Effect of crop configuration (monoculture versus strip cropping) on ground beetle biodiversity.

(a) Location of experimental sites in the Netherlands. (b) Field set-up of the two crop configurations: monoculture and strip cropping. At Lelystad and Wageningen, strip cropping consisted of 3-m wide crop strips of two crops (pairs), and multiple crop pairs were assessed. At Almere and Valthermond, strip cropping consisted of 6-m wide crop strips of eight crops combined (Fig. S10). (c) Sample-based species accumulation curves of all year series from monocultures (brown) and strip cropping (green), in Almere from 2021 and 2022. This was the only location where an equal number of samples were taken in the monocultures and in strip cropping on a similar area. Ground beetle species include Poecilus cupreus (left) and Pterostichus melanarius (right). Photo credit: Ortwin Bleich, retrieved from: www.eurocarabidae.de. (d-e) Overall relative change in field-level ground beetle (d) taxonomic richness and (e) activity density. Positive values indicate higher richness or activity density in strip cropping, negative values in monocultures. (f-j) Overall relative effect of crop configuration on ground beetle (f) taxonomic richness, (g) activity density, (h) absolute evenness, (i) inverse Simpson index, and (j) Shannon entropy. (k) Effect of crop configuration on ground beetle taxonomic richness for each combination of location, year and crop. Barley-mixture consists of a mixture of barley-bean (2020) or barley-pea (2021). Squares indicate estimated means, the bar indicates the 95% confidence interval. Asterisks indicate significant differences among the crop configurations. Empty panels indicate combinations of years and locations that were not sampled. When no estimated mean and confidence interval are shown, crops were not grown or sampled in that year. Open circles indicate individual year series to visualize sample size (Table S7).

Effect of crop configuration on ground beetle community composition.

Results from permanova analysis using Hellinger’s transformation for data from the three locations with species level data (see Table S3 for analyses per location). Crops were a nested variable within years, as these differed among years. Years were nested in locations, as the years that were studied differed among locations. Bold letters indicate significant effects (α = 0.05).

Ground beetle species associated with crop configuration (monoculture (a) versus strip cropping (b)).

Results obtained by generalized linear mixed models on the 12 most common genera of ground beetles with the four locations analysed separately (Table S5). Only those genera are given for which cropping system significantly influence activity density within at least one location (α = 0.05). Locations were the genus had a higher activity density in one of the cropping systems are indicated between brackets (Al=Almere; Le = Lelystad; Va = Valthermond; Wa = Wageningen). For Pterostichus, data from Almere in 2020 was analysed separately, as models did not fit elsewise. The asterisk “*” next to Pterostichus indicates that only in 2020 the difference between monoculture and strip cropping was significant. Photo credit: Ortwin Bleich, retrieved from: www.eurocarabidae.de.