Close coupling between ammonium uptake by phytoplankton and excretion by Antarctic krill, Euphausia superba     

M.J. WhitehouseA. Atkinson  A.P. Rees 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(7):725-732

In this study we examined the hypothesis that, under conditions of replete macronutrients and iron in the Southern Ocean, phytoplankton abundance and specific N uptake rates are influenced strongly by the processes of grazing and NH₄ regeneration. NH₄ and NO₃ uptake rates by marine phytoplankton were measured to the northeast and northwest of the island of South Georgia during January-February 1998. Mean specific uptake rate for NO₃ (vNO₃) was 0.0026 h⁻¹ (range 0.0013-0.0065 h⁻¹) and for NH₄ (vNH₄) was 0.0097 h⁻¹ (0.0014-0.0376 h⁻¹). vNH₄ was related positively with NH₄ availability, which ranged from 0.1 to 1.5 mmol m⁻³ within the upper mixed layer. Ambient NH₄ concentrations and vNH₄ were both positively related to local krill biomass values, computed from mean values along acoustic transect segments within 2 km of the uptake measurement stations. These biomass values ranged from ∼1 g krill fresh mass m⁻² in the northwest to >4 kg krill wet mass m⁻² in the northeast. In contrast to the variability found with NH₄ concentrations and uptake rates, vNO₃ was more uniform across the sampling sites. Under these conditions, increasing NH₄ concentration appeared to represent an additional N resource. However, high vNH₄ tended to be found for stations with lower phytoplankton standing stocks, across a total range of 0.24-20 mg chlorophyll a m⁻³. These patterns suggest a coupling between phytoplankton biomass, vNH₄ and krill in this region of variable but high krill biomass. Locally high concentrations of krill in parts of the study area appeared to have two opposing effects. On the one hand they could graze down phytoplankton stocks, but on the other hand, their NH₄ excretion supported enhanced uptake rates by the remaining, ungrazed cells.  相似文献   

不同更新方式对中亚热带森林土壤理化性质的影响     

邓旺灶 《亚热带资源与环境学报》2011,6(3):18-23

森林的不同更新方式对森林土壤理化性质有重要影响．本研究通过野外调查探讨中亚热带山区杉木人工林和米槠人促更新林2种不同更新方式下林地土壤理化性质的变化特征,并用土壤退化指数定量描述土壤质量变化．结果表明：杉木人工林土壤表层（0—10cm）容重显著高于米槠人促更新林（P〈0．05）;随土壤深度的增加,杉木人工林和米槠人促更...  相似文献   

城市更新之研究   总被引：7，自引：2，他引：5  

严若谷  周素红  闫小培 《地理科学进展》2011,30(8):947-955

城市更新是城市发展到一定阶段所必然经历的再开发过程,不同的时代背景和地域环境中的城市更新具有不同的动因机制、开发模式、权力关系,进而产生不同的经济、环境、社会效应。追溯近年来英文文献中大量出现的有关＂urban regeneration＂的研究及中国近30年来城市更新相关文献,总结地理学视角对城市更新的研究范围、研究领域及研究特点,论述与城市更新相关的理论,阐述城市更新的形成机制,分析各地区在不同阶段采用的更新政策,更新模式,更新手段和方法,以及更新参与主体和更新后的效果,对比分析国内外城市更新研究内容及特点。从城市更新同城市建设、经济发展的内在联系机制,城市更新中微观个体的行为研究,可持续发展观下的综合城市更新研究等3个方面,总结对未来中国城市更新发展的可借鉴性启示。  相似文献   

海泡石持久脱除空气中微量甲醛的方法与机理     

梁凯  彭美勋  赵宏伟  罗莹华 《岩石矿物学杂志》2022,41(5):959-964

为克服海泡石吸附甲醛达到饱和后失去吸附功能的缺陷,利用静态吸附实验研究热处理温度对海泡石吸附微量甲醛的影响,并运用扫描电镜、X射线衍射、红外吸收光谱、热重和BET比表面检测等方法研究相关机理。结果表明,硅胶干燥剂的存在明显提高了海泡石对空气中微量甲醛的吸附能力,并能降低甲醛含量至法定安全上限以下,在≤400℃的温度热处理后海泡石仍能保持良好的甲醛吸附性能,但经≥500℃热处理后甲醛吸附性能显著降低。结合表征研究,认为海泡石相的结晶水对甲醛形成化学吸附,而其以沸石孔洞为主的结构微孔有利于物理吸附的甲醛占位,≥450℃的热处理使结晶水不可逆脱出,沸石孔坍塌,从而吸附性能显著降低。该研究表明海泡石的吸附性能可以在低于450℃的温度下热再生,脱出的甲醛也可以通过燃烧消除。间歇性热再生海泡石的吸附性能可持续脱除空气中的微量甲醛。  相似文献   

Cultural industries, information technology and the regeneration of post-industrial urban landscapes. Poblenou in Barcelona - a virtual city?     

C. Gdaniec 《GeoJournal》2000,50(4):379-387

In a former industrial part of Barcelona, as in the de-industrialising neighbourhoods of many big cities, the ‘new’ economy and the ‘cultural’ economy have started to replace the ‘old’ economy, bringing new life into a declining district but also causing conflicts of land use, housing or the preservation of architectural heritage. The latter is an important part of regeneration and marketing policies of city governments, whereby the ‘new’ economy not only emerges from the old but the physical space of the old industrial quarter becomes the tool and setting in which the city can re-present itself and its success story of transformation and regeneration. Through the increasing use of information and communication technologies, which are at the same time driving this transformation - an industry as such as well as business-aid in various sectors, cultural industries in particular - the city has acquired a second, virtual presence. The city exists and ‘lives’ on numerous websites. Those by city government and city organisations often have the express purpose of marketing and presenting the city, while those by (cultural) businesses and other organisations in the district add to the mosaic of the virtual city. As a result, the old industrial space continues to live and be productive, its economic value having changed largely into a cultural value. This coexistence of the real and the virtual, old and new, also meets with a conflict at certain junctures. There is the positive representation of plans and events on the city's websites on the one hand, and the undercurrent of protest and disenchantment among the local population who find themselves marginalised from the profits and success of development, on the other. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Neighbourhood renewal: A toolkit for regeneration     

Angela Hull 《GeoJournal》2000,51(4):301-310

A major criticism of urban regeneration policies during the 1980s and 1990s in England has been the failure to reduce the gap between the poorest neighbourhoods and the national average for the indices of long-term unemployment, crime rates, health chances and educational qualifications. The UK Government, since election in 1997, has undertaken a wide-ranging review of urban policy. New approaches and more effective use of public sector resources are being piloted in an attempt to identify the pathways to social inclusion, which seem to have been missing in previous regeneration attempts (Audit Commission, 1989; DoEE, 2000). This paper seeks to deepen our understanding of the appropriate balance between physical and social regeneration through proposing an approach that foregrounds the role of residents in neighbourhood regeneration.  相似文献   

From community planning to partnership planning. Urban regeneration and shifting power geometries on the South Bank, London     

Guy Baeten 《GeoJournal》2000,51(4):293-300

This paper seeks to explain the persistence of inner-city deprivation in spite of sustained regeneration efforts, through demonstrating how urban regeneration policies are embedded in peculiar political-institutional power dynamics that actually contribute to the further disempowerment of the already disempowered groups in inner cities. The reconstruction of the post-war planning history of one specific urban neighbourhood, the South Bank in central London, will allow to demonstrate how the constantly reworked urban regeneration models comprise specific power relations that have important repercussions for the success and failure of regeneration programmes. The focus here will particularly be on how the fall of the South Bank's prominent era of community-based development in the 1970s is firmly embedded in changing political-institutional frameworks that, after a spell of `community power', were soon to restore the power of the local cultural, political and business elites over the local regeneration agenda.  相似文献   

Mapping post-fire forest regeneration and vegetation recovery using a combination of very high spatial resolution and hyperspectral satellite imagery     

《International Journal of Applied Earth Observation and Geoinformation》2013

Careful evaluation of forest regeneration and vegetation recovery after a fire event provides vital information useful in land management. The use of remotely sensed data is considered to be especially suitable for monitoring ecosystem dynamics after fire. The aim of this work was to map post-fire forest regeneration and vegetation recovery on the Mediterranean island of Thasos by using a combination of very high spatial (VHS) resolution (QuickBird) and hyperspectral (EO-1 Hyperion) imagery and by employing object-based image analysis. More specifically, the work focused on (1) the separation and mapping of three major post-fire classes (forest regeneration, other vegetation recovery, unburned vegetation) existing within the fire perimeter, and (2) the differentiation and mapping of the two main forest regeneration classes, namely, Pinus brutia regeneration, and Pinus nigra regeneration. The data used in this study consisted of satellite images and field observations of homogeneous regenerated and revegetated areas. The methodology followed two main steps: a three-level image segmentation, and, a classification of the segmented images. The process resulted in the separation of classes related to the aforementioned objectives. The overall accuracy assessment revealed very promising results (approximately 83.7% overall accuracy, with a Kappa Index of Agreement of 0.79). The achieved accuracy was 8% higher when compared to the results reported in a previous work in which only the EO-1 Hyperion image was employed in order to map the same classes. Some classification confusions involving the classes of P. brutia regeneration and P. nigra regeneration were observed. This could be attributed to the absence of large and dense homogeneous areas of regenerated pine trees in the study area.  相似文献   

Maturity Control on the Patterns of Hydrocarbon Regeneration from Coal   总被引：2，自引：0，他引：2  

ZOU Yanrong  Guangzhou Institute of Geochemistry  Chinese Academy of Sciences  Guangzhou YANG Qi  LIU Dameng  KANG Xidong  TANG DazhenChina University of Geosciences  Beijing 《《地质学报》英文版》2000,74(2):370-374

Rock-Eval pyrolysis and Py-GC experiments on naturally and artificially matured coal samples were carried out. The results suggest that both depolymerization and defuctionalization exist during the maturation and evolution of coal. The patterns of hydrocarbon regeneration are diverse at different stages of the maturation and evolution. When the vitrinite reflectance (R0) is 0.7%-0.9%, bitumen is the richest in coal while activation energy is the minimum, and the temperature of peak yield is lower than that of primary hydrocarbon generation. However, if reflectance is greater than 0.9%, defunctionalization predominates and the temperature of peak regeneration is shown in lagging compared with the primary hydrocarbon generation. When reflectance is out of the "oil window", the peak temperature of hydrocarbon regeneration and that of the primary hydrocarbon generation seems to be continuous.  相似文献   

人促常绿阔叶次生林凋落物数量、组成及动态   总被引：4，自引：0，他引：4  

吴擢溪 《山地学报》2006,24(2):215-221

对福建省尤溪通过人工促进天然更新形成的常绿阔叶次生林的凋落物数量、组成及季节动态进行研究,结果表明,常绿阔叶次生林年凋落物量为6870kg/hm2,其中落叶量(3964kg/hm2)和落枝量(1621kg/hm2)分别占57.7%和23.6%。米槠、大叶栲、栲树、檫树和南酸枣5个树种年落叶量分别占年总落叶量的41.5%、21.4%、9.0%、6.3%和3.2%。常绿阔叶次生林总凋落量于4月和12月出现峰值,落叶量最大值出现在4月,落枝量在4月、7月和11月出现峰值,落花量主要集中在5月和6月,而落果量则集中在12月。米槠和栲树落叶量最大值分别出现在4月和5月,大叶栲落叶量主要集中在7～9月,檫树和酸枣落叶量最大值分别出现在11月或12月,其他树种落叶量1年中分布则相对较为均匀。  相似文献