Strip management of wildflower strips promotes beneficial arthropods in the late season via enhanced floral resources
Description
Wildflower strips are among the most widely employed agri-environmental schemes to support beneficial arthropods and enhance biodiversity in agricultural landscapes. However, despite the need for active vegetation management to maintain high flower abundance and stable arthropod populations, evidence on different management techniques is limited. Here, we assessed the impact of three management schemes (whole-strip mulching, strip mulching, and strip mowing) on the species richness, abundance, and community composition of six beneficial arthropod taxa (three pollinator groups and three predator groups). In a 2-year manipulative experiment with 24-m-wide wildflower strips, we sampled multi-taxa arthropod communities using complementary sampling methods in the early, mid, and late seasons and quantified floral abundance and vegetation height. Overall, we found that strip management of wildflower strips was associated with higher late-season richness and abundance of most taxa than full mulching. These benefits were mostly linked to enhanced floral resources, whereas spiders were associated with vegetation height. Strip mulching and strip mowing yielded similar values of richness and abundance throughout the season, suggesting that mulching may not have negative effects on the studied taxa. These results have clear implications for wildflower strip management schemes, as maintaining high floral availability in perennial flower strips is essential for sustaining arthropod populations across time. As many farmers prefer mulching for practical reasons, given that it is a simpler process and biomass from wildflower strips is often of limited value as fodder, we recommend mulching only under strip management to maintain refugia during management events.
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Experimental design and management treatments The study was performed in 2024 and 2025 in the northeast of Prague, Czech Republic. We selected eight conventionally managed arable fields with wildflower strips at their margins. Wildflower strips were sown on April 12th 2024. Each wildflower strip was divided into three segments of at least 100 m long and different management treatments were randomly assigned to each segment: i) Mulching once a year in peak summer, when the entire area of the given wildflower strip segment was mulched (hereafter, full mulching); ii) Strip mulching three times a year, when only half of the given wildflower strip segment was mulched in early summer, peak summer, and autumn; and iii) Strip mowing three times a year, when only half of the given wildflower strip segment was mown in early summer, peak summer, and autumn, with each mowing event followed by plant biomass collection and removal several days later. Arthropod and vegetation sampling Six taxa of beneficial arthropods were sampled. Pollinators were represented by butterflies (Lepidoptera), bees and wasps (Bees and wasps except for Formicidae), and hoverflies (Syrphidae). Predators included spiders (Araneae), ladybirds (Coccinellidae), and true bugs (True bugs). Arthropods were sampled using a combination of sweep-netting and individual sampling. Sampling was conducted three times in 2024 at approximately monthly intervals: in late June, mid-July, and late August. In 2025, sampling was conducted five times at approximately monthly intervals: mid-May, mid-June, mid-July, mid-August, and late September. In the central part of each wildflower strip segment, we established a 24 × 24 m sampling plot. Sweep-netting, consisting of 50 sweeps with a sweep net 35 cm in diameter, was performed evenly across the entire area of each sampling plot. In the strip-mulching and strip-mowing segments, both parts of the plot (i.e., mown/mulched and unmown/unmulched) were swept equally. During individual sampling of butterflies and Hoverflies, all individuals were recorded by an experienced expert for 5 min per plot. Taxonomically problematic specimens were preserved in diluted ethanol for later identification in the laboratory. Sweep-net samples were sacrificed with chloroform and stored in a freezer without preservatives. All stored samples were sorted into the target taxa mentioned above in the laboratory, and all sorted individuals were identified to species level by specialists. For Hoverflies, data from sweep-netting and individual sampling were pooled for each wildflower strip segment and date. During each arthropod sampling period, mean vegetation height (cm) was measured at several randomly selected points per plot and averaged. The availability of flowering dicots was visually assessed at the surface of the sampling plot, and the percentage of the plot surface covered by flowering plants was calculated.
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- Technology Agency of the Czech Republic