Conservation of amenity trees in the Lothian Region of Scotland

Amenity trees, defined as all trees excluding those in Forestry Commission and grant-aided woodlands, worked coppice, commercial orchards and hardy-stock nurseries, were surveyed in the Lothian Region between 1972 and 1975. The Region (c. 188,000 ha or 1,877 km²) was stratified into three land categories-(i) burghs (Scottish equivalent of English boroughs), (ii) lowland rural and (iii) upland rural, parts of at least 10% of the 1 km squares (vide Ordnance Survey maps) of each land category being surveyed; the surveyed squares were selected randomly.Numbers of trees per ha ranged from 59 in burghs to 43 and 24 in lowland and upland (above 150m) rural areas respectively. In total there were 6·7 ± 1·9 million amenity trees in the Region divided as follows: 1·4 ± 0·4, 3·2 ± 0·9 and 2·1 ± 0·6 millions between the burghs and lowland and upland rural areas respectively; c. 1·0 m of the 1·4 million trees in burghs were located in Edinburgh. Approximately 70% of trees were deciduous with a larger proportion of conifers in upland areas than elsewhere; sycamore (Acer pseudoplatanus L.), hawthorn (Crataegus spp.) and Scots pine (Pinus sylvestris L.) were the commonest of 76 species or generic groupings recorded, accounting for 11·6, 11·1 and 10·5% respectively of the regional total. Birch (Betula spp.) was the commonest deciduous tree in upland areas where ash (Fraxinus excelsior L.) and beech (Fagus sylvatica L.) were more abundant than sycamore. In the burghs wych elm (Ulmus glabra Huds.) was more numerous than hawthorn and less than sycamore. Trees in Edinburgh differed greatly from those in the smaller towns (burghs) with more rural atmospheres, where sycamore, wych elm, hawthorn, elder and birch contrasted with apple, lilac, flowering cherry, sycamore and rowan occurring abundantly in Edinburgh.Excluding Edinburgh, over 50% of the Region's trees were identified in broadleaved (26·7%), coniferous (21·4%) and mixed (13·6%) woodlands, with 12·0% and 8·1% occurring in shelterbelts and hedgerows respectively; gardens and parks, of all sorts, only accounted for 4·5% and 1·1% respectively.Size class distribution ssuggest that there are sufficient developing saplings to maintain the existing number of mature trees but that wych elm (Ulmus glabra Huds.), unless devastated by Dutch elm disease, sycamore and ash are likely to increase at the expense of oak (Quercus spp.), lime (Tilia spp.), Scots pine and beech. In some situations, however, the resourse seems to be seriously deficient in saplings, e.g. oaks in parks.     

Heterosis and its possible exploitation in swedes (Brassica napus L. ssp. rapifera)

Summary Considerable heterosis has been demonstrated in inter-cultivar swede hybrids. Increases in dry matter yield of between 5.9 and 25.6% over the superior parent were obtained. Difficulties and possibilities with regard to the commercial exploitation of this phenomenon in swedes are discussed.     

Influence of calcium, magnesium, or potassium ions on the formation and stability of emulsions prepared using highly hydrolyzed whey proteins

Oil-in-water emulsions (4 wt % soy oil) containing 4 wt % whey protein hydrolysate (WPH) (27% degree of hydrolysis) and different levels of calcium, magnesium, or potassium chloride were prepared in a two-stage homogenizer. Other emulsions containing 4 wt % WPH but including 0.35 wt % hydroxylated lecithin and different levels of the above minerals were similarly prepared. The formation and stability of these emulsions were determined by measuring oil droplet size distributions using laser light scattering and by confocal scanning laser microscopy and a gravity creaming test. Both lecithin-free and lecithin-containing emulsions showed no change in droplet size distributions with increasing concentration of potassium in the range 0-37.5 mM. In contrast, the diameter of emulsion droplets increased with increasing calcium or magnesium concentration >12.5 mM. Emulsions containing hydroxylated lecithin were more sensitive to the addition of calcium or magnesium than the lecithin-free emulsions. Storage of emulsions at 20 degrees C for 24 h further increased the diameter of droplets and resulted in extensive creaming in emulsions containing >25 mM calcium or magnesium. It appears that both flocculation and coalescence processes were involved in the destabilization of emulsions induced by the addition of divalent cations.     

Evaluating irrigation performance in a Mediterranean environment

Assessment of irrigation performance is a prerequisite for improving water use in the agricultural sector to respond to perceived water scarcity. Between 1996 and 2000, we conducted a comprehensive assessment of the performance of the Genil–Cabra irrigation scheme (GCIS) located in Andalusia, southern Spain. The area has about 7,000 ha of irrigated lands distributed in 843 parcels and devoted to a diverse crop mix, with cereals, sunflower, cotton, garlic and olive trees as principal crops. Irrigation is on demand from a pressurized system and hand-moved sprinkler irrigation is the most popular application method. Six performance indicators were used to assess the physical and economic performance of irrigation water use and management in the GCIS, using parcel water-use records and a simulation model. The model simulates the water-balance processes on every field and computes an optimal irrigation schedule, which is then checked against actual schedules. Among the performance indicators, the average irrigation water supply:demand ratio (the ratio of measured irrigation supply to the simulated optimum demand) varied among years from 0.45 to 0.64, indicating that the area is under deficit irrigation. When rainfall was included, the supply:demand ratio increased up to 0.87 in one year, although it was only 0.72 in the driest year, showing that farmers did not fully compensate for the low rainfall with sufficient irrigation water. Nevertheless, farmers in the area made an efficient use of rainfall, as indicated by the relatively high values (0.72–0.83) for the ratio of actual:attainable crop yields. Water productivity (WP) in the GCIS oscillated between 0.72 €/m³ and 1.99 €/m³ during the 4 years and averaged 1.42 €/m³ of water supplied for irrigation, while the irrigation water productivity (IWP) averaged 0.63 €/m³ for the period studied. WP is higher than IWP because WP includes production generated by rainfall, while IWP includes only the production generated by irrigation.Communicated by A. Kassam     

Estimation of infectious dose and viral shedding rates for infectious pancreatic necrosis virus in Atlantic salmon,Salmo salar L., post‐smolts

Infectious dose and shedding rates are important parameters to estimate in order to understand the transmission of infectious pancreatic necrosis virus (IPNV). Bath challenge of Atlantic salmon post‐smolts was selected as the route of experimental infection as this mimics a major natural route of exposure to IPNV infection. Doses ranging from 10² to 10^?4 50% end‐point tissue culture infectious dose (TCID₅₀) mL^?1 sea water were used to estimate the minimum infectious dose for a Scottish isolate of IPNV. The minimum dose required to induce infection in Atlantic salmon post‐smolts was <10^?1 TCID₅₀ mL^?1 by bath immersion (4 h at 10 °C). The peak shedding rate for IPNV following intraperitoneal challenge using post‐smolts was estimated to be 6.8 × 10³ TCID₅₀ h^?1 kg^?1 and occurred 11 days post‐challenge. This information may be incorporated into mathematical models to increase the understanding of the dispersal of IPNV from marine salmon sites.     

Tools to study trends in community structure: application to fish and livestock trading networks

Partitioning of contact networks into communities allows groupings of epidemiologically related nodes to be derived, that could inform the design of disease surveillance and control strategies, e.g. contact tracing or design of 'firebreaks' for disease spread. However, these are only of merit if they persist longer than the timescale of interventions. Here, we apply different methods to identify concordance between network partitions across time for two animal trading networks, those of salmon in Scotland (2002-2004) and livestock in Great Britain (2003-2004). Both trading networks are similar in that they moderately agree over time in terms of their community structures, but this concordance is higher--and therefore community structure is more consistent--when only the 'core' network of nodes involved in trading over the whole time series is considered. In neither case was higher agreement found between partitions close together in time. These measures differ in their absolute values unless appropriate standardisation is applied. Once standardised, the measures gave similar values for both network types.     

Global mapping of the yeast genetic interaction network

A genetic interaction network containing approximately 1000 genes and approximately 4000 interactions was mapped by crossing mutations in 132 different query genes into a set of approximately 4700 viable gene yeast deletion mutants and scoring the double mutant progeny for fitness defects. Network connectivity was predictive of function because interactions often occurred among functionally related genes, and similar patterns of interactions tended to identify components of the same pathway. The genetic network exhibited dense local neighborhoods; therefore, the position of a gene on a partially mapped network is predictive of other genetic interactions. Because digenic interactions are common in yeast, similar networks may underlie the complex genetics associated with inherited phenotypes in other organisms.