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81.
Soil erosion is considered as a serious threat to agricultural development in developing countries. Soil and water conservation
measures, such as terraces, are often promoted to combat soil erosion and to increase agricultural production. In this paper,
the short-term impact of bench terraces, 2–4 years after their establishment, on soil properties and maize yield in the Peruvian
Andes is analysed and discussed. The results show that bench terraces did not result in any short term change in soil properties,
such as fertility or infiltration capacity. Nevertheless, the bench terraces resulted in 20% higher yields, due to a higher
planting density, compared with adjacent sloping fields. However, this increase in yield was nullified by the loss of area
occupied by the bench terraces. Bench terraces should therefore be accompanied with other measures to intensify agriculture,
such as irrigation or cash crops, to improve the profitability and uptake of bench terraces in the Andes. 相似文献
82.
Leo Baas 《Journal of Cleaner Production》1998,6(3-4)
This article opens briefly with the recent discussions about the effectiveness of pollution prevention. As pollution prevention and cleaner production are important elements of industrial ecology, the different definitions and approaches of industrial ecology as a term also need clarity. The major part of this article reflects the first results of the cleaner production and industrial ecology concepts, applied in an industrial ecosystem project (INES) in the Rotterdam harbour area. In this industrial area with many refineries and (petro)chemical facilities, the possibilities for companies to reuse waste streams, by-products and energy from each other was researched. The project was initiated by an industrial association. Sixty-nine members of the industrial association joined the INES project and provided confidential information about their resources, products and waste streams to the research team. Based on this information, 15 projects were designed. The selected three projects for further feasibility studies showed the potency to reduce the use of energy, water and bio sludge significantly. 相似文献
83.
Leo C. Osuji Benjamin C. Ndukwu Gordian C. Obute Ikechukwu Agbagwa 《Chemistry and Ecology》2006,22(5):415-424
Reconnaissance survey and laboratory appraisal of the mangrove system in seven communities in the Niger Delta (Nigeria) endangered by seismic and production operations revealed several alterations of soil, sediment, and vegetation. Hydrocarbon content in the range of 0.3-1.1 mg/100 g was extracted within the proximities of spill sources and seismic lines. The prospect area covered by our investigation was characterized by a mixed mangrove forest dominated by Rhizophora racemosa. It was observed that the construction of the seismic lines was responsible for the vegetal disorientation recurrent in the area. The grass, Paspalum vaginatum, and the saltwater fern, Acrostichum aureum, were found at the fringe of most dredge spoils. The characteristic tidal inundation which increases mobility of the substrate, salinity fluctuation, and anoxia may also have contributed, at least in part, to the observed despoliation of some of these species found within the vicinities of the seismic lines and hydrocarbon percolation. Extensive revegetation program is recommended to ensure an effective restoration process of this ecologically fragile zone. 相似文献
84.
Gilbert Decat Leo Deckx Guy Meynen Emmy De Graef Florence Jonlet 《International journal of occupational safety and ergonomics》2006,12(2):169-176
The spectrum and the polarization of the magnetic flux density (B-field) of 6 induction heaters and 1 arc oven were measured by means of a PMM (Italy) spectrum analyser. The spectrum analysis showed that no substantial harmonics were observed while the polarization analysis revealed that the operator's exposure was non-homogeneous within a distance of 1.5 m from the heater. When the distance was larger, the body was homogeneously exposed. In general we can state that the B-field strongly varied between heaters and that exposure exceeded the occupational reference levels recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) (1998) and European Directive 2004/40/EC in 5 of the 7 heaters. Within the framework of the Directive some protection actions should be taken. Whereas mitigation of existing/old induction ovens is difficult, the design of new induction heaters and their housing should be based, among others, on electromagnetic reducing engineering concepts. 相似文献
85.
Environmental effects on sex allocation are common, yet the evolutionary significance of these effects remains poorly understood.
Environmental effects might influence parents, such that their condition directly influences sex allocation by altering the
relative benefits of producing sons versus daughters. Alternatively, the environment might influence the offspring themselves,
such that the conditions they find themselves in influence their contribution to parental fitness. In both cases, parents
might be selected to bias their sex ratio according to the prevailing environmental conditions. Here, we consider sex allocation
in the citrus mealybug Planococcus citri, a species with an unusual genetic system in which paternal genes are lost from the germline in males. We test environmental
factors that may influence either female condition directly (rearing temperature and food restriction) or that may be used
as cues of the future environment (age at mating). Using cytological techniques to obtain primary sex ratios, we show that
high temperature, older age at mating and starvation all affect sex allocation, resulting in female-biased sex ratios. However,
the effect of temperature is rather weak, and food restriction appears to be strongly associated with reduced longevity and
a truncation of the usual schedule of male and offspring production across a female’s reproductive lifetime. Instead, facultative
sex allocation seems most convincingly affected by age at mating, supporting previous work that suggests that social interactions
experienced by adult P. citri females are used when allocating sex. Our results highlight that, even within one species, different aspects of the environment
may have conflicting effects on sex allocation. 相似文献
86.
87.
Sarmiento Jon Marx P. Mendez Queenie Lynly T. Estaña Leo Manuel B. Giray Evette S. Nañola Cleto L. Alviola Pedro A. 《Environment, Development and Sustainability》2021,23(11):16786-16802
Environment, Development and Sustainability - The Philippine fisheries sector continues to play a critical role in the livelihood of coastal households; however, the country’s fisheries... 相似文献
88.
Matthew P. Davis Nancy I. Holcroft Edward O. Wiley John S. Sparks W. Leo Smith 《Marine Biology》2014,161(5):1139-1148
The vast darkness of the deep sea is an environment with few obvious genetic isolating barriers, and little is known regarding the macroevolutionary processes that have shaped present-day biodiversity in this habitat. Bioluminescence, the production and emission of light from a living organism through a chemical reaction, is thought to occur in approximately 80 % of the eukaryotic life that inhabits the deep sea (water depth greater than 200 m). In this study, we show, for the first time, that deep-sea fishes that possess species-specific bioluminescent structures (e.g., lanternfishes, dragonfishes) are diversifying into new species at a more rapid rate than deep-sea fishes that utilize bioluminescence in ways that would not promote isolation of populations (e.g., camouflage, predation). This work adds to our understanding of how life thrives and evolution shaped present-day biodiversity in the deep sea, the largest and arguably least explored habitat on earth. 相似文献
89.
90.
Richard M. Wheeler Leo M. Eisel Gerald D. Seinwill 《Journal of the American Water Resources Association》1980,16(2):326-335
ABSTRACT: The Federal Government's interest and involvement in water resource development in discussed in the context of project financing and cost sharing. After drawing a clear distinction between the two issues - who puts up the money, and who repays over time - the authors survey a number of Federal acts from which have evolved nearly 200 separate cost-sharing rules. Selected cost sharing and financing issues discussed include consistency in policies, rehabilitation of urban water supply systems, multipurpose water quality projects, and ground water management. Two proposals for cost/finance sharing reform introduced in the 96th Congress are discussed in detail and their impacts compared with current policy. The joint venture approach (Administration proposal) results in an effective composite cost share which changes significantly but not drastically (from 19 to 35 percent non-Federal share for a hypothetical project). The block grant approach (Domenici-Moynihan proposal) would alter the regional distribution of Federal water developement funding from the South and West to the Northwest and North Central States. 相似文献