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排序方式: 共有1735条查询结果,搜索用时 31 毫秒
931.
Stohlgren TJ Chong GW Schell LD Rimar KA Otsuki Y Lee M Kalkhan MA Villa CA 《Environmental management》2002,29(4):566-577
Basic information on where nonnative plant species have successfully invaded is lacking. We assessed the vulnerability of
22 vegetation types (25 sets of four plots in nine study areas) to nonnative plant invasions in the north–central United States.
In general, habitats with high native species richness were more heavily invaded than species-poor habitats, low-elevation
areas were more invaded than high-elevation areas, and riparian zones were more invaded than nearby upland sites. For the
100 1000-m2 plots (across all vegetation types), 50% of the variation in nonnative species richness was explained by longitude, latitude,
native plant species richness, soil total percentage nitrogen, and mean maximum July temperature (n = 100 plots; P < 0.001). At the vegetation-type scale (n = 25 sets of four 1000-m2 plots/type), 64% of the variation in nonnative species richness was explained by native plant species richness, elevation,
and October to June precipitation (P < 0.001). The foliar cover of nonnative species (log) was strongly positively correlated with the nonnative species richness at the
plot scale (r = 0.77, P < 0.001) and vegetation-type scale (r = 0.83, P < 0.001). We concluded that, at the vegetation-type and regional scales in the north–central United States, (1) vegetation types
rich in native species are often highly vulnerable to invasion by nonnative plant species; (2) where several nonnative species
become established, nonnative species cover can substantially increase; (3) the attributes that maintain high native plant
species richness (high light, water, nitrogen, and temperatures) also help maintain nonnative plant species richness; and
(4) more care must be taken to preserve native species diversity in highly vulnerable habitats. 相似文献
932.
Evaluating the characteristics of a set of sites as potential scientific research reserves is an example of land suitability
assessment. Suitability in this case is based upon multiple criteria, many of which can be linguistically imprecise and often
incompatible. Fuzzy logic is a useful method for characterizing imprecise suitability criteria and for combining criteria
into an overall suitability rating. The Ecosystem Management Decision Support software combined a fuzzy logic knowledge base
we developed to represent the assessment problem with a GIS database providing site-specific data for the assessment. Assessment
of sites as a potential natural reserve for the new University of California campus at Merced demonstrates the benefits of
fuzzy suitability assessment. The study was conducted in three stages of successively smaller assessment regions with increasingly
fine spatial resolution and specificity of criteria. Several sites were identified that best satisfy the suitability criteria
for a reserve to represent vernal pool habitat. 相似文献
933.
Environmental evaluation of subdivision site developments 总被引:5,自引:0,他引:5
An environmental evaluation was performed at 16 subdivision sites within four communities in east-central Michigan. The primary
objective was to evaluate the fit between environmental ordinances and the physical/environmental conditions to which they
were applied. An environmental response index was developed with indicators to assess water, soil, slope, development density,
roads, vegetation, and ecology. Water-related indicators achieved the highest scores, while soil-related indicators scored
the poorest, with generally poor performance across all indicators. The poor performance indicates there are problems in the
ability of environmental ordinances developed at broader jurisdictional scales (e.g., the state) to address the existing environmental
conditions at smaller geographic scales (subdivisions within communities). Two key problems include the lack of scientific
specificity in the broader state-level ordinances and the lack of local expertise and/or resources to monitor the environment. 相似文献
934.
Construction of 653 ha of salt marsh habitat from dredged material near the Aransas National Wildlife Refuge, Texas, has been
proposed, with the goal of increasing the area of habitat available to endangered whooping cranes (Grus americana). We assessed prototype created wetlands, and their similarity to natural reference sites, in terms of topography, vegetation,
and hydrology. The created sites were steeply sloped relative to natural sites and were dominated by monotypic stands of Spartina alterniflora. Natural sites were dominated by vegetation more tolerant of desiccation and hypersalinity and by unvegetated salt pans.
Differences in vegetation communities and distributions of habitat types resulted from efforts to enhance habitat diversity
in created marsh cells through manipulation of marsh topography. However, the scale at which this diversity occurred in natural
marsh of the study area was not considered. When constructing wetlands in cellular configurations, we recommend creation of
large complexes of adjoining, hydrologically linked, cells wherein the desired habitat diversity is created at the scale of
the entire complex, rather than within a single cell. Suggested design modifications would increase the similarity of created
marshes to natural reference sites, potentially improving habitat function. 相似文献
935.
Senecal G 《Environmental management》2002,30(1):46-58
This article assesses the City of Montréal's éco-quartier program from the viewpoint of managing the urban environment and
improving living environments. It evaluates the actual achievements of the program, looking especially at the ability of local
communities to take effective action to improve their living environments, while under the guidance of the associations mandated
to manage the program at the local level. Our research concentrated on three main areas: a) the development of the City of
Montréal's environmental program; b) the effectiveness of the éco-quartiers in carrying out their mandate; c) the actual impacts
of the program in improving living environments. 相似文献
936.
An extensive road system with rapidly increasing traffic produces diverse ecological effects that cover a large land area.
Our objective was to evaluate the effect of roads with different traffic volumes on surrounding avian distributions, and its
importance relative to other variables. Grassland bird data (5 years) for 84 open patches in an outer suburban/rural landscape
near Boston were analyzed relative to: distance from roads with 3000–8000 to >30,000 vehicles/day; open-habitat patch size;
area of quality microhabitat within a patch; adjacent land use; and distance to other open patches. Grassland bird presence
and regular breeding correlated significantly with both distance from road and habitat patch size. Distance to nearest other
open patch, irrespective of size, was not significant. Similarly, except for one species, adjacent land use, in this case
built area, was not significant. A light traffic volume of 3000–8000 vehicles/day (local collector street here) had no significant
effect on grassland bird distribution. For moderate traffic of 8000–15,000 (through street), there was no effect on bird presence
although regular breeding was reduced for 400 m from a road. For heavier traffic of 15,000–30,000 (two-lane highway), both
bird presence and breeding were decreased for 700 m. For a heavy traffic volume of ≥30,000 vehicles/day (multilane highway),
bird presence and breeding were reduced for 1200 m from a road. The results suggest that avian studies and long-term surveys
near busy roads may be strongly affected by traffic volume or changes in volume. We conclude that road ecology, especially
the effects extending outward >100 m from roads with traffic, is a sine qua non for effective land-use and transportation policy. 相似文献
937.
The impact of disturbance from construction work around Cardiff Bay, south Wales, on the densities and feeding behavior of
seven waterbird species was studied over an 11-year period. Construction of a barrage across the mouth of the bay has subsequently
resulted in its impoundment; other major works included the construction of a bridge carrying a divided highway. Construction
work disturbance significantly reduced the densities of five species—green-winged teal (Anas crecca), Eurasian oystercatcher (Haematopus ostralegus), dunlin (Calidris alpina), Eurasian curlew (Numenius arquata), and common redshank (Tringa totanus)—on adjacent intertidal mudflats, and thus the overall carrying capacity of the bay. Construction work also reduced the feeding
activity of Eurasian oystercatcher, dunlin, and common redshank on these mudflats. The possible impact of the loss of birds
from these mudflats upon the populations that the bay supported is discussed. Evidence from other local studies suggests that
the displacement of common redshank from these mudflats did not contribute to a decline in this species. 相似文献
938.
This paper reviews a series of strategies for improving environmental performance in the small-scale gold mining industry.
Although conditions vary regionally, few regulations and policies exist specifically for small-scale gold mining activity.
Furthermore, because environmental awareness is low in most developing countries, sites typically feature rudimentary technologies
and poor management practices. A combination of policy-, managerial- and technology-related initiatives is needed to facilitate
environmental improvement in the industry. Following a broad overview of these initiatives, a recommended strategy is put
forth for governments keen on improving the environmental conditions of resident small-scale gold mines. 相似文献
939.
Isla Victoria (Nahuel Huapi National Park, Argentina), a large island dominated by native Nothofagus and Austrocedrus forest, has old plantations of many introduced tree species, some of which are famed invaders of native ecosystems elsewhere.
There are also large populations of introduced deer and shrubs that may interact in a complex way with the introduced trees,
as well as a recently arrived population of wild boar. Long-standing concern that the introduced trees will invade and transform
native forest may be unwarranted, as there is little evidence of progressive invasion, even close to the plantations, despite
over 50 years of opportunity. Introduced and native shrubs allow scattered introduced trees to achieve substantial size in
abandoned pastures, but in almost all areas neither the trees nor the shrubs appear to be spreading beyond these sites. These
shrub communities may be stable rather than successional, but the technology for restoring them to native forest is uncertain
and probably currently impractical. Any attempt to remove the exotic tree seedlings and saplings from native forest would
probably create the very conditions that would favor colonization by exotic plants rather than native trees, while simply
clear-cutting the plantations would be unlikely to lead to regeneration of Nothofagus or Austrocedrus. The key to maintaining native forest is preventing catastrophic fire, as several introduced trees and shrubs would be favored
over native dominant trees in recolonization. Deer undoubtedly interact with both native and introduced trees and shrubs,
but their net effect on native forest is not yet clear, and specific management of deer beyond the current hunting by staff
is unwarranted, at least if preventing tree invasion is the goal. The steep terrain and shallow soil make the recently arrived
boar a grave threat to the native forest. Eradication is probably feasible and should be attempted quickly. 相似文献
940.
Modeling of air pollutant dispersion has been undertaken for emissions of sulfur dioxide (SO2) at the Mina Al-Fahal refinery in the Sultanate of Oman. The study was conducted during the period of November 1999 to October
2000. The Industrial Source Complex Short-Term (ISCST32) air pollution model was adopted to predict the ground level concentration
of SO2 in and around the refinery. The modeling results were validated against measured data during the study period. The comparison,
based on the monthly average measurements, showed that the model underestimates the observed SO2 concentrations. However, the predicted ground level concentrations of SO2 during the months of September, October, November, and June were in better agreement with the observations. The predicted
SO2 values are presented in the form of concentration contours to determine the spatial distribution of SO2 and to assess the impact on air quality over the survey area. Predicted SO2 concentrations were found lower than the World Health Organisation (WHO) guideline value of 365 μg/m3, with the maximum ground level concentrations being found to occur relatively close to the sources of emission. Moreover,
concentration contour patterns for the modeled area vary with changes in meteorological conditions. On the basis of this study,
the refinery is not likely to cause any significant deterioration in air quality, and predicted concentrations of SO2 are well below those likely to influence health. 相似文献