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51.
William F. Laurance 《Environmental monitoring and assessment》2000,61(1):113-122
This paper describes four global-change phenomena that are having major impacts on Amazonian forests. The first is accelerating deforestation and logging. Despite recent government initiatives to slow forest loss, deforestation rates in Brazilian Amazonia have increased from 1.1 million ha yr–1 in the early 1990s, to nearly 1.5 million ha yr–1 from 1992–1994, and to more than 1.9 million ha yr–1 from 1995–1998. Deforestation is also occurring rapidly in some other parts of the Amazon Basin, such as in Bolivia and Ecuador, while industrialized logging is increasing dramatically in the Guianas and central Amazonia.The second phenomenon is that patterns of forest loss and fragmentation are rapidly changing. In recent decades, large-scale deforestation has mainly occurred in the southern and eastern portions of the Amazon — in the Brazilian states of Pará, Maranho, Rondônia, Acre, and Mato Grosso, and in northern Bolivia. While rates of forest loss remain very high in these areas, the development of major new highways is providing direct conduits into the heart of the Amazon. If future trends follow past patterns, land-hungry settlers and loggers may largely bisect the forests of the Amazon Basin.The third phenomenon is that climatic variability is interacting with human land uses, creating additional impacts on forest ecosystems. The 1997/98 El Niño drought, for example, led to a major increase in forest burning, with wildfires raging out of control in the northern Amazonian state of Roraima and other locations. Logging operations, which create labyrinths of roads and tracks in forsts, are increasing fuel loads, desiccation and ignition sources in forest interiors. Forest fragmentation also increases fire susceptibility by creating dry, fire-prone forest edges.Finally, recent evidence suggests that intact Amazonian forests are a globally significant carbon sink, quite possibly caused by higher forest growth rates in response to increasing atmospheric CO2 fertilization. Evidence for a carbon sink comes from long-term forest mensuration plots, from whole-forest studies of carbon flux and from investigations of atmospheric CO2 and oxygen isotopes. Unfortunately, intact Amazonian forests are rapidly diminishing. Hence, not only is the destruction of these forests a major source of greenhouse gases, but it is reducing their intrinsic capacity to help buffer the rapid anthropogenic rise in CO2. 相似文献
52.
A. Haurie J.J.E. Kübler A. Clappier H. van den Bergh 《Environmental Modeling and Assessment》2004,9(1):1-12
A method is proposed to build integrated models (also called Metamodels) aimed at quantifying the economic efficiency of air quality policies. This Metamodeling approach is based on the coupling of two complementary models, that operate at different scales in space and time, and which represent the economic and the physical and chemical processes, respectively. The joint consideration of the physico-chemical and techno-economic structure of the pollution control problems permits a comprehensive evaluation of air pollution abatement strategies. The motivating pollution control problems include urban-regional air quality management through efficient energy and traffic control policies. A pilot study, exploiting data collected in the Geneva canton (Switzerland), is used to demonstrate the potential of the approach. 相似文献
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大气微生物与气象条件及大气污染物的灰色关联分析 总被引:4,自引:0,他引:4
根据大气微生物浓度、气象因子和大气污染理化因子的监测结果,应用灰色关联分析原理,分析研究大气微生物浓度与气象条件和大气污染物的关联程度,说明气象因子对各类微生物浓度的影响大于大气污染因子,特别是对耐高渗透压霉菌。 相似文献
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The potential for carbon (C) sequestration was examined in selectedCanadian forest settings and prairie agroecosystems under severalmanagement scenarios. A simple C budget model was developed toquantitatively examine C sequestration potential in living biomass of forestecosystems, in associated forest-product C pools, and in displaced fossil-fuelC. A review of previous studies was conducted to examine C sequestrationpotential in prairie agroecosystems. In the forest settings examined, ourwork suggests that substantial C sequestration opportunities can be realizedin the short term through the establishment of protected forest-C reserves.Where stands can be effectively protected from natural disturbance, peaklevels of biomass C storage can exceed that under alternative managementstrategies for 200 years or more. In settings where it is not feasible tomaintain protected forest-C reserves, C sequestration opportunities can berealized through maximum sustained yield management with harvestedbiomass put towards the displacement of fossil fuels. Because there is afinite capacity for C storage in protected forest-C reserves, harvesting forestbiomass and using it to displace the use of fossil fuels, either directlythrough the production of biofuels or indirectly through the production oflong-lived forest products that displace the use of energy-intensive materialssuch as steel or concrete, can provide the greatest opportunity to mitigategreenhouse gas emissions in the long term. In Canadian prairieagroecosystems, modest C sequestration can be realized while enhancingsoil fertility and improving the efficiency of crop production. This can bedone in situations where soil organic C can be enhanced without relianceupon ongoing inputs of nitrogen fertilizer, or where the use of fossil fuelsin agriculture can be reduced. More substantial C offsets can be generatedthrough the production of dedicated energy crops to displace the use offossil fuels. Where afforestation or reconstruction of native prairieecosystems on previously cultivated land is possible, this represents thegreatest opportunity to sequester C on a per unit-area basis. However,these last two strategies involve the removal of land from crop production,and so they are not applicable on as wide a scale as some other Csequestration options which only involve modifications to currentagricultural practices. 相似文献
57.
本文总结中国东南沿海高钾钙碱性—双峰式火山岩带中已勘查大中型矿床成矿环境的共性:矿床所处区域构造的部位、成岩与成矿时代、矿床与岩浆成因类型、火山构造及其基底构造控矿性、矿床与爆发角砾岩、矿床与矿化类型叠加与共生、矿化与蚀变的分带往、矿床定位深度与剥蚀深度。作者认为这八点可作为找寻与评价大(中)型矿床的地质准则。通过火山地质与矿床地质统一的研究提出本区晚中生代以火山为中心地热体系的成矿模式。并就三个方面作类比:①与现代火山地热体系成矿作用类比;②以紫金山高硫型浅成低温热液矿床与世界同类型矿床作比较;③与环太平洋其他火山岩带同类型矿床模式作类比.通过建立本区的模式与类比获得进一步找矿中值得重视的一些思路. 相似文献
58.
Land degradation is a consequence stemming from both natural processes and social economic activities. On the bases of analyzing general situation of agricultural land degradation in China, the monetary estimating methods such as market value method and shadow engineering method were used to quantitatively assess the economic loss resulting from land deterioration. Results showed that the economic loss in 1999 was 326.8l billion RMB Yuan, which accounted for 4.1% of GDP in the same year of China. If taking five items namely farmland conversion, soil erosion, salinization, decline in reservoir functions, and siltation in waterways and, comparing with that in 1992, the percentage of economic loss to GDP has increased by 1.5 in the only 7 years. 相似文献
59.
IntroductionContaminationofediblevegetationbypersistent,ubiquitouschemicalssuchasPCBs,dioxins,pesticides,andherbicidesprovidesamajorexposureroutetohumans ,domesticanimalsandwildlife .Uptakeoftheseorganicchemicalsbyplant,andsubsequentdistributionintheplan… 相似文献
60.
Anoveralldescriptionofindustrialwastewasgivenfromgeneration;treatment,disposalandemissionandcomprehensiveutilization.Inspiteo... 相似文献