Grazing impacts on Auchenorrhyncha diversity and abundance on a Scottish upland estate

1. Livestock grazing impacts on insect populations in a variety of ways. For phytophagous insects the impact is primarily a result of altering the structure and species assemblage of vegetation. However not all species react in similar ways and even within an order there may be winners and losers from different grazing regimes. 2. A long-term, replicated, controlled experiment, comprising four grazing treatments, was established within an upland acid grassland area in Scotland. Auchenorrhyncha were sampled by suction sampling and sweep-netting in the fifth year following the start of the treatments. 3. A significant treatment effect was apparent in the suction samples with Auchenorrhyncha abundance being three to four times higher in the ungrazed plots compared to the other treatments. Abundance was also highest from the ungrazed plots in the sweep net samples, but this effect was not statistically significant. Redundancy analysis (RDA) showed that a suite of species which are typical of shaded positions responded with increased abundance in the ungrazed plots. 4. The findings demonstrate that the assemblages found in ungrazed areas can be vastly different to those found in even lightly grazed areas and therefore, underline the benefits of varied grazing regimes in maximising diversity. Furthermore, the work underlines the benefit of employing multiple sampling methods.