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排序方式: 共有1004条查询结果,搜索用时 46 毫秒
1.
We report on a year's study of spatial and seasonal patterns of zooplankton abundance in Port Phillip and Westernport Bays, July 1982 to August 1983. These two bays, closely adjacent on the southern coast of Victoria, Australia, differ in several respects: Port Phillip is a nearly landlocked bay with a broad basin, while Westernport is an open tidal embayment with extensive mud and seagrass banks. Both bays have a resident zooplankton fauna distinct from that of Bass Strait. Although these resident communities have many species in common, patterns of abundance and dominance are quite different. We found that the holoplankton of Port Phillip was about half copepods, mostly Paracalanus indicus, with 23% Caldocera and 21% larvaceans. Westernport Bay zooplankton was dominated by Acartia tranteri, with no resident cladoceran fauna. Bass Strait species were more often found in Westernport than in Port Phillip Bay, but the resident community of Port Phillip Bay was more similar to that of Bass Strait than to that of Westernport.Although this study was undertaken in an exceptionally dry year, the available historical data show that the overall patterns found in 1982–1983 are typical for these bays. The differences in community composition probably relate to differences in depth profile, predator abundance, and suspended matter between the bays.  相似文献   
2.
The benthic faunal spectrum including bacteria, protozoans, meiofauna, wrack epifauna and macrofauna, was quantitatively surveyed on two modally reflective, moderate energy, Western Australian beaches. The more exposed beach had coarser sand, no intertidal macrofauna and a poor interstitial fauna. The less exposed beach had a large deposit of wrack totalling 161 kg m?1 dry mass concentrated on the lower shore. The amphipod Allorchestes compressa was abundant in the fresh wrack comprising most of the macrofauna. There were also fairly abundant small epifauna on the wrack. Dry biomass of macrofauna, epifauna, meiofauna, protozoans and bacteria was 0, 0, 15, 4 and 180 g m?1 on the more exposed beach and 160, 3, 112, 9 and 901 g m?1 on the less exposed beach with wrack. On the latter beach there was an inverse correlation between meiofaunal densities and the densities of protozoans and bacteria, suggesting grazing by the former on the latter. On both beaches meiofauna was concentrated in the mid- to upper beach, protozoans near the surface and bacteria in the mid- to lower beach. It is estimated that bacteria are responsible for most of the secondary production on both beaches.  相似文献   
3.
应用车贝雪夫多项式分析过渡季节(6—7月)澳大利亚冷高压与赤道辐合带的关系,得出了对赤道辐合带北移的主要形势以及过程演变特征,最后用合成方法得到它的演变概念模式,为赤道辐合带的北移影响西太平洋及南海地区提供了中期预报的依据。  相似文献   
4.
ABSTRACT. The conceptualization of alien invasive species conflates two axes of variability that have become unhelpfully blurred. The nativeness/alienness axis refers to the presumed belonging of a species in ecological or social space. Invasiveness refers to the behavior of the species in question, particularly in relation to other species. The overlay of nation introduces further variability. Teasing these axes apart is important for more effective environmental management. We examine these concepts using two influential forms of ecological knowledge: the biogeographical and ecological literature and the vernacular experiences of suburban backyarders. Three case studies, the invasive native Pittosporum undulatum and two invasive exotics, Lantana camara and Cinnamomum camphora, illustrate the complex and contingent nature of human interactions with such species and the potential for human interactions to increase and/or reduce the propagation of plant species.  相似文献   
5.
秦思婷  田广  吕良冀  杨莎莎 《地质通报》2015,34(6):1065-1076
澳大利亚世纪(Century)铅锌矿床赋存于中元古代劳恩希尔组页岩和粉砂岩中。矿化主要为细粒闪锌矿,其次为方铅矿和黄铁矿。大部分硫化物(80%~90%)在黑色页岩单元中以易碎的交代层状出现,被富菱铁矿粉砂岩层隔开。矿化具有2个大尺度的变化趋势,在白蚁圈断层由北东至南西,Zn品位显著降低,由南东至北西,Zn品位略有降低。层状闪锌矿主要有2种结构,多孔闪锌矿的焦沥青含量较高,无孔闪锌矿焦沥青含量较低。S同位素研究显示,整个成矿流体系统是一个封闭的储层,重S在变形与成矿事件中进一步富集。世纪矿床由变形作用驱使流体迁移到异常高压(压实作用下的)页岩层位时,页岩容矿的矿化作用形成。较热的富含金属的流体和较深盆地的卤水,使得有机质迅速成熟,最终导致硫酸盐的还原和贱金属的沉淀。  相似文献   
6.
Changes in Global Monsoon Circulations Since 1950   总被引:6,自引:0,他引:6  
Chase  T. N.  Knaff  J. A.  Pielke  R. A.  Kalnay  E. 《Natural Hazards》2003,29(2):229-254
We examined changes in several independent intensity indices of four majortropical monsoonal circulations for the period 1950–1998. Theseintensity indices included observed land surface precipitation andobserved ocean surface pressure in the monsoon regions aswell as upper-level divergence calculated at severalstandard levels from the NCAR/NCEP reanalysis. These values wereaveraged seasonally over appropriate regions of southeastern Asian, western Africa, eastern Africa and the Australia/Maritime continent and adjacent ocean areas. Asa consistency check we also examined two secondary indices: mean sea level pressure trends and low level convergence both from theNCEP reanalysis.We find that in each of the four regions examined, a consistentpicture emerges indicating significantly diminished monsoonalcirculations over the period of record, evidence of diminished spatialmaxima in the global hydrological cycle since 1950. Trends since 1979,the period of strongest reported surface warming, do not indicate any change inmonsoon circulations. When strong ENSO years are removed from each of the time series the trends still show a general, significant reduction of monsoon intensity indicating that ENSO variability is not the direct cause for the observed weakening.Most previously reported model simulations of theeffects of rising CO2 show an increase in monsoonal activity withrising global surface temperature. We find no support in these datafor an increasing hydrological cycle or increasing extremes as hypothesized bygreenhouse warming scenarios.  相似文献   
7.
Several years (7) after incidental lithification by added gypsum, the effect of crushing and phyto-organics on some physical properties of red mud wastes (RMW) was examined under laboratory conditions. It was hypothesized that mechanically breaking up the hardened masses would increase their permeability. However, on the contrary, crushing these rock-hard masses into <2-mm particles did not increase permeability. A phyto-organic treatment on the other hand greatly improved permeability of the crushed entities such that infiltration rates increased from 0 to 10 cm/h. After 24 weeks of incubation, the structure of the newly formed phyto-organically treated gypsum-hardened RMW aggregates was also substantially improved over that of the controls, as a >3-fold increase in resistance to disintegration during wet sieving was exhibited by the phyto-organically treated samples. The increase in water infiltration by combining crushing with phyto-organic applications was ascribed to a decrease in particle dispersion, creating more stable clay clusters, which in turn stabilized channels and pores. Conversely, it was concluded that the singular crushing of gypsum-hardened bauxite waste in the waste dumps is potentially wasteful and ineffective.  相似文献   
8.
Stakeholder consultation is being adopted as standard practice in the planning and management of natural resource management programs. While the utility of stakeholder participation has been investigated for the evaluation and implementation phases of natural resource management programs, few studies have examined the utility of stakeholder consultation during the initial phases of developing such programs. This paper presents a case study from a project developing a marine and coastal monitoring program for the Pilbara and Kimberley region of northern Western Australia. Via a series of workshops held in the region, stakeholders were asked to prioritise future research needs using several voting procedures. During the analyses of the results from the different voting procedures, it became apparent that there were high levels of inconsistency, poor correlation, and contradiction, between participants’ responses. Despite the rigour of the selection process used to identify ‘suitable’ stakeholders for the workshops, these results show that stakeholders did not have the technical or broader contextual knowledge about marine ecosystems to effectively and objectively contribute to the research prioritisation and planning process. Based on the outcomes of this study, we argue that project designers need to be clear about why they are involving stakeholders in a project, particularly in light of the costs involved (financial, time, resources, costs to the stakeholder) in stakeholder consultation. Stakeholder involvement may be appropriate in later stages of developing natural resource management programs (implementation and management), however, stakeholder involvement is not appropriate in the initial phases of such programs, where scientific expertise is essential in formulating scientific concepts and frameworks.  相似文献   
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