Two long-term (16 year) experiments on intensively managed pastures compared extensive grazing, abandonment and continued intensive grazing and were assessed for impacts on soil parameters, plant nutrient content and ecological indicator values. There was a reduction in soil carbon and nitrogen in the abandoned treatment compared to the intensively managed treatment at the wetter site. At the drier site, extensive grazing resulted in a build up of soil carbon. There was a build up of dead organic matter and a reduction in the nutritive value of the vegetation as grazing was reduced. Indicator values confirmed the reduced soil nutrients and a fall in site pH. There was also a rise in the dominance of plants preferring moist conditions, especially at the wetter site. As biodiversity gains are small, the management of these systems could be seen as a trade-off between managing for production and for soil organic carbon.At the drier site this trade-off is apparent, whereas at the wetter site managing for production also maximises soil carbon content. (c) 2010 Elsevier B.V. All rights reserved.

Extensification of grassland management has been put forward as a method of redressing the biodiversity losses seen in agricultural landscapes as a result of increases in production. However, there is little evidence for its success, particularly in upland areas. Two long-term (16 year) experiments at different sites compared extensive grazing, abandonment and continued intensive grazing, assessing impacts on productivity, species composition and plant diversity. Extensive grazing led to slow but continual changes in composition, with some increase in diversity compared to intensive grazing and a broad indication that productivity did not decline with time. At the drier of the two sites it appeared that extensive grazing was better than intensive grazing at buffering the impacts on productivity of year-to-year variations in the weather. Abandonment led to rapid changes in composition followed by stabilisation, as there were no late-successional species to invade and lead to further changes. However, abandonment did not affect diversity. Extensive grazing produced only gradual changes in the diversity of plant species present, indicating that biodiversity gains from extensification within productive landscapes may be a slow process.

Cattle and sheep can create and maintain a mixture of relatively tall and short patches in grass swards through selective grazing. In swards that are grazed by cattle this heterogeneous structure can result in the frequencies of height measurements having a skewed distribution that has variously been better described by the double-normal distribution the gamma distribution and the Weibull distribution than by the more common normal distribution. The fit of these statistical distributions, and the adequacy of the potentially useful log-normal distribution, to sward height frequencies were tested in sown temperate swards grazed by sheep and compared within a single sward. It was concluded that the single-normal and Weibull distributions were inadequate and that overall the log-normal and gamma distributions had the best fit to the measurements.

Sheep systems on upland permanent pastures sown with Lolium perenne/Trifolium repens, have typically been relatively intensively managed, relying on inorganic fertilizers to maintain or increase animal output. However changes in the Common Agricultural Policy have resulted in the development of agri-environment schemes to deliver environmental goals from grasslands. These schemes encourage more extensive grazing systems, and change the emphasis from animal output to issues such as increasing biodiversity. Lower stocking densities provide increased opportunities for diet selection, the development of a heterogeneous habitat and associated changes in species composition. However, will more extensive management increase botanical diversity in upland sown swards? The experiment reported here describes the effect of more extensive management combining cessation of fertilizer and lower grazing intensity on vegetation change, stocking density and lamb output over 14 years.

Agri-environmental policy changes promote more extensive grazing management but the temporal responses of soil nutrients and vegetation biomass and quality to reductions in grazing intensity are still unresolved. We measured soil nutrients and the biomass and nutrient content of vegetation over 5 years following the introduction of extensive management treatments at three sites in Scotland, UK. Five unfertilised treatments, representing different levels of extensive management, were established on existing sown perennial ryegrass/white clover swards. One treatment was ungrazed (UN) and the others had sward surface height treatments of 4 or 8cm during two grazing season treatments, summer and autumn, within each year in a factorial combination (4/4, 4/8, 8/8, 8/4cm). A further treatment, representative of current more intensive systems, received an annual total of 140kgNha−1 plus maintenance P and K and was grazed by sheep to maintain a sward surface height of 4cm (4F). When compared with more intensive management, there was little effect of 5 years of extensive management on soil nutrients at any of the three sites. The extensive treatments created swards with different above-ground biomass during the season, thus changing the balance between the litter and excretal routes for the recycling of plant nutrients. When expressed relative to treatment 4F, the proportion of live dry mass and N, P and K contents in sown species was on average higher in swards maintained at 4cm in summer than at 8cm, and there was evidence of a decline over time in the latter treatments. The proportion of unsown species in live mass increased over time in the unfertilised treatments, and the increase was most rapid in the ungrazed treatment. Nutrient contents of the vegetation in unfertilised swards were lower than those in fertilised swards, and changes over 5 years in the different management treatments differed between sites. However nutrient contents remained above levels that could adversely affect sheep performance throughout this period. Agri-environment schemes that promote extensive grazing management will change vegetation biomass and nutrients but are unlikely to reduce soil nutrients in the short term.

The sustainability of white clover in grass/clover swards of an upland sheep system, which included silage making, was studied over 5 years for four nitrogen fertilizer rates [0 (N-0), 50 (N-50), 100 (N-100) and 150 (N-150) kg N ha(-1)]. A common stocking rate of 6 ewes ha(-1) was used at all rates of N fertilizer with additional stocking rates at the N-0 fertilizer rate of 4 ewes ha(-1) and at the N-150 fertilizer rate of 10 ewes ha(-1). Grazed sward height was controlled, for ewes with their lambs, from spring until weaning in late summer by adjusting the proportions of the total area to be grazed in response to changes in herbage growth; surplus pasture areas were harvested for silage. Thereafter sward height was controlled on separate areas for ewes and weaned lambs. Areas of pasture continuously grazed in one year were used to make silage in the next year. For treatments N-0 and N-150, white clover stolon densities (s.e.m.) were 7670 (205.4) and 2296 (99.8) cm m(-2), growing point densities were 4459 (148.9) and 1584 (76.0) m(-2) and growing point densities per unit length of stolon were 0.71 (0.015) and 0.67 (0.026) cm(-1) respectively, while grass tiller densities were 13 765 (209.1) and 18 825 (269.9) m(-2) for treatments N-0 and N-150 respectively. White clover stolon density increased over the first year from 780 (91.7) cm m(-2) and was maintained thereafter until year 5, reaching 8234 (814.3) and 2787 (570.8) cm m(-2) for treatments N-0 and N-150 respectively. Growing point density of white clover increased on treatment N-0 from 705 (123.1) m(-2) to 2734 (260.7) m(-2) in year 5 and it returned to the initial level on treatment N-150 having peaked in the intermediate years. Stolon density of white clover was maintained when the management involved the annual interchange of continuously grazed and ensiled areas. The non-grazing period during ensiling reduced grass tiller density during the late spring and summer, when white clover has the most competitive advantage in relation to grass. The increase in stolon length of white clover in this period appears to compensate for the loss of stolon during periods when the sward is grazed and over winter when white clover is at a competitive disadvantage in relation to grass. The implications for the management of sheep systems and the sustainability of white clover are discussed.

Modern rural policies that incorporate agricultural and environmental aims within the broader framework of sustainable rural development are being formulated to address the problem of declines in grassland biodiversity and the destruction of sensitive landscapes and habitats in Europe. Extensification is the process of reducing fertiliser inputs, management intensity and stocking rates, and is central to these sustainable rural policies. However, research in the Less Favoured Areas of Europe has been fragmented and highly variable reflecting the different uses and requirements of our upland areas. Information is needed to determine the nature and timescale of changes in such systems, and whether extensive management is sustainable in the long-term. This paper presents results from a range of grassland extensification experiments across Europe, mainly within the European Union, over the past 30 years that quantify the impacts on soil, plant and animal components of the system. All have the common theme of changing the focus of land management from solely the agricultural product to include a broader range of ecological and environmental objectives. Beneficial changes in biodiversity resulted from more extensive management treatments, but at the cost of reductions in total animal output, and in some cases a reduction in individual animal performance. However, it is clear that it is a long-term process to achieve many of these changes in biodiversity, and this must be recognised by policy makers. We recommend that future extensification studies adopt an approach that will allow their results to be applied throughout Europe.

Seasonal cutting treatments were imposed on abandoned perennial ryegrass/white clover swards at three sites in the UK to determine the impact on species diversity and the contribution of different species to biomass. Before the cutting experiment, the abandoned swards had received no fertilizer applications and had been neither grazed nor cut for 3 years. The original sown species, Lolium perenne and Trifolium repens, had virtually disappeared during this period. Self-sown grasses, including Agrostis capillaris, Dactylis glomerata, Festuca rubra, Holcus mollis, Poa pratensis and P. trivialis, had become dominant at two sites. Ranunculus repens was the dominant species at the third site, and self-sown grasses, such as Holcus lanatus and P. trivialis, and Juncus and Carex species were also present. The standing herbage in 2.5 m x 2.5 m subplots was cut to 2.5 cm above ground level and removed annually in either June or October for 7 years at two sites and 6 years at the third site. Total biomass removed was generally <4 t dry matter (DM) ha(-1), and both total and live biomass decreased over time in the June cutting treatment at two sites. There were large changes in species composition after initiating the two cutting treatments. The numbers of grass and dicot species increased, although many new species had a low frequency of occurrence. The contribution of species to biomass changed over time, with species showing a vegetative regenerative strategy decreasing over time at one site. At this site, annual cutting in June was slightly more effective than cutting in October in reducing the dominance of R. repens; cutting in early October effectively reduced Juncus spp. At two sites, there was a decrease in the contribution of the species group showing seasonal regeneration by seed, and differences between cutting dates for two species within this group at one site. L. perenne and T. repens remained at much lower levels than in adjacent unfertilized, grazed swards. Reseeding may be necessary to create species assemblages for ecological and agricultural objectives.

Dawson, L. A., Marriott, C. A., Grayston, S. J., Murray, P. J., Cook, R., Ross, J. M., Pratt, S. M., Duff, E. I., Gange, A. C., Treonis, A. M. (2002). Influence of root herbivory and soil fertility on pasture root system growth and dynamics. In: Durand, J-L.Emile, J-C.; Huyghe, C.; Lemaire, G. (Eds). Multi-Function Grasslands: Quality Forages, Animal Products and Landscapes. Grassland Science in Europe, 7, 672-675. ISBN:2950411037 Multi-Function Grasslands: Quality Forages, Animal Products and Landscapes. Proceedings of the 19th General Meeting of the European Grassland Federation (EGF), La Rochelle, France, 27-30 May 2002.

Abstract Due to economic pressures and policy changes Lolium perenne‐ Trifolium repens sown swards in upland UK sheep systems are likely to become less intensively managed. We present results from the first 5 yr of a long‐term experiment studying vegetation change under more extensive grazing management at three sites. One treatment was representative of current, intensive management and 5 were unfertilized with different intensities of seasonal grazing. The species composition of unfertilized, ungrazed swards changed dramatically within 2 yr and the sown species had virtually disappeared by year 5. Ranunculus repens, Poa trivialis, Agrostis gigantea, Juncus spp. and Carex spp. became dominant at the wettest site. Grasses were dominant at the other sites. In contrast, the sown species were retained in the unfertilized, grazed treatments; there were small shifts in abundance of the species present initially and few additions or losses of species. Some colonizing species were present in the seed bank whereas others with a transient seed bank appeared to have invaded from neighbouring vegetation. Implications of these results for compensation schemes to reduce animal output and increase biodiversity are discussed. Nomenclature: Stace (1991)

Extensification (a reduction in fertilizer inputs and stocking rate of grassland) is seen as one way of increasing the conservation value and of reducing the environmental impact of upland sheep production in the UK, but little is known about the consequences of such a change. This study determines the changes in animal production over ten years following the introduction of four extensive grazing management strategies to perennial ryegrass/white clover pastures at two upland sites. Fertilizer-free treatments were maintained with sward heights of: 4 cm (treatment 4/4U) or 8 cm (8/8U) during the whole of the grazing year, 4 cm during summer and 8 cm during autumn (4/8U) and 8 cm during summer and 4 cm during autumn (8/4U). A control treatment that received 140 kg N ha(-1) year(-1) was also maintained with a sward surface height of 4 cm (4/4F). Scottish Blackface sheep grazed all treatments.The 4/4F treatment carried the greatest number of animals (3746 grazing days ha(-1) year(-1) ); the 4/4U and the 8/8U treatments carried 0.73 and 0.43 of this number respectively. The number on the 4/8U treatment was similar to that on the 4/4U while the 8/4U treatment carried 1.41 of that on the 8/8U treatment (0.61 of 4/4F). Mean individual animal performance was greatest on the 8 cm swards and tended to be lowest on the 4/4F treatment. However, the 4/4F treatment produced the greatest live weight of lamb (623 kg ha(-1) year(-1) ) with the 4/4U producing 0.77, and the 8/8U producing 0.55, of this amount. Although there was year-to-year variation in agricultural output, it was concluded that the lower levels of sheep production that result from a change to extensive systems of grazing management can be maintained for at least 10 years.

The reinstatement of shallow slope failures can be costly and the potential for slips may be reduced by the use of vegetation planted to provide reinforcement, through the plant root system, and a reduction in moisture content and pore water pressure. This report describes trials carried out to assess the suitability of different tree and shrub species. An initial literature survey determined a range of tree, shrub and herbaceous species that had the potential to grow in the environmental conditions alongside highways. A screening trial with 25 species was set up to determine whether the selected species could establish and grow in two different over-consolidated clays. The five species that showed the most successful establishment and growth in the screening trial were then used in a three-year experiment (1997-1999) to measure shoot and root growth. The successful exploitation of the clay mass by the roots of the different species suggests that there could be positive effects on slope stability, as a result of increased soil shear strength and reduction in soil moisture content. The economic costs associated with different vegetation options were also established and provided typical costs for the planting, establishment and ongoing 5-year management of the six vegetation options. The information obtained is useful for allowing a relative comparison between the species options and also to provide absolute values in order to compare vegetation options, in general, to other forms of technical solution where soil stability is an issue on motorway verges. (A)

The effect of extensive grazing management with sheep on vegetation change in sown pastures (initially containing Lolium perenne and Trifolium repens) in the uplands of Scotland was investigated from 1990-1999. One treatment was representative of current more intensive management systems; it was fertilized, and maintained at a sward surface height of 4 cm. Two treatments were unfertilized and were maintained at sward surface heights of 4 cm or 8 cm; the ewe numbers carried on these treatments averaged 74% and 44%, respectively, of those on the fertilized treatment. In all treatments the sheep were Scottish Blackface ewes. Their single lambs also grazed from May until weaning in mid-August. Over 9 years there were only small changes in species composition in the unfertilized treatments. The changes were primarily shifts in abundance of the species present initially, with only a few additions or losses of species. L. perenne made a similar contribution to cover in both the 8 cm and fertilized swards. The highest content of T repens Was in unfertilized swards and the least was in the 4 cm fertilized swards. This study demonstrates that the contribution of the sown species to sward composition remains high in grazed upland swards that are more extensively managed for nearly ten years. Since there was little overall change in species composition, it could be difficult to achieve increased plant biodiversity in these systems simply by removing fertiliser and reducing grazing intensity.

Seasonal dynamics of white clover and perennial ryegrass were examined in sown perennial ryegrass/white clover swards subject to a 2 × 2 factorial treatment combination of defoliation (rotational grazing by sheep and cutting) and nitrogen fertilizer application (0 and 40 kg N ha–1 year–1) in NW Greece. Sward surface height and percentage cover were measured before and after five defoliation periods in 1996 within permanent microplots (30 × 30 cm, divided into nine cells) in which white clover was either initially present or absent. Both white clover and perennial ryegrass achieved maximum height and cover in April–May. Defoliation treatment and whether white clover was present initially significantly affected height and cover of both species. Total plant cover was similar prior to all defoliation periods except in July, a time of drought. Cover of perennial ryegrass was greater where white clover was initially absent, but total plant cover was greater in microplots containing white clover and the extent of the differences varied during the year. In contrast, N fertilizer application had little effect on species cover, other than small reductions in white clover cover. When white clover was present in April, it was found in virtually every microplot cell until July, but if it was absent in April there was little colonization of the microplot.

Tissue flow measurements of leaf material in Lolium perenne (perennial ryegrass), Agrostis capillaris or Poa annua, and Trifolium repens (white clover) were made at three upland sites in Scotland (Hartwood, Sourhope and Fasque) in 1992/93 to determine if there were differences in seasonal growth, senescence and losses to herbivory between species in their response to more extensive award management. The measurements were made monthly from May until October in established predominantly perennial ryegrass/white clover swards receiving three different treatments. One treatment received a conventional annual fertilizer application of 140 kg N/ha plus maintenance P and K and was grazed by sheep at a sward height of 4 cm (4F), whereas the other two treatments were unfertilized and grazed to maintain a sward height of 4 cm (4U) or 8 cm (8U). Significant sources of the variation in leaf appearance, increase in green lamina/petiole length (leaf extension), senescence and losses to herbivory were attributable to site, sward, species and date of measurement. The rate of leaf extension for all three measured species was less in 4U than 4F swards, and less in 4U than 8U swards. Leaf extension of L. perenne exceeded that of the other species, even in unfertilized swards, but rates of leaf appearance were less. There was some evidence in spring of a reduction in net growth as a consequence of removing fertilizer inputs and maintaining a sward height of 4 cm. Species differences in the losses of leaf tissue to herbivory were dependent on sward management. In the 4F treatment, leaf loss to herbivory from L. perenne tillers was greater than that from either A. capillaris, P. annua or T. repens in May, June and September. In the 4U treatment more leaf tissue was also lost from L. perenne than from T. repens. In contrast, there was no difference between grass species in losses to herbivory in either unfertilized sward. The responses of species to changes in fertilizer and grazing management were similar at three sites of differing fertility. The results are discussed in relation to plant competition and species dynamics in extensively managed swards.

In an exploratory study of below-ground trophic relations, natural abundances of the stable isotope pairs 13C/12C and 15N/14N (δ13C and δ15N) were measured on samples of plant shoots, whole soil and soil invertebrates taken in 1994 from two contrasting treatments of a pre-existing experiment: (1) continued grazing by sheep, with N:P:K fertiliser additions from 1990 onward; and (2) no added fertiliser, but sheep grazing removed entirely. Stepwise trophic increases were documented better by seasonal averages of δ13C and δ15N and by seasonal trends, composed of data collected on several occasions, than by instantaneous values. Seasonal changes in plant monocot vs dicot differences for shoot δ13C and δ15N were detected from patterns over several individual sampling dates; instantaneous samples were neither statistically significant nor qualitatively interpretable. Significant isotopic differences between treatments were evident in invertebrates only as seasonal averages or trends. Seasonal variations of δ13C and δ15N in earthworms and slugs may reflect previously unsuspected invertebrate behaviour. Whole soil δ13C was static through time and across treatments. Whole soil δ15N changed seasonally, an effect consistent with 15N/14N fractionation, e.g. during denitrification.

The relationship between vegetation and grazing herbivores is dynamic; the structure and quality of vegetation affect the diet of grazing herbivores and; in turn, the components of grazing (defoliation, excretal return and treading) affect the structure and species composition of the vegetation Both the vertical and horizontal distribution of vegetation are important in understanding plant-animal interactions in grazed plant communities. Mechanisms which confer grazing resistance, through avoidance and tolerance strategies, are discussed. The difficulties in addressing scaling issues at the plant-animal interface are addressed; measurements or events at a small scale cannot be directly extrapolated to a larger scale. Moreover, integration of small-scale functions could result in counter intuitive results at the larger scale. The role of modelling in exploring spatio-temporal heterogeneity in plant-animal interactions is developed. Such models allow the exploration of a large number of hypotheses which cannot be tested under experimental conditions because of logistical, time and money constraints, and provide a framework in which to better understand grazing systems. As a management tool, models have value in their predictive capacity and ability to simulate the complex situations in grazed plant communities. (C) Elsevier/Inra.