Variation in digestibility in nine populations of perennial ryegrass (Lolium perenne) and its genetic basis

Summary Thirty five individuals from each of nine perennial ryegrass populations were sampled from set-stocked and zero-grazed swards and from an old permanent pasture. The swards were 6, 18, 30 months and 11 years old when sampled. The permanent pasture was at least 40 years old.Dry matter digestibility (DMD) and organic matter digestibility (OMD) were determined for green leaf material harvested 4 days after ear emergence. Significant differences were found between the populations, but genotypic differences were found only for OMD. The largest proportion of the total variation was due to differences between blocks. In the zero-grazed populations, DMD and OMD declined significantly with increasing sward age. This was not found for the set-stocked swards. Two sets of pair crosses, from which mid-parent, progeny regressions could be determined, were carried out.The regressions of offspring on mid-parent for set-stocked and zero-grazed swards were used to assess the presence of additive genetic variation and to estimate narrow sense heritability of DMD. The coefficients of correlation, 0.122 and 0.226 respectively, were non-significant, indicating an absence of additive genetic variation.     

Wheat embryogenesis and haploid production in wheat × maize hybrids

Summary Embryogenesis was analyzed in wheat × maize hybrids using paraffin sectioning. Embryogenesis in wheat × maize hybrids is different from that in self-pollinated wheat plants. Development of the embryo is not accompanied by the formation of an endosperm. The endosperm nuclei remain free in the cytoplasm, fail to advance into the cellular stage, and degenerate at a later time. The antipodal cells quickly degenerate in the fertilized ovaries of wheat × maize hybrids similar to self-pollinated ovaries. The antipodal cells remain normal in unpollinated ovaries. The pre-embryo will abort if it is allowed to develop on the plant, because of a nutritional shortage in the absence of an endosperm. Therefore, embryo rescue is necessary for haploid production from a wheat × maize hybrids. Haploid polyembryos were obtained from spikelet culture of wheat × maize hybrids. The formation of polyembryos is due to the cleavage of the pre-embryo and the effect of 2,4-D. The frequency of haploid embryo production and plant regeneration is affected significantly by maize genotypes, but not by wheat genotypes. The concentration of 2,4-D affects only the size of the embryo.     

Biological effects of El Niño on the Galápagos penguin

Long-term monitoring of physical and biological parameters is essential for understanding the effects of El Niño on bird populations, particularly for small or declining populations. We examined the biological effects of El Niño activity from 1965 to 2004 using instrumental sea-surface temperatures from the Galápagos Islands and 20 years of census counts of the Galápagos penguin. Between 1965 and 2004, nine El Niño events were recorded of which two were strong and seven were weak. The two strong El Niño events of 1982-1983 and 1997-1998 were followed by crashes of 77% and 65% of the penguin population, respectively. The evidence suggests that the increased frequency of weak El Niño events limits population recovery. The 2004 penguin population is estimated to be at less than 50% of that prior to the strong 1982-1983 El Niño event. We discuss the biological effects of increased El Niño intensity and frequency within the context of a 6000-year record of El Niño influence and in the light of increasing anthropogenic threats operating after 1535, when the Archipelago was discovered by Europeans.     

A correlation study of vehicle-generated air pollutants

The concentrations of Pb, CO, CH₄ and total hydrocarbons have been measured at a roadside site and at the exit of a multistorey car park. Average concentrations over short periods (10 to 25 min) have been calculated for each pollutant and possible correlations between these average levels of the different pollutants investigated. Significant correlations were found at only one site and the conclusion was drawn that it is only under exceptional conditions that correlations in levels exist over these extremely short averaging periods.     

Relationship between intensity of phosphatase activity and physico-chemical properties in woodland soils

The relationships between intensity of phosphatase activity and soil properties at two depths in some Lake District woodland soils have been examined. Significant relationships were found with soil organic matter, moisture, clay + silt, total nitrogen, isotopically-exchangeable phosphorus, extractable magnesium contents and soil pH. When data from all soils, both 0–5 and 10–15 cm depths, were pooled 66% of the total variation in intensity of phosphatase activity could be accounted for by these soil properties.However, covariance analysis showed that regressions between intensity of phosphatase activity and soil properties differed with soil depth, soil type, season, vegetation type and underlying rock type. When the effects of these interactions were taken into account, up to 99% of the variation in the intensity of phosphatase activity could be accounted for. The relative importance of these interactive factors appeared to be rock type = vegetation type > soil type = season > soil depth.The effects of the soil properties and the interacting factors on the intensity of phosphatase activity in these woodland soils are discussed.     

Carbon sequestration and saving potential associated with changes to the management of agricultural soils in England

Abstract. The potential for soil organic carbon sequestration, energy savings and the reduction of the emission of greenhouse gases were investigated for a range of changes in the management of tilled land and managed grassland. These parameters were modelled on a regional basis, according to local soils and crop rotations in England, and avoided the use of soil related indices. The largest carbon sequestration and saving contribution possible comes from an increase in the proportion of permanent woodland, such that a 10% change in land use could amount to 9 Mt C yr⁻¹ in the initial years (arable and grassland). Changes in arable management could make a significant contribution to an abatement strategy if carried out in concert with greater use of permanent conservation field margins, increased returns of crop residues and reduced tillage systems, contributing 1.3 Mt C yr⁻¹ in the initial years. It should be noted, however, that true soil carbon sequestration would be only a minor component of this (125 kt C yr⁻¹), the main part being savings on CO₂ emissions from reduced energy use, and lower N₂O emissions from reduced use of inorganic nitrogen fertilizer.     

Magnesium deficiency in Douglas-fir and Grand fir growing on a sandy outwash soil amended with sewage sludge

Soil and plant samples were collected from chlorotic plantations of Grand fir (Abies grandis) and Douglas-fir (Pseudotsuga menziesii) in Winter, 1989. The soils had been amended in 1981 with an average of 300 dry Mg ha^?1 of municipal sewage sludge. The sludge amendment resulted in an N application rate of approximately 8000 kg ha^?1. Foliage analysis indicated a severe Mg deficiency (0.25 g kg^?1 in sludge-treated vs. 0.93 g kg^?1 in untreated area) might be the cause of chlorosis. No other nutrient showed concentrations in the deficient or toxic ranges. Trace metal levels in foliage were elevated significantly for Ni, Cd and Cr in sludge-treated sites, but not toxic levels. Soil samples taken to a depth of 1.4 m indicated the potential for soil acidification (up to 0.9 pH unit) in soil surface horizons. In addition, exchangeable Ca, Mg and K may have been depleted in surface horizons. Exchangeable Al and Fe were greater in the surface of sludge-treated sites. These observations and the loss of much of the nitrogen added during the sludge amendment indicated that nitrification and cation leaching was likely the mechanism for acidification and depletion of exchangeable cations. Fertilization of the plantation with MgSO₄ or dolomitic limestone was carried out in Spring 1990. New foliage collected in June, 1990 was non-chlorotic and significantly higher in Mg concentration than unfertilized foliage (1.1. vs. 0.7 g kg^?1, respectively). Results of this study indicate that it is important to assess the potential for initiating a nutrient deficiency due to secondary effects of sludge application in forest systems.     

Development and Implementation of a Forest Nursery Accreditation Policy at a Local Level in Leyte, Philippines

Through a series of workshops with the stakeholders including nursery operators, tree farmers, staff of the Department of Environment and Natural Resources, local government units and the academe, a forestry seedling nursery accreditation policy was developed. The resulting policy was subsequently implemented by the municipal government of Palompon, Leyte. The accreditation policy encouraged nursery operators to follow smallholder-based best management practices for tree nurseries. Implementation of the nursery accreditation policy improved farmers’ knowledge and skills in the production of high quality seedlings, encouraged adoption of BMP for forest nurseries, provided additional source of income for the farmers, enabled members of the groups operating the communal nursery to forge closer relationship with each other, encouraged utilization of farmers’ free time in productive activities, developed farmers’ confidence in producing high quality planting materials, and gained for the farmers favourable attention from various organizations and groups. The Bennett’s hierarchy of project outcomes showed that the implementation of accreditation scheme achieved high levels of outcomes, indicating that it led to substantial improvements in the lives of the farmers.     

European corn borer: pheromone polymorphism or sibling species?

Electrophoretic analyses of the (Z) and (E) pheromone-attracted males of Ostrinia nubilalis (Hübner), the European corn borer, in an area of coexistence indicate that these strains are not freely interbreeding. Although the populations are morphologically indistinguishable, studies of allozyme, pheromone, and hybridization suggest that the (Z) and (E) entities are genetically differentiated, perhaps to the status of semi- or sibling species.