Grassland nature reserves safeguard a high species richness and biomass of grasshoppers
Data files
Aug 17, 2024 version files 7.76 KB
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Data_landscape_scale.csv
2.27 KB
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Data_patch_scale.csv
1.41 KB
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README.md
4.08 KB
Abstract
In the course of land-use change, especially since the mid-20th century, the area of semi-natural (unimproved) grasslands has dramatically decreased. One way to counteract this process is to designate nature reserves. However, the effectiveness of nature reserves is controversial.
The aim of our study was to evaluate the environmental drivers of species richness and biomass of Orthoptera (hereinafter termed ‘grasshoppers’) in grasslands inside nature reserves and within the intensively-used agriculture landscape (hereinafter termed ‘wider countryside’). For this purpose, we sampled the grasshoppers at the landscape scale in 45 randomly selected plots. Each plot had a size of 5 ha. The abundance of grasshoppers, as a basis for the biomass calculation, was recorded at the habitat scale in 20 meadow patches (500 m² each). In addition, various environmental parameters such as habitat diversity, mowing intensity and vegetation structure were determined at the landscape and habitat scale.
Our results illustrate the importance of nature reserves for the conservation of grasshoppers. Control plots in the wider countryside harboured fewer species than plots within nature reserves. The differences were even clearer among threatened species. On average, plots in nature reserves had almost twice as many threatened species than control plots in the wider countryside. The comparison revealed similar patterns at the habitat scale: both the number of species and biomass were higher in nature reserves. At the landscape scale, number of species were best explained by the amount of wet grassland and habitat diversity. We identified mowing intensity and to a lower extend the degree of drainage as the key drivers of species richness and biomass at the habitat scale.
Synthesis and applications: To preserve biodiversity in nature reserves, we recommend (i) leaving uncut refuges during mowing and (ii) blocking drainage to stabilize the water level. Both measures contribute to a high species number and abundance of grasshoppers and many other insects. An effective conservation measure to promote species richness in the wider countryside would be to increase habitat diversity. This can be done by creating or restoring fallow islands, field margins, fringes and hedgerows.
README: Grassland nature reserves safeguard a high species richness and biomass of grasshoppers
https://doi.org/10.5061/dryad.ghx3ffbz9
Description of the data and file structure
These are species (Orthoptera) and environmental data collected in the field at two spatial scales (csv. files). A detailed description of the methodology and structure of the data can be found in Poniatowski et al. (2024): Grassland nature reserves safeguard a high species richness and biomass of grasshoppers. Journal of Applied Ecology.
Files and variables
File: Data_landscape_scale.csv
Description: plots of 5 ha
Variables
no_plot: Name (abbreviation) of the sample site
species_no_all: Number of all species detected
species_no_threatened: Number of threatened species detected
subarea: The study area was divided into six subareas according to landscape configuration
temperature: Summer temperature (°C) (long-term mean: 1991–2020)
precipitation: Annual precipitation (mm) (long-term mean: 1991–2020)
elevation: m a.s.l.
arable_land: Cover of this land-use types (%) within a radius of 200 m around each plot
forest: Cover of this land-use types (%) within a radius of 200 m around each plot
grassland: Cover of this land-use types (%) within a radius of 200 m around each plot
urban_area: Cover of this land-use types (%) within a radius of 200 m around each plot
habitat_diversity: The number and proportion of the habitat types per plot were used to calculate the Shannon index (H′) as a measure of habitat diversity
wet_grassland: Cover within each plot
File: Data_patch_scale.csv
Description: meadow patches of 500 m²
Variables
- no_patch: Name (abbreviation) of the sample site
- species_no_all: Number of all species detected
- biomass_all: To calculate biomass, we used the sampled grasshopper abundance data and the available species- and sex-specific weights (Table S5). In order to get a value for the nymphs, the mean weights of the adults were halved. The result of multiplying abundance and weight was an area-specific grasshopper biomass value (g/10 m²).
- plot_type: Grassland inside or outside nature reserves
- subarea: The study area was divided into six subareas according to landscape configuration.
- mowing_intensity: We used the data set provided by Schwieder et al. (2022) to determine the mowing frequency within the patches. Using a special remote sensing procedure based on a combined "Sentinel-2 and Landsat 8 time series", the authors measured the intensity of land use for mown grassland in Germany between the years 2017 and 2020. The result is a raster data set (spatial resolution 10 m × 10 m) that divides the mowing frequency into seven categories (0 to 6 mowing events per year). To determine the land-use intensity within each meadow patch, the mowing data set was merged with the geometry of the patch. Afterwards, we calculated the mean mowing intensity per year for each patch.
- drainage: To estimate the hydrological conditions in and around the respective patch, we measured the length of the ditches in ArcGIS 10.3.1 and determined the depth of the ditches at five random locations per ditch. A draining index was then calculated from the summed ditch length and the mean value of the ditch depth (draining index = ditch depth [m] × ditch length [m]).
- height_field_layer: The vegetation height of the field layer was measured at five randomly selected points at an accuracy of 2.5 cm within the respective meadow patch and the mean value was then calculated.
- cover_field_layer: We estimated the cover in steps of 5% for the entire meadow patch.
- cover_sedges: We estimated the cover in steps of 5% for the entire meadow patch.
- cover_mosses: We estimated the cover in steps of 5% for the entire meadow patch.
- cover_litter: We estimated the cover in steps of 5% for the entire meadow patch.
- cover_bare_soil: We estimated the cover in steps of 5% for the entire meadow patch.
Code/software
Excel