Individual study: Provision of plant resources for beneficial arthropods in arable ecosystems
MacLeod A. (1994) Provision of plant resources for beneficial arthropods in arable ecosystems. PhD thesis. University of Southampton.
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Create beetle banks
A replicated study on one beetle bank on a mixed farm in north Hampshire, UK (MacLeod 1994) found the densities of both ground beetles (Carabidae) and rove beetles (Staphylinidae) in four grass treatments showed two peaks in density over the study period (the seven winters of 1987-1988 to 1993-1994), in the second and sixth winter after establishment. The pattern was the same for spiders (Araneae) in cock’s-foot Dactylis glomerata, but in Yorkshire fog Holcus lanatus, creeping bent Agrostis stolonifera and perennial rye grass Lolium perenne the densities steadily increased and peaked in the fifth winter. Ground beetle densities over the seven year period in the different grass plots were as follows: cock’s-foot 11-110 individuals/m2, creeping bent 3-15/m2, perennial rye grass 2-11/m2 (only five winters), Yorkshire fog 1-76/m2. The respective rove beetle densities over the seven (or five) winters were: cock’s-foot 1-125 individuals/m2, creeping bent 0-67/m2, perennial rye grass 2-79/m2, Yorkshire fog 2-113/m2. Cock’s-foot and Yorkshire fog generally had the highest densities of predators but not always significantly so. The grass species composition in plots sown with cock’s-foot, Yorkshire fog and creeping bent remained relatively similar (min. 85% of original grass species left) during the study. Plots of false oat-grass Arrhenatherum elatius and red fescue Festuca rubra were created and added to the study in 1991. The 290 m-long beetle bank was created in spring 1987 and split into six blocks, each further sub-divided into eight plots with one treatment/plot. The eight treatments were sown cock’s-foot (3 g/m2), sown Yorkshire fog (4 g/m2), sown perennial rye grass (3 g/m2), sown creeping bent (8 g/m2), mix of three grass species (cock’s-foot, Yorkshire fog, perennial rye grass), mix of four grass species (previous three species plus creeping bent), bare ground, and sown flowering plants to provide pollen and nectar resources. Predatory invertebrates were sampled by taking two 20 x 20 x 10 cm turf samples/plot/winter. Percentage cover of grasses was measured in the four original grass treatments in October 1992 by placing six 25 x 25 cm quadrats in each grass plot, and in winter 1993-1994 it was measured in the collected turf samples. For methods in the first three winters see (Thomas 1991). This study was part of the same experimental set-up as (Thomas 1991, Thomas et al. 1991, Thomas et al. 1992, MacLeod et al. 2004).
Create beetle banks
A replicated study over seven winters from late 1987 to early 1994 on one beetle bank in Hampshire and one in Essex, UK (MacLeod 1994) found sections sown with the grasses cock’s-foot Dactylis glomerata or Yorkshire fog Holcus lanatus generally had highest densities of predatory invertebrates, but not always significantly so. Ground beetles (Carabidae) and rove beetles (Staphylinidae) had higher densities in cock’s-foot (11-110 ground beetles/m², 1-125 rove beetles) and Yorkshire fog (1-76 ground beetles/m², 2-113 rove beetles) than two other grass species (2-15 ground beetles/m², 0-79 rove beetles). Ground beetle and rove beetle densities peaked in the second and sixth winters after banks were established. The pattern was the same for spiders (Araneae) in cock’s-foot but in Yorkshire fog, creeping bent Agrostis stolonifera and perennial ryegrass Lolium perenne the densities steadily increased to a maximum in the fifth winter. The 200 m long beetle bank in Essex had a lower density of ground beetles than a nearby hedge bottom (0.7 individuals/m² vs. 2.6 individuals). The 290 m long Hampshire beetle bank was created in spring 1987 and split into six blocks, each further sub-divided into eight plots with one sown grass treatment/plot. This study was part of the same experimental set-up as Thomas 1991, Thomas et al. 1991, Thomas et al. 1992 and MacLeod et al. 2004.
Plant nectar flower mixture/wildflower strips
A series of four studies from 1991 to 1993 in Hampshire, UK (MacLeod 1994) found the abundance of some hoverfly (Syrphidae) species was higher in areas with sown flower strips than in control sections and hoverflies preferred foraging on certain plant species. Two trials showed hoverflies foraged on sweet alyssum Lobularia maritima, buckwheat Fagopyrum esculentum, coriander Coriandrum sativum, borage Borago officinalis, sunflower Helianthus annuus and dwarf marigold Calendula officinalis compared to other plant species or field margins. A field-scale trial found no difference in the total number of hoverflies, but more marmalade flies Episyrphus balteatus (39 vs 4 individuals/field boundary) in a winter wheat field with a 2 m-wide strip of coriander than a control field. More aphids (Aphidoidea) were found on marked wheat ears in the control field. In 1993 an unreplicated, controlled study found more males and females of three hoverfly species/genera (E. balteatus, Metasyrphus corollae and Eristalis spp.) in a 2 m-wide strip (240 m-long, divided into 0.75 x 10 m plots) sown with 13 plant species (including amaranthus Amaranthus spp., safflower Carthamus tinctorius and quinoa Chenopodium quinoa) in a spring barley field than a control strip on the same field between 7 and 14 July. Plant species used for foraging had small (less than 4 mm diameter) white or yellow flowers and easily accessible anthers and pollen (buckwheat, coriander, gold-of-pleasure Camelina sativa and texsel Brassica carinata). Hoverflies were recorded using transect walks and fluorescent yellow water traps. Ten wheat plants around each yellow water trap were used to count the number of aphids.