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101.
This study was undertaken at Horqin Sand Land, Inner Mongolia, Northern China. Field samples of biological soil crusts (BSCs) and underlying topsoil (0–5 cm under BSC) were taken in areas of different dune stabilization stages, and their physicochemical properties were analyzed, including particle size distribution, bulk density, organic matter, nitrogen, phosphorus, electrical conductivity (EC), pH, and CaCO3 content. The results revealed that semi-mobile dunes, semi-fixed dunes and fixed dunes had developed a physical crust, algae crust and moss crust, respectively. The thickness, hardness, water content, fine fraction and nutrient contents of BSCs were gradually increasing along the dune stabilization gradient. Meanwhile, BSC establishment and development enhanced the bulk density, silt and clay content, and nutrients of the topsoil under it, in an increasing tend from semi-mobile dune to fixed dune. Organic matter concentrations and other nutrients in the 0–5 cm topsoil layer under BSCs were significantly higher compared to unconsolidated soil (control). Moreover, there were strong significant positive correlations between topsoil and BSCs’ organic matter, total nitrogen, available nitrogen, available phosphorus, CaCO3, and <0.05 mm particle content, suggesting that BSCs have an influence on some of the properties of the underlying topsoil.  相似文献   
102.
报道杜氏鰤(Seriola dumerili)人工苗养殖生物学特性及养殖技术研究结果。在海区水温6-30.5℃。海水盐度14.33,溶解氧6.5-7.3mg/L,pH7.5-8.1,水流为15-35cm/s的网箱中,杜氏鰤人工苗叉长40-50mm,体质量1.5-1.7g,经208d养殖,叉长达到330-388mm,体质量达到950-1400g,饲料系数为11,成活率为71.7%;养殖720d,体质量达4.5-6.5k,饲料系数为8;养殖l080d,体质量达7.5-11.5kg,饲料系数为7;养殖l440d,体质量达13.,15.5k异,饲料系数为6;养殖l800d,体质量达15.5-18.5kg,饲料系数为5。第4年性腺发育成熟,4-5月份,海上网箱人工催产,平均每尾雌鱼可产卵1.8kg左右。  相似文献   
103.
Some organisms represent useful Biological Sea‐Level Indicators (Bio SLI) thanks to their constant position relative to sea level and allow the reconstruction of past sea level changes. The sessile gastropods Vermetidae are among the most used indicators, since their shells often resist time averaging and can be easily dated with 14C. However, all these vermetids have a level of precision (± 0.5–1 m), obtained from data on the Mediterranean Dendropoma petraeum (Monterosato, 1884). We found a certain degree of plasticity in this species; it can also live subtidally, not in correspondence with the main sea level, where it feeds adopting a mixed feeding strategy. Considering this variability and the almost complete lack of knowledge for other Bio SLI vermetids, it appears clear that a common value of precision cannot be maintained and the precision of other vermetid species remains to be tested.  相似文献   
104.
The pleated ascidian Styela plicata (Lesueur, 1823) is a solitary species commonly found in ports and marinas around the world. It has been recorded in the Mediterranean region since the mid‐19th century. In the present work, the species’ genetic diversity was analysed, employing a 613‐bp portion of the mitochondrial cytochrome c oxidase subunit I (COI) gene from 149 individuals collected in 14 ports along Italian coasts at spatial scales ranging from 1 to approximately 2200 km. Haplotype and nucleotide diversity values were = 0–0.933 (total = 0.789) and π = 0–0.145 (total π = 0.0094), respectively. A general southward trend of increasing within‐population genetic diversity was observed. Analysis of molecular variance revealed significant genetic structuring but no significant differences were detected among basins, and no isolation by distance was found. Our data were integrated with the COI sequences available from previous studies and re‐analysed in order to investigate the possible routes of introduction of this ascidian into the Mediterranean Sea. The presence of the two COI haplogroups detected in previous molecular investigations on S. plicata at intercontinental spatial scale was confirmed in the Mediterranean Sea. The results revealed multiple introductions of S. plicata, although some locations appear to have experienced rapid expansion from few founding individuals with reduced genetic diversity. However, continuous introductions would confound the pattern deriving from single founder events and make it difficult to estimate the time needed for gene diffusion into established populations. This mixing of effects creates difficulties in understanding the past and current dynamics of this introduction, and managing this alien invasive ascidian whose genetic structure is continuously shuffled by vessel‐mediated transport.  相似文献   
105.
随着察尔汗盐湖资源开发活动强度的不断增加,各种人工设施和水利工程数量日渐增加,对生态环境的影响也逐步明显,因此本研究对盐湖区生态多样性和生态景观格局的变化趋势开展系统调查。主要通过梳理文献和对察尔汗盐湖周边的重点补给河流格尔木河的干支流及附属人工防洪堤水库水体开展生物多样性调查与评估,查明生物种类、分布、数量,评估盐湖区生物多样性现状,并从保护生物多样性的角度为盐湖区生态环境保护提供建议。  相似文献   
106.
The European Water Framework Directive requires that member states assess all their surface waters based on a number of biological elements, including macroinvertebrates. Since 1989, the Flemish Environment Agency has been using the Belgian Biotic Index for assessing river water quality based on macroinvertebrates. Throughout the years, the Belgian Biotic Index has proven to be a reliable and robust method providing a good indication of general degradation of river water and habitat quality. Since the Belgian Biotic Index does not meet all the requirements of the Water Framework Directive, a new index, the Multimetric Macroinvertebrate Index Flanders (MMIF) for evaluating rivers and lakes was developed and tested. This index was developed in order to provide a general assessment of ecological deterioration caused by any kind of stressor, such as water pollution and habitat quality degradation. The MMIF is based on macroinvertebrate samples that are taken using the same sampling and identification procedure as the Belgian Biotic Index. The index calculation is a type-specific multimetric system based on five equally weighted metrics, which are taxa richness, number of Ephemeroptera, Plecoptera and Trichoptera taxa, number of other sensitive taxa, the Shannon-Wiener diversity index and the mean tolerance score. The final index value is expressed as an Ecological Quality Ratio ranging from zero for very bad ecological quality to one for very good ecological quality. The MMIF correlates positively with dissolved oxygen and negatively with Kjeldahl nitrogen, total nitrogen, ammonium, nitrite, total phosphorous, orthophosphate and biochemical and chemical oxygen demand. This new index is now being used by the Flemish Environment Agency as a standard method to report about the status of macroinvertebrates in rivers and lakes in Flanders within the context of the European Water Framework Directive.  相似文献   
107.
川东地区下三叠统嘉陵江组储层沥青的油源   总被引:1,自引:0,他引:1  
用色谱-质谱分析方法鉴定出川东地区下三叠统嘉陵江组储层沥青饱和烃和芳烃馏分中的生物标志物,研究了生物标志物特征及热演化特征,其中以藿烷系列和规则甾烷系列丰度高为最主要特征。上二叠统长兴组和龙潭组烃源岩与该储层沥青具有相似的生物标志物指纹特征及热演化特征,普遍存在γ-胡萝卜烷、β-胡萝卜烷和伽马蜡烷,因此认为它们是该储层沥青的主要烃源岩。  相似文献   
108.
倪春华  包建平 《江苏地质》2008,32(3):161-164
渤中地区普遍存在油气多期运聚成藏。BZ26—2—1井馆陶组原油样品的地球化学分析表明,该原油具有降解和未降解的双重特征:①正构烷烃系列分布完整,且丰度高;②GC/MS分析检出相当丰富的25.降藿烷系列,且绝对浓度较高。这一现象表明馆陶组原油至少存在两期充注过程。  相似文献   
109.
110.
This article discusses the ways in which community protocols might challenge the dominant discourses that guide environmental law and policy at the local, national and international levels and makes suggestions about the conditions that need to be fulfilled if such a challenge is to be effective. Community protocols have attracted the attention of many scholars as they are recognised in the Convention on Biological Diversity’s Nagoya Protocol. They are argued to hold the potential to achieve fair and equitable benefit-sharing by allowing local community voices to express their customary law, worldviews, and ideas of benefit and development among other things. While much of the existing literature discusses community protocols as legal tools, they are also tools that may challenge the dominant discourses argued to guide environmental law and policy. The article takes up this question on the basis of findings from five original case studies. It is argued that community protocols may challenge dominant discourses by: facilitating and articulating the recognition of local communities and indigenous peoples; providing a source for understanding their worldviews; and by empowering them in the long term. In order to achieve these outcomes, community protocol must be understood as processes and pay attention to legal and political contexts, how communities organise, the role of supporting actors, and the articulation of benefits.  相似文献   
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