DOI: 10.5061/dryad.f3b77
title: Data from: Resource-mediated indirect effects of grassland management on arthropod diversity

description: 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, landuse 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.
description: 01_Arthropods_2008The files 01_Arthropods_2008 and 01_Arthropods_2009 include abundance data on adult arthropods per plot and year. SpeciesCode --&gt; Species' identifier, identical across years Author --&gt; Author of species' name Order --&gt; Taxonomic oder Suborder --&gt; Taxonomic suborder Family --&gt; Taxonomic family Body_length_mm --&gt; mean body length [mm] for the species as described in literature Biomass_mg --&gt; estimated species' biomass [mg] which was calculated from Body_length_mm Feeding --&gt; species' feeding guild (predator or herbivor) AEG01 etc. --&gt; plot-specific ID01_Arthropods_2009The files 01_Arthropods_2008 and 01_Arthropods_2009 include abundance data on adult arthropods per plot and year. SpeciesCode --&gt; Species' identifier, identical across years Author --&gt; Author of species' name Order --&gt; Taxonomic oder Suborder --&gt; Taxonomic suborder Family --&gt; Taxonomic family Body_length_mm --&gt; mean body length [mm] for the species as described in literature Biomass_mg --&gt; estimated species' biomass [mg] which was calculated from Body_length_mm Feeding --&gt; species' feeding guild (predator or herbivor) AEG01 etc. --&gt; plot-specific ID02_Plant_cover_2008The files 02_Plant_cover_2008 and 02_Plant_cover_2009 include cover data of vascular plants per plot and year. SpeciesCode --&gt; Species' identifier, identical across years Functional_type --&gt; Species were assigned as grass, herb or shrub species AEG01 etc. --&gt; plot-specific ID02_Plant_cover_2009The files 02_Plant_cover_2008 and 02_Plant_cover_2009 include cover data of vascular plants per plot and year. SpeciesCode --&gt; Species' identifier, identical across years Functional_type --&gt; Species were assigned as grass, herb or shrub species AEG01 etc. --&gt; plot-specific ID03_Landuse_2006to2008The files 03_Landuse_2006to2008 and 03_Landuse_2007to2009 include land-use information per plot and year. ID --&gt; Row name based on year and PlotID Year --&gt; Year for which land-use is given PlotID --&gt; plot specific ID Region --&gt; One of three regions in Germany in which plot is located Fertilization --&gt; intensity of fertilization estimated as kg Nitrogen per hectar Grazing --&gt; intensity of grazing estimated as lifestock-units-days per hectar Mowing --&gt; number of cutting events per year03_Landuse_2007to2009The files 03_Landuse_2006to2008 and 03_Landuse_2007to2009 include land-use information per plot and year. ID --&gt; Row name based on year and PlotID Year --&gt; Year for which land-use is given PlotID --&gt; plot specific ID Region --&gt; One of three regions in Germany in which plot is located Fertilization --&gt; intensity of fertilization estimated as kg Nitrogen per hectar Grazing --&gt; intensity of grazing estimated as lifestock-units-days per hectar Mowing --&gt; number of cutting events per year04_SEMData_2008The files 04_SEMData_2008 and 04_SEMData_2009 include compiled information used for structural equation modeling. PlotID --&gt; plot specific ID Region --&gt; One of three regions in Germany in which plot is located (SEM was conducted for each region separately) Fertilization --&gt; intensity of fertilization, averaged over three years and standardized per region Grazing --&gt; intensity of grazing, averaged over three years and standardized per region Mowing --&gt; intensity of mowing, averaged over three years and standardized per region Time_after_mowing --&gt; Number of days between last mowing event and sampling in the year of sampling Plant_SpeciesRichness --&gt; Number of vascular plant species Plant_biomass --&gt; Plant biomass [g dry weight] Herbivore_SpeciesRichness --&gt; Number of herbivorous arthropod species Predator_SpeciesRichness --&gt; Number of arthropod predator species Herbivore_biomass --&gt; Overall biomass [mg] of herbivore species Predator_biomass --&gt; Overaall biomass [mg] of predator species Lifestock --&gt; Type of lifestock on the plot (only for 2008 data)04_SEMData_2009The files 04_SEMData_2008 and 04_SEMData_2009 include compiled information used for structural equation modeling. PlotID --&gt; plot specific ID Region --&gt; One of three regions in Germany in which plot is located (SEM was conducted for each region separately) Fertilization --&gt; intensity of fertilization, averaged over three years and standardized per region Grazing --&gt; intensity of grazing, averaged over three years and standardized per region Mowing --&gt; intensity of mowing, averaged over three years and standardized per region Time_after_mowing --&gt; Number of days between last mowing event and sampling in the year of sampling Plant_SpeciesRichness --&gt; Number of vascular plant species Plant_biomass --&gt; Plant biomass [g dry weight] Herbivore_SpeciesRichness --&gt; Number of herbivorous arthropod species Predator_SpeciesRichness --&gt; Number of arthropod predator species Herbivore_biomass --&gt; Overall biomass [mg] of herbivore species Predator_biomass --&gt; Overaall biomass [mg] of predator species Lifestock --&gt; Type of lifestock on the plot (only for 2008 data)ReadMe_DatapackageThis file contains a description of the complete datapackage, individual ReadMe files are available for each data file.