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311.
Industrialized agriculture currently substitutes many of the ecological functions of soil micro-organisms, macroinvertebrates, wild plants, and vertebrate animals with high cost inputs of pesticides and fertilizers. Enhanced biological diversity potentially offers agricultural producers a means of reducing the cost of their production. Conservation of biodiversity in agricultural landscapes may be greatly enhanced by the adoption of certain crop management practices, such as reduced pesticide usage or measures to prevent soil erosion. Still, the vast monocultures comprising the crop area in many Canadian agricultural landscapes are often of limited conservation value, thus the inclusion of appropriate wildlife habitat in and around arable lands is a fundamental prerequisite for the integration of wild species within agricultural landscapes. This review of current literature considers the potential for non-crop areas within agricultural landscapes to be reservoirs of agronomically beneficial organisms including plants, invertebrates, and vertebrate species. Non-crop habitats adjacent to crop land have been identified as significant for the maintenance of plant species diversity, for the conservation of beneficial pollinating and predatory insects, and as essential habitat for birds. A key component for enhancement of biodiversity is the reintroduction of landscape heterogeneity by (1) protection and enhancement of key non-crop areas, (2) smaller fields and farms, and (3) a greater mixture of crops, through rotation, intercropping and regional diversification. The benefits of increased biodiversity within arable lands are reviewed for various species groups. In the Canadian context, any serious attempt to derive significant agronomic benefit from increased biodiversity will require considerable changes in the agricultural programs and policies which shape mainstream industrialized agriculture. The problems of crop depredation by vertebrate species, weed and insect competition, which still represent significant impediments to the creation and proper management of wildlife habitat, are also discussed. 相似文献
312.
Pierre Desprairies 《Natural resources forum》1990,14(3):222-226
Between now and 2000, the demand for oil is expected to be moderate and the supply abundant. Economic growth is almost twice as slow as in 1973 and requires 25–30% less energy per unit of GNP. The demand for oil is therefore growing at a rate of two to three times slower. Meeting the demand for oil between now and 2000 is within the capability of the oil-producing countries, in many cases with modest additional investment. Gas and coal will be very cost competitive in relation to oil and will serve as a break on future explosive price increases. 相似文献
313.
Herckes P Wendling R Sauret N Mirabel P Wortham H 《Environmental pollution (Barking, Essex : 1987)》2002,117(1):169-177
Cloud and rainwater samples have been collected at a high elevation site in the Vosges Mountains. An automated collection system has been used to collect bulk cloudwater and small cloudwater droplets. Bulk cloudwater concentrations were up to 10 times more concentrated than rainwater concentrations. Small clouddroplets showed generally higher concentrations than bulk cloudwater. Nevertheless, the enrichment factors depend on the compounds under study and appear to be related to the composition of the cloud condensation nuclei forming small or large clouddroplets. Principal component analysis and factor analysis were applied to the collected datasets and confirmed the influence of the cloud condensation nuclei on the composition difference between small and large cloudwater droplets. 相似文献
314.
Optimal patch time allocation for time-limited foragers 总被引:1,自引:0,他引:1
Eric Wajnberg Pierre Bernhard Frédéric Hamelin Guy Boivin 《Behavioral ecology and sociobiology》2006,60(1):1-10
The Charnov Marginal Value Theorem (MVT) predicts the optimal foraging duration of animals exploiting patches of resources.
The predictions of this model have been verified for various animal species. However, the model is based on several assumptions
that are likely too simplistic. One of these assumptions is that animals are living forever (i.e., infinite horizon). Using
a simple dynamic programming model, we tested the importance of this assumption by analysing the optimal strategy for time-limited
foragers. We found that, for time-limited foragers, optimal patch residence times should be greater than those predicted from
the classic, static MVT, and the deviation should increase when foragers are approaching the end of their life. These predictions
were verified for females of the parasitoid Anaphes victus (Hymenoptera: Mymaridae) exploiting egg patches of its host, the carrot weevil Listronotus oregonensis (Coleoptera: Curculionidae). As predicted by the model, females indeed remained for a longer time on host patches when they
approached the end of their life. Experimental results were finally analysed with a Cox regression model to identify the patch-leaving
decision rules females used to behave according to the model’s predictions. 相似文献
315.
The objective of this study is to optimize experimental conditions of sorbent preparation from sewage sludge using experimental design methodology. Series of carbonaceous sorbents have been prepared by chemical activation with sulfuric acid. The sorbents produced were characterized, and their properties (surface chemistry, porous and adsorptive properties) were analyzed as a function of the experimental conditions (impregnation ratio, activation temperature and time). Carbonaceous sorbents developed from sludge allow copper ion, phenol and dyes (Acid Red 18 and Basic Violet 4) to be removed from aqueous solution as well as VOC from gas phase. Indeed, according to experimental conditions, copper adsorption capacity varies from 77 to 83 mg g(-1), phenol adsorption capacity varies between 41 and 53 mg g(-1) and VOC adsorption capacities (acetone and toluene) range from 12 to 54 mg g(-1). Each response has been described by a second-order model that was found to be appropriate to predict most of the responses in every experimental region. The most influential factors on each experimental design response have been identified. Regions in which optimum values of each factor were achieved for preparation of activated carbons suitable for use in wastewater and gas treatments have been determined using response surfaces methodology. In order to have a high mass yield and to minimize the energetic cost of the process, the following optimal conditions, 1.5 g of H2SO4 g(-1) of sludge, 700 degrees C and 145 min are more appropriate for use of activated carbon from sludge in water and gas treatments. 相似文献
316.
McDonald JD Zielinska B Sagebiel JC McDaniel MR Mousset-Jones P 《Journal of the Air & Waste Management Association (1995)》2003,53(4):386-395
The chemical mass balance source apportionment technique was applied to an underground gold mine to assess the contribution of diesel exhaust, rock dust, oil mists, and cigarette smoke to airborne fine (<2.5 microm) particulate matter (PM). Apportionments were conducted in two locations in the mine, one near the mining operations and one near the exit of the mine where the ventilated mine air was exhausted. Results showed that diesel exhaust contributed 78-98% of the fine particulate mass and greater than 90% of the fine particle carbon, with rock dust making up the remainder. Oil mists and cigarette smoke contributions were below detection limits for this study. The diesel exhaust fraction of the total fine PM was higher than the recently implemented mine air quality standards based on total carbon at both sample locations in the mine. 相似文献
317.
D. V. Chip Weseloh Peter J. Ewins John Struger Pierre Mineau Ross J. Norstrom 《Environmental monitoring and assessment》1994,29(3):229-251
As part of the Great Lakes International Surveillance Plan, 1978–83, egg contaminant levels and reproductive output were determined for Herring Gull colonies on Lake Superior in 1983. Since 1974, the Herring Gull has been widely used in the Great Lakes as a spatial and temporal monitor of organochlorine (OC) contaminant levels and associated biological effects. Most eggs contained a wide range of OCs, the main compounds being DDE, polychlorinated biphenyls (PCBs), dieldrin, heptachlor epoxide, oxychlordane, hexachlorobenzene and mirex. Levels of an additional ten OCs and five polychlorinated dibenzo-p-dioxin (PCDD) congeners were also determined for some sites. Overall, levels varied significantly among colonies, but there was no obvious relationship to spatial distribution of contaminants in sediments or fish species. OC levels in eggs had declined by up to 84% since 1974. Eggshells were only 8% thinner than before the introduction of DDT, and shell thinning was not a cause of breeding failure. Average reproductive output varied from 0.15 to 1.57 young per apparently occupied nest in 1983: at 56% of colonies the value was below that thought necessary to maintain stable populations. The main causes of failure were egg disappearence and cannibalism of chicks. Despite this, the population appeared to have been increasing at about 4% per annum. Reduced availability of forage fish during the early 1980s was the most likely reason for the poor reproductive output in 1983. 相似文献
318.
Chourouk Ibrahim Salah Hammami Nesserine Khelifi Pierre Pothier Abdennaceur Hassen 《Food and environmental virology》2020,12(3):250-259
The molecular detection of Norovirus GI and Norovirus GII in the Tunisian industrial wastewater treatment plant of Charguia I was conducted to test the eff 相似文献
319.
Pierre A. Traore 《Natural resources forum》1994,18(3):207-212
Contrary to expectations, small-scale mining has had little impact on the development of Africa, despite the relative scale of activities in that field. This situation is due to the fact that the sector is facing various constraints and deficiencies, some structural in nature and others technical. However, the analysis of constraints and weaknesses shows that their impact differs according to the country and to the extent to which the government is involved in small-scale mining as well as to its efforts to strengthen this sector. While some drastic and immediate measures could be taken now, in depth scientific research will also be required. 相似文献
320.
Philip K. Thornton Pierre J. Gerber 《Mitigation and Adaptation Strategies for Global Change》2010,15(2):169-184
Livestock production systems will inevitably be affected as a result of changes in climate and climate variability, with impacts
on peoples’ livelihoods. At the same time, livestock food chains are major contributors to greenhouse gas emissions. Agriculture
and livestock in particular will need to play a greater role than they have hitherto in reducing emissions in the future.
Adaptation and mitigation may require significant changes in production technology and farming systems, which could affect
productivity. Given what is currently known about the likely impacts on livestock systems, however, the costs of mitigating
and adapting to climate change in the aggregate may not represent an enormous constraint to the growth of the global livestock
sector, in its bid to meet increasing demand for livestock products. Different livestock systems have different capacities
to adapt or to take on board the policy and regulatory changes that may be required in the future. Vulnerability of households
dependent on livestock, particularly in the drier areas of developing countries, is likely to increase substantially, with
concomitant impacts on poverty and inequity. The capacity of these systems to adapt and to yield up their carbon sequestration
potential deserves considerable further study. Comprehensive frameworks need to be developed to assess impacts and trade-offs,
in order to identify and target adaptation and mitigation options that are appropriate for specific contexts, and that can
contribute to environmental sustainability as well as to poverty alleviation and economic development. 相似文献