Spatial–temporal variability in water quality and macro-invertebrate assemblages in the Upper Mara River basin,Kenya     

《Physics and Chemistry of the Earth》2014

Tropical rivers display profound temporal and spatial heterogeneity in terms of environmental conditions. This aspect needs to be considered when designing a monitoring program for water quality in rivers. Therefore, the physico-chemical composition and the nutrient loading of the Upper Mara River and its two main tributaries, the Amala and Nyangores were monitored. Initial daily, and later a weekly monitoring schedule for 4 months spanning through the wet and dry seasons was adopted. Benthic macro-invertebrates were also collected during the initial sampling to be used as indicators of water quality. The aim of the current study was to investigate the physico-chemical status and biological integrity of the Upper Mara River basin. This was achieved by examining trends in nutrient concentrations and analyzing the structure, diversity and abundance of benthic macro-invertebrates in relation to varying land use patterns. Sampling sites were selected based on catchment land use and the level of human disturbance, and using historical records of previous water quality studies. River water pH, dissolved oxygen, electrical conductivity (EC), temperature, and turbidity were determined in situ. All investigated parameters except iron and manganese had concentration values within allowable limits according to Kenyan and international standards for drinking water. The Amala tributary is more mineralized and also shows higher levels of pH and EC than water from the Nyangores tributary. The latter, however, has a higher variability in both the total phosphorus (TP) and total nitrogen (TN) concentrations. The variability in TP and TN concentrations increases downstream for both tributaries and is more pronounced for TN than for TP. Macro-invertebrate assemblages responded to the changes in land use and water quality in terms of community composition and diversity. The study recommends detailed continuous monitoring of the water quality at shorter time intervals and to identify key macro-invertebrate taxa that can be used to monitor changes of the water quality in rivers of the Mara basin as a result of anthropogenic changes.  相似文献   

新疆塔里木河三源流径流量变化趋势分析   总被引：5，自引：0，他引：5  

凌红波  徐海量  张青青  史薇 《地理科学》2011,31(6):728-733

运用非参数检验、R/S分析和小波分析等方法对塔里木河三源流的年径流序列进行了分析。结果表明:阿克苏河与叶儿羌河的突变点在1993年,而和田河在1978年;阿克苏河径流呈显著增加趋势而叶儿羌河增加不显著,结合其Hurst指数可知,在未来阿克苏河仍将保持增加走势而叶尔羌河将转变为减少;和田河径流呈轻微的减少趋势,其Hurst指数接近于0.5,具有随机性,不可做长程预测;阿克苏河在6、18、22 a周期性明显,和田河主周期为9和17 a,而叶尔羌河在3、9、13和17 a处周期性明显。  相似文献   

中国城镇化地区贡献的内陆化演变与解释——基于1982-2008年省区数据的分析   总被引：11，自引：3，他引：8  

曹广忠  刘涛 《地理学报》2011,66(12):1631-1643

改革开放30 年来,中国持续快速的经济发展和城镇化受到了世界关注.由于政策环境和地理基础的差异性,地带间差异成为中国城镇化空间差异的主要特征:在多元动力的共同推动下,东部十省的快速城镇化为全国的城镇化进程贡献了49%.新世纪以来,随着西部大开发、东北老工业基地振兴和中部崛起三大区域发展战略的相继提出,政策和地理基础的地带间差异逐步缩小,国内外投资重点向内陆转移,外出务工人员的回流与创业成为人口流动的新特征,带动中西部地区对全国城镇化的贡献迅速提升,中国城镇化的重心向内陆转移,省区城镇化趋同现象比较明显.这些新现象在2005 年以来更加强化.实证结果表明,区域发展战略的提出促进内陆省份对全国城镇化的贡献率提高了8.7%,但并没有对中国省区城镇化的动力机制产生影响;沿海地区产业转移和国际市场的开拓将成为内陆地区城镇化的重要依托.  相似文献   

生态系统服务研究动态及地理学研究范式   总被引：20，自引：2，他引：18  

李双成  刘金龙  张才玉  赵志强 《地理学报》2011,66(12):1618-1630

生态系统服务是目前国际上相关研究热点之一.本文综述了国内外生态系统服务研究的进展、存在问题和发展趋势.在此基础上,针对目前生态系统服务研究生态学范式存在的问题,提出了地理学在此领域的研究范式和优先主题.研究认为,从地理学视角研究生态系统服务,应当以空间异质性和区域差异作为切入点,紧紧围绕生态系统结构与功能-生态系统服务-人类社会福祉这一主线,始终将"自然系统提供生态服务与社会经济系统内化消费"之间的耦合联系作为研究核心,综合集成分析社会经济系统对自然资本内化的响应.通过建构生态系统服务的地理学研究范式,不仅可以拓展生态系统服务研究的深度和广度,而且有助于提升自然和社会经济系统的集成分析水平,进而推动地理学综合研究进程.同时,也为地理学的核心命题--人地关系研究提供重要的实践领域.  相似文献   

Hadley环流强度与我国中东部气温的相关分析   总被引：1，自引：0，他引：1  

王玉  庄亮  汤洁 《气象与环境科学》2012,35(2):61-66

利用NCEP／NCAR再分析月平均风场资料和国家气候中心提供的中国160个气象站的月平均气温资料,用质量流函数计算方法描述平均经圈环流,用环流中心值大小表征其强度,分析Hadley环流强度1951--2010年的趋势变化及其与我国中东部气温的关系。结果表明：1）质量流函数能很好地表征平均经圈环流的特征,且环流中心值大小能形象地反映环流强度。2）近60a来,冬季北半球Hadley环流强度呈线性增强的趋势;夏季南半球Hadley环流在20世纪80年代初发生了由减弱趋势转变为显著增强趋势的年代际转折。3）我国中东部大部分地区气温的年代际变化能很好地被Hadley环流强度变化所解释,二者基本呈正相关关系,但显著相关区域随季节变化有所不同。  相似文献   

烟台芝罘湾底质沉积物粒度特征和沉积动力环境研究          下载免费PDF全文

汤世凯  于剑峰  李金鹏  赵辉  王伟  扈胜涛  李鹏程 《山东国土资源》2020,36(1)

根据芝罘湾海域110个底质沉积物样品粒度分析结果,对沉积物类型和粒度参数分布进行了总结。在此基础上,利用粒径趋势分析模型(GSTA)和沉积动力判别图解,探讨了底质沉积物的运移趋势及沉积水动力规律。研究表明,芝罘湾海域底质沉积物类型共有8种,其中砂质泥、砂质粉砂、泥和粉砂分布最广泛;平均粒径值具有从岸向海逐渐增大的趋势,分选性、偏度和峰度分别为差、正偏—极正偏、平坦—中等的特征;粒度运移趋势分析反映出套子湾泥沙向西、西南运移,芝罘湾及以东海域泥沙呈顺时针方向运移;沉积动力判别图解揭示出芝罘湾海域沉积水动力具有整体较弱的特征。  相似文献   

Century‐long records reveal slight,ecoregion‐localized changes in Athabasca River flows          下载免费PDF全文

Stewart B. Rood  Geoff W. Stupple  Karen M. Gill 《水文研究》2015,29(5):805-816

Reports of abruptly declining flows of Canada's Athabasca River have prompted concern because this large, free‐flowing river could be representative for northern North America, provides water for the massive Athabasca oil‐sands projects and flows to the extensive and biodiverse Peace–Athabasca, Slave and Mackenzie River deltas. To investigate historic hydrology along the river and its major tributaries, we expanded the time series with interpolations for short data gaps; calculations of annual discharges from early, summer‐only records; and by splicing records across sequential hydrometric gauges. These produced composite, century‐long records (1913–2011) and trend detection with linear Pearson correlation provided similar outcomes to nonparametric Kendall τ‐b tests. These revealed that the mountain and foothills reaches displayed slight increases in winter discharges versus larger declines in summer discharges and consequently declining annual flows (~0.16% per year at Hinton; p < 0.01). Conversely, with contrasting boreal contributions, the Athabasca River at Athabasca displayed no overall trend in monthly or annual flows, but there was correspondence with the Pacific Decadal Oscillation that contributed to a temporary flow decline from 1970 to 2000. These findings from century‐long records contrast with interpretations from numerous shorter‐term studies and emphasize the need for sufficient time series for hydrologic trend analyses. For Northern Hemisphere rivers, the study interval should be at least 80 years to span two Pacific Decadal Oscillation cycles and dampen the influence from phase transitions. Most prior trend analyses considered only a few decades, and this weakens interpretations of the hydrologic consequences of climate change. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

21世纪以来青藏高寒草地的变化特征及其对气候的响应     

刘正佳  邵全琴  王丝丝 《干旱区地理》2015,38(2):275-282

利用遥感数据和气象观测资料探索气候因子对区域植被变化的驱动作用具有重要意义。以1980-2012年气象数据和2000-2012年MODIS-NDVI数据为数据源,借助线性回归和相关分析分别分析了青海和西藏两个地区21世纪以来气候变化对青藏高寒草地的影响机制。结果表明：（1）1980-2012年,青海和西藏地区均呈暖湿化的发展趋势。但21世纪以来,西藏地区降水呈不显著的减少趋势;整个青藏高原中部和西部地区增温趋势明显（>0.05 ℃·a-1）。（2）在年际尺度（2000- 2012年）上,青海地区NDVI呈显著增加的趋势,增长率为0.003·a-1（P<0.05）;西藏地区NDVI无变化趋势,区域尺度统计中植被退化与改善相互抵消。在空间上,青藏高原东北部地区NDVI呈良性趋势,部分区域增长斜率超过0.01·a-1。青藏高原南部地区NDVI呈变差趋势,变化斜率为0.008·a-1。（3）区域上的相关分析显示,在青海地区,降水量的增加和温度的升高共同促进了该区域植被的良性发展趋势;在西藏地区,降水量的减少和温度的升高可能是南部地区植被变差的重要原因。  相似文献   

夏季浙江沿岸陆架区泥沙输运机制   总被引：3，自引：0，他引：3  

陈斌  高飞  刘健 《海洋学报》2017,39(3):96-105

基于2014年夏季浙江沿岸陆架区的水文、泥沙、底质沉积物等实测资料,运用物质通量分析方法和Gao-Collins粒径趋势分析法,探讨了泥沙的输运通量、输运方向、动力机制及净输运趋势。夏季,近岸含沙量规律性较强,由西至东逐渐降低,由南至北逐渐升高,且与潮流有非常好的对应关系,呈现出明显的潮周期变化特征。研究区净悬沙通量自岸向外海迅速变小,悬沙输运中平流输运占主导地位,其次是垂向净环流对悬沙输运的影响,近岸海域表现为向海输沙,30 m以深海域表现为东北向输沙,同时台湾暖流的屏障作用也影响了悬沙向海扩散。粒径趋势分析显示浙江沿岸陆架表层沉积物的长期输运机制为由东北向西南输运,在流系以及海底地形的影响下,中部海域出现粒径趋势较弱的沉积中心。而在夏季,悬浮泥沙主要为平行岸线向东北输运,估算每天进入研究海域的净悬浮泥沙约为1.9×106 t。  相似文献   

Culture,demography and biogeography of sponge science: From past conferences to strategic research?          下载免费PDF全文

Christine Hanna Lydia Schönberg 《Marine Ecology》2017,38(2)

Perceived changes in the culture of sponge science and sponge conferences served as motivation for an evaluation of the sponge science community and research, over time and at present. Observed changes included a decrease in proceedings publications on sponge fossils and freshwater sponges, sponges from temperate environments, review papers and data syntheses, frequency of aquarium studies, and number of species investigated per publication. Publications on recent sponges, hexactinellids, calcareans, marine, Indo‐Pacific and warm‐water sponges increased, as well as the number of authors per publication and the proportion of field studies. Studies at the level of specimens and ultrastructure were gradually replaced by molecular approaches, but studies at the community level remained stable. The five sub‐disciplines morphology/taxonomy, phylogeny/evolution, physiology, ecology and faunistics also retained about equal proportions over time. Conference publications related to taxonomy, phylogeny and biodiversity prevailed, whereas those on management and conservation were rare, possibly because studies on sponge recovery, survival and mortality were also scarce. The community of sponge scientists has grown and become more diverse over time, presently representing 72 nations. The gender distribution evened out since the first sponge conference and presently favours women at early and men at late career stages. Although stated research interests are generally dominated by physiology and ecology, taxonomy and evolution are favoured after retirement. Sponge science has become more dynamic, but maybe also more competitive and less inclusive. We now face the dual challenge of safeguarding against the loss of some sub‐disciplines, and fostering the collaborative, helpful culture characteristic of sponge science.  相似文献