Responses of grassland invertebrates to management by cutting. II. Heteroptera.
Abstract
Adult Heteroptera were sampled regularly in 1973-75 in experimental plots of Arrhenatherum-dominated calcareous grassland in Cambridgeshire, UK. The experiment, in four replicates of four randomised block treatments, compared grassland cut in May or July or in both months with untreated grassland. Eighteen species were sufficiently abundant for statistical analysis. The data were pooled for three periods of the year: before the May cut (January to May), between cuts (May to July) and after the July cut (July to December). Fourteen species showed statistically significant effects of the cutting treatments in at least one period of the year; only once were numbers greater on a treatment than on the controls: in 1974, before the May cut, there were significantly more (P < 0.05) Notostira elongata (Geoffr.) on plots cut the preceding May than on the untreated grassland. In every other case where there were significant differences, there were fewer on cut plots. Stygnocoris pedestris (Fall.), all species of Nabidae, Tytthus pygmaeus (Zett.) and Megaloceroea recticornis (Geoffr.) were severely reduced. Some, especially M. recticornis, were less severely reduced by the May cut than by the July one, whether as a single application or in combination with the May one. The timing of cutting in relation to the life-cycles of the different species is shown to be important. N. elongata, a double-brooded species, was less susceptible to cutting than other Stenodemini, and Leptopterna ferrugata (Fall.) was reduced by the May cut in the period between cuts when most individuals became adult. The effects of cutting are compared with those of other types of grassland management. Timing of cutting and its catastrophic nature compared with grazing, are emphasised. Objectives of management and alternative methods of achieving them are considered. Reclamation and maintenance management, single and multiple treatments, rotational, winter and seasonal treatment, and the size and kind of nature reserves to be managed, are discussed.