bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of roads on wildlife in an intensively modified landscape
Authors: Underhill J E , Angold P G
Published: April 2011

This paper examines the ecological impacts arising from road networks and the potential ameliorating effects of roadside habitat in a highly modified landscape. A U.K. focus has been adopted to illustrate the effects of roads in a landscape with a long history of land use and intensive land management where the impacts and the potential for improvement are considerable. The impacts of roads in the ecological landscape include habitat loss, fragmentation, and degradation. These interrupt and modify natural processes altering community structures and in the longer term, population dynamics. The large number of fauna fatalities each year from road traffic accidents is also of concern. Road verges can however also provide habitat opportunities and restore connectivity in an otherwise fragmented landscape offering potential to offset some of the adverse impacts of the existing road network. This review demonstrates that roads can present both ecological costs and ecological benefits although currently there is insufficient evidence to confirm some of the key theories which relate to the impact of the barrier effects (at population level) or the value of road verges as ecological corridors. In the absence of complete information the full extent of the problems and opportunities cannot be gauged and every effort should be made therefore to enhance the habitat adjacent to existing roads and to constrain further fragmentation caused by the development of the existing road network. Where further construction is unavoidable conditions should be enforced to prevent roads from reducing further the remaining habitats of conservation value and the connectivity between such habitats.Key words: roads, wildlife, fragmentation, corridor, barrier, environmental impact.
The nature conservation value of European traditional farming systems
Authors: Bignal E M , McCracken D I
Published: April 2011

The European landscape reflects many centuries of dynamic interaction between people and their natural environments. Indeed, much of the current biological and aesthetic value of the wide variety of "cultural" landscapes has been created and is now maintained by long-established farming systems. Such traditional systems (many of which are pastoral based) are generally well integrated with the environment and involve management practices that do not over-exploit the natural carrying capacity of the land. However, the rapid modernisation of agriculture that occurred after the 1939-1945 war resulted in an intensification of many European farming systems and has had severe negative effects on the environment. This modernisation initially occurred primarily in northwest Europe fuelled by the European Union (EU) Common Agricultural Policy (CAP), but with the expansion of the EU it is continuing and is certain to increase in southern, central, and eastern Europe. The response of the EU to this fundamental imbalance between farming and the environment has included the introduction of compulsory regulations to ensure the implementation of minimum environmental standards in the production processes and the promotion of agri-environment programmes to encourage farmers to undertake positive environmental management on their farmland. The ongoing reforms of the CAP will undoubtedly place greater emphasis on agri-environment programmes and increasingly on the concept of "integrated rural development." There is, however, still a pressing need for detailed information to justify to the EU and world markets why certain types of farming system should be central to future European rural development policies.Key words: biodiversity, wildlife value, farming systems, European policy, agri-environment.
Comparisons between wildfire and forest harvesting and their implications in forest management
Authors: McRae D J , Duchesne L C , Freedman B , Lynham T J , Woodley S
Published: April 2011

Emulation silviculture is the use of silvicultural techniques that try to imitate natural disturbances such as wildfire. Emulation silviculture is becoming increasingly popular in Canada because it may help circumvent the political and environmental difficulties associated with intensive forest harvesting practices. In this review we summarize empirical evidence that illustrates disparities between forest harvesting and wildfire. As a rule, harvesting and wildfire affect biodiversity in different ways, which vary a great deal among ecosystem types, harvesting practices, and scale of disturbance. The scales of disturbance are different in that patch sizes created by logging are a small subset of the range of those of wildfire. In particular, typical forestry does not result in the large numbers of small disturbances and the small number of extremely large disturbances created by wildfires. Moreover, the frequency of timber harvesting is generally different from typical fire return intervals. The latter varies widely, with stand-replacing fires occurring in the range of 20 to 500 years in Canada. In contrast, harvest frequencies are dictated primarily by the rotational age at merchantable size, which typically ranges from 40 to 100 years. Forest harvesting does not maintain the natural stand-age distributions associated with wildfire in many regions, especially in the oldest age classes. The occurrence of fire on the landscape is largely a function of stand age and flammability, slope, aspect, valley orientation, and the location of a timely ignition event. These factors result in a complex mosaic of stand types and ages on the landscape. Timber harvesting does not generally emulate these ecological influences. The shape of cut blocks does not follow the general ellipse pattern of wind driven fires, nor do harvested stands have the ragged edges and unburned patches typically found in stand-replacing fires. Wildfire also leaves large numbers of snags and abundant coarse woody debris, while some types of harvesting typically leave few standing trees and not much large debris. Successional pathways following logging and fire often differ. Harvesting tends to favor angiosperm trees and results in less dominance by conifers. Also, understory species richness and cover do not always recover to the pre-harvest condition during the rotation periods used in typical logging, especially in eastern Canada and in old-growth forests. As well, animal species that depend on conifers or old-growth forests are affected negatively by forest harvesting in ways that may not occur after wildfire. The road networks developed for timber extraction cause erosion, reduce the areas available for reforestation, fragment the landscape for some species and ecological functions, and allow easier access by humans, whereas there is no such equivalency in a fire-disturbed forest. Key words: silviculture, forest management, clearcutting, forest conservation, wildfire, biodiversity.
Health effects of aluminum: a critical review with emphasis on aluminum in drinking water
Authors: Nieboer Evert , Gibson Brian L. , Oxman Andrew D. , Kramer James R.
Published: April 2011

A critical assessment of the epidemiologic evidence indicates that a real association between aluminum in drinking water and dementia (including Alzheimer's disease, AD) cannot be dismissed. However, all of the study designs had inherent weaknesses and the results could easily be produced by confounding factors. AD appears to be a multifactorial disease in which multiple genes interact with multiple exogenous factors. Genetic loci for AD have been assigned to chromosomes 14, 19, and 21. Head trauma is a recognized environmental risk factor and aluminum in drinking water possibly is another. Aluminum might accelerate the processes involved in AD pathology. Alternatively, it may act as a neurotoxic agent that has independent dementing effects. The positive findings in the drinking water studies would, therefore, constitute an additive phenomenon. Evidence that aluminum is neurotoxic comes from the exposure during dialysis of patients with chronic renal failure and from the mild neuropsychological deficits reported for aluminum workers. Aluminum bioavailability and mass balance considerations indicate that the contribution from drinking water to the daily gastrointestinal uptake of aluminum may not be insignificant. Since renal disease and perhaps age and AD, as well as natural chelating agents, appear to enhance gastrointestinal aluminum absorption, aluminum in drinking water is considered a public health issue. Even though aluminum is unlikely to be responsible for a major burden of illness from dementia, the level of concern warrants stricter enforcement of the 100 μg/L drinking water guideline used in many jurisdictions. Prudent avoidance by the elderly is recommended of products containing potentially bioavailable quantities of aluminum.Key words: aluminum, Alzheimer's Disease, drinking water, human toxicology, epidemiology, absorption, bioavailability.
Occurrence of nickel in the Canadian environment
Authors: Chau Y. K. , Kulikovsky-Cordeiro O. T. R.
Published: April 2011

Nickel is present in Canadian freshwater and terrestrial environments because of human activities including mining, smelting, refining, alloy processing, scrap metal reprocessing, other metal operations, fuel combustion, and waste incineration. Nickel can also enter the environment as a result of the natural weathering and leaching of rocks. Entry to the Canadian environment from anthropogenic activities results in measurable concentrations of nickel in various media to which organisms may be exposed. Although current anthropogenic rates of emission per tonne of nickel produced are less than 20 years ago, large quantities are still being emitted to the Canadian environment. Nickel is persistent in terrestrial and aquatic environments. While a large data base is available on concentrations of nickel in freshwater, sediment, soil, and terrestrial plants in Canada, relatively few data on concentrations in aquatic and terrestrial organisms are available. From data collected from 1981 to 1992, most unpolluted rivers and lakes in Canada contained between 0.1 and 10 μg nickel/L with the exception of the naturally elevated site of Smoking Hills, N.W.T. (which is at least three orders of magnitude greater), while industrial sites generally contained between 50 and 2000 μg nickel/L. Nickel levels in sediment collected from 1983 to 1992 from polluted sites such as the Welland River, some Sudbury lakes, and Hamilton and Toronto Harbours ranged between 20 and 5000 μg/g dry weight, while natural or background levels in the Niagara River, Lake Erie, Lake Superior, and Lake Huron were a full two orders of magnitude lower. With respect to drinking water sampled from 1984 to 1991, the trend has been a slight decrease in nickel levels with time but with a greater range emerging, which could be due to more sensitive detection equipment installed in 1986 (minima dropped from 1.0 μg/L to an order of magnitude lower). From data collected from 1984 to 1991, the more urbanization and industrialization associated with the city, the higher the means and medians of nickel levels in air. For example, Halifax, Montréal, Quebec, Windsor, Hamilton, and Toronto had greater air nickel levels than Ottawa, Winnipeg, and Edmonton. This trend was also confirmed with the subgroup of data collected from 1987 to 1990. Sudbury was by far the site with the greatest nickel concentrations (average 124 ng/m3). Furthermore, nickel accumulation in wildlife varied with species. For example, mice seemed to accumulate more nickel in their organs than did rats and other larger rodents, while beavers and minks, on average, accumulated more nickel in their livers than did birds in similar sites near Sudbury. Similar trends have been found in Canadian soil pore water, flora, and soil.Key words: nickel compounds, occurrence, Canadian environment.
The relationship between forest management and amphibian ecology: a review of the North American literature
Authors: deMaynadier Phillip G. , Hunter Jr. Malcolm L.
Published: April 2011

Questions about the compatibility of forest harvesting practices and conservation of biological diversity are largely driven by concerns that habitat quality for many species may be degraded in intensively managed forest landscapes. We review the literature on relationships between common forest harvesting practices and the distribution and abundance of amphibians, a group that has attracted considerable attention in recent years because of their potential ecological importance in forest ecosystems and because of reports of widespread population declines. Clear-cut harvesting generally has negative short-term impacts on local amphibian populations, especially salamanders. An analysis of the results of 18 studies that examined the effects of clear-cutting on amphibians yielded a 3.5-fold median difference in abundance of amphibians on controls over clear-cuts. However, research on the influence of forest age suggests that the long-term effects of forest harvesting on amphibians are variable, and for many species these effects can be mitigated if regeneration practices leave adequate microhabitat structure intact. In contrast, long-term effects can be significant in forest plantations, which are often associated with intensive site preparations and stand management practices that modify levels of coarse woody debris and other microhabitats. Other forest practices reviewed for their effect on amphibians include prescribed fire, logging roads, and streamside harvesting. We discuss problems commonly encountered in the experimental design and measurement of forest amphibian populations, including a notable lack of pretreatment data, and outline several aspects of amphibian–forestry relationships in need of further research. Management recommendations relevant to conserving upland and riparian zone amphibian habitat during forest harvesting are offered.Key words: amphibians, clear-cutting, coarse woody debris, forest management, logging roads, plantations, prescribed fire, riparian, succession.
The history and possible causes of forest decline in central Europe, with particular attention to the German situation
Authors: Ulrich Bernhard
Published: April 2011

The elasticity (nutrient storage, litter decomposition, bioturbation of soil) and diversity of central European forest ecosystems has been reduced by centuries of overutilization. Since the middle of the nineteenth century, their development has been influenced by silvicultural measures, as well as by the deposition of acids and nutrients, especially nitrogen from anthropogenic sources, i.e., by a mixture of stabilizing and destabilizing external influences. During recent decades, most forest soils have been acidified by acid deposition resulting in low levels of nutrient cations and negative alkalinity in the soil solution. Widespread acute acidification of soil in the rooting zone is indicated by extremely high manganese (Mn) contents in leaves (fingerprint). Soil acidification has caused drastic losses of fine roots in subsoil, indicated by denuded structural root systems where adventitious fine root complexes exist only sporadically. Research at the organ (leaf, fine root, mycorrhiza) and cellular levels has provided much information on the effects of air pollutants and soil acidification on leaves and roots. There are considerable uncertainties, however, as to how changes in the status of leaves or roots are processed within the tree and ecosystem from one level of hierarchy to the next on an increasing spatial and time scale, and how these lead to decline symptoms like crown thinning, stand opening (as a consequence of dieback or perturbations), and changes in species composition (soil biota, ground vegetation, tree regeneration). At the tree level, nutrient imbalances (due to cation losses from soil, changes in the acid/base status of the soil, proton buffering in leaves, and N deposition), as well as disturbances in the transport system of assimilates and water, are suspected of causing the decline symptoms. Information on the filtering mechanisms at various hierarchical levels, especially in the case of a break in the hierarchy, is missing. The null hypothesis (no effects of air pollutants on forest ecosystems) can be considered to be falsified. Forest ecosystems are in transition. The current state of knowledge is not sufficient to define precisely the final state that will be reached, given continuously changing environmental conditions and human impacts. The hypothesis, however, of large-scale forest dieback in the near future is not backed by data and can be discarded.Key words: forest ecosystem, process hierarchy, air pollution, deposition, acidity, nitrogen.
Biogeochemical pathways of arsenic in lakes
Authors: Rodie Andrew , Gerits Jan J. P. , Azcue Jose M.
Published: April 2011

Owing to various human activities, arsenic (As) concentrations have increased in lakes and other aquatic ecosystems around the world. This increase of As concentrations has become a concern because of the known toxic, carcinogenic, mutagenic, and teratogenic effects of As on ecosystem organisms and humans. Understanding the biogeochemistry of As in the aquatic environment is therefore a topic of fundamental interest. This study presents a review of the major biogeochemical processes controlling the concentration of solid and dissolved As in freshwater lakes. These processes are dynamic and vary both temporally and spatially because of a complex relationship between microbial activity and various geochemical processes. Particularly the oxidation of As sulphides and the reduction of Fe and Mn oxyhydroxides at the sediment–water interface play an important role in the mobilization of As. These and other interactions among the various biogeochemical processes are synthesized in a conceptual model of As mobility in lakes.Key words: arsenic cycling, biogeochemistry, freshwater lakes.
Effect of N deposition on decomposition of plant litter and soil organic matter in forest systems
Authors: Berg B , Matzner E
Published: April 2011

The effects of nitrogen (N) deposition on plant litter and soil organic matter decomposition differ depending on the stage of decomposition (early, late, and final stages). The effects can be divided further into direct and indirect ones. Direct effects: additions of ammonium and nitrate to fresh, newly shed litter stimulate the initial decomposition of celluloses and solubles. By contrast, addition of the same compounds to humus (final stages) clearly suppresses activity. This was seen in all studies reviewed and for several types of humus. Indirect effects: long-term deposition leads to increases in litter concentrations of N and other nutrients. This N in litter forms "natural" organic compounds and the resulting effects are similar to those resulting from natural variation among litter types. Thus, initial decomposition is generally higher for N (nutrient) rich plant litters than for litters with a lower N (nutrient) content. In later stages, at which lignin-degradation rates regulate litter decomposition, N has a retarding effect on decomposition. Significant negative correlations have also been found between N concentrations in humus and respiration rate. There probably is a sink for deposited N in the humus. We may conclude that N storage in humus is regulated by a positive feedback mechanism. Raised levels of N resulting from N deposition cause more humus to be left in the system, and the resulting lower levels of Mn further retards humus decomposition, thus leading to an increased storage of N in humus. Thus, when calculating critical loads it would be incorrect to assume that N pools in the humus remain at a steady state.
Long-range atmospheric transport of mercury to ecosystems, and the importance of anthropogenic emissionsa critical review and evaluation of the published evidence
Authors: Jackson T A
Published: April 2011

Literature on the long-range atmospheric transport of both anthropogenic and naturally occurring mercury (Hg) to terrestrial and aquatic ecosystems was reviewed for the purpose of assessing the quantitative importance and environmental significance of the anthropogenic emissions. The weight of evidence, comprising many different kinds of data that corroborate each other independently, supports the following conclusions. (i) Approximately 5000 t of anthropogenic Hg are introduced into the atmosphere every year, both by direct emission from sources of pollution and by reemission of previously deposited Hg from diffuse secondary sources in the environment. The primary emissions ( 4000 t) result from various human activities, especially the combustion of fossil fuels (notably coal) and solid wastes. Natural emissions amount to about 2000 t/year. (ii) Although some of the annual anthropogenic Hg output (about half the quantity emitted by primary sources) is deposited near its point sources, the rest (a total of 3000 t) is subject to transport over great distances by atmospheric circulation, resulting in measurable contamination of terrestrial and aquatic environments and organisms up to several thousand kilometers from the points of origin. Indeed, a number of remote ecosystems receive most of their Hg input from the atmosphere. (iii) The available evidence supports the generally accepted conclusion that the Hg enrichment commonly seen in the uppermost horizons of sediment cores from remote lakes is due primarily to contamination by airborne anthropogenic Hg in the recent past, rather than postdepositional redistribution of Hg. Although postdepositional alteration may result in detectable remobilization of sedimentary Hg, its effects on total Hg profiles in lake sediment cores have been found, thus far, to be negligible. (iv) Atmospheric transport of anthropogenic Hg to aquatic and terrestrial ecosystems is a cause for concern, as the Hg is accumulating, to a greater or lesser extent, in organisms (e.g., fish in remote lakes). Moreover, the Hg is associated with, and interacts with, other by-products of fossil fuel combustion, including the strong acids responsible for acid precipitation. The acids aggravate the effects of Hg pollution by furthering the accumulation of methyl Hg in fish inhabiting ill-buffered lakes. Contamination of the atmosphere with Hg and associated pollutants is a serious international problem that calls for reduction or elimination of emissions.
An evaluation of the use of dendrochemical analyses in environmental monitoring
Authors: Watmough Shaun A
Published: April 2011

Dendrochemical techniques have been used to monitor historical changes in soil and atmospheric chemistry since the early 1970s. The development of dendrochemistry in environmental monitoring was prompted by early studies which reported that changes in Pb deposition along roadsides and in industrial areas were reflected by changes in the Pb content of tree rings. Early studies were inconclusive; some authors have stated that tree-ring chemistry is not a useful indicator of pollution episodes and that some tree species are clearly better spatial indicators of pollution than historical monitors. This is due to a number of complicating factors, including potential radial translocation of elements, radial tendencies in element concentration from pith to bark, and physiological differences between heartwood and sapwood. A more detailed understanding of element cycling in trees is needed, as at present, the application of dendrochemistry to historical environmental monitoring is strongly dependent on the choice of tree species and the elements to be studied. There is no general consensus as to which tree species are best suited for dendrochemical studies. There are many reports in which the analyses of tree-ring chemistry have been successfully used to reconstruct trace-metal deposition from a variety of sources, including automobiles, metal refineries, and coal burning. Changes in tree-ring chemistry in recent decades have coincided with hypothesized changes in soil chemistry believed to be a result of acidic deposition onto poorly buffered soils. Indications of changes in groundwater quality, volcanic eruptions, and even climate change have been reported to be preserved in the chemical composition of tree rings. An improvement in analytical techniques has allowed multielement analysis on whole wood samples, with very low detection limits and extremely high spatial resolution, enabling intra-annual changes in element composition of tree rings to be determined. The application of dendrochemistry in environmental monitoring is promising, and with a more detailed understanding of nutrient and metal cycling in trees, dendrochemical studies will continue to provide useful information on historical pollution loadings and changes in soil and atmospheric chemistry that is unobtainable from any other source.
Effects of fires on carbon cycling in North American boreal peatlands
Authors: Zoltai S C , Morrissey L A , Livingston G P , Groot W J
Published: April 2011

Boreal peatlands occupy about 1.14 x 106 km2 in North America. Fires can spread into peatlands, burning the biomass, and if moisture conditions permit, burning into the surface peat. Charred layers in peat sections reveal that historically bogs in the subhumid continental regions and permafrost peatlands of the subarctic regions have been the most susceptible to fires. Fire return periods were estimated from the numbers and ages of the charred peat layers. Based on average moisture conditions of the surface, about 0.5% of the peatlands (6420 km2) can be expected to burn annually, but the surface peat layer is expected to burn only in a small portion of this area (1160 km2). Carbon losses from aboveground combustion, in the form of CO2, CO, CH4, and nonmethane hydrocarbons, are the highest in forested swamps at 2.03 Tg C ·year-1. Carbon losses due to combustion of surface peat is the highest in the driest peatlands (e.g., raised bogs underlain by permafrost) at 5.82 Tg C ·year-1. The total estimated carbon release due to aboveground combustion is 2.92 Tg C ·year-1 and due to belowground peat combustion is 6.72 Tg C ·year-1. These estimates of direct carbon emissions to the atmosphere due to wildfires suggest a globally significant, but relatively small source in contrast with emissions from wildfires in uplands. The effects of a possible climate change are expected to be most prominent in the continental and northern parts of North America. A lower water table would result in increased CO2 but decreased CH4 emissions from the peatlands. A drier climate may mean increased fire frequency and intensity, resulting in more fires in peatlands and an increased probability of the fires consuming part of the peat.Key words: fire, peatlands, carbon, boreal, permafrost, gas flux.
Effects of acid rain on bird populations
Authors: Graveland Jaap
Published: April 2011

In this paper the effects of anthropogenic acidification of soils and waters on bird populations are reviewed. Acidification causes (i) declines in the reproductive success and the density of piscivorous birds through declines in the fish populations, (ii) shifts in the forest bird community from forest birds to birds of open woodland through large-scale forest dieback, and (iii) leads to a lower reproductive success of birds in calcium-poor areas through a decline in the availability of calcium-rich material (needed for eggshell formation and skeletal growth). Acidification may also affect the availability of food and nest sites for insectivorous and hole-nesting birds, but there are no consistent effects on the population sizes of these birds. Effects of declines in populations of invertebrates in aquatic habitats may be mitigated by reduced competition from fish, and acidification in forests in less-advanced stages of dieback can both lead to an increase and a decrease in insect and seed abundance in forests, the outcome depending on species, extent of leaf and needle loss, and other factors. There is some evidence that acidification may strongly affect avian reproduction through an increased exposure to toxic metals such as aluminium. Anthropogenic acidification on a worldwide scale is expected to continue during the next decades. Future research on the effects of acidification on bird populations should focus on remedial action and effects on population sizes in moderately acidified areas, and should more often apply an experimental approach than in the past.Key words: acid rain, birds, reproduction, calcium, toxic metals, forest dieback.
Copper pipes as a source of copper exposure in man and environment
Authors: Oskarsson Agneta , Norrgren Leif
Published: April 2011

Copper pipes in the water distribution system are widely used all over the world. Corrosion of the pipes causes elevated copper levels in the drinking water. The corrosion depends on the water composition and the stagnation time of the water in the pipes. Low pH is a main factor determining the release of copper, and high alkalinity is also an important contributing factor, especially at a low pH. This is in contrast to corrosion of iron pipes, which is prevented by increasing the alkalinity. Copper in drinking water may contribute significantly to the dietary intake of copper, and sometimes drinking water is the major source. However, it is difficult to calculate the intake of copper from drinking water, as the concentrations can vary one or two orders of magnitude, depending on the flushing habits. Gastrointestinal effects (e.g., nausea, vomiting, diarrhea, and abdominal pains) have been reported after exposure to high concentrations of copper in drinking water. Owing to lack of data, the tolerated level of copper in water can not be firmly established, but guideline values of 1-2 mg/L have been recommended. A higher sensitivity in newborns to elevated copper exposure has been suggested. Release of copper from the pipes will also result in elevated copper concentrations in waste-water sludge and may limit the use of sludge for agricultural purposes. The critical concentration at which copper must be considered from ecotoxicological aspects depend on the biota and exposure conditions at the actual site. Major effects due to elevated copper concentrations in the environment includes decreased growth of plants, disturbed reproduction in several species of invertebrates, and copper poisoning in livestock and fish. Aquatic organisms, especially certain species of crustaceans, have the highest sensitivity to copper toxicity. Effects on fish can be significant already at levels below 0.01 mg/L. The consequences of the extensive and widespread environmental pollution of copper from the intentional use of copper as piping material need to be investigated and thoroughly evaluated.Key words: copper, drinking water, plumbing, health effects, toxicity, sewage sludge.
An assessment of the potential hazards of environmental selenium for Canadian water birds
Authors: Outridge P M , Scheuhammer A M , Fox G A , Braune B M , White L M , Gregorich L J , Keddy C
Published: April 2011

Elevated dietary intake of selenium (Se) causes dramatic teratogenic and other reproductive effects in water birds at dietary levels only a few times greater than those that are generally regarded as nutritionally essential. Possible risks to the health of Canadian water birds and other wildlife from Se may be posed by seleniferous habitats in western Canadian provinces, and over-wintering by migratory water birds in some National Wildlife Refuges in the western U.S.A. where Se-related deaths and embryonic deformities in birds have occurred. These Refuges have in common an arid climate, closed drainage basins, seleniferous Cretaceous geology, and they receive irrigation drainage water from nearby agricultural areas. Similar conditions occur in SW Saskatchewan and SE Alberta, and these areas overlap parts of the critical water bird habitat of the region. Selenium concentrations in wetland ponds, agricultural tile drainage water and bird tissues in the western provinces are, with a few exceptions, generally lower than threshold concentrations for reproductive toxicity. However, some surface waters and aquifers contain dissolved Se concentrations that exceed guidelines for the protection of aquatic life, irrigation uses, and human and livestock drinking water. Use of this aquifer water for irrigation or replacement of freshwater flows into wetlands would greatly increase the risk of Se bioaccumulation to hazardous levels in water bird food chains.Key words: selenium, toxicity, birds, wildlife, Canada.
A quarter century of environmental surveillance: The Canadian Wildlife Service's Great Lakes Herring Gull Monitoring Program
Authors: Hebert C E , Norstrom R J , Weseloh DVC
Published: April 2011

The Great Lakes Herring Gull Monitoring Program has annually provided information concerning levels of environmental contaminants in herring gull eggs since 1974, making it one of the longest running biomonitoring programs in the world. The program was initiated in response to observations of poor reproductive success in colonial waterbirds on the Great Lakes. Initial studies examined the role of halogenated hydrocarbons (HAHs) in causing this reproductive dysfunction. By the late 1970s, reproductive success in herring gulls had improved greatly and emphasis was placed on developing more sensitive indicators to measure the subtle effects associated with HAH exposure. Geographic and temporal trends in Great Lakes contamination were also elucidated. Analysis of herring gull tissues led to the identification of HAHs (mirex, photomirex, polynuclear aromatic hydrocarbons, chlorobenzenes, dioxins) previously undetected in Great Lakes upper trophic level biota. Data collected as part of this program have improved our understanding of contaminant sources and fate in the Great Lakes and have provided us with a means to assess our progress in controlling contaminant inputs. The extensive nature of this dataset has allowed detailed examination of the factors that regulate contaminant levels in this species. Most monitoring programs rely on less extensive datasets for the interpretation of environmental trends and may benefit from the mechanisms identified here. Research has also identified other stressors, e.g., dietary deficiencies, that may affect the success of Great Lakes herring gull populations. Ongoing monitoring of this species will continue to provide new insights into the dynamic Great Lakes ecosystem.Key words: herring gull, Larus argentatus, Great Lakes, environmental monitoring, halogenated hydrocarbons, contaminants.
Associations between microfungal endophytes and roots: do structural features indicate function?
Authors: Peterson R. Larry , Wagg Cameron , Pautler Michael
Published: April 2011

Roots encounter a plethora of microorganisms in the soil environment that are either deleterious, neutral, or beneficial to plant growth. Root endophytic fungi are ubiquitous. These include dark septate endophytes whose role in plant growth and the maintenance of plant communities is largely unknown. The objectives of this review were to assess the structural features of the interactions between dark septate endophytic fungi and the roots of both angiopsperms and conifers, and to suggest avenues for further research. Several light microscopy studies of endophyte–root interactions have revealed a variety of structural features, depending on host species and plant growth conditions. In some cases, when fungal hyphae enter roots they cause cell breakdown, whereas in other situations there is little noticeable effect. In some tree species, associations with these endophytes may mimic ectomycorrhizas or ectendomycorrhizas. The few ultrastructural studies indicate that intracellular hyphae lack a host-derived perifungal membrane and interfacial matrix material, features typical of biotrophic fungus – plant cell interactions. This raises questions concerning nutrient exchange between these fungi and plant cells. Further research in this area is needed. New approaches that include molecular cytology and live-cell imaging are needed to determine early changes in plant cells when challenged with these fungi.
Simulated herbivory reduces seed production in Vincetoxicum rossicum
Authors: Doubleday Laura A.D. , Cappuccino Naomi
Published: April 2011

Vincetoxicum rossicum (Kleopow) Barbar. (Apocynaceae) is an exotic invasive perennial vine that is spreading rapidly throughout northeastern North America. Its spread threatens native plant communities and the animals that depend on them. While V. rossicum is known to have specialist insect herbivores in its native range, it has escaped herbivory in its introduced range. A biological control program is currently being developed to identify an insect agent that could be released in North America to control V. rossicum . In this study, we simulated leaf and root herbivory on individual plants in naturally occurring populations of V. rossicum to estimate the impact of different feeding guilds and damage levels on seed production in sunny and shady sites. Damage intensity (0%, 30%, 60%, or 90% tissue removal) had a greater impact on seed output than damage type (root vs. leaf), although root damage was slightly more effective than leaf damage. We discuss the implications for biological control programs targeting this invasive exotic plant.
A NEW METHOD FOR THE RAPID ESTIMATION OF MOISTURE IN WHEAT
Authors: Burton E. F. , Pitt Arnold
Published: April 2011

A rapid method of estimating the moisture in a sample of wheat is described. This method depends on the effect produced in a specially arranged radio circuit in which an alternating current of high frequency is generated. When a container holding some of the wheat under examination is introduced into the rapidly alternating electric field, a change occurs in the strength of the current which may be measured by an ammeter in the circuit and which may be immediately interpreted as a measure of the moisture content of the wheat.
THE GEOLOGY OF CEYLON
Authors: Adams Frank Dawson
Published: April 2011

The Island of Ceylon is composed almost entirely of crystalline rocks of Archean or pre-Cambrian age. In the extreme north these are overlain by limestones of Miocene or later age. At one point on the northwest coast a very small area of Jurassic rocks lies on the surface of the coastal plain.The ancient crystalline rocks resemble in many respects the Grenville series of the Canadian Shield. They are largely biotite gneisses, interstratified with which are at least two great beds of white crystalline limestone, often dolomitic, with associated beds of quartzite and of sillimanite-bearing rocks of undoubted sedimentary origin. Charnockite and allied rocks are present also in large amount, especially in the higher parts of the island. The petrography of these rocks is described, and is illustrated by a series of chemical analyses, the first that have been made of the rocks of this island. In structure Ceylon is a portion of a great syncline, deeply eroded, closed on the south, open to the north, where it plunges beneath the Miocene cover.Three distinct plains of denudation can be clearly recognized in Ceylon. The coastal plain, about 100 ft. above sea-level, a second plain at about 1,600 ft., and a third at 6,000 ft. above sea-level.The paper presents the first account which has been given of the geological structure of the island, and the accompanying geological map of the island is the first which has been prepared.
STUDIES ON REACTIONS RELATING TO CARBOHYDRATES AND POLYSACCHARIDES. XXVII. SYNTHESIS AND STRUCTURE OF TRICHLOROETHYLIDENE GLYCEROL
Authors: Hibbert Harold , Morazain J. G. , Paquet A.
Published: April 2011

A discussion is given as to the nature of the factors involved in the mechanism of the formation of cyclic acetals and ketals from carbonyl and polyhydroxy derivatives. It is shown that in the two reactions involved, namely, the primary formation of a half-acetal, followed by removal of water and ring-closure, the polarity of the carbonyl derivative plays a very important rôle. Chloral combines with polyhydroxy compounds to give exceptionally stable half-acetals, which can be converted into the cyclic derivatives by the use of strong dehydrating agents.In contrast with the behavior of other aldehydes it is found that the condensation of chloral with glycerol yields only one ring compound, namely the five-membered derivative. No satisfactory explanation of this can, as yet, be given.The identity of the trichloroethylidene glycerol obtained by the condensation of glycerol and chloral under the influence of concentrated sulphuric acid has been established as a five-membered cyclic acetal by a comparison of the properties of its methyl ether with those of trichloroethylidene glycerol α-methyl ether prepared from glycerol α-methyl ether.
THE OXIDATION OF XANTHATES AND SOME NEW DIALKYL SULPHUR- AND DISULPHUR- DICARBOTHIONATES
Authors: Cambron Adrien , Whitby George Stafford
Published: April 2011

Sodium tetrathionate and cyanogen bromide in water have a specific oxidizing action on alkali xanthates, the latter being smoothly converted to xanthogen disulphides without the formation of by-products. Cyanogen bromide in alcohol converts xanthates into xanthogen monosulphides. Other new reagents for the oxidation of xanthates to xanthogen disulphides under certain conditions are—nitrous acid, nitrosyl chloride, chloramine-T, benzene sulphonyl chloride.The following new xanthogen disulphides, viz., n-hexyl (liquid), β-ethoxyethyl (liquid), β-phenylethyl (m.p. 49.5–50°), and the following new xanthogen monosulphides, viz., n-hexyl (liquid), benzyl (m.p., 82.5°), β-ethoxyethyl (liquid), are described. β-phenylethyl xanthogenamide (m.p., 79°) is also described.Pyrolysis of β-phenylethyl xanthogen disulphides yields styrene.
THE TRANSFUSION OF MATTER FROM ONE SOLID TO ANOTHER UNDER THE INFLUENCE OF HEAT—A NEW FACTOR IN THE PROCESS OF METAMORPHISM
Authors: Adams Frank D.
Published: April 2011

This paper describes a case of the transfusion of material from one solid to another under the influence of heat, which, it is suggested, may throw light upon certain metamorphic processes at work in the earth's crust.
STUDIES ON LIGNIN AND RELATED COMPOUNDS: I. A NEW METHOD FOR THE ISOLATION OF SPRUCE WOOD LIGNIN
Authors: Hibbert Harold , Rowley H. J.
Published: April 2011

A description is given of a new method for the isolation from spruce meal of lignin in apparently a relatively unchanged form. The method consists in first extracting the spruce meal with a mixture of equal volumes of benzene and alcohol, followed by an extraction with water. The dried meal is then digested for 6–8 hr. at 110 °C. with 8–10 times its weight of ethylene glycol containing 0.2% of iodine, calculated on the weight of spruce meal taken. The reaction mixture is filtered, and the lignin isolated by pouring the filtrate into a large excess of cold water. Other catalysts such as hydrochloric acid may be used in place of iodine and the glycol may be replaced by a variety of hydroxy-compounds such as glycol mono-ethyl ether, glycerol, chlorhydrins, hydroxyacids, etc.
SPECIFIC HEATS AND LATENT HEAT OF FUSION OF ICE
Authors: Barnes W. H. , Maass O.
Published: April 2011

Values for the heat capacities of ice and resulting water from initial temperatures of between 0 °C. and − 78.5 °C. to a final temperature of + 25.00 °C. are measured to ± 0.05% or better with an improved adiabatic calorimeter previously described. The specific heats of ice over the temperature range 0° C. to − 80 °C. are found and the latent heat of fusion of ice at 0 °C. is obtained from these heat capacity determinations.
A STUDY OF THE HEAD LENGTH VARIABILITY OF EQUINE SPERMATOZOA
Authors: Savage A. , Williams W. L. , Fowler N. M.
Published: April 2011

The head lengths of horse spermatozoa have been measured in 51 samples and the measurements plotted in frequency distribution curves. These curves are unimodal and their coefficients of variation range from 4.00 to 6 00 (or slightly less). A coefficient in excess of 6.00 indicates an unsound sire, and animals from which skew curves are obtained may be regarded with extreme suspicion since they are not obtained in the case of normal animals. Generally the findings are in harmony with cytological data available, but both require further study before they can be reduced to a systematic basis.
A SIMPLE APPARATUS FOR PURIFYING RADON
Authors: Henderson G. H.
Published: April 2011

A description is given of a simple and efficient apparatus for purifying radon, which has given several years effective service in connection with radium therapy. Potassium hydroxide is used to remove carbon dioxide and most of the water. Since phosphorus pentoxide for drying has been dispensed with, only one Toepler pump and fewer valves and stopcocks are necessary. The number of stopcocks has been reduced to three and there is but one large bulb and one float valve. The impurities are removed by sparking and allowing excess hydrogen to escape through a palladium tube heated electrically; thus there is no danger of clogging the tap with particles of loose reagent. All parts are made of Gundlach glass. Purification takes from two to five minutes.
EPIDEMICS AMONG SLEDGE DOGS IN THE CANADIAN ARCTIC AND THEIR RELATION TO DISEASE IN THE ARCTIC FOX
Authors: Elton Charles
Published: April 2011

An enquiry was made by the Hudson's Bay Company into the origin and spread of a serious disease resembling epidemic encephalitis of silver foxes which periodically destroys large numbers of sledge dogs in the arctic and subarctic regions of Canada. A similar disease occurs in the arctic fox, and is associated with an important four-year cycle in the numbers of the fox, which may thus form a permanent reservoir for the disease organism, or organisms. General forecasting of this fox cycle is possible, and is dependent on knowledge of the lemming cycle in the arctic, and associated climatic phenomena.
HYPHAL FUSIONS IN DERMATOPHYTES
Authors: Davidson A. M. , Dowding Eleanor S. , Buller A. H. R.
Published: April 2011

Hyphal fusions have been recognized as an important character of dermatophytes.In Microsporon audouini, M. lanosum, and Trichophyton gypseum hyphal fusions: (1) are formed between hyphae of one and the same mycelium isolated from a single patient, (2) are formed between any two mycelia of the same species isolated from two different patients, and (3) are not formed between a mycelium of one species and a mycelium of another species.The occurrence or non-occurrence of hyphal fusions between hyphae of two mycelia of different origin may be applied as a criterion for identifying species of dermatophytes whose specific nature is uncertain.
THE ELECTRICAL CONDUCTIVITY OF AQUEOUS SOLUTIONS OF HYDROGEN SULPHIDE AND THE STATE OF THE DISSOLVED GAS
Authors: Wright R. H. , Maass O.
Published: April 2011

This paper is the last of three dealing with the equilibria between hydrogen sulphide and water, and is a continuation of a series of researches designed to investigate the equilibria existing in gaseous aqueous systems.Electrical conductivities of aqueous solutions of hydrogen sulphide have been measured between 5° and 60 °C. The results lead to the conclusion that hydrogen sulphide resembles certain other gaseous solutes and forms with water a complex which undergoes electrolytic dissociation. The constant k of the Ostwald dilution law therefore appears to be an apparent, rather than a real, dissociation constant.The complete analysis of the equilibria involved and the evaluation of the constants must depend on accurate measurements at low concentrations, which are not yet completed.