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701.
Peter J. Smailes 《The Australian geographer》1995,26(2):140-150
While much previous work has been done on the general concept of ecological sustainability, there is relatively little that examines the likely spatial aspects of a socially sustainable rural system. Having defined essential concepts, this study first identifies major current forces for rural change likely to influence any future sustainable system. It goes on to specify those features of modern rural social formations which I believe deserve retention. Finally, some essential requirements for a socially sustainable system are established. 相似文献
702.
Zongguo Huang 《海洋学报(英文版)》2003,22(3)
From 1980 to 1998, biofouling communities in Hong Kong waters, the Zhujiang RiverEstuary and the Mirs Bay were studied and a total of 610 samples. The samples were collected from ves-sels, buoys, piers and cages. Totally, 340 species (see Appendix Ⅰ ) have been recorded and identified,six of which are new. At the same time, research on the biology of the cirripede, bryozoan, polychaeteand mollusc communities were also conducted. Twenty-three related papers have been published. Thisreview summarizes works in Hong Kong over past twenty years, and some unpublished data are also re-ported. 相似文献
703.
Abstract. The wide range of macroscopic mucus aggregates in the Adriatic Sea is documented. These structures arc considered to be initially produced by diatoms. A differentiation into five states or stages: macroflocs, stringers, clouds, creamy surface layers, and gelatinous surface layers is proposed. This classification is based not only on size and shape, but also takes relative position in the water, stability, behavior, and effect on benthos into consideration. An interrelationship between these aggregates - as different manifestations or phases of the same phenomenon - is postulated.
Macroflocs and stringers arc more common. Larger aggregates (clouds, creamy layers, gelatinous layers) arc less frequent. The general term "marine snow" is inadequate to describe the entire range of aggregate sizes and shapes, while the Italian designation "mare sporco" (dirty sea) is misleading. Two massive occurrences of dense clouds coupled with surface accumulations were recorded in the Adriatic in 1988 and 1989. The effect of the various stages on the shallow coastal ecosystem of the Northern Adriatic Sea is discussed. 相似文献
Macroflocs and stringers arc more common. Larger aggregates (clouds, creamy layers, gelatinous layers) arc less frequent. The general term "marine snow" is inadequate to describe the entire range of aggregate sizes and shapes, while the Italian designation "mare sporco" (dirty sea) is misleading. Two massive occurrences of dense clouds coupled with surface accumulations were recorded in the Adriatic in 1988 and 1989. The effect of the various stages on the shallow coastal ecosystem of the Northern Adriatic Sea is discussed. 相似文献
704.
Abstract. The effects of industrial pollution were determined by comparing the pattern of development of marine fouling communities situated along a pollution gradient within Port Kembla Harbour (Australia) with those from nearby Wollongong Harbour, a relatively unpolluted area. Fifty-three fouling species were found in the communities from Wollongong Harbour compared to only 40 in those from Port Kembla Harbour. Twenty-eight species (including many bryozoans) occurred only in the former, while 15 species occurred solely in the latter. Ten of the 25 species common to both areas were more numerous in Port Kembla Harbour, probably because of the greater availability of free substratum and food in this area. The species richness of fouling communities in Port Kembla Harbour was found to decrease as pollutant concentrations increased. In both study areas, communities established in summer showed significantly higher species richness than those whose development was initiated in winter. This difference was less pronounced in Port Kembla Harbour and was attributed to the effects of pollution on larval settlement. Although species richness increased at all sites through time, Wollongong Harbour communities contained a greater number of species at the end of the experiment than communities from Port Kembla Harbour. Despite this, fewer species were found in the very early developmental stages of the communities from Wollongong Harbour. This result highlights the inherent problems associated with using species richness or diversity measures as a means of determining marine environmental quality. 相似文献
705.
Abstract. Cladocora caespitosa is a relatively common, colonial, symbiotic, scleractinian coral in the Mediterranean Sea. It inhabits a wide ecological range: hard and soft bottoms, shallow waters or depths to about 50m, calm water or sites exposed to strong currents and wave action. The present study compares the distribution of this coral at two sites, one shallow (3m — wave exposed) and one deeper (12m — soft bottom).
Different parameters including dry weight, volume, and skeletal growth rates were investigated. The polyp biomass, carbon content, and overall area of fully expanded polyps were also measured. Equations are given for the relationship of skeleton diameter to polyp tissue dry weight as well as skeleton diameter to the possible filter area of fully expanded polyps.
C. caespitosa harbors a rich community of vagile and sessile organisms within the skeleton. The cryptofauna was sorted to higher taxonomic levels and their biomass determined. Several highly significant linear relationship were found between skeleton dry weight, volume and cryptofauna biomass. Thus, the determination of colony volume allows the prediction of cryptofauna biomass.
The interstitial space is dominated by sponges - many of them borers - which erode the corallites close to the living tissue until they break off from the colony. At the deeper sampling site, 26% of all colonies are smaller than 2 cm and 48% are smaller than 5 cm. The fragmentation process is discussed with respect to reproduction. 相似文献
Different parameters including dry weight, volume, and skeletal growth rates were investigated. The polyp biomass, carbon content, and overall area of fully expanded polyps were also measured. Equations are given for the relationship of skeleton diameter to polyp tissue dry weight as well as skeleton diameter to the possible filter area of fully expanded polyps.
C. caespitosa harbors a rich community of vagile and sessile organisms within the skeleton. The cryptofauna was sorted to higher taxonomic levels and their biomass determined. Several highly significant linear relationship were found between skeleton dry weight, volume and cryptofauna biomass. Thus, the determination of colony volume allows the prediction of cryptofauna biomass.
The interstitial space is dominated by sponges - many of them borers - which erode the corallites close to the living tissue until they break off from the colony. At the deeper sampling site, 26% of all colonies are smaller than 2 cm and 48% are smaller than 5 cm. The fragmentation process is discussed with respect to reproduction. 相似文献
706.
Abstract. A shallow water fish community in the inner Oslofjord, Norway, was sampled with a beach seine at 4h intervals over two 36 h periods (25-26th May and 28-29th September, 1982). Night length varied from 1 h in May to 11 h in September. Differences in the community composition were observed between May and September. The diversity of the fish community changed between the two months although the interpretation of the change was dependent on the method used to analyse the community. The three dominant species ( Gasterosteus aculeatus, Sprattus sprattus , and Ammodytes tobianus ) showed diel variations in catch rate which were out of phase with each other. The percentage overlap in abundance of the dominant species was low. The summation of the individual periodicities resulted in aperiodicity at the community level. There were fluctuations, over a diel cycle, in all the community parameters (number of individuals, number of species, species diversity [H'J, species richness [D] and evenness [J']) which affect measures of resource partitioning in fish communities and which should therefore be considered in ecological studies. Diel fluctuations in abundance of some individual shallow water species varied between seasons causing problems in population estimates. 相似文献
707.
本文主要阐述了利用Excel2003和CGIS结合计算村庄压煤储量的简便方法。这种方法较之以前原始的计算村庄压煤的方法很简便,节省了时间和人力、财力,可以说是十分行之有效的方法。 相似文献
708.
709.
利用江苏和山东地区70个农田和非农田表土样品研究不同土地类型的花粉特征,为使用孢粉作为研究手段分析古代农业提供重要参考资料。结果表明所有植被类型的花粉谱均以草本花粉为主,但是含量明显不同,表现为农田>荒地>林地。其中禾本科谷物类型含量的变化最大,农田最高达41%,荒地高于11%,林地低于8%。谷物类禾本科花粉传播距离很短,其百分含量在10~20m内急剧衰减至27.6%,500m以外降低至20%以下;十字花科花粉也有相似的变化规律。藜科花粉对农田和荒地具有同等指示意义,可能与人类活动强度与方式有关。中华卷柏含量增加表明人类活动加强。油菜、水稻、小麦和玉米等谷物类花粉产量或者在土壤中保存存在差异:十字花科>玉米型禾本科>水稻型禾本科>小麦型禾本科。降趋势对应分析(DCA)结果表明,通过花粉相对百分含量,可以较好地区分水田、麦田和非农田,但油稻田与麦稻田、荒地与林地难以区分。 相似文献
710.
JACQUELYN CHASE 《Geographical review》2008,98(4):476-495
ABSTRACT. This study examines the role of service workers in creating a secure landscape in a zone of gated communities near Belo Horizonte, Brazil. Most research on gated communities emphasizes their segregation and formal security apparatuses. In fact, gated communities interact with surrounding rural settlements because they draw their service employees from them. Security emerges from informal relationships of trust that property owners establish with service workers. Gardeners, especially, enable homeowners to project their property investment to others through landscaping. Equally of importance, a manicured garden conveys the message that a home is receiving daily attention—and is secure—even if the owner is not present. The study probes this interdependence from the point of view of gardeners in the context of one gated community in an area south of Belo Horizonte and the attempts by members of its homeowners association to minimize the sense of fear they associate with the Brazilian city. 相似文献