Effects of reduced grazing intensity on pasture vegetation and invertebrates

The lack of invertebrate prey on intensively grazed agricultural grassland can limit reproductive success in farmland birds. The impacts of lenient early season grazing followed by early cessation of grazing on sward structure and invertebrate communities on improved agricultural grassland were tested. The experiment was conducted on 13 pasture fields in south-west England over four successive years. Lenient early season grazing increased total invertebrate abundance by 71% after 4 years, the most responsive groups being Araneae, Auchenorrhyncha, Collembola and Heteroptera. Early cessation of grazing led to increased cover of Holcus lanatus and Agrostis spp. and increased litter accumulation; clover cover and sward structural heterogeneity declined. These sward changes are likely to have reduced agricultural productivity and may have inhibited access to invertebrate prey for foraging birds.

► Lenient grazing increased sward height but reduced sward heterogeneity.
► Grass cover and the abundance of leaf litter increased during the study.
► Invertebrate abundance rose and a shift to detritivores and grass feeders occurred.
► A balance between invertebrate abundance and accessibility for birds must be found.