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Keywords:

  • Agriculture;
  • Auchenorrhyncha;
  • Cicadellidae;
  • Delphacidae;
  • grassland;
  • grazing;
  • Hemiptera;
  • heterogeneity;
  • Linyphiidae;
  • Lycosidae

Abstract.  1. Cattle avoid grazing around their dung. This pattern persists after the decomposition of the initial dung patch leading to the formation of taller grass patches, termed islets. It is known that islets hold a disproportionate amount of the arthropods in grazed grasslands.

2. An experimental manipulation was set up to investigate the relative effects of vegetation structure and nutrient input on arthropod distributions. Herbivorous bugs (Hemiptera) and predatory spiders (Araneae) were sampled in artificially generated islets treated with dung, fertiliser, a cutting regime to mimic grazing and a fallow control.

3. The densities of both Hemiptera and Araneae were affected by the presence of increased nutrient input through dung and fertiliser. The densities of different herbivore taxonomic families were influenced by food plant quality and the predators by the subsequent increase in prey density.

4. Delphacidae (Hemiptera) showed a preference for taller more nutrient rich swards treated with fertiliser, whereas Cicadellidae (Hemiptera) were more abundant in those swards treated with dung. Lycosidae (Araneae) were more common in dung-treated swards, whereas Linypiidae (Araneae) were more common in the taller fertiliser-treated swards.

5. Higher Hemiptera species richness was found in the fertiliser- and dung-treated swards. It is believed that this effect was because of nutrient availability.

6. It is likely that the presence of cattle dung islets in grazed grassland plays an important role in the maintenance of biodiversity, through increasing structural heterogeneity.