FRESHWATER ALGAE COMMUNITY OF A MELTWATER RUNNEL,REEVE HILL, CASEY STATION, ANTARCTICA     

FaradinaMerican WanMaznahWO WanAsmadiWA MashhorMansor 《湿地科学》2007,5(3):243-252

Researches on the Antarctic microalgal diversityand distributions in the freshwater environment ran-ging from snow to large lakes and well-definedstreams are extensive.For instance,studies on thestream microalgal community have been conducted onthe Pervay…  相似文献   

安徽牯牛降的植物多样性垂直分布特征——兼论山顶效应的影响   总被引：5，自引：0，他引：5  

沈泽昊  胡志伟  赵俊  王会 《山地学报》2007,25(2):160-168

牯牛降国家级自然保护区是我国生物多样性热点地区之一——黄山-武夷山区的一部分,人为干扰较轻,植被保存状况良好,是这一生物多样性中心基本特征的代表性区域。牯牛降地区的植物物种多样性和群落的分布特征尚缺少系统的研究报道。对牯牛降南坡的植被垂直带进行样方和样带调查,探讨其植物群落和植物物种多样性的海拔梯度格局,及其影响因素。通过对样方数据的数量分类和CCA排序,结合分析群落生活型构成、物种丰富度、α多样性、β多样性的结果表明:(1)牯牛降南坡随着海拔的上升,依次出现常绿阔叶林(400-1 100 m)、常绿落叶阔叶混交林(1 100-1 350 m)、针阔混交林(1 350-1 600 m)和常绿针叶林(1 600-1 728 m)。(2)物种丰富度和多样性指数大致表现了沿海拔梯度降低的趋势;但低海拔人为活动的干扰、海拔1 400 m处样方小地形的显著变化、海拔1 500-1 600 m之间历史上的火干扰等因素,导致了物种多样性海拔梯度特征的复杂化;常绿阔叶林和常绿落叶针阔叶混交林的种-面积曲线差异反映了不同植被类型中物种分布的尺度效应的差异。(3)海拔梯度、局部地形及其他生境条件的变化共同影响着物种多样性的格局。山地常绿落叶阔叶混交林、针阔叶混交林和黄山松纯林等是发育在同一气候垂直带条件下,主要由地形引起的土壤与小气候差异导致的植被斑块。山顶效应对植物群落类型和物种多样性变化具有显著影响,对于理解牯牛降植物物种多样性垂直梯度特征和模式具有重要意义。  相似文献   

Sedimentary dynamics and ecological state of Nakta tidal flat (littoral), South of Sfax, Gulf of Gabès, Tunisia     

Gargouri-Ben Ayed Z.  Souissi R.  Soussi M.  Abdeljaouad S.  Zouari K. 《中国地球化学学报》2007,26(3)

The tidal flat of Nakta is located in the northern part of the gulf of Gabes and in the southern coast of Sfax. It corresponds to a flat reef protected from less topography, with a slope ranging between 2° and 4°, which borders the Gargour Wadi. The study sector is renowned to have moderate hydrodynamics which lasts almost for two millenary (14C isotopic dating).The sedimentological study of the Nakta tidal flat revealed different facies: fine-grained sand in the intertidal zone and carbonated muddy sand in the infratidal zone.Equilibrium state of the Nakta ecosystem depends entirely on tide currents, which mainly inhibit drift currents. The Nakta tidal flat is characterized by a variety of faunal species (Cerastoderma glaucum, Arca noe, Cardita antiquatus, Chlamys varied, Ruditapes deccussatus, Tapes rhomboids, Pinctada radiate, etc.) and floristic diversities (Halocnemum strobilacum, Halimione portulacoides, Enteromorpha linza, Ulva rigida, Cymodocea nodosa, Posidonia oceanica). The species are abundant in the infratidal zone, while in its intertidal zone, faunal species remain little diversified and are dominated by limivorous diggering.The paleogeographic study of the Nakta tidal flat showed the alternation of regression and transgression periods.  相似文献   

Molluscs in Kongsfjorden (Spitsbergen, Svalbard): a species list and patterns of distribution and diversity     

Maria W&#;odarska-Kowalczuk 《Polar research》2007,26(1):48-63

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Long-term macrozoobenthos changes in a shallow boreal lagoon: Comparison of a recent biodiversity inventory with historical data     

Michael L. Zettler  Darius Daunys 《Limnologica》2007,37(2):170-185

The European water framework directive (WFD) aims at achieving good ecological status of water bodies, which implies assessment of their current ecological quality status in respect to defined reference (pristine) conditions. In this paper, two historical biodiversity datasets (from 1920s and 1950s) and results from the recent inventory are used to trace the long-term changes of the macrozoobenthos in the eutrophic boreal lagoon of the Baltic Sea.In comparison of datasets the highest congruence was obtained for molluscs and malacostracan crustaceans, which also had a similar level of taxonomic emphasis between studies. Considering inconsistencies in methodology and taxonomic determination, only few species extinctions in these groups did likely occur during the last 100 years. Two amphipod species (Gammarus pulex and Gammarus lacustris) were not found during the recent survey, whereas five new species of this taxonomic group occurred in the lagoon since 1950s. The causes of these extinctions remain unclear; however displacement by established new amphipods cannot be excluded. Theodoxus fluviatilis was recently recorded in the very restricted area of the lagoon, while in earlier studies the species was mentioned as common and widely distributed in the water body. On the other hand, 10 gastropod species and 9 bivalves were reported for the first time in the lagoon and most likely have been overlooked in earlier surveys. Approximately 10% of the species have their origin outside the Baltic Sea basin and the number of invasions considerably exceeds the number of likely extinctions. Assessment scheme of such changes is unclear following WFD guidelines, therefore elaboration of a framework for evaluation of the alien species diversity in a context of local biodiversity should attain more effort when implementing the WFD.  相似文献   

International aspects of invasive species management: a research agenda     

Amitrajeet A. Batabyal 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(6):717-727

We propose a research agenda for studying six basic questions about the impacts of alternate international invasive species control mechanisms on economic agents in a nation such as the USA. The six questions are as follows. First, when can one justify a trade ban as an effective regulatory policy? Second, what are the properties of control rules that vary by port of entry and whether a shipment is viewed as a routine or as a first-time entry? Third, when should a port manager in the USA use information about the dollar value of the products being transported by ships from two exporting firms and the expected time it takes to inspect ships from these two firms to grant preferential treatment to one or the other firm? Fourth, what are some reasonable measures of the trade related risk from invasive species? Fifth, how useful is strategic trade policy as an invasive species management tool? Finally, when analyzing a biological invasion, is it more appropriate to focus on the likelihood of this event or, instead, on the magnitude of the event?  相似文献   

Toward better understanding of the status of mercury in the environment in China and its contribution to the global mercury cycle     

《中国地球化学学报》2006,25(B08):237-238

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A proscoliine wasp (Insecta: Hymenoptera: Scoliidae) from Shandong peninsula, East Asia     

Junfeng Zhang   《Cretaceous Research》2006,27(6):788-791

A new species of wasp from the Laiyang Formation in Shandong, China is described and named Cretaproscolia asiatica sp. nov. It is the second record of the genus Cretaproscolia Rasnitsyn and Martínez-Delclòs, 1999, and extends the distribution of the genus from the Lower Cretaceous of South America into the upper Mesozoic of East Asia. The diagnosis of Cretaproscolia is emended based on the new material.  相似文献   

Stakeholders’ perceptions of the impacts of invasive exotic plant species in the Mediterranean region   总被引：1，自引：0，他引：1  

Douglas Bardsley  Gareth Edwards-Jones 《GeoJournal》2006,65(3):199-210

Invasive species pose an increasing environmental problem across the globe, but to date socio-economic perspectives on this problem have been limited. In this study stakeholder perceptions of the impacts of invasive exotic plant species on the islands of Mallorca, Sardinia and Crete are examined through the use of semi-structured interviews, Likert scales and Contingent Valuation. Results showed substantial concerns about the impact of invasive exotic plant species on the islands, particularly on Mallorca where awareness of the issue has increased in recent times due to campaigns to eradicate terrestrial and aquatic invasive plants. Not all perceptions are negative and several respondents suggest that a turnover in local species is an inherent part of the sense of the place in the region. If the management of invasive exotic plant species in the Mediterranean region is to improve then there is a need to raise awareness of the impact of invasive species amongst both the general public and professional stakeholders.  相似文献   

科尔沁沙地植物多样性对生产力的影响及分布格局   总被引：1，自引：3，他引：1  

郭俊理  常学礼  张安定  宋彦华 《干旱区地理》2006,29(4):527-531

采用种丰富度和以Shannon-Wiener指数为计算方法的功能多样性和组成多样性为指标,探讨了植物多样性对科尔沁沙地草场生产力的影响以及其分布格局特征。结果表明,科尔沁沙地植被不同的物种多样性指数对系统生产力的影响以组成多样性最大,功能多样性次之,植物种丰富度最小。在小尺度上,组成多样性只存在一种格局且具有分形结构,其格局对干扰过程反应不明显;功能多样性有多种格局存在,对多种干扰过程反应敏感。从提高沙地草场生产力和增强系统的稳定性角度出发,草场改良的依据应建立在种的引进和引进种所产生的组成多样性上。  相似文献