A battle on two fronts: competitive urges 'inside' Atlanta     

Drew Whitelegg 《Area》2002,34(2):128-138

This paper argues that intra –regional competition is as important as intra –regional in the shaping of an urban region. Recent concentration on urban promotion within the discipline places an emphasis on competition between cities that should be counterbalanced by stressing the degree of competition between cities and their suburban peripheries. Using the case of Atlanta, Georgia, and in particular its Vision 2020 initiative, the paper explores how regionalist approaches can easily unravel due to continued rivalries from individual constituents. Placing its theoretical grounding within David Harvey's notion of 'structural coherence', the paper argues that regional policies within a capitalist environment of uneven development tend towards only temporary solutions.  相似文献   

Interspecies competition for nutrients between Prorocentrum donghaiense Lu and Skeletonema costatum (Grev.) Cleve in mesocosm experiments   总被引：1，自引：1，他引：0  

ZHU Mingyuan  XU Zongjun  LI Ruixiang  WANG Zongling  SHI Xiaoyong 《海洋学报(英文版)》2009,28(1):72-82

Three mesocosm experiments were conducted in the East China Sea during blooms of Prorocentrum donghaiense Lu in May of 1998, 2002 and 2003 to examine the role of nutrients in the formation of these harmful algae blooms (HABs). The results showed that there was interspecies competition between P. donghaiense and Skeletonema costatum (Grev.) Cleve. The cell number of P. donghaiense and S. costatum accounted for about 85% and 11% of the total cell number of phytoplankton respectively at the beginning of the experiment in May 1998. In May 2002, at the beginning of the experiment, the cell number of P. donghaiense accounted for 55%—66% of the total and S. costatum accounted for 32%—42%. The density of P. donghaiense and S. costatum was over 95% and 1%—5% respectively in May 2003. The results of these three mesocosm experiments showed that the dominant species in this specific community varied with different nutrient availability. Under lowphosphate conditions, the dominant species was P. donghaiense, while S. costatum became dominant in phosphatereplete cases. The average growth rate (1.08 d-1) of S. costatum in exponential growth phase was higher than that (0.39 d-1) of P. donghaiense. In the mesocosm, S. costatum predominated in the mesocosm by its rapid growth. When phosphorus was depleted, the cell number of S. costatum dropped rapidly, while P. donghaiense Lu decreased more slowly. The results from mesocosm experiment may explain why: (1) P. donghaiense bloom usually occurs in May, when phosphate concentration is low; (2) the bloom of S. costatum appears in early spring and summer time, when nutrients increase with increasing Changjiang River (Yangtze River) runoff; (3) the bloom of S. costatum is short and that of P. donghaiense Lu can last more than a month in the East China Sea.  相似文献   

新经济地理学与传统经济地理学之比较研究   总被引：1，自引：0，他引：1  

刘安国  杨开忠  谢燮 《地球科学进展》2005,20(10):1059-1066

自20世纪90年代以来，藤田、克鲁格曼、维纳布斯等以迪克西特和斯蒂格利茨垄断竞争模型为基础，用不完全竞争、报酬递增和市场外部性等理念构建新的经济地理模型，掀起了一场“新经济地理学”革命。新经济地理学在理论基础、研究特点和方法等方面与传统经济地理学表现出明显不同，其理论创新受到经济学界和地理学界的普遍关注。但是，也有一些学者对它提出了同样引人注目的抨击。通过对新经济地理学与传统经济地理学进行比较，对一些重大理论假设、研究方法与特点进行简要分析，有助于廓清对新经济地理学与传统经济地理学之异同的正确认识，以期推动新经济地理学的理论研究与应用以及新经济地理学与传统经济地理学领域的学术交流。  相似文献   

Demographic variation in a desert shrub, Larrea tridentate, in response to a thinning treatment     

Richard E. Miller  Laura F. Huenneke 《Journal of Arid Environments》2000,45(4):315

We performed a perturbation experiment to determine the relative importance of intra-specific competition on the demographic performance of a population of creosotebush, Larrea tridentata. From 1992 to 1995, we followed 1000 individuals, half of which were in plots subjected to a thinning treatment, and the other half were in unmanipulated plots. We found no significant response to the thinning treatment for any of the traits studied. The strict interpretation of these results is that intra-specific competition is not important in this Larrea population.  相似文献   

Effects of fishing power and competitive interactions among vessels on the effort allocation on the trip level of the Dutch beam trawl fleet   总被引：9，自引：7，他引：2  

Rijnsdorp  A. D.; Dol  W.; Hoyer  M.; Pastoors  M. A. 《ICES Journal of Marine Science》2000,57(4):927-937

  相似文献   

中国沿海集装箱港口体系的形成演化机理   总被引：30，自引：5，他引：25  

曹有挥  曹卫东  金世胜  李海建  王黎明 《地理学报》2003,58(3):424-432

立足当今中国的现实,从现代经济学观点与港口地理学原理相结合的新视角,对沿海集装箱港口体系的形成演化机理进行理论探索,揭示出竞争与合作机制的交互作用是推动沿海集装箱港口体系形成演化的内在动力,并归纳演绎了由低级均衡→非均衡相对集中→非均衡高度集中→高级均衡的沿海集装箱港口体系的一般演化模式。实证分析表明,中国沿海集装箱港口体系正处于由非均衡相对集中向非均衡高度集中阶段演化的过渡时期,其动力机制主要有：转型经济的促进作用、政府行为的调控作用和中心枢纽港的极化作用。  相似文献   

盐度与种间竞争对漂浮生态型浒苔微繁体萌发和生长的影响     

赵瑾  马莹莹  解威峰  吴春辉  姜鹏 《海洋与湖沼》2018,49(5):991-998

黄海绿潮源自苏北浅滩,暴发后期浒苔向北漂移至山东半岛南岸,会集中释放大量微繁体。虽然构成严重的繁殖体压力,但尚未发生大面积定生。为了明确漂浮生态型浒苔北侵定居的关键限制因素,本研究于2015年7月漂浮浒苔在青岛沿海大量堆积期间,采集潮间带表层沉积物样本,分别在盐度25和32下进行培养,试验不同盐度对漂浮生态型浒苔微繁体萌发和幼苗生长的影响。进一步通过单藻种培养,分析漂浮生态型与定生浒苔群体、以及青岛定生近缘种缘管浒苔对盐度的适应性差异。结果表明,盐度对微繁体萌发与幼苗生长两个阶段均构成重要影响,但具有不同的影响方式。在萌发阶段,单藻培养条件下,盐度对浒苔各群体和缘管浒苔的萌发率均无显著影响,但在混合培养条件下,盐度则通过种间竞争对萌发率产生显著影响,青岛的高盐条件更加有利于当地种,而苏北海域的低盐条件会显著提高漂浮生态型的萌发率。在幼苗的生长阶段,盐度可直接产生影响,高盐条件显著降低浒苔所有群体幼苗的生长率,对缘管浒苔则无显著影响,表现明显的种间差异。上述结果提示,盐度与种间竞争的协同作用可能是限制漂浮生态型浒苔大规模北侵定居的重要因素,这为预测漂浮生态型的扩散范围与黄海绿潮的变异趋势提供了理论依据。  相似文献   

栖息地分布与种内竞争对刺参集群特征的影响     

辛孝科  张立斌  于正林  杨红生 《海洋科学》2018,42(5):138-144

为探究刺参(Apostichopusjaponicus)种内竞争与栖息地对其群体分布的影响,作者通过缩时摄像机拍摄及视频分析,研究了刺参集群分布特征,结果发现:刺参在礁石栖息地的栖息时间显著高于在缸壁处的栖息时间(P 0.05),刺参对栖息地有明显偏好性;刺参在运动时并未聚集在同一栖息地,而离散分布在多处栖息地中(P 0.05);当密度增大到15头/缸(11.31头/m~2, d=1.3 m)时,刺参在栖息地内的平均聚集率和平均聚集时间比例会显著下降(P 0.05),种内竞争加剧,刺参多呈斑块状分布,在密度过高时种内竞争压力上升,刺参个体间选择分散以减少竞争。本研究查明了实验室条件下栖息地分布和种内竞争对刺参集群特征的影响,可为野外刺参增养殖与资源持续利用提供理论参考。  相似文献   

Development of a SCAR marker for male gametophyte of Gracilariopsis lemaneiformis based on AFLP technique   总被引：1，自引：0，他引：1  

周伟  丁弘叶  隋正红  王钟霞  王津果 《中国海洋湖沼学报》2014,32(3):522-526

The red alga Gracilariopsis lemaneiformis （Bory） is an economically valuable macroalgae. As a means to identify the sex of immature Gracilariopsis lemaneiformis, the amplified fragment length polymorphism （AFLP） technique was used to search for possible sex- or phase-related markers in male gametophytes, female gametophytes, and tetrasporophytes, respectively. Seven AFLP selective amplification primers were used in this study. The primer combination E-TG/M-CCA detected a specific band linked to male gametophytes. The DNA fragment was recovered and a 402-bp fragment was sequenced. However, no DNA sequence match was found in public databases. Sequence characterized amplified region （SCAR） primers were designed from the sequence to test the repeatability of the relationship to the sex, using 69 male gametophytes, 139 female gametophytes, and 47 tetrasporophytes. The test results demonstrate a good linkage and repeatability of the SCAR marker to sex. The SCAR primers developed in this study could reduce the time required for sex identification of Gracilariopsis lemaneiformis by four to six months. This can reduce both the time investment and number of specimens required in breeding experiments.  相似文献   

UV-B辐射对强壮前沟藻（Amphidinium carterae）和等鞭金藻（Isochrysis galbana）种间竞争的影响   总被引：1，自引：1，他引：0  

谢志浩  俞泓伶  曹鲁妍 《海洋与湖沼》2011,42(6):857-862

采用共培养的方法,研究了UV-B辐射对不同起始密度强壮前沟藻和等鞭金藻种间竞争的影响。结果表明,在单养时,随着起始密度的增加,2种微藻在生长过程中进入指数生长期和平台期的时间逐渐缩短,所达到的最大种群密度都依次降低。在混养时,当接种比例为A∶I=1∶4和A∶I=1∶1时,等鞭金藻在种间竞争中占有优势;当接种比例为A∶I...  相似文献