Is there a benefit of excluding sheep from pastures at flowering peak on flower-visiting insect diversity?

Abstract

Permanent grasslands are an important habitat for insect communities, including pollinator populations which are in pan-European decline. Here, we investigated the benefits of temporarily excluding sheep from pastures on butterfly (Lepidoptera: Rhopalocera and Zygaenidae) and bumblebee (Hymenoptera: Bombidae) communities in two semi-natural grasslands differing in soil fertility and surrounding landscapes. We compared the impact of continuous grazing against rotational grazing (RG) at the same stocking rate but in which a subplot was excluded from the rotation during the main flowering period. We predicted that the diversity of flower-visiting insect community would be improved by RG due to the preservation of flower-rich patches and the maintenance of sward heterogeneity. Benefits of RG management were mainly evidenced on bumblebee density and species richness, with some additional effects on local density of butterflies during the subplot-exclusion period. Temporarily excluding sheep from pastures during peak flowering could thus offer an opportunity to preserve the diversity of flower-visiting insects, in spite of weaker benefits than could have been expected from previous surveys with cattle.

Flower abundance and vegetation height as predictors for nectar-feeding insect occurrence in Swedish semi-natural grasslands

“…Numbers to the right are species-wise information on number of occurrences and total number of sites in the models. Dewenter and Tscharntke, 1997;Franzén and Nilsson, 2008;Wallis de Vries et al, 2012;Scohier et al, 2013). However, Sjödin et al (2008) found that butterflies only responded to vegetation height and not to flower abundance.…”

Forty research issues for the redesign of animal production systems in the 21st century

“…For instance, the analysis of underlying mechanisms involved in grazing management (i.e. relationships between stocking rate and sward heterogeneity, animal selectivity) can explain the success or failure of grazing practices aiming to combine production and biodiversity conservation (Scohier et al, 2013). In addition, the ecological rationale of traditional small-scale systems needs to be analyzed to understand the mechanisms contributing to their success.…”

Effects of different types of low‐intensity management on plant‐pollinator interactions in Estonian grasslands

“…Body size class is a three-level factor (small, medium, large), but the level "small" has been excluded from the analysis, since it was represented by only one pollinator species (see Appendix B1 for details on the assignment of insect traits). Significant (p < .05) results are printed in bold and their differences are visualized in Figure 6 Explanatory factors reducing the diversity of pollinator groups (Scohier et al, 2013).…”