect ecosystem responses to anthropogenic disturbance and form a basis for management decisions in conservation. To mitigate negative effects on saproxylic beetle diversity after windthrows, we recommend preserving single windthrown trees or at least their tops with exposed branches during salvage logging. Such an extension of the green-tree retention approach to windthrown trees will preserve natural succession and associated communities of disturbed spruce forests. © 2014 Thorn et al.

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