Responses of grassland invertebrates to management by cutting. I. Species diversity of Hemiptera.
Abstract
The effects of cutting calcareous grassland on its invertebrate fauna were examined in an Arrhenatherum-dominated grass plot in eastern England. Four treatments (cutting in May, in July, in both May and July, and control (untreated)) were applied annually to four randomised blocks of plots, each of which was sampled regularly with a vacuum insect net. Adult Hemiptera (Heteroptera and Auchenorhyncha) were identified to species and the effects of cutting on their numbers, abundance and diversity determined. Simpson's and Brillouin's indices of species-diversity were preferred for statistical and practical reasons and to maintain continuity with previous work, but Simpson's index proved to be rather insensitive to changes brought about by cutting. Cutting in May slightly reduced the abundance and diversity of Heteroptera, the effects being short-lived. The effects on the abundance and species-richness of Auchenorhyncha were more marked and more persistent, but diversity was scarcely reduced. Abundance, richness and diversity of both groups were consistently reduced by cutting in July. The effects on Heteroptera persisted until about January, but those on Auchenorhyncha until shortly before the May cut; there was little difference between the effects of cutting in both May and July and cutting in July only. The results show that cutting only in May can maintain a high richness and diversity of Hemiptera on areas of grassland, including nature reserves, where management is necessary or imposed. Rotational management by cutting is advocated as a system of managing grassland nature reserves, and it is easier to establish than rotational grazing.