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排序方式: 共有1933条查询结果,搜索用时 218 毫秒
491.
FunctionalfeaturesoftheecosystemintheprimitivesubtropicalkarstmountainareaandtheirdegradationundertheinfluenceofhumanactivitiesInthepast 50years ,humanactivitieshavebroughtaboutthefollowinggreatchangesintheecosystemofthesubtropicalkarstmountainarea :(1 )FromtheinvestigationandanalysisofMaolanKarstNaturalConservationDistrictinGuizhouandNonggangKarstNaturalConservationDistrictinGuangxi,andtheresearchesonthechangesinthenaturalandgeographicalenvironmentinthekarstmountainareainRenhuaiCity ,Gu… 相似文献
492.
DUAN Guang-ming ZHAO Jing-zhu LIU Guo-hu KE Bing XIAO Han WU Gang DENG Hong-bing 《环境科学学报(英文版)》2004,16(2):308-315
This paper assess the eco-environmental benefits that may come from the middle route project of China‘s South-North Water Transfer Scheme(SNWT) with principles and methods of eco-economics and planning reports of SNWT‘s middle route project. Some benefits were calculated in monetary units. To make sure that the results can be comparable with normal monetary indices, concrete assessment objects and the parameters are prudently selected according to the major characteristics of the project and its water import region. Primary assessment revealed that in different project construction stages, the benefit could be more than 13.07 billion RMB Yuan in 2010 and 19.79 billion RMB Yuan in 2030, respectively. The monetary value tends to increase with social-economic development. To realize these potential benefits, however, calls for more endeavors. 相似文献
493.
总结了洪泽湖湿地的11种生态服务功能,采用生态服务功能相容性分析方法,将洪泽湖湿地生态系统划分为6个功能区:重要物种栖息区、湖体水产养殖区、水产品精养区、水源供应区、社会文化功能区和污染物降解区,并提出了相应的保护措施。 相似文献
494.
Sulfikar Hanafi Michael R. Grace Barry T. Hart 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):403-411
Nutrient spiralling measurements were conducted in Lyrebird Creek, a forested stream in the Dandenong Ranges, Victoria, Australia.
Spiralling indices from several nutrient (, ) enrichment experiments were correlated with seasonal variation in factors thought to control nutrient uptake, i.e., temperature,
light and algal biomass. It was hypothesized that nutrient uptake would be higher in summer as increased temperatures would
promote both biotic and abiotic processes and higher light levels in summer would stimulate photosynthesis. However, results
did not support this hypothesis. Uptake length for and and uptake velocity were not correlated with chlorophyll-a, light or temperature (r
2 < 0.30, P > 0.1) despite the seasonality of these biophysical factors (r
2 > 0.42, P < 0.02). Lyrebird Creek might had no seasonal trend in nutrient uptake and/or nutrient spiraling measurements only appears
suitable for contrasting streams with large differences in biophysical factors that supports biotic and abiotic nutrient processing.
In addition, small errors in measuring a nutrient concentration can result in a large range in the estimated S
w and increased difficulty in determining significant differences in nutrient spiralling indices. 相似文献
495.
Development of a Bird Integrity Index: Measuring Avian Response to Disturbance in the Blue Mountains of Oregon, USA 总被引:1,自引:0,他引:1
Bryce SA 《Environmental management》2006,38(3):470-486
The Bird Integrity Index (BII) presented here uses bird assemblage information to assess human impacts to 28 stream reaches
in the Blue Mountains of eastern Oregon. Eighty-one candidate metrics were extracted from bird survey data for testing. The
metrics represented aspects of bird taxonomic richness, tolerance or intolerance to human disturbance, dietary preferences,
foraging techniques, and nesting strategies that were expected to be positively or negatively affected by human activities
in the region. To evaluate the responsiveness of each metric, it was plotted against an index of reach and watershed disturbance
that included attributes of land use/land cover, road density, riparian cover, mining impacts, and percent area in clearcut
and partial-cut logging. Nine of the 81 candidate bird metrics remained after eliminating unresponsive and highly correlated
metrics. Individual metric scores ranged from 0 to 10, and BII scores varied between 0 and 100. BII scores varied from 78.6
for a minimally disturbed, reference stream reach to 30.4 for the most highly disturbed stream reach. The BII responded clearly
to varying riparian conditions and to the cumulative effects of disturbances, such as logging, grazing, and mining, which
are common in the mountains of eastern Oregon. This BII for eastern Oregon was compared to an earlier BII developed for the
agricultural and urban disturbance regime of the Willamette Valley in western Oregon. The BII presented here was sensitive
enough to distinguish differences in condition among stream riparian zones with disturbances that were not as obvious or irreversible
as those in the agricultural/urban conditions of western Oregon. 相似文献
496.
497.
Changes of Land Use and of Ecosystem Service Values in Sanjiang Plain, Northeast China 总被引:6,自引:0,他引:6
Wang Z Zhang B Zhang S Li X Liu D Song K Li J Li F Duan H 《Environmental monitoring and assessment》2006,112(1-3):69-91
Agricultural activities, especially reclamation, are considered major threats to the wetland ecosystems in Sanjiang Plain,
the largest concentrated area of the freshwater wetlands in China. In the past decades, the area of the cultivated land and
its grain production have been increased at the cost of wetlands shrinkage. The large-scale land reclamation severely affected
the ecosystems in this region. However, such effects at the regional scale are seldom evaluated quantitatively. We used three
datasets of LANDSAT MSS and/or TM imagery to estimate the area changes and the transition of land use types from 1980 to 2000.
We also valued changes in ecosystem services delivered by each land category using value coefficients published by Costanza
et al. [Nature 387, 1997, 253–260]. Sensitivity analysis suggested that these estimates were relatively robust. Finally, the contribution
of various ecosystem functions was ranked to the overall value of the ecosystem services in this study. According to our estimates,
the total annual ecosystem service values in Sanjiang Plain have declined by about 40% between 1980 and 2000 ($156284–182572.18
million in total over 20 years). This substantial decline is largely attributed to the 53.4% loss of wetlands. For individual
ecosystem functions, waste treatment, water supply and disturbance regulation account for more than 60% to the total ecological
values. During those two decades, the contribution of disturbance regulation, cultural and recreation decreased, while the
contribution of water regulation, nutrient cycling, food production, raw materials and climate regulation increased during
the same period. We also put forward a few proposals concerning the future land use policy formulation and sustainable ecosystems.
They are adjusting the ‘food first’ agricultural policy, establishing more nature reserves for wetlands, creating systems
for the rational use of water, harnessing the degraded cultivated land and encouraging eco-tourism. 相似文献
498.
An international workshop held in the spring of 2002 convened a group of technical experts to address monitoring, modeling,
and management of PCBs within the Detroit River-Western Lake Erie basin. Participants shared and discussed a diverse set of
research data bases pertaining to PCB levels within the region, discussed observed changes within different components of
the local ecosystem, and identified several primary issues impacting future PCB management strategies. Results presented at
the workshop indicate dramatic reductions in PCB contamination levels have been observed in much of study area between the
late 1970s and mid-1990s. Estimates of loadings attributable to water and atmospheric sources have generally declined, as
have PCB concentrations in herring gull eggs, smelt and walleye. Nevertheless, additional improvements have not been observed
during recent years and elevated contamination levels remain a concern within local hot spots, particularly in the lower Detroit
River and Trenton Channel. A primary recommendation broadly supported by workshop participants is the need to maintain, support,
and coordinate a comprehensive ecosystem monitoring program for the Detroit River-Western Lake Erie basin, one that incorporates
both near-field and far-field monitoring elements. Such a program is crucial to provide necessary data in support of understanding
ecosystem trends, calculating annual mass loadings to the system, assessing impacts of remediation actions, developing improved
modeling frameworks, and formulating cost-effective management strategies for the future. 相似文献
499.
Giulia Castellani Gaëlle Veyssire Michael Karcher Julienne Stroeve S. Neil Banas A. Heather Bouman S. Andrew Brierley Stacey Connan Finlo Cottier Fabian Große Laura Hobbs Christian Katlein Bonnie Light David McKee Andrew Orkney Roland Proud Vibe Schourup-Kristensen 《Ambio》2022,51(2):307
The Arctic marine ecosystem is shaped by the seasonality of the solar cycle, spanning from 24-h light at the sea surface in summer to 24-h darkness in winter. The amount of light available for under-ice ecosystems is the result of different physical and biological processes that affect its path through atmosphere, snow, sea ice and water. In this article, we review the present state of knowledge of the abiotic (clouds, sea ice, snow, suspended matter) and biotic (sea ice algae and phytoplankton) controls on the underwater light field. We focus on how the available light affects the seasonal cycle of primary production (sympagic and pelagic) and discuss the sensitivity of ecosystems to changes in the light field based on model simulations. Lastly, we discuss predicted future changes in under-ice light as a consequence of climate change and their potential ecological implications, with the aim of providing a guide for future research. 相似文献
500.
Overall, the greatest threats to Canadian and global biodiversity are associated with conversions of natural ecosystems to anthropogenic ones, and over-exploitation of biological resources. This circumstance does not, however, trivialize the importance of atmospheric influences. Although scientific understanding of the risks is incomplete, it is nevertheless clear that anthropogenic changes in atmospheric stressors are potentially damaging to biodiversity and other ecological values over medium- and longer-term scales. It is important that greater investments be made in support of longer-term monitoring and research designed to understand the effects of atmospheric and other environmental stressors on the biodiversity and structure and function of Canadian ecosystems. 相似文献