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291.
The way the Water Resources Council proposes to measure the beneficial effects of national economic development and recreation is questioned and alternatives suggested. In measuring the former, the assumptions specified by the Council are questioned because they do not hold true in the market place. In addition, the Council's method of simulating a price per recreation day implies that an arbitrary price be selected from a range and multiplied times the number of days at no charge for use of the facilities. It is contended that these procedures would over state the economic benefits which in the real market would be measured by the selected price times the quantity demanded at that price.  相似文献   
292.
OBJECTIVES: To examine the frequency of underage drinking, driving after drinking and alcohol-related crashes, trends in these behaviors, and promising interventions. METHODS: We examined drinking and drinking- and-driving behaviors reported in the United States in the 2001 U.S. National Household Survey of Drug Abuse, the Centers for Disease Control and Prevention 2001 Youth Risk Behavior Survey, the 1992 National Longitudinal Alcohol Epidemiologic Study, and the 1999 National Survey of Drinking and Driving conducted for the National Highway Traffic Administration. We also examined the 1999 European School Survey Project on Alcohol and Other Drugs. Alcohol-related fatal crashes were examined from the U.S. Fatality Analysis Reporting System. Evaluation of interventions to reduce teenage drinking and driving after drinking were reviewed. RESULTS: In the United States, 19% of youth ages 12-20 consumed five or more drinks on an occasion in the past 30 days. Although European nations have lower legal drinking ages (16-18) than in the United States (21), similar proportions engage in underage drinking. In two-thirds of European countries, a greater percentage of 15-16 year-olds drank five or more drinks on an occasion in the past month than in the United States. In both the United States and Europe, the earlier people begin to drink, the greater the likelihood of developing alcohol dependence and other alcohol-related problems, including alcohol-related crash involvement, during adolescence and adult years. During the past 20 years alcohol-related traffic deaths among people younger than 21 have been cut in half in the United States, but progress has halted since 1995 and the problem is still large. Interventions shown by research to reduce alcohol-related crashes among youth include raising the legal drinking age to 21, zero tolerance laws, and some interventions that are family, school, or community based. CONCLUSIONS: Despite research showing that a variety of interventions can reduce underage drinking and alcohol-related crash fatalities, the frequency of these behaviors remains high and the average age of drinking initiation is declining in the United States. Efforts are needed to enhance publicized enforcement of underage drinking laws. Comprehensive community interventions that include enforcement of these laws also are needed.  相似文献   
293.
For decades, wind erosion has triggered dust and sand storms, buffeting Beijing and areas of northwestern China to the point of being hazardous to human health while rapidly eroding crop and livestock productivity. The EPIC (Environmental Policy Integrated Climate) field-scale simulation model was used to assess long-term effects of improved crop rotations and crop residue management practices on wind erosion in Wuchuan County in Inner Mongolia. Simulation results indicate that preserving crop stalks until land is prepared by zone tillage for the next year's crop in lieu of using them as a source of heating fuel or livestock fodder significantly reduces wind erosion by 60%. At the same time, grain and potato (Solanum tuberosum L.) yields were maintained or improved. Significant reductions in erosion, 35 to 46%, also resulted from delaying stalk removal until late January through late April. Yearly wind erosion was concentrated in April and May, the windiest months. Additionally, the use of alternative crop rotations resulted in differences in wind erosion, largely due to a difference in residue stature and quality and differences in biomass produced. As a result, altering current crop rotation systems by expanding corn (Zea mays L.), wheat (Triticum aestivum L.), and millet [Sorghum bicolor (L.) Moench] and reducing potato and pea (Pisum sativum L.) production significantly reduced simulated wind erosion, thus diminishing the severity of dust and sand storms in northwestern China. Saving and protecting topsoil over time will sustain land productivity and have long-term implications for improving conditions of rural poverty in the region.  相似文献   
294.
Soil-derived dissolved organic matter (DOM) has been shown to form stable complexes with the herbicide napropamide [2-(alpha-naphthoxy-N,N-diethylpropionamide] capable of enhancing the transport of napropamide through soil columns. Two soils, one containing sewage sludge-derived organic matter (SS) and the other having only natural organic matter (NoSS) were treated with napropamide and allowed to dry to promote complex formation. Soil columns were prepared by packing a 10-cm layer of untreated, dry, sieved soil followed by an overlying 5-cm layer of napropamide-treated soil. Columns were irrigated and the effluent collected and placed in dialysis chambers. After equilibration napropamide concentrations were determined on both sides of the membrane and complex and quantified based on the amount of napropamide unable to cross the membrane. it was found that for the SS soil 7% and for the NoSS 2.4% of the applied napropamide underwent facilitated transport. In addition, most of the complex transported through the columns had a molecular weight between 500 and 1000 Daltons (Da). The solutions from the SS soil were also found to have formed at least two distinct complexes that were resolved after passing through the untreated soil layer. The results obtained were in agreement with other published results and the techniques used offer a way to separate and concentrate DOM complexes from column effluents for further characterization.  相似文献   
295.
Stream restoration and enhancement projects: is anyone monitoring?   总被引:3,自引:2,他引:1  
Declines in salmon stocks and general watershed health in Washington State, USA, have led to an increase in stream restoration and enhancement projects initiated throughout the state. The increasing number of projects has also raised questions regarding the monitoring of these efforts. Project managers receiving hydraulic project approvals (HPAs) were surveyed to determine whether monitoring was taking place on their projects. About half the project managers surveyed reported the collection of baseline data and the use of biological, physical, chemical, or other water quality measures for their projects. Of those who reported collection of monitoring data, only 18% indicated that monitoring was required. Respondents were also asked to rank the importance of various project goals on a Likert scale. Project managers with projects focusing on “engineering” goals (e.g., roadbed stabilization) were less likely than other project managers to collect baseline monitoring data. Project managers with projects focusing on “restoration/ecological” or “fisheries” goals were more likely than other project managers to collect monitoring measures. Although monitoring appears to be taking place in slightly more than half of the projects surveyed, the nature of the data collected varies widely across projects, and in most cases the monitoring effort is voluntary. This suggests that project sponsors, funders, and managers must consider the issues involved in requiring appropriate monitoring, establishing standardized monitoring guidelines, the time frames in which to monitor, providing other incentives for conducting monitoring, and ensuring adequate funding for monitoring efforts.  相似文献   
296.
Ecological surprises, substantial and unanticipated changes in the abundance of one or more species that result from previously unsuspected processes, are a common outcome of both experiments and observations in community and population ecology. Here, we give examples of such surprises along with the results of a survey of well-established field ecologists, most of whom have encountered one or more surprises over the course of their careers. Truly surprising results are common enough to require their consideration in any reasonable effort to characterize nature and manage natural resources. We classify surprises as dynamic-, pattern-, or intervention-based, and we speculate on the common processes that cause ecological systems to so often surprise us. A long-standing and still growing concern in the ecological literature is how best to make predictions of future population and community dynamics. Although most work on this subject involves statistical aspects of data analysis and modeling, the frequency and nature of ecological surprises imply that uncertainty cannot be easily tamed through improved analytical procedures, and that prudent management of both exploited and conserved communities will require precautionary and adaptive management approaches.  相似文献   
297.
Associated bacteria from Stichodactyla haddoni are found maximum in tentacle tissues than the body tissue. There are eight associated bacterial species viz., Alcaligenes sp, Corynebacterium sp, Aeromonas sp, Sporosarcina sp, Renibacterium sp, Camobacterium sp1, Camobacterium sp2 and Salinococcus sp were recorded. The culture extracts from the associated bacterial species showed sensitivity against human bacterial and fungalpathogens. However, the hexane tissue extract of sea anemone showed maximum sensitivity (24 mm dia.) against the fish bacterial pathogen Aeromonas hydrophila than the other chosen pathogens. Comparatively the tissue extracts showed promising antimicrobial sensitivity than the cell free extracts of associated bacteria, and hence, the tissue samples from the sea anemone Stichodactyla haddoni is recommended for further exploration of novel antimicrobial drugs than the associated bacteria.  相似文献   
298.
Inoculation of azotobacter has significant positive effects on the growth characteristics and pigments in mangrove seedlings of Avicennia marina and Ceriops decandra. The bacterial inoculation significantly increased the root dry biomass at the maximum of 75.8% at 30 gl(-1) salinity in Ceriops decandra. But in Avicennia marina, the shoot dry biomass was increased significantly at the maximum of 56.12% at 30 gl(-1) salinity in general, the Azotobacter beijerinkii improved the growth characteristics better in both species of mangroves preferably at higher salinity levels in A. marina and at a range of salinity in C. decandra. The results recommend this forraising vigorous seedlings under nursery conditions.  相似文献   
299.
300.
Protected area delineation and conservation action are urgently needed on marine islands, but the potential biodiversity benefits of these activities can be difficult to assess due to lack of species diversity information for lesser known taxa. We used linear mixed effects modeling and simple spatial analyses to investigate whether conservation activities based on the diversity of well‐known insular taxa (birds and mammals) are likely to also capture the diversity of lesser known taxa (reptiles, amphibians, vascular land plants, ants, land snails, butterflies, and tenebrionid beetles). We assembled total, threatened, and endemic diversity data for both well‐known and lesser known taxa and combined these with physical island biogeography characteristics for 1190 islands from 109 archipelagos. Among physical island biogeography factors, island area was the best indicator of diversity of both well‐known and little‐known taxa. Among taxonomic factors, total mammal species richness was the best indicator of total diversity of lesser known taxa, and the combination of threatened mammal and threatened bird diversity was the best indicator of lesser known endemic richness. The results of other intertaxon diversity comparisons were highly variable, however. Based on our results, we suggest that protecting islands above a certain minimum threshold area may be the most efficient use of conservation resources. For example, using our island database, if the threshold were set at 10 km2 and the smallest 10% of islands greater than this threshold were protected, 119 islands would be protected. The islands would range in size from 10 to 29 km2 and would include 268 lesser known species endemic to a single island, along with 11 bird and mammal species endemic to a single island. Our results suggest that for islands of equivalent size, prioritization based on total or threatened bird and mammal diversity may also capture opportunities to protect lesser known species endemic to islands. Beneficios de los Taxa Poco Estudiados para la Conservación de la Diversidad de Aves y Mamíferos en Islas  相似文献   
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