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排序方式: 共有188条查询结果,搜索用时 593 毫秒
101.
Francis J. Singer 《Environmental management》1981,5(3):263-270
Populations of introduced European wild boar, feral pigs, and combinations of both types (all Susscrola L.) inhabit thirteen areas in the National Park Service system. All parks have relatively stable populations, with the exception of Great Smoky Mountains National Park, which reported a rapidly expanding wild boar population. Suspected and documented impacts were apparently related to pig densities and sensitivity of the ecosystem; the three largest units with dense wild pig populations reported the most damage. Overall, wild pigs are a relatively minor problem for the Park Service; however, problems are severe in at least three parks, and there is potential for invasion of wild boars into several additional parks in the Appalachian Mountains. More specific information is needed on numbers of wild pigs and their impacts in the various parks. 相似文献
102.
Stanley A. Changnon 《Journal of the American Water Resources Association》1971,7(3):473-483
ABSTRACT Existing meteorological controls of water exchange by precipitation and evaporation on the Great Lakes are almost entirely inadvertent and related to man's urban-industrial complexes and their effect upon precipitation processes. These inadvertent effects have led to 10 to 40% increases in precipitation in localized areas within the basin. Envisioned growth of urban-industrial complexes within the Great Lakes region should lead to more inadvertent weather modification in the Basin. The only existing planned weather modification efforts are those at Lake Erie which are attempting to eliminate by redistribution the concentration of lake-derived heavy snowfall along the south shore. It appears reasonable to assume that practical increases of lake precipitation on the order of 5-20% could be achieved on an operational basis over the Great Lakes in the next 10 years, but the time of accomplishment will depend on national priorities, international cooperation, and economic factors. These activities would certainly produce a sizeable increase in the water quantity of the Great Lakes and should result in an improvement in water quality. Operational methods of evaporation suppression applicable to the lakes are just not available. Meteorological controls to ameliorate certain undesirable lake-effect snowstorms are a near reality. 相似文献
103.
Dale D. Meredith 《Journal of the American Water Resources Association》1975,11(3):526-535
ABSTRACT: The individual hydrologic components are assumed to be normally distributed for each month and linear regression equations are estimated for predicting the value of the individual monthly hydrologic components. It is shown that some of the hydrologic components for downwind (in this case downstream) lakes are dependent upon hydrologic events for the upwind lakes. This is particularly so for precipitation in the downwind lake basins which appears to be dependent upon evaporation values for upwind lakes. 相似文献
104.
Contaminated sediments are receiving increasing recognition around the world, leading to the development of various sediment quality indicators for assessment, management, remediation, and restoration efforts. Sediment chemistry represents an important indicator of ecosystem health, with the concentrations of contaminants of potential concern (COPCs) providing measurable characteristics for this indicator. The St. Louis River Area of Concern (AOC), located in the western arm of Lake Superior, provides a case study for how numerical sediment quality targets (SQTs) for the protection of sediment-dwelling organisms can be used to support the interpretation of sediment chemistry data. Two types of SQTs have been established for 33 COPCs in the St. Louis River AOC. The Level I SQTs define the concentrations of contaminants below which sediment toxicity is unlikely to occur, whereas the Level II SQTs represent the concentrations that, if exceeded, are likely to be associated with sediment toxicity. The numerical SQTs provide useful tools for making sediment management decisions, especially when considered as part of a weight-of-evidence approach that includes other sediment quality indicators, such as sediment contaminant chemistry and geochemical characteristics, sediment toxicity, and benthic macroinvertebrate community structure. The recommended applications of using the numerical SQTs in the St. Louis River AOC include: designing monitoring programs, interpreting sediment chemistry data, conducting ecological risk assessments, and developing site-specific sediment quality remediation targets for small, simple sites where adverse biological effects are likely. Other jurisdictions may benefit from using these recommended applications in their own sediment quality programs. 相似文献
105.
We sent out a targeted questionnaire to organizations and private individuals across the UK that have expressed an interest
in squirrel management and conservation. Respondents were asked to evaluate shooting, trapping, poisoning and immunocontraception
(IMC), according to their perceived efficacy, cost efficiency, and whether they were considered to be humane. The majority
of both professionals and enthusiasts indicated support for grey squirrel control to help conserve red squirrels and to reduce
economic damage to timber crops. Respondents\' comparative evaluations of current forms of control showed that trapping is
the most acceptable method. When IMC is compared with the other methods, it was considered to be more humane and acceptable.
In contrast, poisoning was seen as humane or acceptable by the fewest respondents. Furthermore, poisoning elicited the greatest
difference in opinion between the professional and enthusiast groups. This difference (34\%) may be interpreted partly as
concern over the type of death that results from poisoning and partly as due to the possibility of poisoning nontarget species.
Our findings indicate a need for more public information regarding secondary poisoning hazards to other species and their
predators. Interest and concern about squirrel control correlated with the overlap between contemporary areas of distribution
of the two species. It is these areas where consultation and education programs about control methods should be targeted.
This research indicates that there would be support for grey squirrel control using IMC from both lay and professional interest
groups. It demonstrates the existence of a sound basis for constructive dialog that can lead to the design and implementation
of acceptable and efficient control strategies. 相似文献
106.
中国长城沿线生态脆弱性分析及生态保护对策 总被引:2,自引:0,他引:2
孔繁德 《中国环境管理干部学院学报》2002,12(3):12-15
中国长城沿线是半湿润—半干旱和半干旱—干旱气候的过渡地带,也是农牧业的交错地带,生态极其脆弱,生态压力又大,容易发生生态破坏,而且很难恢复。为了保护中国长城沿线的生态环境,必须调整产业结构,合理布局,采用先进技术,加大投入,提高生态意识,加强法制建设。 相似文献
107.
Ronald B. Zelt Jack T. Dugan 《Journal of the American Water Resources Association》1993,29(6):939-948
ABSTRACT: Soil-water conditions provide valuable insight into the hydrologic system in an area. A soil-water balance quantitatively summarizes soil-water conditions and is based on climatic, soil, and vegetation characteristics that vary spatially and temporally. Soil-water balances in the Great Plains of the central United States were simulated for 1951–1980. Results of the simulations were mean annual estimates of infiltration, runoff, actual evapotranspiration, potential recharge, and consumptive water and irrigation requirements at 152 climatic data stations. A method was developed using a geographic information system to integrate and map the simulation results on the basis of spatially variable climatic, soil, and vegetation characteristics. As an example, simulated mean annual potential recharge was mapped. Mean annual potential-recharge rates ranged from less than 0.5 inch in much of the north-central and southwestern Great Plains to more than 10 inches in parts of eastern Texas and southwestern Arkansas. 相似文献
108.
Locally designed, institutional frameworks are being used to develop and implement remedial action plans (RAPs) to restore
beneficial uses in 43 Great Lakes areas of concern. A 1993 Canada-United States roundtable was convened to learn from case
studies and to develop recommendations regarding essential characteristics of RAP institutional frameworks, guidance to ensure
linkages to other related plans, and ways of embracing new institutional frameworks from RAP development to implementation.
Major roundtable recommendations are: (1) RAP institutional frameworks should be empowered to pursue their mission of restoring
uses. Empowerment would be demonstrated by: a watershed focus, inclusive and shared decision-making, clear responsibilities
and sufficient authority, creative funding capability, flexibility and continuity in the process, an iterative process of
continuous improvement, and commitment to education and outreach. (2) RAP institutional frameworks should be used as mechanisms
to coordinate programs at the local level. Such local coordination should be complemented with governmental commitments to
intra- and interagency coordination in work plans. (3) RAP institutional frameworks can help build the capacity of governments
to achieve their goals. Therefore, governments must adopt long-term, visionary goals and commit to a customer-driven RAP process
of continuous improvement. 相似文献
109.
Virginia Carter Mary Keith Garrett Patricia T. Gammon 《Journal of the American Water Resources Association》1988,24(2):297-306
ABSTRACT: A weighted average method was used to analyze transition zone vegetation in the Great Dismal Swamp to determine if a more uniform determination of wetland boundaries can be made nationwide. The method was applied to vegetation data collected on four transects and three vertical layers across the wetland-to-upland transition zone of the swamp. Ecological index values based on water tolerance were either taken from the literature or derived from local species tolerances. Wetland index values were calculated for 25-m increments using species cover and rankings based on the ecological indices. Wetland index values were used to designate increments as either wetland, transitional, or upland, and to examine the usefulness of a provisional wetland-upland break-point. Most increments were designated wetland or transitional when all species were used. Removal of three or five ubiquitous species either gave a wider range of wetland index values with a more variable designation of increments or caused designation of increments to be similar for all layers. The use of locally-derived rankings showed the sensitivity of the weighted averages method to ecological indices of species with large importance values. The weighted average method did not provide for an objective placement of an absolute wetland boundary, but did serve to focus attention on the transitional boundary zone where supplementary information is necessary to select a wetland-upland breakpoint. 相似文献
110.
Henry H. Sprague Richard Block Jonathan W. Bulkley 《Journal of the American Water Resources Association》1983,19(6):1003-1006
ABSTRACT: The production of videotape as a product of a water resources seminar is an innovative approach to graduate education. The research effort required builds upon the traditional graduate seminar approach. The videotape production requires research effort to be focused into a coherent body of information which may be widely disseminated and effectively communicates information to the public. The use of outside speakers and field trips blends very well into the preparation of a videotape. The requriement to present the many sides of a complex water resource issue in a fair and equitable manner requires maturity and professional capability on the part of the students. The research effort requires the students to meet their professional obligation to present an objective, factual, and accurate statement of the issues studies. 相似文献