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Marie-Elodie Perga 《Journal of Paleolimnology》2010,44(2):387-395
Stable isotope analyses on cladoceran subfossil exoskeletons retrieved from sediment cores could allow the reconstruction
of past changes in lake food webs provided the δ13C and δ15N values of the exoskeletons reflect those of the organisms’ whole body. The relationships between the C and N stable isotope
compositions of the exoskeletons and those of the whole body were investigated for two freshwater cladoceran taxa (Bosmina sp. and Daphnia sp.) from modern samples. The C and N stable isotope compositions of the exoskeleton and those of the whole body were strongly
correlated. Exoskeleton δ13C was similar to the whole body δ13C for both taxa. Daphnia exoskeletons were strongly depleted in 15N (−7.9‰) compared to the whole body. Stable isotope analyses were thereafter performed on cladoceran remains from five downcore
samples from Lake Annecy, France. Results showed that Bosmina δ15N values increased by more than 4‰, between the early twentieth and twenty first centuries. Such changes might be the result
of changes in nitrogen sources or cycling in the lake and/or of major shifts in Bosmina trophic position within the lake food web. This study sets up the potential of stable isotope analyses performed on cladoceran
subfossil remains for paleo-ecological purposes. 相似文献
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We discuss the issues related to the human colonization of the Tuva landscapes in the Scythian time. An analysis is made of the spatial and landscape confinedness of archaeological sites having regard to the Late-Holocene rhythms of climate change in the mountains. For the historical-landscape analysis the MapInfo 12.0 GIS technologies were used in compiling the landscape map of the Tyva Republic, the scheme of physical-geographical regionalization and the schematic map of spatial distribution of archaeological sites from the Scythian time. The then most developed landscapes include the steppe mountain-valley and forest-steppe low- and mid-mountain landscapes, which was associated with the main economic sector, namely nomadic stockbreeding. The culture of the Scythian time existed under a colder and more humid climate than at present. An increase in humidity in originally dry areas led to an increase in steppe vegetation productivity growing in depressions and on slopes of mountain ranges. These factors created favorable conditions for the development of nomadic stockbreeding. A spatial analysis of the distribution of archaeological sites in the physical-geographical provinces of Tuva intimates that depression landscapes were colonized mostly in the Scythian time. The Tuvinian depression province (the archaeologically richest area of Tuva) and the Ubsunur depression account for 52 and 21% of the sites, respectively. The mountain landscapes were colonized to a considerably lesser extent; the largest number of sites are located in the Western-Tuva mountain province. In the Scythian time, the cores of development of the Tuva territory were represented by the intermontane depressions (Tuvinian and Ubsunur), the connections between which were provided by a small number of large valleys and mountain passes. 相似文献
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The characteristic features of the transformation of the territorial geospace structure in the African Christianity religious geospace during 1910–2010 have been revealed. African countries within the boundaries of 2010 are used as territorial cells that have been fixed retrospectively over the course of the period analyzed. We used indicators, such as Ryabtsev’s index of relative structural shifts and the trajectory of the demographic center of the Christianity to assess changes in the inertia level of the territorial structure for the entire time interval as a whole and for each of the components of its 20-year long periods. It is found that to date the adherents of Christianity are extremely unevenly distributed in the countries of Africa; however, over the course of the period under consideration there was taking place a homogenization of their settlement. In accordance with changes of the values of the indicators used, we identified two development stages of geospace of African Christianity: colonial and post-colonial. It is determined that the colonial stage (1910–1970) is characterized by a “compression” of territorial structure from east and north, and by a predominance of the south-westward direction of movement of the demographic center because of a decrease in the proportion in the Christian population of East Africa first on account of Egypt and Ethiopia and Madagascar (1910–1930) and then North Africa on account of Egypt and Algeria (1930–1950). The territorial structure of Christianity’s geospace during the post-colonial stage is characterized by a higher degree of inertia at the background of the westward ”expansion” and the “compression” from the south as well as by a change of the vector of movement of the demographic center for north-westward. 相似文献
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Isabela C. Torres Patrick W. Inglett Mark Brenner William F. Kenney K. Ramesh Reddy 《Journal of Paleolimnology》2012,47(4):693-706
Lake sediments contain archives of past environmental conditions in and around water bodies and stable isotope analyses (δ13C and δ15N) of sediment cores have been used to infer past environmental changes in aquatic ecosystems. In this study, we analyzed
organic matter (OM), carbon (C), nitrogen (N), phosphorus (P), and δ13C and δ15N values in sediment cores from three subtropical lakes that span a broad range of trophic state. Our principal objectives
were to: (1) evaluate whether nutrient concentrations and stable isotope values in surface deposits reflect modern trophic
state conditions in the lakes, and (2) assess whether stratigraphic changes in the measured variables yield information about
shifts in trophic status through time, or alternatively, diagenetic changes in sediment OM. Three Florida (USA) lakes of very
different trophic status were selected for this study. Results showed that both δ13C and δ15N values in surface sediments of the oligo-mesotrophic lake were relatively low compared to values in surface sediments of
the other lakes, and were progressively lower with depth in the sediment core. Sediments of the eutrophic lake had δ13C values that declined upcore, whereas δ15N values increased toward the sediment surface. The eutrophic lake displayed δ13C values intermediate between those in the oligo-mesotrophic and hypereutrophic lakes. Sediments of the hypereutrophic lake
had relatively higher δ13C and δ15N values. In general, we found greater δ13C and δ15N values with increasing lake trophic state. 相似文献
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F. Verbruggen O. Heiri G.-J. Reichart J. W. De Leeuw K. G. J. Nierop A. F. Lotter 《Journal of Paleolimnology》2010,43(4):857-872
Stable oxygen isotope measurements on fossil chironomid head capsules from lake sediments show that these chitinous remains
can be used to reconstruct past lake water δ18O and, indirectly, past climate change. We examined the impact of chemical pretreatment procedures on the chemical and stable
oxygen isotope composition, and morphology of chironomid cuticles. Use of alkali, acids, and sodium chlorite alters the chemical
composition and the morphological structure of chironomid cuticles by selective removal of chitin or proteins. Gas chromatograms
of pyrolyzates show that NaClO2 causes deproteination, whereas the combined use of HCl and HF results in partial chitin removal. Head capsules pretreated
with KOH contained both chitin- and protein-derived moieties, although the concentration of protein was reduced, especially
after KOH treatment at high concentration (28%) and temperature (100°C). Scanning electron microscopy confirmed that a proteinaceous
matrix is still present in modern and fossil head capsules after KOH treatment. This matrix, however, is largely absent in
head capsules pretreated with NaClO2. A change in the proportion of chitin and proteins in our samples was associated with differences in chironomid δ18O values. Our results suggest that deproteination results in a relative increase of chironomid δ18O, whereas removal of chitin leads to decreased δ18O values. We therefore discourage the use of acids or prolonged (≥1 h) exposure to hot alkali (70°C) prior to chironomid δ18O analysis. Chitin purification by sodium chlorite causes significant weight loss, which may preclude down-core chironomid
δ18O measurements. Caution and standardization are required when pretreating samples for chironomid δ18O analysis to ensure reliable, comparable, and reproducible results. 相似文献
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S.Ting 《地理学报(英文版)》1947,(2)
In May 1945, the author flew to Urumuchi vis the Kansu Corridor. There are evidently streamflood cournes on the no 'thern front the Chilienshan and great pediments have been formed. Former erosional surface on the Chilienshan were seen in two localities. They ars well preserved flat-topped benches sloping towards the north; and flanked by gullies, These lie at the altitude 3,200 meters above the sea. 相似文献
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In May 1945, the author flew to Urumuchi vis the Kansu Corridor. There are evidently streamflood cournes on the no 'thern front the Chilienshan and great pediments have been formed. Former erosional surface on the Chilienshan were seen in two localities. They ars well preserved flat-topped benches sloping towards the north; and flanked by gullies, These lie at the altitude 3,200 meters above the sea. 相似文献
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Deinstitutionalisation of psychiatric patients since the 1980s has introduced a new population and a new land use to New Zealand's urban areas. This paper reviews the geography of deinstitutionalisation, and investigates whether the North American phenomenon of a service-dependent ghetto can be identified in Dunedin. 相似文献
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2011-2015年《地理学报（英文版）》引证指标分析 总被引：1，自引：1，他引：0
依据美国科技信息研究所公布的《期刊引证报告》、Web of Science数据库、Springer数据、来稿刊稿统计等资料,检索并分析了2011-2015年《地理学报（英文版）》的稿件来源、刊稿量、网络下载量、影响因子、被引频次、被引期刊、施引期刊和高被引论文等主要载文和引证指标。2011-2015年间,该刊国际来稿比例由26.5%增加到47.9%,影响因子由2011年的0.832提高到2015年的1.923。通过对该刊近5年发展状况的全面分析,为期刊未来发展方向提供科学决策依据,为我国地理学期刊质量提升提供参考。 相似文献
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以中国的《地理学报》中、英文版和美国的AAAG (Annals of the Association of American Geographers, 美国地理学家协会会刊)、英国的TIBG (Transactions of the Institute of British Geographers,英国皇家地理学会会刊) 作为中西方主流地理期刊的代表案例,以各刊网站的资料和文献作为数据源,对比各刊的办刊背景、发展历史,重点从办刊宗旨、报道内容、国际化程度、办刊特色、用稿要求等几个方面来对比分析中西方主流地理期刊的办刊实践,结果显示：1) 办刊宗旨上,AAAG和TIBG将重点落实在学科建设服务上,明确宣称其国际权威的高端定位,强调刊文对学科知识性的贡献,即对创新性有特别具体和明确的要求;《地理学报》中、英文版除了服务于学科建设外,明确提出为国民经济建设服务的宗旨。2) 学科内容上,AAAG创刊前20年偏重自然地理,之后人文地理刊文一直处于优势地位;环境科学和方法研究近年来受到重视,基础研究不断深入;《地理学报》自然和人文地理的刊文总体上趋于合理和平衡,其英文版偏重自然地理学、自然与人文相结合的综合性研究。3) 国际化程度方面,被研究期刊的作者群均以本国作者为主,国际作者群体以来自美国、英国、加拿大等国家的作者占优势,其中,AAAG作者的国际化程度最高。4) 办刊特色方面,《地理学报》中、英文版注重实证研究类刊文;AAAG主要体现在其专刊 (special issue) 及主席演讲等方面,TIBG主要体现在虚拟期刊 (virtual issue) 及对刊文质量的贡献要求等方面。 相似文献
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依据2015年6月发布的2014年度国际期刊引证报告,将SCI收录的46种地理学期刊按学科分为5大类,对各学科期刊的影响因子、总被引频次等相关引证指标进行分析,并对各专业地理学期刊2009-2014年间的学术影响力增长情况进行总结。同时,整理国际地理学期刊的年刊文量、出版国别、出版周期和出版公司等期刊出版资料,对国际地理学期刊的学科类型分布、学术影响指标、编辑出版状况之间的相关影响特征进行探讨。 相似文献
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中国地学类SCIE收录期刊的学术影响力分析 总被引：1，自引：0，他引：1
依据美国科技信息所 (ISI) 公布的2009-2013年连续5年JCR数据,选择17种中国地学及相关学科英文版期刊作为研究对象,对其影响因子、五年影响因子、总被引频次、源论文数、自引率等指标进行了五年的统计分析,同时利用web of science检索平台分析了各期刊的篇均被引频次、单篇被引最高频次、国际论文比情况。分析表明,五年间SCIE收录的地学类期刊的学术影响力有所增大,各刊的影响因子总体上呈逐年上升的趋势。但从国际论文比来看,大多期刊国际稿源量少,国际化水平较低;而且中国地学类期刊虽然研究范围较广,但影响因子、被引频次、篇均被引频次均不高。因此,需要着眼于刊文的高质量和知识创新,进一步提高期刊的学术质量;实现从稿源、编辑加工、出版和发行等方面与国际接轨。 相似文献
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中国地理学期刊编辑出版研究的综述 总被引：1，自引：0，他引：1
通过全面收集和系统整理中国地理学类期刊编辑发表的编辑出版研究成果,总结分析中国地理期刊在期刊发展方面的特点,包括地理期刊的总体发展、主要期刊的发展历程、英文期刊的发展、中外期刊发展对比等。概括分析了中国主要地理期刊载文、人文地理学科刊文、主要期刊引文分析等方面的统计结果。最后,对中国地理期刊编辑在期刊与学科发展关系、期刊选题和办刊思路、提高期刊编辑质量、防止稿件重复发表、电脑与网络使用方法等5方面的研究做出了全面总结。 相似文献
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中国地理研究特点与态势——基于“四地”刊物高被引论文的分析 总被引：3，自引：2，他引：1
本文基于文献计量与数据挖掘的原理与方法,以《地理学报》《地理研究》《地理科学》《地理科学进展》(以下简称“四地”或四刊)创刊以来发表的学术论文为基础数据,选取各刊被引量前500位的论文,从时间特征、位次特征、关键词、作者、研究机构、所属地区等角度进行统计分析,旨在揭示中国地理研究的特点与态势。结果表明：①四刊论文贡献量的时间分布存在差异,但高被引论文年代区间集聚特征明显;②高被引论文同位次被引量变化曲线是比较期刊影响力的一种较好方法,四刊曲线均呈现负幂函数曲线衰减态势;③四刊论文作者个数及关键词个数变化整体上较为同步,论文数量随着作者数的增加而呈现“倒勺”变化,关键词个数总体上呈现“趋多避少”的态势;④关键词大类统计反映了四刊的关注重点与差异,核心词根统计揭示了研究焦点与学术支点,空间、城市、土地、变化、生态、中国、区域、旅游、环境、发展等词根出现频次最高;⑤入围量排名靠前的作者大多从事人文经济地理研究,一批领军人物和活跃研究者贡献突出且优势明显;⑥《地理学报》、中国科学院地理科学与资源研究所、北京在各自层面首位度明显。最后,从研究时效及结果解释力、中外研究数据统筹、学术贡献综合评价指标体系构建、研究团队评价及中国地理研究均衡化、本土化与国际化等方面指出了未来的努力方向。 相似文献
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《地理学报》中、英文版创刊以来的国际化进展 总被引：3，自引：1，他引：2
全面回顾《地理学报》创刊80 年来在期刊国际化发展方面做出的努力;系统分析《地理学报(英文版)》创刊23 年来在扩大期刊国际影响方面取得的进展.《地理学报》中、英文版国际化的主要标志包括:期刊编辑出版形式国际化、国际出版与发行业务扩大、国际来稿量和刊稿量增加、国际网络下载量和引证数量等国际影响力指标提高. 相似文献
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基于CNKI的1982-2014年《地理研究》载文情况统计分析 总被引：1，自引：0，他引：1
基于中国知网（CNKI）的“中国学术期刊网络出版总库”、中国科学引文数据库（CSCD）等,对1982-2014年《地理研究》的载文情况进行了总体回顾和客观评价,主要内容包括33年间所发表的学术论文的年际变化、第一作者及核心作者群、作者所属研究机构、各类资金资助情况、论文关键词及被引用情况等几个方面。研究表明：① 《地理研究》的载文量呈现波动增长趋势,具有明显的阶段性变化特征;② 《地理研究》拥有庞大的作者数量,但以第一作者发表3 篇及以上论文的核心作者占第一作者的9.5%;③ 第一作者所属研究机构在区域分布上存在明显的地域集中性,主要集中在中东部地区;④ 国家级基金是地理学研究的主要项目资助类型;⑤ 在热点内容、区域（尺度）和方法等方面体现了学科特点;⑥ 《地理研究》在地理学及其相关研究领域的学术影响力显著提高。研究结果客观地展示了《地理研究》33年来的办刊历程及学术影响,同时在一定程度上揭示出地理学相关领域的研究热点和趋势,可为《地理研究》今后发展以及中国地理学相关研究提供科学参考。 相似文献
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In academia, publication productivity, defined as the number of peer-reviewed articles published and the frequency of citations, is a primary factor in the assessment of tenure and promotion. One of the most cited gender differences in academia is the “productivity puzzle,” which suggests that women publish less than men, thereby affecting every aspect of a woman's academic career. Peer-reviewed articles published in the Annals of the Association of American Geographers (Annals) and The Professional Geographer (PG) between 1995 and 2006, and in four subdisciplinary journals between 2005 and 2009, as well as citation reports, were used to explore whether gender differences are present in publication productivity. Gender differences were evident in the proportion of women authors, the frequency of collaboration, and the number of citations across a broad range of prestigious geographic journals. For all journals studied, women were underrepresented, especially in the authorship positions that equate to notions of respect and merit. Although the number of collaborative articles increased during the study period, single-authored papers are the dominant mode of publication for both men and women for most geographic journals. The authorship patterns for frequently cited articles generally mirror those for all articles. Because the frequency of collaborative publication was high for women, the dual trends of a general increase in publication collaboration and increasing participation of women in academic geography bodes well for increased female productivity as it relates to publishing. Nevertheless, it is important to note that, currently, males as lead or single authors represent the predominant voice of geography within the journals examined in this study. 相似文献