J. Hodgson

Seed size and shape predict persistence in soil.

An understanding of seed persistence in the soil is important to vegetation management and weed control, but experimental collection of seed bank data is tedious and expensive. We report a rapid, simple method for predicting seed persistence in the soil. The method is tested on a range of British, mostly herbaceous, species. Diaspore (seed or fruit) weight is plotted against variance of the three linear dimensions of the diaspore. All diaspores within an area of the graph defined by a maximum weight and variance are persistent in the soil. The critical weight is the same for fruits and seeds, but the critical variance of diaspore dimensions appears slightly higher for fruits. The great majority of diaspores outside this region are short lived, and the relatively few ambiguous cases can be resolved by reference to habitat (...)

The ecology and management of grazing systems

Part 1 Plants and plant populations: tissue flows in grazed plant communities, D. Chapman and G. Lemaire survival strategies under grazing, D. Briske plant competition and population dynamics, J. Bullock community and ecosystem processes under grazing, S. Archer. Part 2 Animal and animal populations: foraging strategies of grazing animals, M. Demment biochemical aspects of grazing behaviour, K. Launchbaugh ingestive behaviour and diet selection, E.D. Ungar nutritive value of herbage and nutrient requirements of large herbivores, H. Dove animal populations in grazing systems - intra- and inter-specific interactions, M. Murray. Part 3 Grazing systems and their management: complexity and stability in grazing systems, N. Tainton management of temperate pastures, G.W. Sheath and D. Clarke management of rangelands, M. Stafford Smith management of Mediterranean grasslands, N. Seligman management of tropical grasslands, M.J. Fisher.

Grassland ecophysiology and grazing ecology.

Environmental constraints and plant responses to defoliation morphogensis of pasture species and adaptation to defoliation animal interactions sustainable grazing management of natural pastures.

Grazing management. Science into practice.

Part 1 Principles grassland and grazing management the grazing system the grazed sward the grazing animal herbage production and utilization plant composition and nutritive value herbage intake food conversion efficiency sward conditions, herbage intake and animal performance output from grazing systems. Part 2 Resources: plants soils and fertilizers animals supplements. Part 3 Application: seasonality of herbage supply and feed requirements grazing methods sward control and grazing management sward measurements enterprise planning and feed budgeting.

Long-term resistance to simulated climate change in an infertile grassland

Climate shifts over this century are widely expected to alter the structure and functioning of temperate plant communities. However, long-term climate experiments in natural vegetation are rare and largely confined to systems with the capacity for rapid compositional change. In unproductive, grazed grassland at Buxton in northern England (U.K.), one of the longest running experimental manipulations of temperature and rainfall reveals vegetation highly resistant to climate shifts maintained over 13 yr. Here we document this resistance in the form of: (i) constancy in the relative abundance of growth forms and maintained dominance by long-lived, slow-growing grasses, sedges, and small forbs; (ii) immediate but minor shifts in the abundance of several species that have remained stable over the course of the experiment; (iii) no change in productivity in response to climate treatments with the exception of reduction from chronic summer drought; and (iv) only minor species losses in response to drought and winter heating. Overall, compositional changes induced by 13-yr exposure to climate regime change were less than short-term fluctuations in species abundances driven by interannual climate fluctuations. The lack of progressive compositional change, coupled with the long-term historical persistence of unproductive grasslands in northern England, suggests the community at Buxton possesses a stabilizing capacity that leads to long-term persistence of dominant species. Unproductive ecosystems provide a refuge for many threatened plants and animals and perform a diversity of ecosystem services. Our results support the view that changing land use and overexploitation rather than climate change per se constitute the primary threats to these fragile ecosystems.

COMPARATIVE STUDIES OF DIET SELECTION BY SHEEP AND CATTLE: THE HILL GRASSLANDS

SUMMARY (1) A comparative study was made of the seasonal variation in floristic composition of the diets selected by sheep and cattle grazing together on Agrostis-Festuca, Nardus, and Molinia grassland communities in southern Scotland. Fenced plots at each site were grazed in sequence with the experimental animals moved between sites as appropriate. (2) For each period at each site, sward biomass, species and morphological composition and canopy structure were characterized. Diet samples were collected from three to five oesophageally-fistulated animals of each species from four to seven, separate, two-week periods of observation at each site over three years. (3) Sheep diets were more variable than cattle diets, both between and within animals, for all sites. Sheep and cattle differed significantly for almost all major dietary components; exceptions were Molinia leaf, grass sheath and dead material at the Molinia site. (4) At all sites in summer, sheep diets contained more forbs and less grass flowerstem than did cattle diets. (5) At the Agrostis-Festuca and Nardus sites, sheep diets contained more live components than did cattle diets on all sampling dates. At the Molinia site, sheep and cattle diets contained similar proportions of live components in early summer, but in autumn after the Molinia and Holcus leaves died, sheep grazed other grass species and their diets contained less live components than those of the cattle which grazed Junlcus spp. (6) At the Nardus site, both sheep and cattle preferentially grazed the Festuca and Deschamnpsia (from between the Nardus tussocks) and the small patches of broad-leaved grasses. The progressive reduction in herbage biomass and height on the preferred areas in successive grazing periods was associated with a marked increase in the Nardus content of cattle diets but not of sheep diets. (7) Differences between sheep and cattle diets were explicable by (i) a difference in the height at which the animals grazed in relation to differences in the distribution of plant species within the sward canopy, (ii) the greater ability of sheep to select from fine-scale mixtures; and (iii) the greater readiness of cattle to graze tall, more fibrous components. (8) The implications of the differences in diet selection between sheep and cattle for sward responses and grazing management are discussed.

Sward structural characteristics and herbage accumulation of Panicum maximum cv. Mombaça subjected to rotational stocking managements

Grazing strategies promote changes in sward structure that can affect patterns of herbage accumulation and sward flexibility to management. This experiment evaluated sward structural characteristics and herbage accumulation of Mombaca guinea grass (Panicum maximum Jacq. cv. Mombaca) subjected to rotational stocking managements. Treatments involved grazing when swards reached either 95 or 100% interception of the incident light (LI), to post-grazing heights of 30 and 50 cm, and were allocated to 2,000 m2 paddocks according to a randomised complete block design in a 2 × 2 factorial arrangement with four replications, from January 2001 to February 2002. Sward canopy changed from a vertical to a more horizontal orientation as the light interception area index and height increased from post to pre-grazing. Leaf canopy height pre-grazing was stable throughout the year and around 90 and 115 cm for the 95% and 100% LI treatments respectively, indicating a potential for development and use of target-based grazing management practices. Herbage mass pre and post-grazing was lower for the 95% than the 100% LI treatments, but with higher proportion of leaf and lower proportions of stem and dead material. Treatment effects on herbage accumulation were cumulative and became more evident as the experiment progressed, with up to 6 t ha-1 DM advantage to the 95/30 treatment. Although based on a single year experiment, grazing management should aim for low herbage mass during the transition period from winter to spring in order to allow fast recovery of swards and favour herbage accumulation during the following growing season.

COMPARATIVE STUDIES OF DIET SELECTION BY SHEEP AND CATTLE: BLANKET BOG AND HEATHER MOOR

(1) A comparative study was made of the seasonal variation in floristic composition of the diets selected by sheep and cattle grazing together on blanket bog (with Calluna vulgaris and Eriophorum vaginatum as co-dominants) and on species-poor Calluna vulgaris heather moor. The sites were grazed in sequence with the experimental animals moved between sites as appropriate. (2) For each period at each site, sward biomass, species and morphological composition and canopy structure were characterized. Diet samples were collected from three to four oesophageally-fistulated animals of each species in four to five, separate, twoweek grazing periods at each site over four years. (3) Sheep diets were slightly more variable than cattle diets: on the blanket bog between-animal variation was similar for sheep and cattle while within-animal variation was greater for sheep; on the Calluna moor, between-animal variation was greater for sheep than cattle whereas within-animal variation was similar for both animal species. (4) Though the proportions of most dietary components differed significantly between sheep and cattle in at least one period, it was clear that there were many components which were selected or avoided in common by sheep and cattle. (5) Species which were avoided included Calluna vulgaris, Erica spp. and Empetrum nigrum: their seasonal patterns of use, mainly outside the growing season, reflected periods of shortage of the preferred species. (6) Species which were selected included Molinia caerulea, other grasses and Carex spp. and Trichophorum cespitosum on the blanket bog and Vaccinium spp., Juncus spp. (mainly J. squarrosus) and grasses and Carex spp. on the Calluna moor. The ability of cattle to match the sheep in the dietary proportions of these preferred components was influenced by their distribution in the sward. (7) On the blanket bog, cattle diets contained more Eriophorum spp. leaf than sheep diets, except in April when the dietary proportions were similar. Sheep diets in April contained very high proportions of the immature flowers of E. vaginatum which were strongly selected. (8) Cattle diets contained more dead components than did sheep diets in every period at both sites. (9) Differences between sheep and cattle were mainly attributable to the greater ability of sheep to select from fine-scale mixtures; differences in grazing height between sheep and cattle were secondary to selection in the horizontal plane. (10) The much lower similarity coefficients between sward composition and diet composition for both sheep and cattle on the blanket bog and Calluna moor compared with the hill grasslands in summer, when the widest range of species was present, indicated that the drive to select was greater on the dwarf shrub communities. (11) The implications of the results for grazing management are discussed briefly.

Seed size, shape and persistence in the soil in an Iranian flora

Previous studies on several floras have shown that species with small, rounded seeds tend to accumulate persistent seed banks in the soil, while species with larger, less compact seeds do not. The suggested underlying mechanism is predation. Small seeds experience less predation and are more likely to become buried, which itself offers significant protection from predation by vertebrates. The relationship between seed size and shape and persistence in the soil was examined for the flora of the Arasbaran Protected Area in northwest Iran. Seed size was related to persistence in the soil in Iran in the same way as in most other floras examined, but seed shape was not. It is suggested that predation prevents persistence of large seeds in most floras. Where large-seeded persistent species predominate, for example in Australia and (to a lesser extent) in New Zealand, other factors may interfere with the relationship between seed size and predation.

Effect of spring grazing management on perennial ryegrass and ryegrass‐white clover pastures

Abstract The objective of this study was to investigate the effects of timing and duration of lax spring grazing on tiller dynamics in perennial ryegrass swards, with and without white clover. Two periods of lax grazing—short release (SR) from 26 October to 8 December and long release (LR) from 15 September to 8 December—were compared with a conventional hard grazing—early control (EC). These treatments were applied to swards of perennial ryegrass, with and without white clover, and grazed by sheep. Tiller weight, tiller population density, tiller appearance and death, and stolon population were analysed in a factorial design with three (Experiment 1) and four (Experiment 2) replicates. Tiller weight was increased during the reproductive period, particularly in SR and LR treatments. Also, tiller appearance rate increased in all treatments from September to late January, and was particularly high late in December after grazing of the apices of the main group of reproductive tillers. Lax grazing management ...