Grass strip corridors in agricultural landscapes enhance nest-site colonization by solitary wasps
This study is summarised as evidence for the following.
Connect areas of natural or semi-natural habitatAction Link
Connect areas of natural or semi-natural habitat
A replicated study in 2004 in Lower Saxony, Germany (Holzschuh et al. 2009) found that the numbers of cavity nesting wasp (Hymenoptera) species, brood cells and caterpillar-hunting wasp (Eumenidae) brood cells in trap nests, were higher in grass strips connected to forest edges than in trap nests in isolated grass strips. The number of wasp species was significantly higher in connected (2.3 species) than in highly isolated grass strips (0.8), differences were not significant between connected and slightly isolated (1.2) or between slightly and highly isolated strips. Numbers of wasp brood cells were significantly higher in connected (30 brood cells) than slightly (7) and highly isolated grass strips (4), caterpillar-hunting wasps showed the same pattern. Numbers did not differ between strip types for spider-hunting wasps (Sphecidae), species richness of parasitoids or numbers of parasitized brood cells. At each of 12 arable sites, 9-12 traps were placed in three types of 3 m-wide grass strip: ‘connected’ strips connected via a corridor to a forest edge (traps set 200 m from forest), ‘slightly isolated’ strips separated from forest by a cereal field (traps 200 m from forest, no connecting corridor) and ‘highly isolated’ strips 600 m from the nearest forest edge (no connecting corridor). Distances between trap nests were at least 600 m. Trap nests consisted of four plastic tubes filled with common reed Phragmites australis sections (2-10 mm diameter) and were installed at a height of 1.0-1.2 m from April-September 2004.