Grassland In England Research Articles

Use of a nitrification inhibitor reduces nitrous oxide (N2O) emissions from compacted grassland with different soil textures and climatic conditions

Grassland accounts for 70 % of the global agricultural area. Grassland amended with N fertiliser, although increasing productivity, encourages the emission of the greenhouse gas nitrous oxide (N2O). Soil compaction can result in impeded water movement and the development of anaerobic conditions that favour N2O production and emissions from denitrification. Soil compaction has become more prevalent in grassland with the use of increasingly heavy machinery and the extension of seasonal animal grazing periods, especially when soil moisture is high; close to field capacity. The effect of a nitrification inhibitor - dicyandiamide (DCD) on emissions of N2O from grassland moderately compacted from animal trampling or a tractor were investigated at two experimental field sites in the UK; a silt clay loam soil in a wet climate (SRUC) and a sandy loam in a drier climate (HAU). Compaction treatments repeated annually over three years (2011–2013) gave an overall increase in soil bulk density for the tractor compaction and animal trampling at both sites but to different degrees related to soil texture. Cumulative N2O emissions from tractor compaction for both SRUC and HAU were significantly greater than from the uncompacted control over the three years, with changing climate, soil texture and soil pH influencing the magnitude of N2O emissions. The use of DCD decreased cumulative N2O emissions at both sites, with the reduction greatest under tractor compaction, especially for the drier, sandier soil with the greater porosity. DCD appeared to decrease soil nitrate (NO3−) concentrations and decreased potential NO3− losses from leaching and run-off. Extrapolating from these data, the presence of moderate compaction, as identified in grasslands in England and Wales, could result in an estimated annual increase in N2O emissions of between 0.10 and 0.78 Mt of N2O, but these emissions could be reduced by up to 16 % and 51 % through the use of DCD, depending on compaction depth and soil texture. Although no yield increases were seen from the use of the DCD at both sites, N2O emissions were reduced.

Assessing the bioenergy potential of grassland biomass from conservation areas in England

Bioenergy may be one of the ‘ecosystem services of the future’ for grasslands managed for conservation as the concept of bio-based economies is embraced worldwide. Although the idea of producing biogas and bioethanol from lignocellulosic material is not new, there are currently few regional-level comparisons of the bioenergy potential of high-diversity grasslands that would establish whether this could be a competitive bioenergy feedstock for farmers. Comparing the chemical composition and biogas yields of biomass samples from 13 grasslands in England and 73 other bioenergy feedstocks reveals that the lignin content of biomass from grasslands managed for conservation was up to 50% less than other bioenergy crops. Grasslands managed for conservation yielded up to 160% more biogas per ton dry matter than cereals or crop waste and only slightly less than Miscanthus. GIS modeling of the estimated biogas yields of grasslands managed for conservation and fields currently sown with Miscanthus show that grasslands are larger (20.57 ha) than Miscanthus fields (5.95 ha) and are projected to produce up to 117% more biogas per average field. Future incorporation of high-diversity grasslands into local and nation-wide energy plans may help reduce global fossil-fuel use in the 21st century.

Targeted and Untargeted Metabolic Profiling of Wild Grassland Plants identifies Antibiotic and Anthelmintic Compounds Targeting Pathogen Physiology, Metabolism and Reproduction

Plants traditionally used by farmers to manage livestock ailments could reduce reliance on synthetic antibiotics and anthelmintics but in many cases their chemical composition is unknown. As a case study, we analyzed the metabolite profiles of 17 plant species and 45 biomass samples from agricultural grasslands in England using targeted and untargeted metabolite profiling by liquid-chromatography mass spectrometry. We identified a range of plant secondary metabolites, including 32 compounds with known antimicrobial/anthelmintic properties which varied considerably across the different plant samples. These compounds have been shown previously to target multiple aspects of pathogen physiology and metabolism in vitro and in vivo, including inhibition of quorum sensing in bacteria and egg viability in nematodes. The most abundant bioactive compounds were benzoic acid, myricetin, p-coumaric acid, rhamnetin, and rosmarinic acid. Four wild plants (Filipendula ulmaria (L.) Maxim., Prunella vulgaris L., Centuarea nigra L., and Rhinanthus minor L.) and two forage legumes (Medicago sativa L., Trifolium hybridium L.) contained high levels of these compounds. Forage samples from native high-diversity grasslands had a greater abundance of medicinal compounds than samples from agriculturally improved grasslands. Incorporating plants with antibiotic/anthelmintic compounds into livestock feeds may reduce global drug-resistance and preserve the efficacy of last-resort drugs.

Fate of semi-natural grassland in England between 1960 and 2013: A test of national conservation policy

It is well documented that significant losses in semi-natural grassland occurred across Europe during the second half of the twentieth century. However, comparatively few studies have investigated and quantified the fate of large numbers of individual grassland areas. This is important for understanding the causes of decline, and consequently establishing new policies to conserve and restore lost habitats. This study addresses this problem; GIS was used to compare historic survey data collected between 1960 and 1981 with two contemporary spatial datasets of habitats in England. The datasets included the Priority Habitats Inventory 2013 and the Land Cover Map 2007 and this was undertaken for different types of semi-natural grassland across England. Considerable decreases occurred across the different grassland types, with a loss of 47% of studied semi-natural grasslands sites in England over 32–53 years. Of this, the majority of grassland was lost to conversion to agriculturally-improved grassland or arable cultivation, 45% and 43% respectively. Changes to woodland and urban areas were also evident, but on a much smaller scale. Sites receiving statutory protection as a Site of Special Scientific Interest were found to have retained more grassland (91%), compared with non-protected sites (27%), thus highlighting the effectiveness of this aspect of current conservation policy in England, and the need for this to continue in the future.

Evaluating the Success of Seed Sowing in a New England Grassland Restoration

Grassland habitat is declining in the northeastern United States, leading to a decline in associated native species. Consequently, there is considerable interest by land managers in conserving and restoring grassland habitats in the Northeast. However, unlike the Great Plains and Europe, quantitative monitoring of restoration sites is uncommon, making it difficult to improve new restoration projects. Here we evaluate a grassland restoration in Waterford, Connecticut, to determine if mechanical clearing of woody vegetation combined with sowing 23 native grasses and forbs led to successful establishment of these species. We also compared cover, diversity, and colonization by exotic and woody species in planted and unplanted areas over time. In the third and fifth growing seasons after planting in 2006, we sampled the vegetation in the planted site, an unplanted zone within the planted grassland, and an adjacent unplanted grassland. Twenty of the 23 sown species established by 2010, and sown species dominated the planted area (70% of total cover). Despite the successful establishment of most sown species, species richness and diversity were no higher in the sown grassland than in adjacent unseeded areas. However, the sown grassland contained lower cover of non-native and invasive species. Big bluestem (Andropogon gerardii Vitman) established aggressively, potentially reducing both exotic colonization and native diversity. This study shows that sowing native grassland species can lead to the successful development of native-dominated grasslands. Results can inform future grassland restoration efforts in the Northeast and show that seeding with aggressive grass species may greatly impact restored plant communities.

Effects of predator functional diversity on grassland ecosystem function

Predator species individually are known to have important effects on plant communities and ecosystem functions such as production, decomposition, and elemental cycling, the nature of which is determined by a key functional trait, predator hunting mode. However, it remains entirely uncertain how predators with different hunting modes combine to influence ecosystem function. I report on an experiment conducted in a New England grassland ecosystem that quantified the net effects of a sit-and-wait and an actively hunting spider species on the plant composition and functioning of a New England grassland ecosystem. I manipulated predator functional diversity by varying the dominance ratio of the two predator species among five treatments using a replacement series design. Experimentation revealed that predator functional diversity effects propagated down the live plant-based chain to affect the levels of plant diversity, and plant litter quality, elemental cycling, and production. Moreover, many of these effects could be approximately by the weighted average of the individual predator species effects, suggesting that this kind of predator diversity effect on ecosystems is not highly nonlinear.

Soil organic carbon contents in long‐term experimental grassland plots in the UK (Palace Leas and Park Grass) have not changed consistently in recent decades

AbstractA recent report of widespread declines in soil organic C (SOC) in the UK over the 10–25 years until the early 2000s has focussed attention on the importance of resampling previously characterized sites to assess long‐term trends in SOC contents and the importance of soils as a potentially volatile and globally significant reservoir of terrestrial C. We have used two sets of long‐term experimental plots which have been under constant and known management for over a century and for which historical data exist that allow comparison over recent decades to determine what, if any, changes in SOC content have occurred. The plots used are the Palace Leas (PL) Meadow Hay Plots in north‐east England (UK) established in 1897, and from the Park Grass (PG) Continuous Hay experiment established in 1856 at Rothamsted in south‐east England. Collectively, these plots represent the only grassland sites in the UK under long‐term management where changes in SOC over several decades can be assessed, and are probably unique in the world. The plots have received different manure and fertilizer treatment and have been under known management for at least 100 years. In 1982, total SOC contents were determined for the 0–27 cm layer of six of the PL plots using measurements of SOC concentrations, bulk density and soil depth. In 2006, the same six PL plots were resampled and SOC contents determined again. Four of the plots showed no net change in SOC content, but two plots showed net loss of SOC of 15% and 17% (amounting to decreases of 18 and 15 t C ha−1) since 1982. However, these differences in total SOC content were in a similar range to the variations in bulk density (6–31%) with changing soil water content. In 1959, the soil masses and SOC concentrations to 23 cm depth were measured on six PG plots with fertilizer and manure treatments corresponding closely with those measured on PL. In 2002, the SOC concentrations on the same plots were measured again. On three of the PG plots, SOC concentrations had declined by 2–10%, but in the other three it had increased by 4–8% between 1959 and 2002. If it is assumed that the soil bulk density had not changed over this period, the losses of SOC from the top soils ranged range from 10 to 3 t C ha−1, while the gains ranged from 4 to 7 t C ha−1. When the differences with time in SOC contents for the six PL and the six PG plots were examined using paired t‐tests, that is, regarding the plots as two sets of six replicate permanent grasslands, there were no significant differences between 1982 and 2006 for the PL plots or between 1959 and 2002 for the PG plots. Thus, these independent observations on similar plots at PL and PG indicate there has been no consistent decrease in SOC stocks in surface soils under old, permanent grassland in England in recent decades, even though meteorological records for both sites indicate significant warming of the soil and air between 1980 and 2000. Because the potential influences of changes in management or land use have been definitively excluded, and measured rather than derived bulk densities have been used to convert from SOC concentrations to SOC amounts, our observations question whether for permanent grassland in England, losses in SOC in recent decades reported elsewhere can be attributed to widespread environmental change.

Changing land management of lowland wet grasslands of the UK: impacts on snipe abundance and habitat quality

AbstractSnipe Gallinago gallinago breeding on lowland wet grasslands in England have undergone widespread and dramatic declines in abundance and distribution since at least the 1970s. There are many potential drivers of the decline but reductions in habitat quality, driven by land management, are often proposed as a contributing factor in the historical declines of breeding waders. Breeding snipe are now restricted to a few key places such as nature reserves and environmentally sensitive areas where management for breeding waders is implemented. On average, populations have continued to decline, even in these key areas, though population trends vary from a decline of 98% to an increase of 61% between the early 1990s and 2006. We examined the relationship between regional variation in snipe population trends and soil conditions, other habitat features and land management. Snipe were more likely to persist in fields where the soil conditions were wet and soft. Fields are wetter and softer now than in the early 1990s and management influenced these conditions. Soil softness increased with decreasing grazing pressure and increasing surface flooding. Soil moisture increased with surface flooding and was higher in organic soils. Changes in field condition were consistent with decreases in grazing pressure and increases in surface flooding. In spite of habitat condition being altered in a way that should have been beneficial to snipe, the numbers have continued to decline. Thus, it is unlikely that the measures of habitat condition examined here have been the driver of the decline and other factors must be involved. Research efforts should now focus on alternative explanations of the decline, for example, changes in other key aspects of habitat quality such as prey abundance, or changes in snipe productivity or mortality.

Has golf-course management had an effect on the plant species composition and character of a calcareous grassland?

Lowland calcareous grassland in the UK is a priority habitat designated under the UK Biodiversity Action Plan. Calcareous grasslands used to be common in north-western Europe and were utilized for grazing livestock such as sheep and cows. Many calcareous grasslands in England have been either agriculturally ‘improved’ through the addition of fertilizer and herbicides to increase productivity or have been ploughed up to make way for arable production, which has led to a dramatic decrease in the area of calcareous grassland.Minchinhampton Common is an area of lowland calcareous grassland located within the English county of Gloucestershire. In 1889, a golf course was laid out on the common for the use and enjoyment of local people.The first objective of this project was to investigate whether the presence of the golf course on Minchinhampton Common and associated golf-course management activities have had an effect on the composition and character of the calcareous grassland. The second objective was to investigate whether abandoned golf-course features on Minchinhampton Common, such as old fairways and old greens can recover to resemble undisturbed calcareous grassland.Significant differences were found between the undisturbed calcareous grassland and the fairways, greens and pathways in terms of vegetation height, plant species composition, botanical diversity and soil characteristics. This demonstrates that the presence of the golf course and the management carried out to maintain it has had an effect on the composition and character of the calcareous grassland.Significant differences were found when the fairways and greens were compared with the abandoned old fairways and old greens. This shows that after 15 years of abandonment the old fairways and old greens are no longer similar to the fairways and greens, but they are still different from the undisturbed calcareous grassland. It is hypothesized that to aid recovery, the abandoned features should be cut annually and the clippings removed. This will decrease the nutrient status of the soil and reduce the competitiveness of grasses, thus providing greater opportunities for the establishment of forb species typical of nutrient poor calcareous grasslands in north-western Europe.

Predation of Lapwing Vanellus vanellus nests on lowland wet grassland in England and Wales: effects of nest density, habitat and predator abundance

There is concern that predation of Lapwing Vanellus vanellus nests may create additional pressure on declining populations of this species in Europe. At seven sites in England and Wales, daily nest predation rates on 1,390 nests were related to variables using Generalised Linear Mixed Models. The strongest predictor was Lapwing nest density (number of nests within 100 m): predation rates declined as nest density increased. Since nocturnal species, probably mammals, have been identified as the major predators of Lapwing nests at these sites, these results suggest that Lapwings are able to deter mammalian predators or may settle to nest at high densities in areas with low predation pressure. At the site level, there was no relationship between Lapwing nesting density and fox density, and a positive relationship with Carrion Crow Corvus corone nesting density. There was a weaker effect of distance to field boundary: nests closer to boundaries were more likely to be predated. Weak interactive effects between crow density and both nest visibility and distance to vantage point were identified in models using a reduced subset of nests. These were counter-intuitive, did not persist in the larger data set, and do not have obvious explanations. If Lapwings nesting at high density are able to deter predators, there are implications for land management. Smaller areas could be managed within potential breeding habitat to encourage Lapwings to nest in dense colonies. Selection of larger fields for such management, where nests could be located far from the field boundary should improve the value of such measures.

Yield and spatial supply of bioenergy poplar and willow short‐rotation coppice in the UK

Limited information on likely supply and spatial yield of bioenergy crops exists for the UK. Here, productivities are reported of poplar (Populus spp.) and willow (Salix spp.) grown as short-rotation coppice (SRC), using data from a large 49-site yield trial network. A partial least-squares regression technique was used to upscale actual field trial observations across England and Wales. Spatial productivity was then assessed under different land-use scenarios. Mean modelled yields ranged between 4.9 and 10.7 oven-dry tonnes (odt) ha(-1) yr(-1). Yields were generally higher in willow than in poplar, reflecting the susceptibility of older poplar genotypes to rust and their tendency for single stem dominance. Replacing 10% of arable land, 20% of improved grassland and 100% of set-aside grassland in England and Wales with the three most productive genotypes would yield 13 Modt of biomass annually (supplying 7% of UK electricity production or 48% of UK combined heat and power (CHP) production). Results show existing SRC genotypes have the immediate potential to be an important component of a mixed portfolio of renewables and that, in future, as new and improved genotypes become available, higher yields could extend this potential further.

Spatial and structural uniformity of lowland agricultural grassland in England: a context for low biodiversity

AbstractThe contention that agricultural grassland within the UK is spatially and structurally uniform across wide differences in livestock farming intensity is examined. Total nitrogen (N) input was used as a surrogate for management intensity. Farms with average annual N inputs of >200 kg ha−1 were categorized as highly intensive, those with N inputs of 50–200 kg N ha−1 as moderately intensive and those with inputs of <50 kg N ha−1 were categorized as extensive. Four farms within each management category were selected in two discrete regions: one in south‐west England, typifying a landscape dominated by agricultural grassland, the other in south‐east England with a more mixed‐farming landscape. Specific N input and management data, and sward botanical composition and structure, were obtained on four fields per farm. The south‐west region had a higher proportion of farms with dairy cattle than in the south‐east England region. The average N input and stocking rates were higher within the intensive‐management category farms in south‐west England than in south‐east England. Old permanent grasslands contained variable amounts of sown species, such as Lolium perenne, and were dominated by a few (generally <5) non‐sown grass species. Grassland that received >75 kg N ha −1 year−1 contained <7 plant species and <3 forb species m−2. Grassland communities with >12 plant species and >5 forb species m−2 were only found in study fields that received <50 kg N ha−1 year−1. Grasslands with >10 forb species m−2 were found only in sites receiving <15 kg N ha−1. Of importance at a landscape scale was ubiquity of species‐poor and similar grassland plant communities across the management intensity range within and between livestock farms. Grassland in the extensive management category was similar in structure in terms of sward height and/or sward density to more intensively managed grasslands. This study revealed, albeit in two lowland sample regions in the UK, the ubiquity of grass‐dominated, species‐poor and structurally uniform grasslands, irrespective of apparently broad differences in farming intensity. The consequences of this spatial uniformity on grassland biodiversity are likely to be profound.

Changes in the numbers of breeding waders on lowland wet grasslands in England and Wales between 1982 and 2002

Capsule Lapwing, Snipe, Curlew and Redshank decreased significantly between 1982 and 2002, while over the same period Oystercatcher increased. Aims To provide current status and population trends for waders breeding on lowland wet grassland in England and Wales. Methods Waders were counted and mapped on three visits to 1051 lowland wet grassland sites, between April and June 2002. Data were compared with those gathered using identical methods in a survey in 1982 and related to land use characteristics and conservation designation. Results Between 1982 and 2002 there were significant declines of 38% for Lapwing Vanellus vanellus, 61% for Snipe Gallinago gallinago, 40% for Curlew Numenius arquata and 29% for Redshank Tringa totanus. Oystercatcher Haematopus ostralegus increased significantly by 47% in the same period. Populations of all species were highly aggregated with most of the birds found on a small number of key sites. Site designation was found to be an important predictor of breeding wader distribution, density and density change. Conclusions The marked population declines of four grassland wader species over the last 20 years are of considerable concern. Careful management of nature reserves and other key sites is essential to halt these declines, while wider scale and more carefully targeted agri-environment schemes may hold the key to reversing declines in the longer term. The efficacy of site designation and current agri-environment schemes for conserving breeding waders on wet grasslands needs to be reviewed.

Changes in breeding wader populations on lowland wet grasslands in England and Wales: causes and potential solutions

Populations of waders breeding on lowland wet grassland in England and Wales have declined markedly in recent decades; the loss of once widespread species such as Lapwing Vanellus vanellus, Snipe Gallinago gallinago and Redshank Tringa totanus from many areas is of particular conservation concern. These declines are due to loss of grassland to other land uses, and to significant changes in grassland management. Drainage, reseeding and changes in grazing regimes have all been particularly detrimental to lowland wet grassland in terms of a breeding habitat for waders. Careful management of key sites, many of them managed as nature reserves, has shown that wader declines can be halted or even reversed. Aspects of this management can be applied to larger areas through agri‐environment schemes, such as the Environmentally Sensitive Areas (ESA) scheme, Tir Gofal (in Wales) and Countryside Stewardship (in England) but these need be carefully targeted to ensure that the benefits for waders are maximized. In particular, it has been shown that higher tier management options within the ESA scheme (those that enhance the landscape) are more cost‐effective than lower tier options (those that maintain the landscape). The extent and suitability of lowland wet grassland will face further pressure in years to come as a result of climate change, the impacts of which need to be assessed and mitigated against.

Use of unimproved and improved lowland grassland by wintering birds in the UK

In the last 50 years, intensification of agricultural grassland management has led to over 97% of all grassland being ‘improved’ in the UK. Despite grassland being an important habitat for birds in Europe, both in terms of area and preference by several species of conservation concern, the impact of grassland intensification on both breeding and wintering birds is poorly understood. This study compared habitat characteristics and bird diversity, in winter, between improved and unimproved lowland grassland in England comprising 44 unimproved fields (350 ha) and 59 improved fields (290 ha) at 7 paired sites. Key habitat differences were found between grassland types. These included, on improved fields, a denser sward, less surface water, more dung flies and more fields with seeding grass. Species that are dependent on soil invertebrates (particularly earthworms) were found to be more numerous on unimproved grassland, whilst generalist insectivores such as corvids were much more numerous on improved grassland. Grassland improvement may have been one important factor behind the recent increases in numbers of some corvid species in the UK.

Dispersal biology of Liatris scariosa var. novae‐angliae (Asteraceae), a rare New England grassland perennial

Propagule dispersal biology is a crucial avenue of research for rare plant species, especially those adapted to disturbance, such as northern blazing star (Liatris scariosa var. novae-angliae), a rare, early-successional New England grassland perennial. We examined the dispersal ability of northern blazing star propagules collected from 14 populations covering the entire latitudinal range of the taxon. Multiple regression demonstrated that dispersal ability, as measured by drop time in still air and flight distance in a low-speed wind tunnel, decreased significantly with propagule size and achene length, and increased with achene width and (for flight distance) pappus length. We used this multiple regression model to test for differences in predicted dispersal capability among maternal families, populations, and inland, coastal, and island habitats. Dispersal capability differed significantly among families and populations but not regions, and allometric relationships between morphological measurements were consistent across populations. Overall, dispersal capability was negatively correlated with germination success in a common greenhouse environment. However, germination success for a given dispersal ability, as well as achene shape, differed among populations. These results suggest specific populations to be targeted for management efforts promoting dispersal and establishment.

Association between lowland grassland plant communities and soil properties

Soil properties should be taken into account when managing and restoring semi-natural grasslands. Topsoils sampled at 462 sites in temperate lowland grasslands in England, UK, were analysed for pH, extractable phosphorus (P), potassium (K) and magnesium (Mg), total nitrogen (N), organic matter (OM), and estimated available water capacity. Soil-plant community relationships were determined using Canonical Correspondence Analysis. Mesotrophic semi-improved grasslands had soil nutrient levels closer to semi-natural communities than to agriculturally improved grasslands, and will be suitable targets for restoration. Unimproved mesotrophic sub-communities were distributed along a pH gradient and will be sensitive to soil pH changes. Wet grasslands were differentiated at the community level; the most species-rich had low extractable P and K levels and will require high levels of soil wetness. Calcareous grasslands were less well differentiated from one another but had lowest ecological amplitudes. Soil summary data for communities are presented to assist site managers and policy makers.

Grassland nature reserves for breeding wading birds in England and the implications for the ESA agri-environment scheme

The two principal mechanisms available to conserve breeding wading birds on lowland wet grassland in England are nature reserves and agri-environment schemes, particularly the Environmentally Sensitive Area (ESA) scheme. ESAs offer payments to landowners in return for maintaining (‘low tiers’) or enhancing (‘high tiers’) the landscape, biodiversity and historic value of the land. Lowland wet grassland nature reserves managed by the Royal Society for the Protection of Birds (RSPB) have been successful at conserving breeding lapwings and redshank but habitat management usually only results in short-term increases in numbers of breeding snipe. Within ESAs, populations of breeding wading birds fare better on land managed under high tiers than on land managed under low tiers. Land managed under high tiers also supports more pairs of breeding wading birds per £ of ESA grant received than land managed under low tiers. Means of increasing the cost-effectiveness of the ESA scheme in conserving breeding wading birds are discussed in the light of these results.

Potential climate change effects on the distribution of agricultural grassland in England and Wales

Abstract. The spatial distribution of agricultural grassland in England and Wales has been assessed using a land evaluation model applied to information describing soils, climate and topography on a 5 × 5 km grid. The model calculates land suitability for grassland from assessments of trafficability/poaching risk and yield class. The spatial distribution of agricultural grassland was modelled for a 30 year climatic baseline (1941–1970) and for incremental changes in temperature and proportional changes in precipitation relative to that baseline.Model estimates for the current distribution of grassland suitability agree well with observed data of actual grassland distribution. The best suited land occurs in south west England, Wales, the Welsh borders and Cheshire with fragmented areas of well suited land in north west England and on the Pens and Humberhead levels.The climatic sensitivity analysis suggests that grassland production in England and Wales is resilient to small perturbations in mean temperature (up to +2°C) and precipitation (±10%). The effect of increasing temperature by 1°C is almost completely offset by precipitation increases of 10% resulting in little change to the distribution of grassland suitability. However, greater temperature changes (+ 4°C) have a major influence on the ability of land to support intensively managed grassland because of increased drought stress. Results indicate that a change in the climate comparable with current best estimates for the future would benefit grassland on good quality land at higher altitudes.

Distribution and abundance of three species of Sitona (Coleoptera: Curculionidae) in grassland in England

SummaryThe distribution and abundance of weevils of the genus Sitona was assessed at 16 sites in England. The sites were chosen to cover a wide range of geographical and agricultural regions. Adult weevils were sampled on four occasions, from May to August 1993. Numbers of adults, larvae and pupae were determined for each site on four occasions from June to September 1994. Numbers of larvae declined throughout the year in which they were sampled and pupae were most numerous in July. The population density of adults increased through the sampling period in both years. Sites close to pulse crops had the largest population levels of weevils, with Sitona lineatus L. the dominant species. No differences in the population levels of Sitona hispidulus (F.) or S. flauescens (Marsh.) were detected. Evidently populations of the latter two species are fairly constant in grassland and most of the variation in the population densities of these three species found in English grassland can be attributed to the migratory behaviour of S. lineatus and the proximity of pulse crops.