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