Uncut grass refuges mitigate the impact of mechanical meadow harvesting on orthopterans

Semi-natural grasslands require regular harvesting (cutting) or grazing to avoid vegetation succession, and this is well known to promote plant diversity. However, recent studies have shown that meadow harvesting has a severe direct negative impact on orthopterans and other grassland invertebrates. In view of this, leaving areas of uncut grass as refuges has often been recommended as a mitigation measure. Yet to date no studies have tested this hypothesis. We experimentally investigated the direct influence of leaving a 10% uncut grass refuge in the centre of 50 m diameter meadow plots on orthopteran population. During harvest, orthopteran densities dramatically declined within mown areas and doubled within refuges, showing that during the mowing stage some individuals actively moved to uncut areas, safe from the impact of post-mowing stages. After baling, final orthopteran population sizes were on average 53% higher in plots with an uncut refuge, compared to plots without. To maximise the benefit of refuges, we recommend mowing towards the refuge, as this is likely to drive field invertebrates into the refuge. (C) 2012 Elsevier Ltd. All rights reserved