福建省富营养化水库沉积物磷形态及对水体的贡献   总被引：1，自引：1，他引：1       下载免费PDF全文

苏玉萍  郑达贤  林婉珍  薛丽群 《湖泊科学》2005,17(4):311-316

2003年7月至2004年4月，每季度对武汉市南湖大型底栖动物进行定量和定性的采样分析，共发现大型底栖动 物30种；优势种为霍甫水丝蚓和刺铗长足摇蚊，均呈聚集分布；大型底栖动物的年均密度和生物量分别为4437 ind/m~2和 17．79 g/m~2，其密度和生物量春季最高，Shannon-Wiener 多样性指数和 Margalef 多样性指数的年均值分别为1．515和 1．123．比较分析了南湖大型底栖动物组成的历史变化，对水环境进行了生物学评价，并提出了南湖大型底栖动物合理利 用的建议．  相似文献   

Depth-related distribution of bacterial community in sediments of eutrophic Guanting reservoir   总被引：1，自引：0，他引：1  

QU Jianhang  YUAN Hongli  HUANG Huaizeng  WANG Entao 《中国科学D辑(英文版)》2005,48(Z2)

In this study, DNAs were extracted from sediment samples at depths of 5, 35, and 69 cm from eutrophic Guanting reservoir, China. 16S rDNAs were amplified by PCR and clone libraries were constructed. The depth-related distribution of bacterial community in the sediment was characterized by using amplified 16S rDNA restriction analysis (ARDRA) and sequencing of the dominant clones. The results indicated that species diversity in the sediment of Guanting reservoir was rather high with the Shannon-Wiener index about 5.8. Bacterial richness varied in different depths: the highest in the sample of 35 cm in depth; followed by the sample of 5 cm in depth; and the lowest bacterial richness in the sample of 69 cm. Dominant species from the three samples were different although there were some common clones. PhyIogenetic analysis showed that all of the dominant clones in the three layers were uncultured bacteria and distantly related to the previously reported species in beta or gamma subclass of proteobacteria, including bacterial groups that have the ability to degrade aromatic hydrocarbons, n-all:anes, chlorinated organic compounds, or to accumulate polyphosphate, etc. Changes of deptt-related bacterial community in the Guanting reservoir sediment might reflect the pollution history and the water quality of the reservoir. In addition, the cloned sequences from the Guanting reservoir sediment were all different from the presently reported ones, indicating that there were some particular bacteria in that environment.  相似文献   

新疆塔里木河下游物种多样性变化与地下水位的关系   总被引：21，自引：0，他引：21  

陈亚宁  张宏锋  李卫红  陈亚鹏 《地球科学进展》2005,20(2):158-165

根据塔里木河下游9个断面40眼地下水位观测井和8个植物样地野外采集的数据，运用物种多样性指数对塔里木河下游物种多样性与地下水位变化进行了分析计算。研究表明，塔里木河下游物种多样性与地下水位变化有着密切的关系，地下水位对物种多样性的变化起着主导作用。塔里木河下游浅层地下水位埋深较大，并且表现为由上游段至下游段逐渐加深这样一个明显的递减变化。塔里木河下游物种多样性指数较低，Shannon Weiner指数和Simpon指数分别变化在1.93~0.53之间和0.82~0.35之间；随着由上游段至下游段地下水位埋深的加大，塔里木河下游植物种类减少、群落结构简单、物种多样性指数和丰富度指数呈明显降低的态势。反映了干旱区水分胁迫对生态系统的强烈影响。  相似文献   

Unique recovery stage of reef communities after F/F event in a huge coral reef of Carboniferous, Southern Guizhou,China   总被引：7，自引：0，他引：7  

GONG Enpu  YANG Hongying  GUAN Changqing  SUN Baoliang & YAO Yuzeng Department of Geology  Northeastern University  Shenyang  China 《中国科学D辑(英文版)》2004,47(5)

Carboniferous is a global recession period of reef-building. There were fewer reefs at that times due to massive extinction and the great glacial catastrophe in the southern hemisphere in Frasnian/Famennian[1]. So far, however, most of the researches concerning Carboniferous reefs have been limited, which leads to insufficient knowledge regarding the composition, structure, ecological characteristics of reef-building communities, the reef growth models, etc. Interna-tional studies conducted o…  相似文献   

三江平原湿地毛果苔草群落的演替特征   总被引：15，自引：6，他引：15  

汲玉河  吕宪国  杨青  赵魁义 《湿地科学》2004,2(2):139-144

为了说明三江平原湿地植物物种多样性近30年的演替特征，选择三江平原湿地中分布最广泛的毛果苔草群落为研究对象，进行了广泛的野外样方调查。研究发现毛果苔草群落的物种丰富度呈明显减少趋势。毛果苔草的平均高度减少了约为18cm。Drude多度级几乎降低了一个级别。物种构成发生了重大改变，物种重要值≥0．3的一些优势物种的重要性降低，物种重要值≥0．2的物种数目明显减少。群落演替处于快速衰落阶段，退化迹象十分明显。而水量的减少是导致毛果苔草群落快速退化的主要的因素。  相似文献   

Economic Revitalization: Cases and Strategies for City and Suburb     

《The Professional geographer》2004,56(3):442-443

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TENDING CULTURAL LANDSCAPES AND FOOD CITIZENSHIP IN TORONTO'S COMMUNITY GARDENS*     

LAUREN E. BAKER 《Geographical review》2004,94(3):305-325

ABSTRACT. Scattered throughout the city of Toronto are more than no community gardens, sites of place‐based politics connected to the community food‐security movement. The gardens, spaces where passions for plants and food are shared, reflect the city's shifting cultural landscape and represent an everyday activity that is imbued with multiple meanings. Toronto's community food‐security movement uses gardens as one strategy to regenerate the local food system and provide access to healthy, affordable food. Three garden case studies expand on the complexities of “food citizenship,” illustrating the importance of that concept to notions of food security. The gardens reveal the role gardeners play in transforming urban spaces, the complex network of organizations working cooperatively and in partnership to implement these projects, and the way in which social and cultural pluralism are shaping the urban landscape.  相似文献   

THE POLITICAL ECONOMY OF FOREST POLICY IN MEXICO AND CHILE     

Eduardo Silva 《Singapore journal of tropical geography》2004,25(3):261-280

Widespread agreement exists on the broad outlines of the concept of sustainable development for developing countries. This calls for a development model capable of meeting basic needs without depleting natural resources at a rate that robs future generations of their use. In this regard, citizen participation is also considered key to legitimise such policy choices. However, there is considerable disagreement over the substance and meaning of the major components of the concept and the relationship between them. This paper argues that positions in policy disputes over the sustainable development of the forest cluster in two distinct approaches: market‐friendly initiatives and grassroots development. Since market economies prevail almost everywhere, the question that is posed concerns the conditions under which the grassroots development approach is included as a significant complement to market‐friendly initiatives. This is a political question, requiring an examination of actors, interests and power resources. The paper thus applies a political economy framework to a paired comparison of Mexico, where grassroots development approaches (community forestry) had notable successes, and Chile, where market‐friendly forest policy crowded out alternatives.  相似文献   

Geochemistry of Peruvian near-surface sediments   总被引：6，自引：0，他引：6  

Philipp Böning  Michael E. Böttcher  Cornelia Kriete  Sven Lars Borchers 《Geochimica et cosmochimica acta》2004,68(21):4429-4451

Sixteen short sediment cores were recovered from the upper edge (UEO), within (WO) and below (BO) the oxygen minimum zone (OMZ) off Peru during cruise 147 of R/V Sonne. Solids were analyzed for major/trace elements, total organic carbon, total inorganic carbon, total sulfur, the stable sulfur isotope composition (δ³⁴S) of pyrite, and sulfate reduction rates (SRR). Pore waters were analyzed for dissolved sulfate/sulfide and δ³⁴S of sulfate. In all cores highest SRR were observed in the top 5 cm where pore water sulfate concentrations varied little due to resupply of sulfate by sulfide oxidation and/or diffusion of sulfate from bottom water. δ³⁴S of dissolved sulfate showed only minor downcore increases. Strong ³²S enrichments in sedimentary pyrite (to −48‰ vs. V-CDT) are due to processes in the oxidative part of the sulfur cycle in addition to sulfate reduction. Manganese and Co are significantly depleted in Peruvian upwelling sediments most likely due to mobilization from particles settling through the OMZ, whereas release of both elements from reducing sediments only seems to occur in near-coastal sites. Cadmium, Mo and Re are exceptionally enriched in WO sediments (<600 m water depth). High Re and moderate Cd and Mo enrichments are seen in BO sediments (>600 m water depth). Re/Mo ratios indicate anoxic and suboxic conditions for WO and BO sediments, respectively. Cadmium and Mo downcore profiles suggest considerable contribution to UEO/WO sediments by a biodetrital phase, whereas Re presumably accumulates via diffusion across the sediment-water interface to precipitation depth. Uranium is distinctly enriched in WO sediments (due to sulfidic conditions) and in some BO sediments (due to phosphorites). Silver transfer to suboxic BO sediments is likely governed by diatomaceous matter input, whereas in anoxic WO sediments Ag is presumably trapped due to sulfide precipitation. Cadmium, Cu, Zn, Ni, Cr, Ag, and T1 predominantly accumulate via biogenic pre-concentration in plankton remains. Rhenium, Sb, As, V, U and Mo are enriched in accordance with seawater TE availability. Lead and Bi enrichment in UEO surface sediments is likely contributed by anthropogenic activity (mining). Accumulation rates of TOC, Cd, Mo, U, and V from Peruvian and Namibian sediments exceed those from the Oman Margin and Gulf of California due to enhanced preservation off Peru and Namibia.  相似文献   

Vessel biofouling as an inadvertent vector of benthic invertebrates occurring in Brazil     

Farrapeira CM  Tenório Dde O  Amaral FD 《Marine pollution bulletin》2011,62(4):832-839

This article reviews the literature involving benthic invertebrates that are cited in association with hull fouling, reporting the species that occur on the Brazilian coast and evaluating the importance of this vector for the introduction of nonindigenous and cryptogenic invertebrates in Brazil. It discusses some of the strategies that were used by the species that allowed for their overseas transport and made it easier to cross natural barriers that otherwise would have been obstacles to their dispersion. The compiled data list 343 species (65% nonindigenous and 35% cryptogenic), mainly from the northwestern Atlantic Ocean. The traveling fauna, composed mostly of cosmopolitan species (70.3%), is primarily euryhaline and marine stenohaline, with sessile and sedentary habits. After delineating the shipborne species’ ecological profiles and traveling strategies and evaluating their overlapping vectors, we concluded that hull vessels were the main vector of introduction to the Brazilian coast for 89.8% of the compiled species.  相似文献