A biodiversity-friendly rotational grazing system enhancing flower-visiting insect assemblages while maintaining animal and grassland productivity
Résumé
Grazing management is an important tool to preserve insect biodiversity. Although literature has
discussed the importance of grazing pressure adjustment to support grassland insect communities for
the ecosystem services they provide, little has been published on the economic sustainability of such
management adjustments to date. This study compared continuous grazing (CG) to an innovative
rotational grazing system (the biodiversity-friendly rotation – BR), where a subplot was excluded from
grazing for two months during the main
flowering period. The effects of grazing two different species
(cattle and sheep) within both systems were also evaluated. The aims were to assess the effects on
butterfly, bumblebee, and ground beetle assemblages, along with the impact on herbage mass and animal
performance. The BR enhanced both the abundance and species richness of
flower-visiting insect
assemblages and it was observed that cattle provided better results than sheep grazing. A multivariate
redundancy analysis highlighted that most of the
flower-visiting species (including almost all the
endangered and locally rare species) were favoured by BR-cattle treatment, mainly due to the high
percentage of
flower cover and sward heterogeneity involved in this treatment. However, grazing system
and grazer species did not affect ground beetle species richness or abundance. Moreover, herbage mass
and animal performance (live weight and body condition score) were comparable between CG and BR
throughout the grazing season. The BR could be a useful management system to enhance grassland
flower-visiting insect assemblages whilst meeting farm production objectives, especially in protected
environments where insect conservation is a major target.
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