Aspects of oyster culture in Strangford Lough,Northern Ireland

The hypothesis that mixed culture of C. gigas and O. edulis accelerates growth in the latter is disproved. A comparative assessment of scallop culturing lanterns, imported from Japan, and traditional wood and plastic oyster trays demonstrated the superiority of lantern grown oysters. Oysters grown by this method had higher dry meat condition indices and higher levels of glycogen, protein and fat than those grown by other methods. The results obtained are attributed to a better flow of water through lanterns compared with the other tray types investigated. A cost analysis of the three culture methods demonstrated the economic feasibility of scallop lanterns for oyster cultivation.     

Macrophytes promote aquatic insect conservation in artificial ponds

相似文献   

Benchmark stem densities for forests and woodlands in south-eastern Australia under conditions of relatively little modification by humans since European settlement

Estimates of forest and woodland structure prior to major periods of modification (e.g. prior to European settlement) are routinely used to inform decisions relating to biodiversity conservation, silviculture and carbon sequestration potential in natural forests and woodlands. The techniques used to derive these estimates often demand that data be collected from specific geographic locations (e.g. locations for which historic survey records exist, where pollen accumulates, or where there is little modification by humans since European settlement) and therefore are often inherently biased. In this study we predicted numbers of trees by diameter class for several widespread forest and woodland types in south-eastern Australia under conditions of relatively little modification by humans since European settlement. To do this we fitted Generalised Additive Models (GAMs) separately to counts of stems in eight diameter classes from 495 plots using explanatory variables representing human modification, environmental variation and natural disturbances. We predicted stem densities under conditions of relatively little modification by humans since European settlement from these models by holding the significant explanatory variables representing modification by humans at minimum observed values. We compared these predictions with published estimates of pre-European stem densities and estimates that we derived for stands at theoretical equilibrium using the quotient of diminution (q). Our mean predictions were broadly comparable with estimates derived from both of these sources; however, we appeared to over-estimate numbers of stems in the smaller diameter classes for some vegetation alliances. A key outcome of this research – and rarely reflected in other techniques used to predict pre-European forest structure – was the amount of variation in stem numbers even within a single diameter class and vegetation alliance. For example, in the white box vegetation alliance, flat parts of the landscape supported 5 times the number of large trees (>80 cm DBH) found on upper slopes under conditions of relatively little modification by humans since European settlement. Our results therefore suggest that these forests and woodlands are more structurally heterogeneous than typically reflected in pre-European estimates and vegetation alliance should not be the unit for managing these stands. The methodology we present is applicable in many forests where the objective is to predict forest structure under conditions of relatively little modification by humans.     

Rapidly quantifying reference conditions in modified landscapes

Reference conditions remain widely used as a benchmark for ecosystem management, but there remains conjecture about the definition of the reference state. Many techniques used to predict reference conditions are difficult to apply operationally because they are resource-intensive, subjective, or applicable for a limited suite of environmental variables or over a narrow range of environmental variation. We defined the reference state as variation in native vegetation exhibiting relatively little evidence of modification by humans since European settlement. Using data from 462 sites supporting native vegetation in a fragmented landscape in south-eastern Australia, we demonstrated a relatively quick and cost-effective way of objectively predicting reference conditions for various surrogates of biodiversity. We predicted reference values for several variables that are used as biodiversity surrogates (i.e., tree densities by diameter class, trees with hollows, tree regeneration, trees with mistletoe, fallen timber, vegetation cover by vertical stratum, litter cover, cryptogam cover and native plant species richness) using generalized additive models (GAMs) fitted with predictors representing measures of human modification since European settlement (exotic plant cover, number of stumps, evidence of firewood collection, evidence of rabbits, evidence of recent grazing by stock, surrounding land use) and measures of environmental variation (floristic composition, mean annual precipitation, mean annual temperature, solar insolation, aspect, slope). Reference values for each response variable were predicted from these models by holding the significant explanatory variables representing modification since European settlement at their minimum observed values, that is, our definition of the reference state. We demonstrated the importance of independently evaluating predictions of this type using generic ecological models and estimates of reference conditions derived from other sources.     

Identification of low productivity sites for European larch (Larix decidua Miller) in Maine,USA

As silvicultural capital becomes limited, allocation of funds to high quality sites becomes critical and sites with low productivity potential should be avoided. Data collected from 31 plots located in 12 plantations established between 1930 and 1982 throughout central Maine were used to develop a soil-based rule to identify sites having a low productivity potential for European larch in Maine, thereby removing them from consideration for plantation establishment. Stepwise regression and discriminant analyses identified several variables that were associated with site index at an index age of 20 years breast height (SI₂₀): solum thickness, B horizon clay content, and B horizon exchangeable K. Using these variables, a classification rule was developed to classify sites into 2 categories (poor, average SI₂₀=14.7 m; and good, average SI₂₀=17.7 m). Cross-validation demonstrated that the classification functions correctly identified 88% of the poor sites and 81% of the good sites.     

Relation between work and phosphate metabolite in the in vivo paced mammalian heart

Nuclear magnetic resonance (NMR) spectroscopy was used to monitor, on a beat-to-beat basis, the concentration of creatine phosphate and adenosine triphosphate during alterations in the work output of canine hearts in vivo. Over a wide range of rate-pressure products (5,000 to 25,000 mmHg/min), the relative amounts of creatine phosphate and adenosine triphosphate within the heart remained constant. The relative concentration of free adenosine diphosphate was calculated under the reasonable assumption that the creatine kinase-catalyzed reaction is near equilibrium in this tissue. The free concentration of adenosine diphosphate also did not change over this range of rate-pressure products. The data demonstrate that the concentration of these compounds is highly regulated in vivo and suggest that factors other than their concentration may be involved in the modulation of steady-state myocardial work output with oxygen consumption.     

In vivo function and membrane binding properties are correlated for Escherichia coli lamB signal peptides

Wild-type and pseudorevertant signal peptides of the lamB gene product of Escherichia coli interact with lipid systems whereas a nonfunctional deletion mutant signal peptide does not. This conclusion is based on interaction of synthetic signal peptides with a lipid monolayer-water surface, conformational changes induced by presence of lipid vesicles in an aqueous solution of signal peptide, and capacities of the peptides to promote vesicle aggregation. Analysis of the signal sequences and previous conformational studies suggest that these lipid interaction properties may be attributable to the tendency of the functional signal peptides to adopt alpha-helical conformations. Although the possibility of direct interaction between the signal peptide and membrane lipids during protein secretion is controversial, the results suggest that conformationally related amphiphilicity and consequent membrane affinity of signal sequences are important for function in vivo.     

Early generation selection for yield and breadmaking quality of hard red spring wheat (Triticum aestivum L. em thell.)

Summary Evaluation of the effect of selection in 3 different F₃ populations of hard red spring wheat was achieved for yield and breadmaking quality parameters by examining the subsequent performance of F₃ selections as populations of F₅ lines. For baking absorption the mean performance of the F₅ populations was positively related to the performance of the F₃ selections in each of the 3 population-years. A significant relationship between the performance in F₃ and in F₅ was not obtained in any of the 3 years for bushel weight, flour ash, remix loaf volume, farinograph mixing tolerance index or for flour color grade. A high positive relationship between performance in F₃ and F₅ was found in two out of three years for protein content, flour protein content and 1,000-kernel weight. Predictive ability for sedimentation value, flour yield, farinograph development time and blend loaf volume was inconsistent for different population-years.A positive relationship between the yield of F₃ plots and the mean yield of F₅ populations was found in only 1 year. In the other 2 years the relationship between F₃ and F₅ yields ranged from nonsignificant to low, negative and significant. The latter results were possibly related to the relatively narrow high yielding range of the total F₃ variability for yield which was sampled in each of those years. In all 3 population-years the highest yielding F₅ populations were derived from F₃ lines which were high yielding on a plot basis and also very high yielding relative to the yield of their adjacent control in the F₃ nursery.Broad sense heritabilities calculated for the F₅ generation support the thesis that selection between F₃-derived populations would be a worthwhile plant breeding procedure for many of the breadmaking quality parameters.Contribution number 267 of the Department of Plant Science, University of Manitoba.     

Antioxidant‐Rich Foods Retard Lipid Oxidation in Extruded Corn

Antioxidant‐rich plant materials could provide protection against oxidation in extruded foods and feeds, but their efficacy is not well established. Degermed yellow cornmeal was mixed with 0.02% (w/w) ascorbic acid or quercetin, or with 2% (w/w) spray‐dried ginkgo extract, onion powder, potato peels, or wheat bran. The mixtures were processed in a laboratory‐scale twin‐screw extruder at a feed rate of 227 g/min. Water pump rate was 16 g/min; screw speed was 200 rpm. Mass temperature during extrusion averaged ≈170°C. Samples were cut into small spheres, dried to 5% moisture, then stored in trilaminate bags at 25°C. Ground sample headspace was assayed for hexanal and other volatile indicators of oxidation by gas chromatography. Ginkgo and potato peels significantly darkened the extrudates. Total soluble phenolics, as ferulic acid equivalents, were highest in the ginkgo sample. Volatile compounds were lower in several treatments during storage compared with the control. These findings suggest that manufacturers may be able to formulate products with improved shelf‐life through addition of antioxidant‐rich food materials.     

Soil organic carbon under a linear simultaneous agroforestry system in Uganda

The objective of this study was to quantify and compare the amount and distribution of soil organic carbon (SOC) under a linear simultaneous agroforestry system with different tree species treatments. Field work was conducted at Kifu National Forestry Resources Research Institute in Mukono District, Central Uganda, in a linear agroforestry system established in 1995 with four different tree species and a crop only control treatment. Soil samples were collected in 2006 at three depths; 0–25, 25–50, and 50–100 cm, before planting and after harvesting a maize crop. The results indicate that an agroforestry system has significant potential to increase SOC as compared to the crop only control. There was no significant difference in the amount of SOC under exotic and indigenous tree species. Among the exotic species, Grevillea robusta had higher SOC than Casuarina equisetifolia across the entire depth sampled. There is significant difference in SOC among the indigenous species, where Maesopsis eminii has more SOC than Markhamia lutea. Distance from the tree row did not significantly influence SOC concentration under any of the tree species. In selecting a tree species to integrate with crops that will sequester reasonable quantities of carbon as well as boost the performance of the crops, a farmer can either plant an exotic species or an indigenous. In this study, the soil under Grevillea robusta and Maesopsis eminii have the highest potential to store organic carbon compared to soil under other tree species.