title: Resource-mediated indirect effects of grassland management on arthropod diversity.
abstract: Intensive land use is a driving force for biodiversity decline in many ecosystems. In semi-natural grasslands, land-use activities such as mowing, grazing and fertilization affect the diversity of plants and arthropods, but the combined effects of different drivers and the chain of effects are largely unknown. In this study we used structural equation modelling to analyse how the arthropod communities in managed grasslands respond to land use and whether these responses are mediated through changes in resource diversity or resource quantity (biomass). Plants were considered resources for herbivores which themselves were considered resources for predators. Plant and arthropod (herbivores and predators) communities were sampled on 141 meadows, pastures and mown pastures within three regions in Germany in 2008 and 2009. Increasing land-use intensity generally increased plant biomass and decreased plant diversity, mainly through increasing fertilization. Herbivore diversity decreased together with plant diversity but showed no response to changes in plant biomass. Hence, land-use effects on herbivore diversity were mediated through resource diversity rather than quantity. Land-use effects on predator diversity were mediated by both herbivore diversity (resource diversity) and herbivore quantity (herbivore biomass), but indirect effects through resource quantity were stronger. Our findings highlight the importance of assessing both direct and indirect effects of land-use intensity and mode on different trophic levels. In addition to the overall effects, there were subtle differences between the different regions, pointing to the importance of regional land-use specificities. Our study underlines the commonly observed strong effect of grassland land use on biodiversity. It also highlights that mechanistic approaches help us to understand how different land-use modes affect biodiversity.
authors.affiliation: Terrestrial Ecology Research Group, Department of Ecology and Ecosystem Management, School of Life Sciences Weihenstephan, Technische Universität München, Freising, Germany.
authors.forename: Nadja K
authors.initials: NK
authors.lastname: Simons
authors.affiliation: Terrestrial Ecology Research Group, Department of Ecology and Ecosystem Management, School of Life Sciences Weihenstephan, Technische Universität München, Freising, Germany.
authors.forename: Martin M
authors.initials: MM
authors.lastname: Gossner
authors.affiliation: Department of Animal Biology, Institute of Biology, University of Campinas, Campinas, Sao Paulo, Brazil.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Lewinsohn
authors.affiliation: Institute of Plant Sciences, University of Bern, Bern, Switzerland.
authors.forename: Steffen
authors.initials: S
authors.lastname: Boch
authors.affiliation: Max-Planck-Institute for Biogeochemistry, Jena, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Lange
authors.affiliation: Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Müller
authors.affiliation: Terrestrial Ecology Research Group, Department of Ecology and Ecosystem Management, School of Life Sciences Weihenstephan, Technische Universität München, Freising, Germany.
authors.forename: Esther
authors.initials: E
authors.lastname: Pašalić
authors.affiliation: Institute of Plant Sciences, University of Bern, Bern, Switzerland.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Socher
authors.affiliation: Terrestrial Ecology Research Group, Department of Ecology and Ecosystem Management, School of Life Sciences Weihenstephan, Technische Universität München, Freising, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Türke
authors.affiliation: Institute of Plant Sciences, University of Bern, Bern, Switzerland; Biodiversity and Climate Research Centre, Senckenberg Gesellschaft für Naturforschung, Frankfurt/Main, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Fischer
authors.affiliation: Terrestrial Ecology Research Group, Department of Ecology and Ecosystem Management, School of Life Sciences Weihenstephan, Technische Universität München, Freising, Germany.
authors.forename: Wolfgang W
authors.initials: WW
authors.lastname: Weisser
mesh_terms: D000383:Agriculture / Q000379:methods*; D000818:Animals; D001181:Arthropods / Q000145:classification* / Q000502:physiology; D044822:Biodiversity; D018533:Biomass; D060435:Carnivory / Q000502:physiology; D020387:Food Chain; D005858:Germany; D065948:Grassland; D060434:Herbivory / Q000502:physiology; D006801:Humans; D015233:Models, Statistical; D006109:Poaceae / Q000502:physiology