Action: Create uncultivated margins around intensive arable or pasture fields
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- Thirty-nine studies (including 13 replicated controlled trials of which three also randomized and four reviews) from eight European countries compared wildlife on uncultivated margins with other margin options. Twenty-four found benefits to some wildlife groups (including 11 replicated controlled trials of which one also randomised, and four reviews). Nineteen studies (including one randomized, replicated, controlled trial) from Germany, Ireland, Lithuania, Norway, the Netherlands and the UK found uncultivated margins support more invertebrates (including bees) and/or higher plant diversity or species richness than conventionally managed field margins or other field margin options. One replicated, controlled study showed that uncultivated margins supported more small mammal species than meadows and farmed grasslands. Four studies (two replicated UK studies, two reviews) reported positive associations between birds and field margins including food provision. A review from the UK found grass margins (including naturally regenerated margins) benefited plants and some invertebrates.
- Fifteen studies (including one randomized, replicated, controlled trial) from Germany, the Netherlands, Norway and the UK found that invertebrate and/or plant species richness or abundance were lower in naturally regenerated than sown margins. Six studies (including one randomized, replicated, controlled trial) from Belgium, Germany and the UK found uncultivated margins did not have more plant or invertebrate species or individuals than cropped or sown margins. A review found grass margins (including naturally regenerated margins) did not benefit ground beetles. or
- Five studies (including three replicated controlled trials) from Ireland and the UK reported declines in plant species richness and invertebrate numbers in naturally regenerated margins over time. One replicated trial found that older naturally regenerated margins (6-years old) had more invertebrate predators (mainly spiders) than newly established (1-year old) naturally regenerated margins.
- Five studies (including one replicated, randomized trial) from the Netherlands and the UK found that cutting margins had a negative impact on or no impact on plant species. One replicated controlled study found cut margins were used more frequently by yellowhammers when surrounding vegetation was >60 cm tall.
- Seven studies (including four replicated controlled trials and a review) from Ireland, the Netherlands, Norway and the UK reported increased abundance or biomass of weed species in naturally regenerated margins.
This intervention allows the field margin vegetation to regenerate naturally, without planting, although it can involve subsequent mowing. The field margins are not fertilized and only spot-treated with herbicides if injurious weeds occur.
Supporting evidence from individual studies
A replicated study in 1988 in East Anglia, UK (Hassall et al. 1992) found that ground beetles (Carabidae), true bugs (Heteroptera) and spiders (Araneae) were more abundant in uncropped headlands than cropped conservation (restricted pesticides) and conventional headlands. For each group, significantly more individuals were found in uncropped headlands (average number of individuals per site; spiders: 210; ground beetles: 260; true bugs: 50) than in conservation or sprayed headlands or in crops (spiders: 100-110; ground beetles: 70-160; true bugs: 15-30). Ground beetles were twice as abundant in crops adjacent to uncropped and conservation headlands than adjacent to sprayed headlands. Numbers of species were higher in uncropped headlands (ground beetles: 21 species; true bugs: 5; spiders: 26) than conservation and sprayed headlands (ground beetles: 15-18 species; true bugs: 2-3; spiders: 15-17). Spider diversity was significantly higher in uncropped (Simpson’s index: 6) than conservation and sprayed headlands and in the crop (2-3); ground beetles (4-8) and true bug (1-3) diversity did not differ. True bug nymphs Nabis ferus penetrated further into crops adjacent to uncropped and conservation headlands than sprayed headlands. Headlands represented the outer 6 m of eight barley fields at three locations. Parallel grids of 6 x 50m were set up in the headlands and the crop (8-14m from the headland), and sub-divided into fifteen 10 x 2 m sections. One pitfall trap was placed in each section (15 traps/grid). A further 2 x 50m grid was set up in the verge parallel to the field margin and divided into five 2 x 10m sections (5 traps/grid). Traps were emptied after 14 days in June-July 1988. A Dietrick Vacuum sampler was used along five transect lines (0-15 m into the crop), two samples consisting of five subsamples (each 0.4 m²) were taken three weeks apart.
Further results for ground beetles (Carabidae) from the same study (Hassall et al. 1992) are presented in a second paper (Cardwell et al. 1994) which found that ground beetles were more abundant in uncropped headlands than conservation headlands (restricted pesticides), fully sprayed headlands and crops. There were significantly more ground beetles on uncropped headlands (3-21/trap) than fully sprayed headlands (3-6/trap) or the main crop (3-9/trap). Conservation headlands tended to have lower numbers than uncropped headlands (3-14/trap). There also tended to be more ground beetles in the crop adjacent to uncropped headlands than conservation or fully sprayed headlands, but the difference was not significant. There were significantly more ground beetle species (total number of species across all sites) on uncropped headlands (36 species across three sites) compared to sprayed headlands (conservation: 32 across four sites; fully sprayed: 24 across two sites) or the crop (31 in eight sites). There was no significant difference between the vegetation cover under different treatments. Plant cover was also measured in five 25 x 25 cm quadrats in each grid.
A randomized, replicated trial from 1987 to 1991 in Oxfordshire, UK (Feber et al. 1994) found more adult meadow brown butterflies Maniola jurtina on 2 m-wide naturally regenerated field margins left uncut, or cut in spring or autumn than on margins cut in summer (4-10 meadow browns/50 m with summer cut, 4-15 meadow browns/50 m without). Unsown margins had 4-10 meadow browns/50 m in 1991 and 1992, fewer than margins sown with a wildflower mix (4-52 meadow browns/50 m). There was no difference between treatments in abundance of meadow brown larvae (3 larvae/plot on average). There were more meadow browns on all the experimental field margins than on narrow, unmanaged field boundaries of a neighbouring farm (numbers not given). Two metre-wide field margins were established around arable fields in October 1987. They were either left to naturally regenerate or sown with a wildflower seed mix in March 1988. Both treatments were rotavated before sowing. Fifty metre-long plots were managed in one of the following ways: uncut; cut once in June hay collected; cut April and June hay collected; cut in April and September hay collected; cut April and June hay left lying (unsown margins only); sprayed once a year in summer (unsown margins only). There were six replicates of each treatment. Adult meadow brown butterflies were monitored weekly along walked transects in the experimental plots from June to September 1989 and from April to September 1990 and 1991. Meadow brown larvae were sampled in spring 1991 by sweep netting and visual searching. This study was part of the same experimental set-up as Feber et al.1996, Baines et al. 1998, Bell et al. 1999, Haughton et al. 1999, Smith et al. 2010).
A small replicated, controlled study from 1990 to 1992 in East Anglia, UK (Hawthorne & Hassall 1995) found that ground beetles (Carabidae) were more abundant in uncropped headlands than conservation headlands (cropped, no herbicides or insecticides) and sprayed headlands (as main wheat field). Uncropped strips had a significantly greater abundance of ground beetles (2,487) compared to conservation (1,474) and sprayed headlands (938). Species diversity tended to be higher in uncropped headlands (43) compared to conservation (41) and sprayed headlands (35). Different species reacted differently to treatments. There were a number of species that were restricted to uncropped or conservation headlands and one restricted to sprayed headlands. Numbers of species and overall abundance varied with season. Two 120 m strips of each treatment were established in a randomized block design along one headland of a 19 ha wheat field. Ground beetles were sampled using 3-5 pitfall traps in the middle of each plot, 3 m from the field boundary. Catches were collected every 1-2 weeks from February to August. Aphid numbers were also sampled but are not presented here.
A randomized, replicated study from 1989 to 1991 in Oxfordshire, UK (Feber et al. 1996) (same study as Feber et al. 1994) found that butterfly (Lepidoptera) abundance and species richness was lower in unsown, naturally generated margins (14-39 individuals, 6-9 species) than in sown wildflower margins (21-91 individuals, 7-10 species) from the second year after establishment. Spraying with herbicides (RoundupTM) and cutting during summer reduced butterfly diversity and density in the margins, but there were no such effects of cutting in spring and autumn. Both cutting in summer and spraying led to an immediate decline in the number of flowering plants directly after the treatment. In the cut margins, however, the number of flowers had increased by September when it was higher than in uncut margins. Butterflies were monitored weekly along transects from June to September 1989 and from April to September 1990 and 1991. Transects were divided into 50 m sections corresponding to the experimental plots. Monitoring was done according to standard methods and only under suitable conditions. This study was part of the same experimental set-up as Feber et al.1994, Baines et al. 1998, Bell et al. 1999, Haughton et al. 1999, Smith et al. 2010).
A replicated, controlled, randomized study of four field margins in three Environmentally Sensitive Areas in England (West & Marshall 1996) found that plant cover was higher in margins sown with grass or grass/wildflower mixtures than those naturally regenerated, but plant diversity within naturally regenerated margins was similar to some margins sown with diverse seed mixtures. In 1994 plant diversity was higher in plots sown with more complex seed mixtures (32-37) than those sown with grass only (22-27) or regenerated naturally (21-25). In 1995, grass seed only plots tended to be the least diverse (15-21), but naturally regenerated plots (18-28) were as diverse as some complex seed mixtures (23-31). Species diversity did not differ between management treatments. Margins were created in each field and divided into six plots (4 x 30 m). Each was (randomly) sown with a seed mixture: grass, low cost mix (3 grass: 7 wildflower), alkaline soil (6:16), neutral soil (5:15), acid soil (6:16) and one natural regeneration. Plots were divided into 10 m sub-plots, which were either: unmanaged, cut once or received grass herbicide. Plants were sampled in each sub-sub-plot in summer 1994-1995. The three Environmentally Sensitive Areas studied were: the Breckland Environmentally Sensitive Area in Suffolk, the Somerset Levels and Moors Environmentally Sensitive Area and the South Wessex Downs Environmentally Sensitive Area in Wiltshire and Dorset. The same study is presented in Marshall et al. 1994.
Marshall E.J.P., West T.M. & Winstone L. (1994) Extending field boundary habitats to enhance farmland wildlife and improve crop and environmental protection. Aspects of Applied Biology, 40, 387-391.
A replicated, controlled study in summer 1995 in an intensively farmed landscape near Göttingen, Germany (Denys 1997) found higher arthropod species richness on potted mugwort Artemisia vulgaris plants placed in uncultivated margins (one and six years old) compared to a cereal field, but not compared to other margin types. The predator-prey ratio was significantly higher in the 6-year-old margin than in all other margin types and the control. The effect of uncultivated margins on individual arthropod numbers was species-dependent but slightly more individuals were found in the 1-year-old than in the 6-year-old uncultivated margins. Investigated margin types besides the two types of uncultivated margin were wildflower strips (wildflower seed mixture or Phacelia spp. only) and cereal strips/headlands. Potted mugwort plants (four pots) were placed in all margin types and the control (one winter wheat field). All herbivores and their predators on the plants were recorded during six visits in June and July. In September, all mugwort plants were dissected in the lab to assess numbers of arthropods feeding inside the plants. Results from the same study are also presented in (Denys et al. 1997, Denys & Tscharntke 2002).
A replicated, controlled study in summer 1995 near Göttingen, Germany (Denys et al. 1997) found higher species richness of arthropods colonizing potted mugwort Artemisia vulgaris plants in naturally regenerated margins than in unsprayed cereal control edges. However arthropod species numbers on mugwort did not differ between any of the established margin types or between mugwort plants placed in one or six-year-old regenerated margins and mugwort plants in larger set-aside areas of the same vegetation and age. Effects of the margins on individual abundance was not clear, but polyphagous spiders of the genus Theridion were recorded in significantly higher numbers on mugwort in 6-year-old regenerated margins than in 1-year-old margins, wildflower strips and sprayed cereal edges. Besides the 1- and 6-year-old naturally regenerated margins, wildflower strips (19 species sown), Phacelia strips (P. tanacetifolia plus three species), sown cereal strips and cereal control edges were investigated. Potted mugwort plants (four pots) were placed in all margin types and the controls. Mugwort plants were visited six times in June and July to count all herbivores and their predators on the plants before being taken to the lab in September to assess all arthropods feeding inside the plants. Vegetation of all margins was surveyed in June. Results from the same study are also presented in (Denys 1997, Denys & Tscharntke 2002).
A replicated study in 1994-1996 in Gloucestershire, UK (Feber & Hopkins 1997) (same study as Hopkins & Feber 1997) found that plant species richness as well as abundance and diversity of butterflies (Lepidoptera), was lower in naturally regenerated margins than in sown wildflower margins (for plants: 19 vs 23 species). Cutting and subsequent grazing of naturally regenerated margins significantly decreased butterfly diversity (3 vs 6 species) but not abundance (5 vs 10 individuals). Margins were established around two organically-managed arable fields by either sowing a seed mix (containing five grasses, six forbs) or by natural regeneration in 1994. In 1996, part of the margins were cut in June and grazed in July. The rest was left untreated. Butterflies were monitored along transects weekly from May to September 1996. Abundance of all plants present as well as flower abundance at the time of the survey was recorded in May and in September 1996.
A replicated study in summer 1996 in Gloucestershire, UK (Hopkins & Feber 1997) (same study as Feber & Hopkins 1997) found lower overall butterfly (Lepidoptera) abundance and species richness in ten naturally regenerated experimental plots than in ten plots sown with a wild grass/flower seed mixture. Vegetation removal (plots cut for silage in June, grazed by cattle in July) had no effect on butterfly abundance however butterfly species richness was lower in cut/grazed plots. Plant species richness was on average lower in naturally regenerated plots than in sown plots (19 vs 23 species). Vegetation removal had no effect on plant species richness but non-defoliated plots had more wildflower species in flower in July. In September 1994, 20 contiguous 50 m-long experimental plots were created in the margins of two adjoining organic fields on one farm by widening the existing 0.5 m margin to 2 m width. Presence of all sown and unsown plant species were recorded as well as wildflowers in flower (May and July 1996). Butterflies were monitored weekly June-September along a transect route.
A replicated trial from 1993 to 1996 on farmland near Wageningen, Netherlands (Kleijn et al. 1997) found that 4 m-wide field margins left to naturally regenerate had more plant species than margins sown with rye grass Lolium perenne, two years after establishment. On average there were 9 plant species/0.25 m2 in naturally regenerated margins, compared to 6 in grass-sown margins and 14 in margins sown with 30 non-grass wildflower species. Two prominent arable weeds, creeping thistle Cirsium arvense and couch grass Elymus repens both had higher biomass in the naturally regenerated margins than in wildflower or grass-sown margins (33 g/m2 and 28 g/m2 respectively in naturally regenerated plots, compared to 0-8 g/m2 and 6-9 g/m2 in sown margins). In 1993, experimental plots (8 x 4 m) were established on boundaries of three arable fields. All plots were mown once a year, without removing cuttings. There were three replicates of each treatment on each field. Plant biomass and number of species were measured in eight 0.5 m x 0.5 m plots on a single transect line across each margin, in August 1995.
A replicated study in summer 1996 in central Germany (Weiss & Buchs 1997) found that spider (Araneae) abundance in naturally regenerated plots (97 and 56 individuals in pitfall traps and photoeclectors respectively) was significantly lower than plots containing sundial lupin Lupinus perenne and common vetch Vicia sativa (155 and 124 individuals in pitfall traps and photoeclectors) and similar to plots with fodder radish Raphanus sativus oleiferus (104 and 49 individuals). Note that most results in this study are not statistically tested. Eight different types of strip with three replicates each were tested: six seed mixtures contained mainly flowering plants (1-12 species), one mixture contained mainly grass seeds (two species plus white clover Trifolium repens) and one naturally regenerated treatment. Spiders were sampled using two pitfall traps and two photoeclectors in each plot.
A randomized, replicated before-and-after trial from 1987-1991 in Oxfordshire, UK (Baines et al. 1998) (same study as Feber et al. 1994) found that spider (Araneae) abundance and species richness were higher after field margins were established on unmanaged plots (from <5 species at the start of the study to between 5 and 12 species following field margin establishment). Naturally regenerated field margins had fewer spiders, but not fewer spider species, than field margins sown with a wildflower seed mix on all dates. Cutting, especially summer cutting, significantly reduced the abundance of spiders. Spraying with herbicide reduced the numbers of spiders, but not the number of spider species, relative to control plots in two of the three years. Spiders were sampled using a suction trap (D-vac) in September 1987 and 1988, and in May, July and September in 1989, 1990 and 1991. This study was part of the same experimental set-up as Feber et al.1994, Feber et al. 1996, Bell et al. 1999, Haughton et al. 1999, Smith et al. 2010).
A randomized, replicated trial from 1987 to 1996 in Oxfordshire, UK (Bell et al. 1999) (same study as Feber et al. 1994) found that pseudoscorpions (Pseudoscorpionida) favoured unmanaged field margins (not cut or sprayed), but there was no difference in numbers between naturally regenerated margins and those sown with a wildflower mix. More pseudoscorpions (Chthonius ischnocheles and C. orthodactylus) were found in unmanaged field margin plots (95 pseudoscorpions in total on sown and unsown plots) than in cut or sprayed treatments (19-53 pseudoscorpions). Plots cut in April and June with hay removed, or sprayed with herbicide in summer, had fewer pseudoscorpions than other margins (19 and 21 pseudoscorpions respectively). Plots cut just once in June, cut twice but not in June or cut in April and June but with hay left lying, had intermediate numbers of pseudoscorpions (29, 53 and 30 pseudoscorpions). Pseudoscorpions were sampled from the litter layer (not the soil) using a suction trap (D-Vac) in May, July and September 1995 and 1996. This study was part of the same experimental set-up as Feber et al.1994, Feber et al. 1996, Baines et al. 1998, Haughton et al. 1999, Smith et al. 2010).
A trial from 1995 to 1998 in Hampshire, UK (Carreck et al. 1999) found the same number of bee (Apidae) species (9), but fewer flowering plant, fly (Diptera) and butterfly (Lepidoptera) species, on a single naturally regenerated field margin strip established for three years than on three strips sown with a diverse wildflower seed mix in the same study (16, 4 and 6 species respectively on the naturally regenerated margin vs 24, 7 and 8 species on the sown margins). The field margins were established (or sown) in 1995. The number of flowers and flower-visiting bees, wasps, flies and butterflies were counted on a 200 x 2 m transect in each strip, once a month from May to August 1998.
A randomized, replicated study from 1995 to 1996 in Oxfordshire, UK (Haughton et al. 1999) (same study as Feber et al. 1994) found that total numbers of invertebrates and leafhoppers (Auchenorrhyncha) were significantly lower in unsown, naturally generated margins than in sown wildflower margins. Cut plots (in summer alone, spring and summer or spring and autumn) had significantly lower numbers of all invertebrates, spiders (Araneae), true bugs (Heteroptera) and leafhoppers than uncut plots in all seasons, apart from spiders and true bugs in May. There was no effect of cutting frequency or timing or leaving/removing hay on invertebrate numbers. Invertebrates were sampled using a D-Vac suction sampler at 10 m intervals along each plot in May, July and September in 1995-1996. This study was part of the same experimental set-up as Feber et al. 1994, Feber et al. 1996, Baines et al. 1998, Bell et al. 1999, Bell et al. 2002, Smith et al. 2010).
A 1999 review of literature (Kromp 1999) found that uncropped field margins, left to naturally regenerate, were shown to increase ground beetle (Carabidae) numbers by three studies (Müller 1991, Cardwell et al. 1994, plus one unpublished study). In one case (Cardwell et al. 1994) there were more beetles than in conventional crop margins.
Müller L. (1991) Auswirkungen der extensivierungsförderung auf Wirbellose. Faunistisch-Okologische Mitteilungen, S10, 41-70.
A randomized, replicated controlled trial from 1993 to 1996 in Bristol, UK (Thomas & Marshall 1999), found that 4 m-wide field margins left to naturally regenerate had more suction-sampled invertebrates but not more ground beetles (Carabidae) than control cropped margins or margins sown with grass. There were around 180 invertebrates per sample on naturally regenerated margins, compared to 110-130 invertebrates/sample on control or grass-sown plots. There was no difference in the number of ground beetle species (average of 8 species/plot), nor in the numbers of the four most commonly caught ground beetle species, between margin types. In a 2 m-wide margin, there were more over-wintering invertebrates in the soil of the wildflower sown half than the naturally regenerating half, but this difference was not found in 4 m-wide replicated experimental plots. Three field margins were established in spring 1993 at one site. Experimental plots 10 x 4 m were either sown with arable crop (control), rye grass Lolium perenne or a wildflower and grass seed mix, or left to naturally regenerate. There were three replicate plots in each margin. All plots were cut annually after harvest, and cuttings left in place. Another 100 x 2 m wide field margin, with 50 m sown with a wildflower mix and 50 m unsown, was used to monitor wintering invertebrates. Ground beetles were sampled in eight pitfall traps in or near each margin, for a week in June for four years, 1993-1996. Invertebrates were sampled using a vacuum sampler on plots of two of the three margins in June 1994. Arthropods were extracted from soil samples taken from plots of two margins in December 1993 and February 1994.
A 2000 literature review (Aebischer et al. 2000) found that the UK population of Eurasian thick-knees Burhinus oedicnemus increased from 150 pairs in 1991 to 233 in 1999, following an agri-environment scheme designed to provide uncultivated plots in fields and set-aside.
A replicated controlled trial in 1999 of arable field margins in the UK (Kells et al. 2001) found that margins allowed to regenerate naturally for one year supported significantly more honey bees Apis spp. and bumblebees Bombus spp. than unsprayed cropped margins managed as conservation headlands (average 10-50 bees/transect on naturally regenerated margins compared to <3 bees/transect in conservation headlands). The trial was replicated once on each of five farms, with two uncropped field margins and one control conservation headland margin per farm. Margins were 4-6 m wide and located on the boundary of spring-sown cereal fields. Transects (0.5 x 50 m2) parallel to the field edge were walked at 8-10 day intervals over a 40-day period in each margin to record bee numbers, species and flower preferences.
A randomized, replicated trial from 1987 to 1996 in Oxfordshire, UK (Bell et al. 2002), found greater numbers of predatory sheet web spiders Lepthyphantes tenuis on field margins left uncut and unsprayed with herbicide. In September, when most of the spiders were caught, there were significantly fewer L. tenuis spiders in margins (sown and unsown) that were cut in June (around 10 spiders/m2, compared to >15 spiders/m2 in plots cut in spring and autumn, or not cut). In May and July, plots with a recent cut (April or June-cut treatments respectively) also had lower numbers of L. tenuis than other plots. Spraying unsown plots with herbicide reduced the numbers of L. tenuis later in the same year (average 4 and 10 spiders/m2 in sprayed plots in July and September respectively, compared to 8 and 20 spiders/m2 on unsprayed plots in July and September). Plots where the vegetation was cut but not removed did not have more spiders than plots where cut vegetation was removed. L. tenuis individuals were counted in invertebrate samples collected using a suction trap (D-Vac) in May, July and September 1990, 1991, 1995 and 1996. This study was part of the same experimental set-up as Feber et al. 1994, Feber et al. 1996, Baines et al. 1998, Bell et al. 1999, Haughton et al.1999, Smith et al. 2010).
A replicated study from April to September 1995 near Göttingen, Germany (Denys & Tscharntke 2002) found higher predator abundance (mainly spiders Araneae) and higher predator-prey ratios in 6-year-old than in 1-year-old naturally developed field margins. In addition, predator-prey ratios were higher in large, naturally developed fallows than in the field margins. These results emphasize the importance of habitat age and area for the establishment of natural enemy populations. However, arthropod species richness in naturally developed margins did not differ from other margins types. Potted plants of mugwort Artemisia vulgaris (four pots per margin) and red clover Trifolium pratense (three pots per margin) were used to study plant-arthropod communities. Red clover pots were also set out in winter wheat fields at 4, 8 and 12 m distances adjacent to strips sown with cereal and wildflower mix. Red clover pots were set out in April 1995. On five visits in June and July 1995, flower heads of red clover were sampled, dissected and the larvae and pupae of arthropods feeding inside the plants reared in the lab for species determination. Results from the same study are also presented in (Denys 1997, Denys et al. 1997).
A review (Evans et al. 2002) of two reports (Wilson et al. 2000, ADAS 2001) evaluating the effects of the Pilot Arable Stewardship Scheme in two regions (East Anglia and the West Midlands) from 1998 to 2001 found that grass margins benefited plants, bumblebees Bombus spp., true bugs (Hemiptera) and sawflies (Symphyta), but not ground beetles (Carabidae). The grass margins set of options included sown grass margins, naturally regenerated margins, beetle banks and uncropped cultivated wildlife strips. The review does not distinguish between these, although the beneficial effects were particularly pronounced on sown or naturally regenerated grassy margins for true bugs. The effects of the pilot scheme on plants, invertebrates (bumblebees, true bugs, ground beetles, sawflies) were monitored over three years, relative to control areas. Grass margins were implemented on total areas of 361 and 294 ha in East Anglia and West Midlands respectively.
Wilson S., Baylis M., Sherrott A. & Howe G. (2000) Arable Stewardship Project Officer Review. F. a. R. C. Agency report.
ADAS (2001) Ecological evaluation of the Arable Stewardship Pilot Scheme, 1998-2000. ADAS report.
A small replicated, controlled trial in the summer of 2000 in North Yorkshire, UK (Meek et al. 2002) found that four naturally regenerated field margins had higher plant diversity, but not more bumblebees Bombus spp. or butterflies (Lepidoptera) (species or individuals) than four cropped margins. A number of rare or uncommon arable weeds were recorded in naturally regenerated margins, but also a much higher abundance of barren brome Anisantha sterilis than in any other treatment. Spring numbers of ground beetles (Carabidae) and ground-dwelling spiders (Araneae) were higher in naturally regenerated margins than cropped margins. Harvestmen (Opiliones) avoided naturally regenerated margins in favour of any sown habitat in autumn. Four margins of winter cereal fields, all adjacent to hedges, were split into 72 m long plots and sown in September 1999 with either grass, grass and wildflowers, cereal crop or left to regenerate naturally on two farms. Ground and canopy-dwelling invertebrates, butterflies and plants were surveyed from late April to late September 2000 using pitfall traps, sweep netting, transects and quadrats.
A replicated trial in 2001-2002 in the UK (May & Nowakowski 2003) found that margins of sugar beet Beta vulgaris fields left to naturally regenerate had more invertebrates (individuals and species) but not more plant species than margins sown with wildflowers, crops or grasses. Naturally regenerated margins had over 1,700 invertebrates in total, from 45 groups. However the difference in invertebrate numbers between different treatments was fairly small (over 900 to over 1,700 individuals, 35-45 groups caught). Naturally regenerated margins had around 17 plant species/m, compared to 35 plant species/m on wildflower margins, 15 species/m for grass margins and 6-11 species/m for barley or beet margins. In autumn 2001, 50 m x 6 m margins at the edges of beet fields were planted with either sugar beet, spring barley, grasses (eight species), nothing (natural regeneration) or wildflowers. There were two replicates of each treatment at each of three sites. In summer 2002, plants (including crop plants) were counted in the margins and invertebrates sampled using pitfall traps, set for two weeks.
A replicated trial from 1998 to 2000 in Wiltshire, UK (Asteraki et al. 2004) found that naturally regenerated field margins had more undesirable weed species than sown field margin plots, but more predatory beetles (Coleoptera) in the second year. There was no difference in the total abundance of invertebrates between field margin treatments. Eleven 100 x 2 m field margin plots were left to regenerate naturally on one farm. Thirty-eight were sown with a grass seed mix of either three grass species (12 plots), six grass species (13 plots) or six grass and four herb species (13 plots) in autumn 1998. The plots were around four fields under a Countryside Stewardship Agreement on the Harnhill Manor Farm. Invertebrates were sampled using pitfall traps (five traps/plot) in spring and autumn and suction traps in summer. Plants were recorded in four 1 m2 quadrats/plot in summer.
A replicated controlled study between 1988 and 1997 in Sweden (Bokenstrand et al. 2004), found higher plant species richness in experimental field margin plots allowed to regenerate naturally than in plots sown with a clover and grass seed mixture after one year. Seven years after establishment, naturally regenerated plots, clover and grass plots and control boundaries had higher cover of weeds in total and of couch grass Elytrigia repens than plots planted with rose bushes Rosa canina and/or meadow plants. Couch grass increased in all treatments but significantly so in naturally regenerated plots and plots with clover and grass. Plots with meadow plants and naturally regenerated plots had similar species richness but quite different species compositions due to a high cover of annual weeds in the latter. In 1990, four replicates of each treatment (naturally regenerated, planted with rose bushes and/or sown with meadow plants, sown with clover Trifolium spp. and grass mixture) were established randomly along the stretch of a previously removed dirt road. All plots were cut annually in late summer and the cuttings removed. Vegetation surveys were carried out twice in experimental plots (1991 and 1997) and once in control boundaries (1997) in three to five 0.25 m2 quadrats. It is not clear whether the results for clover and grass plots were a direct result of planting nectar flowers or grass.
A replicated controlled trial from 1999 to 2002 on arable field margins in North Yorkshire, UK (Carvell et al. 2004) found 6 m-wide naturally regenerated, uncultivated field margin plots supported significantly more foraging bumblebees Bombus spp. than margins sown with tussocky grass, or control cropped field margins, but only in one year (2001) of this three year study. In 2001, the bumblebees were mostly foraging on spear thistle Cirsium vulgare, a pernicious agricultural weed that had to be controlled by cutting at the end of that summer. In the other two years (2000 and 2002), the naturally regenerated field margins did not support significantly more bumblebees than the control or grass-sown sites. Naturally regenerated margins were the only treatment that did not support consistent numbers of bumblebees in all three years. The naturally regenerated field margins supported fewer bumblebees (18 individuals and 2.7 species/100 m on average) than margins sown with a wild flower seed mixture (29 individuals, 3.0 species/100 m), but the two treatments were not directly compared in the analysis. Three cereal field margins on one farm were divided into five 72 m x 6 m long plots and subjected to five different treatments: natural regeneration (6 m wide), sown ‘tussocky’ grass mixture (6 m wide), sown ‘grass and wildflower’ mixture (6 m wide), split treatment of 3 m wide ‘tussocky’ grass mixture adjacent to hedge and 3 m wide sown ‘grass and wildflower’ mixture adjacent to crop, and margin cropped to the edge. Plots were cut and herbage removed following establishment of the seed mixtures. Wildflower plots were cut in August 2001 and 2002 and the herbage removed. Transects were walked along the central line of each plot recording bumblebee activity and identifying foraging bumblebees to species level.
A replicated study in the summers of 1999-2000 on arable farms in the UK (Critchley et al. 2004) found that naturally regenerated grassy margins had more plant species than sown grassy margins, but were not considered one of the best options for the conservation of annual herbaceous plant communities. The naturally regenerated margins were dominated by three grasses (different species from the sown margins) and thistles. Average numbers of plant species in the different conservation habitats were wildlife seed mixtures 6.7, uncropped cultivated margins 6.3, undersown cereals 5.9, naturally regenerated grass margins 5.5, no-fertilizer conservation headlands 4.8, spring fallows 4.5, sown grass margins 4.4, overwinter stubbles 4.2, conservation headlands 3.5, grass leys 3.1. Plants were surveyed on a total of 294 conservation measure sites (each a single field, block of field or field margin strip), on 37 farms in East Anglia (dominated by arable farming) and 38 farms in the West Midlands (dominated by more mixed farming). The ten habitats were created according to agri-environment scheme guidelines. Vegetation was surveyed once in each site in June-August in 1999 or 2000. The vegetation was examined in thirty 0.25 m2 quadrats randomly placed in 50-100 m randomly located sampling zones in each habitat site. Top cover and plant cover was estimated with 1-30 pin hits.
A replicated, paired site comparison study in 2000 in Ireland (Feehan et al. 2005) found that wider, uncultivated margins (average 181 cm wide) with reduced agrochemical inputs on Rural Environment Protection Scheme (REPS) farms did not have higher plant or ground beetle (Carabidae) diversity or abundance than margins on non-Rural Environment Protection Scheme farms (average 145 cm). There were around 11 plant species and 21-22 ground beetle species/margin on both types of farm. Fourteen arable farms with Rural Environment Protection Scheme agreements at least four years old were paired with fourteen similar farms without agreements. On each farm, two randomly selected field margins were surveyed for plants and ground beetles.
A small-scale controlled study in 2000-2001 in Essex, UK (Gardiner & Hill 2005) found densities of lesser marsh grasshoppers Chorthippus albomarginatus (69% of all grasshoppers found) and meadow grasshoppers C. parallelus (31% of all grasshoppers found) in two Countryside Stewardship Scheme field margins (one margin naturally regenerated, one margin created from existing grass ley) were not statistically different than in intensively managed habitats (arable field, heavily grazed cattle and sheep pastures). Adult density of both grasshopper species was higher on lightly grazed pasture and a disused farm track than in either field margin. Grasshopper density was initially higher in the sown grass margin than the naturally regenerated margin or control grazed pasture three years after establishment (0.4, 0.1 and 0.3 grasshoppers/m2 respectively). Seven years into the 10-year agreement, grasshopper density had decreased in the sown and naturally regenerated margins (0.05 grasshoppers/m2) but increased substantially in the control grazed pasture (1.2 grasshoppers/m2). The authors suggested that annual cutting for hay was the reason for the reduced grasshopper populations in the margins. In each of nine study sites (two field margins, one arable field, one lightly grazed pasture, one heavily grazed cattle pasture, one heavily grazed sheep pasture, one hay meadow, one set-aside grassland, one disused farm track), 10 quadrats (2 x 2 m2) were randomly positioned in a 100 m2 plot. Grasshoppers were counted in quadrats once in July and once in August (2000 and 2001).
A site comparison study from 2001 to 2005 of organic arable fields in the Netherlands (Alebeek et al. 2006) found that greater numbers of overwintering generalist predators were recorded in unmown perennial field margins compared to mown grass strips and bare fields. Higher numbers of generalist predators (ground beetles Carabidae, spiders Araneae, rove beetles Staphylinidae) were found in unmown margins (202 individuals/m²) than mown strips (124/m²) and bare fields (152/m²). Over twice as many overwintering ground beetles were found within margins (101/m²) than mown strips and fields (33-48/m²). The same was true for other beetles (margins: 112/m²; mown grass strips: 45/m²; bare fields: 36/m²). One farm system sampled had numerous field margins (21% of area), whilst the other had few (5% area). To catch overwintering arthropods, pitfall traps were set within enclosures (1 x 1 m²) in March-May 2004, three within unmown field margins, three within short-mown grass strips and six in bare soil plots in fields. Pests and pest predation were also sampled, but results are not presented here.
A replicated trial from 2001 to 2004 in Belgium (Cauwer et al. 2006), found that naturally regenerated margins had similar numbers of plant species to margins sown with wildflower mix after three years. In naturally regenerating plots, the number of plant species increased (unshaded margin only) or remained similar from 8-15 species/plot in July 2002 to 12-15 species/plot in July 2004. The relative abundance of perennial plants increased and the relative abundance of annuals decreased over time on all the field margin plots, regardless of treatment. In naturally regenerated margins the proportion of legumes increased over time whilst in sown margins the proportion of legumes decreased significantly. In September 2001, 10 m lengths of two 10 x 180 m arable field margins were either left to naturally regenerate or sown with one of two wildflower/grass species mixtures containing 63 or 77 plant species. One margin was in a sunny location, the other shaded by trees. The margins were mown twice, in late June and September, each year from 2002 to 2004. Each combination of treatments was replicated three times. Plants were recorded in July and October from 2002 to 2004.
A replicated study in 1999 and 2003 on arable and pastoral fields in the UK (Stevens & Bradbury 2006), found that a combination of creating uncultivated and planted margins around fields was strongly positively associated with the presence of four out of twelve farmland bird species analysed. These species were Eurasian skylark Alauda arvensis (a field-nesting species), chaffinch Fringilla coelebs, whitethroat Sylvia communis and yellowhammer Emberiza citrinella (all boundary-nesting species). The other species analysed were corn bunting Miliaria calandra, lapwing Vanellus vanellus, yellow wagtail Motacilla flava, dunnock Prunella modularis, greenfinch Carduelis chloris, linnet C. cannabina, reed bunting E. schoeniclus and tree sparrow Passer montanus. The study did not distinguish between uncultivated and planted margins. On the 256 study fields, birds were recorded using territory-mapping techniques between 1 April and 31 July 2003. Sites were visited eight times and all registrations plotted on a farm map. Territories were assigned a habitat unit based on their location.
A replicated, controlled study in the summer of 2003 in central Switzerland (Aschwanden et al. 2007) found that small mammal density was higher in herbaceous strips than in low-intensity meadows, conventionally farmed artificial grasslands and autumn-sown wheat fields. Small mammal species richness in herbaceous strips (six species) was higher than in any other studied habitat (two species each). The increase in small mammal density over the summer was higher in herbaceous strips and wild-flower strips than in the other three habitats. Herbaceous strips consisted mainly of herbaceous plants, such as thistles Cirsium spp., common teasel Dipsacus sylvestris, St John’s wort Hypericum perforatum, common mallow Malva sylvestris and mulleins Verbascum spp. On the 15 study sites, herbaceous strips and wild-flower strips were not regularly cut during the growing season, whereas other grassland habitats were cut at least twice. Small mammals were trapped and individually marked during 60 hour trapping sessions in March, May and July. Traps were checked every eight hours. A capture-recapture method was used to estimate small mammal densities.
A replicated controlled trial in central and eastern England (Carvell et al. 2007) found that naturally regenerated field margins supported a greater number and diversity of foraging bumblebees Bombus spp. than cropped margins (including conservation headlands), but only in the first year of the study. In subsequent second and third years, bumblebee numbers were not significantly different from cropped treatments, but this may be due to the presence of more attractive floral resources planted on the same field margins for the experiment. Six sites were studied and two experimental plots (50 x 6 m) established in each cereal field along two margins. Six treatments were assigned to plots: conservation headland, natural regeneration, tussocky grass mixture, wildflower mixture, pollen and nectar mixture, crop (control treatment). Foraging bumblebees were counted from May to late August, on 6 m-wide transects between six and 11 times in each margin.
A replicated, controlled study in the summers of 1997-2000 and 2003 in Essex, UK (Field et al. 2007) found that naturally regenerated 6 m margins had higher plant species richness (35 species) than grass-sown 6 m-margins (20 species), seven years after margin establishment under the Countryside Stewardship Scheme. Butterfly (Lepidoptera) abundance was higher in 6 m-wide Countryside Stewardship Scheme margins (naturally regenerated and grass-sown margins not distinguished) than in control margins. Comparisons between 6 m-margins (naturally regenerated and grass-sown margins not distinguished) and control sections showed 54 vs 19 butterflies/km/visit. The meadow brown butterfly Maniola jurtina also occurred in higher numbers in Countryside Stewardship Scheme field margins: 6 m-margins (naturally regenerated and grass-sown margins not distinguished) and their control sections had 22 vs 5/km/visit. Butterfly abundance and species richness did not change over the study period in either 6 m-margins or in a transect across farmland. Six metre-margins were established on three farms either through natural regeneration or by sowing with a grass-seed mixture, and all cut annually after 15 July.
A replicated controlled trial in 2005-2006 in Warwickshire, UK (Pywell & Nowakowski 2007) found that field corners or margins left to naturally regenerate for one year had more bumblebees Bombus spp. (species and individuals) than control crop plots, or plots sown with wild bird seed or wildflower seed mix. There were 55 bumblebees and five bumblebee species/plot on average on naturally regenerated plots, compared to no bumblebees on control crop plots and seven bumblebees of two species/plot on sown plots. Naturally regenerated plots also had more butterfly and plant species than control cereal plots (5-6 butterfly species/plot and 7 plant species/m2, compared to 1 butterfly species/plot and 2 plant species/m2 in cereal crop plots). Naturally regenerated plots did not have more butterfly individuals, or more birds in winter (species or individuals) than control crop plots. Plots were located on one farm and were left as unmanaged wheat stubble for all of 2006. Each treatment was tested in one section of margin and one corner in each of four fields. Plants were monitored in three 1 m2 quadrats/plot in July 2006. Butterflies, bumblebees and flowering plants were recorded in a 6 m wide transect, five times between July and September. Farmland birds were counted on each plot on seven counts between December 2006 and March 2007.
A replicated trial in Lithuania in 2006-2007 (Balezentiene 2008) found that uncropped field margins had significantly higher plant diversity than margins within wheat crops, on both organic and intensive farms. Fifteen field margin areas were left to regenerate naturally (uncropped) and compared with fifteen margins of a winter wheat crop, across three farms in Lithuania. One farm was managed organically, the other two conventionally. Plants in the margins were monitored in June and July 2006 and 2007 in 0.5 m2 sample plots.
A replicated paired site comparison study in 2003 in three regions of Germany (Holzschuh et al. 2008) found that 21 uncultivated fallow strips adjacent to organic wheat fields had an average of 6.3 bee (Apidae) species, 2.6 solitary bee individuals/100 m2 and 8.5 bumblebee Bombus spp. individuals/100 m2/. Uncultivated fallow strips adjacent to conventional wheat fields had an average of 3.9 bee species, 1.1 solitary bee individuals/100m2 and 3.7 bumblebees/100m2. Bee species richness was 60% higher on uncultivated strips adjacent to organic wheat fields than those adjacent to conventional wheat fields, and had 136% more solitary bees and 130% more bumblebees. Strips adjacent to organic wheat fields also had more flowering plant species and higher flower cover. Species richness and abundance of bees in fallow strips appeared to be limited by foraging resources, which were more abundant when adjacent fields were organic. However, only bees that gather pollen from a range of plants were found on fallow strips during surveys. Specialist bees did not appear to benefit from fallow strips, suggesting that they do not completely compensate for missing semi-natural habitats. Bees were surveyed along 100 m transects four times in May-June 2003 in 42 paired fallow strips adjacent to organic/conventional fields. Flowering plants were surveyed in bee transects and in two transects along the centre and edge of the adjacent field. All fallow strips were mown once a year, with an average width of 2.6 m.
A replicated, controlled study in 2000-2003 of a grass crop field in Norway (Hovd 2008) found that plant species diversity was higher in strips sown with a grass/wildflower mixture than strips left to regenerate naturally or in the grass crop. There were 10-12 plant species/quadrat in four 2 m-wide naturally regenerated strips on average, compared to 17-18 species/quadrat in a strip sown with grass and flower mixture, and 7-9 species/quadrat in a control strip of the main grass crop. Naturally regenerated strips were dominated by grasses and perennial weeds. Four strips (2 m wide) were ploughed, perpendicular to an existing semi-natural margin, in May 2000. One half of each was left to regenerate naturally, the other half was sown with a grass/meadow flower (22 species) seed mixture. Sown strips did not receive fertilizer and were cut once (late September). Permanent quadrats (0.5 x 0.5 m) were sampled in the grass crop and strips in June 2000-2003.
The second monitoring year of the same replicated, controlled study as Pywell & Nowakowski 2007 in the UK from 2005-2007 (Pywell & Nowakowski 2008) found that naturally regenerated plots had more plant species and more vacuum-sampled invertebrates (individuals and groups) than control plots, but not more butterflies (Lepidoptera) or birds in winter. Naturally regenerated plots had 6 plant species/m2; 7 bumblebee Bombus spp. individuals/plot; 5 butterfly individuals and two butterfly species/plot, compared to 3 plant species/m2; 0 bumblebee individuals, and 1 butterfly individual/plot on control cereal plots. Control plots had 254 vacuum-sampled canopy-dwelling invertebrates/m2 on average, compared to 840-1,197/m2 on other treatments. Plants were monitored in three 1 m2 quadrats per plot in June 2007. Butterflies, bumblebees and flowering plants were recorded in a 6 m-wide transect six times between July and September in 2006 and 2007. Invertebrates in the vegetation were vacuum-sampled in early July 2007. Farmland birds were counted on each plot on four counts between December 2007 and March 2008. The crop control in year two was winter wheat.
A replicated, controlled trial from 2002-2004 in County Wexford, Ireland (Sheridan et al. 2008) found that 1.5-3.5 m wide margins of permanent pasture fields fenced to exclude livestock had more springtails (Collembola: Anthropleona) and spiders (Araneae) than control margins. Margins that were rotavated and left to naturally regenerate also had more flies (Diptera) and plant species than control plots. These margins had around 12 plant species/plot in 2002, degrading to just over 5 plant species/plot in 2004, compared to less than five plant species/plot throughout the study in control plots and unrotavated fenced margins. Some undesirable weeds, such as broad-leaved dock Rumex obtusifolius established in rotavated plots. Margin width made no difference to plant species richness. Allowing grazing on half of each plot from 2003-2004 (one year after margin establishment) did not affect the number of plant species the following year. Plots were 30 m long, with three replicates of each treatment combination. Plants were monitored in permanent quadrats in July 2002, May and July 2003 and May 2004. Invertebrates were sampled in six emergence traps per plot, between May and September 2003. Ground areas under the emergence traps were sampled with a vacuum sampler.
A replicated, controlled study in 2005-2006 on mixed lowland farms in Scotland (Douglas et al. 2009), found that a larger proportion of early-summer yellowhammer Emberiza citrinella foraging flights were in field margins (32% of 233 flights from 10 nests), compared to cereal crops (8%). However, in late summer, cereal fields were used more (up to 56% of 506 flights) and field margins less (down to 15%). Field margins supported higher total invertebrate abundance than spring or winter barley across the summer period (average total invertebrate abundance was 45 in margins compared to 28 and 23 in spring and winter barley respectively). In 2006, sections of margins around some nests were cut down to the soil. These patches measured 15 x 1 m and comprised 2% of margin area. They were used for 3% of 172 foraging flights in early summer and 34% of 77 foraging flights in late summer. Cut patches were used more frequently in margins with swards >60 cm tall. The authors suggest that yellowhammers used cut patches disproportionately as the uncut sections grew taller and so reduced access to invertebrates. The study was carried out on five farms. Yellowhammer foraging flights were recorded from May-August 2005. Thirty yellowhammer nests with nestlings were observed, each for a three hour period between 07.00 h and 11.00 h. Foraging locations of adult birds from the nest site were recorded on sketch maps, and following the observation period each foraging site was visited and the distance from the nest measured.
A replicated, controlled study in summer 2006 in north Germany (Haenke et al. 2009) found that species richness and abundance of hoverflies (Syrphidae) during the wheat peak-ripening stage was higher in naturally developed grass strips (3 m wide, seven sites) than in wheat-wheat boundaries (seven sites) and within the wheat fields adjacent to the margins (seven sites), but lower than in sown flower strips (seven sites each). Hoverfly density and species richness increased with increasing amount of arable land at smaller scales (0.5 and 1 km around site) but not at larger scales (2 and 4 km). This was true for all hoverflies and all aphid-eating hoverfly species. Margins were located along a gradient of different habitat complexities in the surrounding landscape, ranging from 30% to 100% arable land. Hoverflies were captured by sweep netting (one sweep per footstep) along 100 m transects.
A literature review in 2009 of European farmland conservation practices (Vickery et al. 2009) found that sown uncropped field margins were used by foraging bumblebees Bombus spp. more than other margin types, including naturally regenerated margins. Naturally regenerated margins were found to hold many important food species for birds (both invertebrate and plant). In addition rare plants, such as rough poppy Papaver hybridum, may be found in naturally regenerating margins. The authors argue that on poor soils with a diverse seed bank naturally regenerating margins may have a greater diversity of plants and be of greater conservation value than seeded grass margins, but if soils are rich then they can become dominated by a few species.
A replicated, site comparison study in 2010 on lowland farmland in England (Davey et al. 2010) found no consistent association between the provision of uncultivated field margins on arable or pastoral farmland and farmland bird numbers three years after the 2005 introduction of the Countryside Stewardship Scheme and Entry Level Stewardship agri-environment schemes. Although plots with field margins did see more positive population changes (increases or smaller decreases relative to other plots) of rook Corvus frugilegus, starling Sturnus vulgaris and woodpigeon Columba palumbus, the effect was small. For example, starlings showed increases of only 0.0002 individuals for every 0.001 km² of margin in mixed farmland plots. Other species expected to benefit from margin provision including corn bunting Emberiza calandra, grey partridge Perdix perdix, kestrel Falco tinnunculus, jackdaw Corvus monedula, reed bunting E. schoeniclus, and common whitethroat Sylvia communis showed no effect of margin management. Yellowhammers Emberiza citrinella, which were also expected to benefit from margin creation, showed a positive association in mixed landscapes, but a negative association on grassland plots. The 2,046 1 km² lowland plots were surveyed in both 2005 and 2008 and classified as arable, pastoral or mixed farmland. Eighty-four percent of plots included some area managed according to Entry Level or Countryside Stewardship agri-environment schemes. In both survey years, two surveys were conducted along a 2 km pre-selected transect route through each 1 km² square, with all birds seen or heard recorded in distance bands.
A replicated study in 2007 in Gloucestershire and Oxfordshire, England (Rantanen et al. 2010) found that grey partridge Perdix perdix released in pairs in the spring used field margins more frequently than birds released in coveys in the autumn. Four farms were studied. Birds were radio-tagged and their positions marked on a 1:5000 map.
A randomized, replicated trial from 1987 to 2000 in Oxfordshire, UK (Smith et al. 2010) found that the number of plant species on naturally regenerated 2 m-wide margins declined by about half over 13 years. There were 13-15 plant species/quadrat in 1988 and 7-9 plant species/quadrat in 2000. The most rapid decline was in the first two years, when many annual species were lost. Herbicide-sprayed plots had fewer perennial plant species than other management treatments from 1989 onwards (<6 perennial species/quadrat in 2000, compared to 6-8 for other treatments). After 13 years, naturally regenerated plots tended to have fewer species than plots sown with a wildflower seed mix (9-12 species/plot in 2000), but this difference was not statistically significant. There was no effect of different mowing regimes on the numbers of plant species, although in the early years mown plots had more plant species than uncut plots. Plant species were monitored three times a year from 1988 to 1990, and once in July 2000 in three 0.5 x 1 m quadrats/plot. This study was part of the same experimental set-up as Feber et al. 1994, Feber et al. 1996, Baines et al. 1998, Bell et al. 1999, Haughton et al. 1999, Bell et al. 2002).
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