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241.
Mehrey G. Vaghti Marcel Holyoak Amy Williams Theresa S. Talley Alexander K. Fremier Steven E. Greco 《Environmental management》2009,43(1):28-37
Societal constraints often limit full process restoration in large river systems, making local rehabilitation activities valuable
for regeneration of riparian vegetation. A target of much mitigation and restoration is the federally threatened Valley elderberry
longhorn beetle and its sole host plant, blue elderberry, in upper riparian floodplain environments. However, blue elderberry
ecology is not well understood and restoration attempts typically have low success rates. We determined broad-scale habitat
characteristics of elderberry in altered systems and examined associated plant species composition in remnant habitat. We
quantified vegetation community composition in 139 remnant riparian forest patches along the Sacramento River and elderberry
stem diameters along this and four adjacent rivers. The greatest proportion of plots containing elderberry was located on
higher and older floodplain surfaces and in riparian woodlands dominated by black walnut. Blue elderberry saplings and shrubs
with stems <5.0 cm in diameter were rare, suggesting a lack of recruitment. A complex suite of vegetation was associated with
blue elderberry, including several invasive species which are potentially outcompeting seedlings for light, water, or other
resources. Such lack of recruitment places increased importance on horticultural restoration for the survival of an imperiled
species. These findings further indicate a need to ascertain whether intervention is necessary to maintain functional and
diverse riparian woodlands, and a need to monitor vegetative species composition over time, especially in relation to flow
regulation. 相似文献
242.
R. Morgan E. Gatell R. Junyent A. Micallef E. Özhan A. T. Williams 《Journal of Coastal Conservation》2000,6(1):41-50
In many coastal resort areas of the world, it is likely that optimal climatic conditions for beach use might occur outside
the peak of the tourist season. Investigation of this issue together with associated publicity might help to spread the tourism
load and hence reduce undesirable social and environmental effects of extreme seasonality in tourist demand. For this to take
place, better knowledge of beach user preferences in terms of climate and bathing water temperature is required. Questionnaire
surveys were carried out in Wales, Malta and Turkey to establish the preferences of north European beach users for thermal
sensation and bathing water temperature, plus priority levels for other climatic attributes. A user-based beach climate index
based on these preferences and priorities was formulated. Linkage was made between the user-generated ratings for various
climatic conditions and published climate data to evaluate most major Euro-Mediterranean/Black Sea and a range of other beach
tourism areas on a month-by-month basis. Results showed excessively hot thermal sensation in many southern and eastern Mediterranean
coastal destinations during July and August, the present peak of the beach tourism season. Highest preference was given to
water temperatures rather lower than those found in these areas during late summer. Many long haul coastal destinations popular
with north European visitors had similar unpleasant thermal sensations over several months. Uncertainties and deficiencies
still exist with the system, but from the point of view of north European beach users the final scores generated in this study
may be regarded as good approximations of the quality of resort area climates for sedentary beach use. 相似文献
243.
R. H. F. Curr A. Koh E. Edwards A. T. Williams P. Davies 《Journal of Coastal Conservation》2000,6(1):15-22
The Mediterranean region plays host to ca. 33% of the world’s tourism industry. This population of visitors (ca. 147 million
in 1990) inevitably exerts an enormous impact on the natural resources of this coastal zone. In May 1997, a new generation
Aerial Digital Photographic System [ADPS] configured with a Kodak Digital Science 460 CIR digital camera was used to acquire
colour infrared digital photographs of the sand dune systems along the Mediterranean coast of France, from Le Barcares to
St-Cyprien-Plage. These have been used to assess the condition of the dunes along this coast. A series of simple analytical
techniques to identify and measure features indicative of public pressure using image processing software has been devised.
The dune manager with basic computer skills can analyse such indicators as path length, vegetation cover (and conversely the
extent of bare sand) to enable monitoring of the performance of their dune systems under particular management regimes. These
photographs have been compared with similar digital photographs of dune sites in SW France to allow a comparison of dune degradation
in a region with a different population pressure and climate regime. Dune systems sampled from the Mediterranean coastal zone
showed more evidence of anthropogenically induced change than those sampled in SW France. 相似文献
244.
In this paper we combine a climate-forecasting model, COSMIC, with a global impact model, GIM, to compare the market impacts of climate change projected by 14 general circulation models. Given a specific date (2100), carbon dioxide concentration (612 ppmv), and global temperature sensitivity (2.5°C), predicted impacts to economies are calculated using climate-response functions from Experimental and Cross-sectional evidence. The Cross-sectional impact model predicts small global benefits across all climate models, whereas the Experimental impact model predicts a range from small benefits to small damages. High-latitude countries are less sensitive to temperature increases than low-latitude countries because they are currently cool. Uniform global temperature changes overestimate global damages because they underestimate the benefits in polar regions and overestimate the damages in tropical regions compared to the GCM predictions. 相似文献
245.
Ronald A. Burt Gregory L. Christians Samuel P. Williams David J. Wilson 《Environmental monitoring and assessment》2001,72(3):297-326
Two dense nonaqueous phase liquid (DNAPL) tracer tests werecarried out in a shallow aquifer north of Fort Worth, TX. i-Propanolwas used as the nonpartitioning tracer; n-hexanol and n-octanol werethe partitioning tracers. Field data, mathematical modeling, theresults of column tests, and field tracer tests with NaCl were usedin designing the DNAPL tracer tests. The results indicated the presenceof DNAPL at both sites tested; semi-quantitative estimates of theamounts of DNAPL present were obtained by mathematical modeling.Interpretation was complicated by heterogeneity of the aquifer andmass transport effects. 相似文献
246.
Reaction-rate parameters are given for the detailed chemistry of gas-phase hydrogen combustion, involving 21 reversible elementary steps. It is indicated that, when attention is restricted to specific combustion processes and particular conditions of interest, fewer elementary steps are needed. In particular, for calculating autoignition times over a wide range of pressures for temperatures between about 1000 and 2000 K, five irreversible elementary steps suffice, yielding a remarkable reduction in complexity. It is explained that, from a mathematical viewpoint, in terms of global reaction-kinetic mechanisms, the hydrogen–oxygen system in principle comprises only six overall steps. Rational reduced chemical mechanisms for hydrogen combustion therefore necessarily must have fewer than six overall steps. For autoignition over the range of conditions specified above, ignition times can be determined accurately by considering, in addition to an elementary initiation step and an elementary termination step, at most three overall steps for reaction intermediaries, which reduce to two for very fuel-lean conditions and to one for stoichiometric or fuel-rich conditions. The resulting reductions can simplify computations that need to be performed in risk analyses for hydrogen storage and utilization. 相似文献
247.
Jo Williams 《Environment, Development and Sustainability》2007,9(3):325-354
This paper seeks to test the hypothesis that growth in one-person households will increase the domestic consumption of energy,
land and household goods in England and Wales. It concludes that if current consumer behaviour of one-person households persists
there will be a significant increase in the consumption of all three resources in the future. However, it argues that that
many opportunities exist in England and Wales for tackling this problem. For example the new housing programme, increasing
ability amongst one-person households to afford “green alternatives” and the search amongst some one-person households for
alternative lifestyles (which could be potentially more resource efficient). The paper suggests that providing one-person
households with opportunities to live in more resource efficient housing and adopt pro-environmental behaviour could significantly
reduce their future environmental impact. Various design, fiscal and awareness-raising solutions are presented in the paper
and their viability is assessed. These include ecological homes, collective housing forms, occupancy tax, relocation packages,
educational programmes and targeted advertising campaigns. The paper proposes that using a combination of these more innovative
solutions to the problem could significantly reduce the future environmental impact of one-person households. 相似文献
248.
CVS direct preparations usually achieve limited resolution and are better at detecting numerical rather than structural abnormalities. A CVS direct preparation analyzed using G-banding revealed a 47,XY,+G karyotype in 5 of 11 cells and was reported as mosaic for trisomy 21. Subsequent analysis of the CVS culture found only normal male cells. Amniocentesis revealed both normal male cells and cells with an extra F-group chromosome. Fluorescence in situ hybridization (FISH) identified this chromosome to be an isochromosome from the short arm of chromosome 12 [i(12)(p10)]. The amniocyte karyotype was reported as 47,XY,+i(12)(p10)[12]/46,XY[8].ish i(12)(p10)(wcp12+), which is associated with Pallister–Killian syndrome. Reexamination of the CVS direct preparation by FISH with a chromosome 12 centromere probe confirmed the karyotype of this tissue to be 47,XY,+mar[5]/46,XY[6].nuc ish 12cen(D12Z3 × 3)/12cen(D12Z3 × 2). Thus, multiple studies, including amniocentesis and fluorescence in situ hybridization, may be required to fully and accurately evaluate abnormalities detected by CVS. This case also indicates that mosaicism for supernumerary isochromosomes may have a complex origin. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
249.
250.