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941.
Thomas R. Wentworth George P. Johnson Russell L. Kologiski 《Journal of the American Water Resources Association》1988,24(2):389-396
ABSTRACT: Weighted averages (WA) was investigated as a vegetation-based method for wetland designation, to be used in conjunction with the wetland indicator status of plants from Wetland Plants of the United States of America 1986 (Reed, 1986). Ecological indices were assigned to indicator groups and were used to compute weighted averages for quantitative data obtained from four studies of wetland vegetation conducted in various regions of the United States. Weighted averages of vegetation data proved to be a useful tool for assessing wetland status of the vegetation types included in our study: (1) rankings of vegetation stands or types by WA correlated well with their positions on environmental moisture gradients; and (2) the results of WA could be used, together with a wetland/upland break-point, to designate vegetation types as wetland or upland in a way that agreed well, in three of the four studies, with an alternative classification of wetland habitats. The variation of weighted averages among the sampling units representing a vegetation type was generally small relative to the range of ecological indices assigned. However, designations based on weighted average scores close to the break-point should be considered provisional and must be verified with supplementary data on soils and hydrology. 相似文献
942.
Elon S. Veny 《Journal of the American Water Resources Association》1986,22(6):1039-1047
ABSTRACT: The impact of forests on water has- been a subject of argument for more than a century. It still is; and many studies conform that there is no single right answer in the debate. In the Lake States, clearcutting natural peatlands will not change annual stream-flow nor will it seriously impact water quality if logging is done on frozen soils. However, clearcutting will cause water tables to fluctuate more, ranging from 9 cm higher to 19 cm lower than in peatlands with mature forests. Clearcutting upland hardwoods or conifers will increase annual strearnflow by 9 to 20 cm (a 30- to 80-percent increase). Streamfiow returns to preharvest levels in 12 to 15 years. Annual peak flows are at least doubled and snowmelt flood-peak increases may persist for 15 years. Water quality is not widely impacted, but operating logging equipment in stream channels will cause channel clogging by filamentous algae and loss of fish habitat. Permanent changes from forest to agricultural and urban land use on two-thirds or more of a watershed will significantly increase the size of flood peaks in the 2- to 30-year return interval storm or snowmelt. 相似文献
943.
Charles T. Roman Robert A. Zampella Andrew Z. Jaworski 《Journal of the American Water Resources Association》1985,21(6):1005-1012
Wetland protection regulations and guidelines often require the delineation of precise wetland boundaries on a case-by-case basis. In this study, conducted in the New Jersey Pinelands, an ecological characterization of vegetation composition, soil and hydrologic relationships along upland to wetland Pinus rigida - dominated transittions provided the basis for a multiparameter approach to wetland boundary delineation. The transitional data set was analyzed by direct gradient analysis, cluster analysis and ordination. It is concluded that vegetation composition can be a principal factor in delineating wetland boundaries along natural upland to wetland transitions. However, where distinct vegetation changes are not observed, a feature of our study sites, a multiparameter approach should be used. 相似文献
944.
一种地铁综合监控系统安全性分析方法研究 总被引:2,自引:0,他引:2
地铁综合监控系统的安全直接影响整个地铁系统的安全,根据地铁综合监控系统的特点建立该系统的安全性评价模型,将层次分析法和模糊综合评判法相结合用于地铁综合监控系统的安全性分析。用层次分析法确定各影响因素的权重,模糊综合评判法评定地铁综合监控系统的安全等级。该评定方法能较好地反映地铁综合监控系统的实际安全状况,可为地铁的安全运营提供决策依据,并且评价结果简单直观。 相似文献
945.
山东半岛城市群中心城市城市化水平综合评价 总被引:1,自引:0,他引:1
城市化是一种复杂的社会经济现象,受到多方面的影响,单一的指标不能清楚地反映一个城市的综合发展水平,对城市化的评价应建立综合的评价体系。以山东半岛8个地级城市为例,建立指标系,运用数学模型对各城市的城市化进行了综合评价,客观地反映了各城市发展的优劣,最后提出了各城市在未来城市建设方面的建议。 相似文献
946.
Two media bed (gravel and Filtralite NR) were tested in a mesocosm to evaluate the removal of organic matter (as chemical oxygen demand (COD)),ammonia (NH4-N),nitrite,nitrate and solid matter (as total suspended solids (TSS)) for a synthetic wastewater (acetate-based) and a domestic wastewater.The use of Filtralite allowed average removal rates (6–16.8 g COD/(m2·day),0.8–1.1 g NH4-N/(m2·day) and 3.1 g TSS/(m2·day)) and removal effciencies (65%–93%,57%–85% and 78% for COD,NH4-N and TSS,respectively),higher than that observed in the experiments with gravel.The applied loads of COD,ammonia,nitrate and TSS seem to influence the respective removal rates but only for the treatment of domestic wastewater with higher correlation coefficients for Filtralite.Regardless the type of media bed and the type of wastewater,nitrate was completely removed for nitrogen loading rates up to 1.3 g NO3-N/(m2·day).There was no evidence of the influence of nitrate loads on the removal of organic matter. 相似文献
947.
948.
综合应用国内外湖库营养控制标准的制订方法的基础上,提出了湖泊富营养化评价的综合营养指数校验法,并对三峡库区支流进行了富营养化评价.结果显示,调查期间,30条支流中,19条支流的平均营养状态指数为富营养化水平,11条支流的平均营养状态指数为中营养水平.4~9月各支流的平均综合营养状态指数值均达到富营养化水平,8月份出现最大值(55.43),显示春、夏季节库区支流发生富营养化的风险较高,应为控制库区富营养化发生的敏感时期.与目前国内传统的由"七五"期间调查的26个湖泊总结得出的"湖库富营养化评价方法及分级技术规定"的评价方法相比,综合营养指数校验法的评价结果比较符合三峡水库支流的实际水质状况,适用于三峡水库支流的富营养化评价. 相似文献
949.
3种湿地植物在水培条件下的生长状况及根系分泌物研究 总被引:6,自引:2,他引:4
湿地植物是人工湿地的核心部分,其根系分泌物是人工湿地的主要内部碳源.本研究分析了美人蕉、茭白、水柳等3种湿地植物在水培条件下的生长状况和根系分泌物特性.本实验条件下美人蕉、茭白、水柳在120 d的平均生物量/初始生物量分别为9.1、 3.7和4.7.植物根系分泌物的量与生物量正相关,分泌能力随生物量的增加而降低,生长期内,水柳的平均分泌能力为0.92 mg·(g·d)-1,美人蕉为0.47 mg·(g·d)-1,茭白为0.43 mg·(g·d)-1.通过三维荧光光谱分析,3种植物的根系分泌物均以小分子有机酸和芳香族蛋白质为主.本研究表明,美人蕉、水柳为适宜的湿地植物. 相似文献
950.