The response of epigeal beetles (Col: Carabidae, Staphylinidae) to varied grazing regimes on upland Nardus stricta grasslands

Published source details Dennis P., Young M.R., Howard C.L. & Gordon I.J. (1997) The response of epigeal beetles (Col: Carabidae, Staphylinidae) to varied grazing regimes on upland Nardus stricta grasslands. Journal of Applied Ecology, 34, 433-443.
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Summary

The effect of different livestock (sheep and cattle) grazing regimes on epigeal (surface dwelling) Carabid and Staphylinid beetles in an upland, semi-natural, mat-grass Nardus stricta-dominated grassland in an experiment established in 1991 was measured in 1993 and 1994.

Study site: The experiment, established in 1991, was undertaken on species poor mat-grass Nardus stricta grassland on Blackdean Curr (National Grid ref. NT 8321/8421 -22) at 450-500 m a.s.l.

Grazing regimes: Grazing by sheep, or sheep and cattle, to achieve two different inter-tussock sward heights (4.5 cm and 6-7 cm), provided four treatments. In addition, a further treatment was ungrazed from 1992 to test the impact on beetles of a short-term cessation of grazing, trampling and dung inputs.

Pitfall trapping: Pitfall traps (from April to October in 1993 and 1994; years three and four of the experiment) sampled epigeal Carabid and Staphylinid beetles within the Nardus stricta-dominated grassland. The epigeal Coleoptera species were ranked by decreasing abundance in traps, where the captures in traps were accumulated for both trapping seasons.

The responses to the grazing regimes were analyzed using ANOVA, applied to the most abundant species that together represented 99% of the two seasons' catch.

Vegetation: The treatments grazed to 4-5 cm sward height, particulary sheep and cattle combined, were characterized by larger open patches of Agrostis (bent) - Festuca (fescue) dominated sward with smaller Nardus tussocks. The vegetation in the ungrazed control was taller, with inter-tussock growth greater than the tussocks themselves thus giving a more homogeneous appearance compared to grazed areas.

BeetlesA total of 36,176 beetles of 68 species was captured during the two trapping periods in 1993 and 1994. The five most abundant species, Calathus melanocephalus, Tachinus signatus, Pterostichus madidus, Carabus problematicus and violet ground beetle Carabus violaceus, accounted for 84% of the catch; 16 species accounted for 95% and 32 species for 99% of the total captures.

There were significant experimental effects of grazing regime on five of these 32 Coleopteran species i.e. violet ground beetle Carabus violaceus, Othius angustus, Pterostichus strenuous, Xantholinus linearis and Olophrum piceum.

Twenty-four of the 32 most abundant Coleopteran species correlated with the effects of different grazing regimes on the Nardus grassland. Greater abundances of C.violaceus, O.angustus, X.linearis and Tachinus corticinus were indicative of the typical upland grassland and heathland Coleoptera assemblage.

Sheep and cattle grazing to a sward height of around 6-7 cm favoured a large number of species, whilst also preventing expansion of N.stricta. Further analysis also suggested that grazing regimes should be varied in rotation over time to achieve a mosaic of structurally different grassland patches (0.70-4.73 ha) because this encourages a greater overall species diversity.

Conclusions: Benefits to Coleopteran diversity on Nardus grassland was achieved through appropriate grazing regimes. Sheep and cattle grazing to a sward height of around 6-7 cm favoured a large number of species, whilst also preventing expansion of N.stricta. A rotation of varied management using different combinations of grazers and different grazing intensities would encourage a wider beetle diversity by creation of a structurally varied mosaic of grassland patches.

Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://links.jstor.org/sici?sici=0021-8901%28199704%2934%3A2%3C433%3ATROEB%28%3E2.0.CO%3B2-1