空间线群目标方向相似度计算模型

本文提出了3种空间线群目标方向相似度的计算模型。依据风向玫瑰图的原理,将空间线群目标的方向特征进行定量统计生成对应的方向玫瑰图,在此基础上,生成对应的标准差椭圆和统计直方图,从而分别建立基于线目标方向玫瑰图、基于标准差椭圆和基于统计直方图的方向相似度计算模型,并进行了实验验证和分析。     

临夏台地电阻率变化与震兆现象分析

以甘肃省临夏台1981年以来的地电阻率资料为基础,利用数理统计和相关分析方法,分析该台地电阻率的变化特征,探讨EW和NS两测向之间数据的相关性,以及与大夏河流量变化的对应关系,认为该台两测向数据间具有很高的相关性,可能与区域地下介质具有较均匀的电性结构有关;分析了该区降水和地下静水位对地电阻率的影响,认为地下静水位的影响更显著.此外,探讨了临夏台地电阻率资料作为地震前兆的意义,认为该台资料对甘东南及甘青交界地区的中强地震反应敏感,以下降型破年变异常为主,呈现出震级越大,异常持续时间越长的特点.该台资料同时对甘青地区成组中强地震有所反应,显示出异常持续时间长、幅度大和恢复慢的特点.     

Dividing the algal soup: is there niche separation between native bivalves (Echyridella menziesii) and non-native Daphnia pulex in New Zealand?

ABSTRACT

New Zealand's native freshwater mussels (kākahi, kāeo) are considered to be in decline, yet the mechanisms driving this are unclear. The widespread establishment of highly efficient filter-feeding, non-native Daphnia in New Zealand lakes may have led to competition for algae with kākahi. We conducted a controlled laboratory experiment to determine whether differences exist in algal resources utilised by kākahi and North American Daphnia pulex. Echyridella menziesii (adults and juveniles) and D. pulex were exposed to mixed algal samples for three hours to determine whether similar algal resources were removed by the grazers. Relative to controls, both adult and juvenile E. menziesii removed a broad range of algal taxa including diatoms, green algae and filamentous species, ranging in size from 33.6 to 348.0?μm. High densities of D. pulex were unable to cause depletion of these same algae species. Our results suggest niche overlap is limited between the two grazers; E. menziesii utilises larger particles than D. pulex.     

丹江口水库浮游植物时空变化特征

为研究丹江口浮游植物的群落特征,探讨影响浮游植物时空分布的环境因子,于2014年5月2015年4月对丹江口水库进行了为期1年的调查.此次调查共采集到浮游植物66种,隶属于7门21科38属.浮游植物全年平均生物量为0.35 mg/L,平均密度为9.08×10~5cells/L.优势种为脆杆藻、小环藻、直链藻和栅藻,其中脆杆藻所占比例最大,平均生物量为0.089 mg/L,占总生物量的25.43%.近些年丹江口水库营养水平的提高可能是脆杆藻生物量升高的主要原因.绿藻和蓝藻在夏季大量繁殖,硅藻为春、秋和冬季优势门类.汉江库区浮游植物生物量大于丹江库区,两个库区的浮游植物种类组成存在明显的差异,丹江库区优势门类为硅藻门,而汉江库区为绿藻门.浮游植物生物量与环境因子的相关分析表明,浮游植物生物量的主要影响因子是总磷浓度、pH值和溶解氧浓度.RDA分析表明,影响浮游植物组成的主要环境因子是溶解氧浓度、pH值、总磷浓度和水温.为控制浮游植物的生物量,防止其异常增殖造成水华,应严格控制外源营养盐特别是磷元素的输入.本研究可为丹江口水库的水质改善及富营养化防治提供一定的科学依据.     

舟山群岛海域网采浮游植物分布与多样性

于2014年夏、秋两季在舟山海域进行了浮游植物拖网采集和环境理化因子测定,共鉴定浮游植物6门92属184种,其中硅藻门127种,甲藻门30种,为调查海域主要浮游植物类群。夏季骨条藻Skeletonema spp.为绝对优势种,秋季优势种由琼氏圆筛藻Coscinodiscus jonesianus、虹彩圆筛藻Coscinodiscus oculus-iridis、蛇目圆筛藻Coscinodiscus argus、星脐圆筛藻Coscinodiscus asteromphalus、骨条藻Skeletonema spp.、尖刺伪菱形藻Pseudo-nitzschia pungens、并基角毛藻Chaetoceros decipiens、伏氏海毛藻Thalassiothrix frauenfeldii及中间肋缝藻Frustulia interposita等9种硅藻构成。调查海域夏季浮游植物平均丰度(1 713.58×10⁴个/m³)高于秋季(1 430.30×10⁴个/m³)。冗余分析表明,温度、盐度、悬浮物、溶解无机磷及溶解无机氮等环境因子对夏、秋两季浮游植物群落影响较大。结合历史数据分析可知,舟山海域近30 a来富营养化程度严重且日益加剧,富营养化指数明显升高;同时浮游植物群落变化也十分显著,主要体现为细胞丰度增加和优势种更替。     

上海港港区区位与功能演变及动力机制

随着全球经济一体化,港口发展迈入了新阶段。上海港是世界大港,其发展、演变过程既具备一般性规律又不乏自身特色,对揭示单体港口的功能拓展和空间扩张具有积极意义。论述了上海港的港区区位和功能演变过程,并总结了港口的空间演化轨迹、功能拓展路径等规律,创建上海港演变模式,最后考察上海港区位与功能演变的动力机制。研究发现：港口港区区位遵循了从支流向门户、从内河向深海、从单一区位向多体系的演变规律,功能演变形成了从服务于村镇向国际区域、从渔港向综合港的演变过程,形成“河流单港区阶段→河流双向延伸阶段→工业化岸线拓展阶段→集装箱化离岸外迁阶段”的上海港演变模式。鸦片战争之前,上海港因长江流域门户港变迁规模和功能不断提升;开埠后,西方介入使港口空间和功能进一步扩展;1949年以来,工业化导致上海港向多区位系统和多元化功能演进;21世纪以来,技术进步、全球化及政策制度等因素促使老港区外迁和功能升级。研究丰富了港口地理学的理论研究,为单体港口的优化与枢纽建设提供了借鉴。     

淮河中上游浮游植物时空分布特征及关键环境影响因子识别

浮游植物是水生态系统的初级生产者,直接影响着水生态系统的结构、功能与稳定性。基于2012-2014年淮河流域沙颍河—淮干中游浮游植物和水质4次汛期和非汛期采集数据,利用物种优势度和多样性指数对浮游植物的时空分布进行表征,并利用冗余度分析、偏相关性分析等方法探索了淮河中上游流域的多种水环境因子对浮游植物时空分布的影响。结果表明,从时间变化上看,2012-2014年浮游植物密度呈现逐年递减趋势;从空间变化上看,物种丰度呈现从上游至下游逐渐减少趋势。从时空变化的影响因素上看,非汛期总磷和电导率影响最大,其解释度分别为：10.96%和8.36%;汛期总磷、总氮和氨氮影响最大,其解释度分别为9.47%、8.08%和6.96%。     

Lagged response of phytoplanktonic photosynthetic competence to variation of nitrogen concentration in Jiaozhou Bay, China

Fluorescence-based maximal photochemical efficiency, Fv/Fm, is widely used as an indicator to photosynthetic competence in marine systems. It has been considered a useful parameter diagnosing the nutrient stress on phytoplankton photosynthesis, but many studies argue its usefulness. In the present study, we try to find a temporal relationship between Fv/Fm and nitrogen concentration, and provide a possible explanation on the controversy. We continuously measured Fv/Fm and nitrogen concentration once every 10 days from September 2003 to March 2004 at two stations in Jiaozhou Bay, northern China. It was found that Fv/ffm did not significantly correlate to synchronous nitrogen concentration, but the variation （i.e. the change between two adjacent cruises） of nitrogen concentration of the previous cruise and the variation ofFv/Fm of the current cruise were strongly correlated. This result indicates that a time lag exists between the variation of nutrient status and the subsequent Fv/Fm response. Length of the time lag seems just matched the interval of our measurements （10 days）. In the field, direct dependence of Fv/Fm on nitrogen concentration may not be found because of the lagged response of Fv/Fm to nitrogen concentration variations or physiological acclimation. Our results provide a possible way to explain the previously reported conflicting results on the relationship between Fv/Fm and nutrient status. To give a more-accurate estimate about the length of the time lag, an investigation that includes more frequent measurements is needed.     

Seasonal succession of phytoplankton in response to the variation of environmental factors in the Gaolan River, Three Gorges Reservoir, China

To understand the responses of a freshwater ecosystem to the impoundment of the Three Gorges Reservoir (TGR), phytoplankton was monitored in the tributaries of the TGR area. From August 2010 to July 2011, algal species composition, abundance, chlorophyll a and other environmental parameters were investigated in the Gaolan River, which is a tributary of Xiangxi River. Thirty-one algal genera from seven phyla were identified. Results show that the lowest concentrations of total phosphorus (TP) and total nitrogen (TN) were 0.06 mg/L and 1.08 mg/L, respectively. The values of TP and TN exceeded the threshold concentration of the eutrophic state suggested for freshwater bodies. In the Gaolan River, the succession of phytoplankton showed clear seasonal characteristics. Different dominant species were observed among seasons under the control of environment factors. In spring and summer, the dominant species were Nitzschia sp. and Aphanizomenon flos-aquae (L.) Ralfs, the limiting nutrient was NO ₃ ^? -N, and the key environmental factor for phytoplankton population succession was water temperature (WT). In autumn and winter, the dominant species were A. flos-aquae and Chlorella sp., the limiting nutrient was PO ₄ ^3? -P, and the key environmental factors were transparency and WT. This study illustrates the influence of physical and chemical factors on phytoplankton seasonal succession in a tributary of TGR since the downstream regions of Xiangxi River and Gaolan River became reservoirs after impoundment of the Three Gorges Dam. We suggest that this activity has significantly affected water quality in the dam area.