Evaluation of aquatic ecological systems through dynamics of ichthyofaunal diversity in a Himalayan torrential river,Murti     

《Limnologica》2020

The biodiversity hotspot region of the Eastern Himalayas consists of a vast freshwater network enriched with species diversity. Many small-scale torrential rivers and water reaches contribute to the species pool of all the major rivers by converging downstream. These reaches are most likely to be degraded at a faster rate as compared to the large-scale rivers following an increased rate of urbanization, habitat alterations, and changing climatic conditions. Therefore, this study aims to explore River Murti, which is a representative small scale river system characterized by a large altitudinal gradient and a diverse watershed area. Ichthyofaunal diversity (i.e., diversity, evenness & richness) and 21 environmental variables are measured through a tri-seasonal sampling effort conducted along 14 selected locations. A total of 41 fish species (including species belonging to 4 Near Threatened, 8 Vulnerable, and 1 Endangered) are found inhabiting this river. Ichthyofaunal assemblage is found to be primarily modulated by habitat diversity and landscape variables. Three Aquatic Ecological Systems (AES) have been identified along this river in a top-down approach based on recorded environmental variables. We have calculated an observed/expected ratio for each diversity indices along 14 locations based on predicted temporal variability using boosted regression (BRT) models. The evaluation of diversity status has been kept at 0.5 to account for a 50% loss or deviation from observed (O/E50). This evaluation has been successfully used to delineate AES1 with majorly “Impaired” status and thus ensures its importance in terms of species conservation. Our study indicates the contribution of 11 major environmental drivers modulating the species assemblage patterns in these AES. Amongst them, altitude, substrate coarseness, river morphology, and shelter availability are strongly associated with species diversity as per the BRT models. These underlying factors are also correlated with “basin pressure,” suggesting that anthropogenic disturbances, as well as the changing climate, might play an important role in the gradual change in environmental conditions, which in turn could cause a shift in species assemblage structure.  相似文献   

前苏联七十年海冰研究回顾     

曲维政  李若钝 《海洋预报》1993,10(3):31-42

本文简要介绍了前苏联近七十年来海冰研究的主要成果及其采用的一些预报方法。  相似文献   

改进的超级集成预报方法在长江三角洲地区O₃预报中的应用     

姚雪峰  葛宝珠  王自发  范凡  汤莉莉  郝建奇  张祥志  晏平仲  张稳定  吴剑斌 《大气科学》2018,42(6):1273-1285

针对当前单模式系统臭氧（O₃）预报的不确定性问题,提出了一种基于活动区间的多模式超级集成的、高效的预报方法。本研究基于长江三角洲（长三角）地区多模式空气质量预报系统,将改进后的超级集成预报方法（AR-SUP）运用到2015年长三角地区的O₃预报中,并与滑动训练期的超级集成预报（R-SUP）、多模式集成平均预报（EMN）、消除偏差的集成平均预报（BREM）对比,结果表明AR-SUP对预报效果的改善最明显,其在暖季和冷季的均方根误差（RMSE）较最优单模式平均下降了20%和23%。将AR-SUP运用到48 h和72 h预报中发现,当预报时效增加时该方法依旧保持较高的预报技巧。多项统计数据均证明AR-SUP在研究时段内所有站点均能显著减小O₃预报误差、提高整体相关性和一致性,有效提高当前短期（三天）预报准确率。  相似文献   

Running waves observed by Hinode     

H.F. Liang  W.G. YangL. Ma  R.J. Yang 《New Astronomy》2012,17(2):112-116

  相似文献   

Hydrogeochemistry and strontium isotopes in the Arno River Basin (Tuscany, Italy): Constraints on natural controls by statistical modeling   总被引：2，自引：0，他引：2  

B. Nisi  A. Buccianti  O. Vaselli  G. Perini  F. Tassi  A. Minissale  G. Montegrossi 《Journal of Hydrology》2008,360(1-4):166-183

In this paper the chemistry of major and trace elements and, for the first time, strontium isotopic ratios measured in running waters from the Arno River Basin (Tuscany, central-northern Italy) and thermal springs discharging in the same hydrographic system are presented and discussed. Classical graphical methods (e.g. mixing diagrams) have here been improved to identify, in a correct statistical sample space, extreme chemical compositions attributable to the action of geochemical processes and/or inherited from specific lithologies (namely contributions or components 1, 2 and 3) to be used in inverse modeling procedures, due to the absence of clear end-members. A linear least squares problem, with non-negativity constraints and distances, as required for compositional data (convex linear mixing) was solved by considering the contribution of the most discriminant variables given by the ⁸⁷Sr/⁸⁶Sr isotopic ratios and the concentration of Ca²⁺, Mg²⁺, Sr and Rb. Following such approach, it can be assumed (p < 0.05) that component 1, characterized by a Ca²⁺(Mg²⁺)– radiogenic-rich (⁸⁷Sr/⁸⁶Sr = 0.71274; Rb/Sr = 0.039), represents a dominant feature at basin scale, with a weight ranging from 69% to 100%. Much lower percentages are related to component 2, represented by a Ca²⁺(Mg²⁺)– facies with intermediate ⁸⁷Sr/⁸⁶Sr (0.70874) and low Rb/Sr (2.8 × 10⁻⁴) ratios and component 3, identified by Ca²⁺– facies with less radiogenic ⁸⁷Sr/⁸⁶Sr (0.70827) and low Mg²⁺/Ca²⁺ (0.011) ratios. These components are mainly dominated by the dissolution of evaporitic rocks and/or mixing with thermal waters in the southern part of the Arno River Basin and by dissolution of the carbonatic fraction, kinetically favored with respect to that of the silicatic minerals, in the upper reaches of the main course and its tributaries, respectively.  相似文献   

云宵县5月暴雨客观预报模型     

赖惠贞陈荣平  朱昌桂廖燕珍 《河南气象》2004,(3):9-11

采用文献[1]提出的技术模型，研制了云宵县5月暴雨预报方法，建立了4个因子结构简单而天气学意义明了的客观预报模型。经2000～2003年试用，这种基于场量因子的预报模型，未漏报，严格评定的准确率为67％，明显优于主观预报。  相似文献   

区域经济与环境协调发展的综合决策研究   总被引：12，自引：0，他引：12  

方创琳 《地球科学进展》2000,15(6):699-704

实施我国区域经济与环境协调发展的综合决策是提高经济运行质量和环境质量的关键。立足于区域经济与环境协调发展综合决策的运行机制,提出我国区域经济与环境协调发展综合决策的主要途径为:建立和完善经济与环境协调发展的综合决策制度;严格禁止产业结构优化升级中污染物的超标迁移;确保三大经济核心区成为经济与环境协调发展的核心区;重点开发轴线地区应率先成为重点环保轴线地区;各类经济技术开发区应建成经济与环境协调发展的示范区。  相似文献   

CSAO多通道GPS／GLONASS接收机试运行结果   总被引：4，自引：0，他引：4  

王正明  董绍武  任燕  漆溢  刘春侠  王改霞 《时间频率学报》2001,24(2):106-114

陕西天文台(CSAO)的多通道GPS/GLONASS接收机(R100/30T)自2001年6月起处于试运行阶段,经过系统调整和反复调试,两套接收机从8月8日以来取得正常接收结果.对两套接收机作了零基线共视比对,单通道GPS的单个记录的比对精度达±1.79ns;在同一时间多通道GPS比对平均值的精度达±0.82ns.GLONASS P码单通道的单个记录比对精度达±0.82ns,多通道平均值的精度达±0.57ns.上述精度与国际上同类型接收机相比较说明,CSAO的这两套R100/30T的质量较好(噪声小).CRL和CSAO的R100/30T数据的共视比对结果说明,把多通道GPS/GLONASS接收机用于远距离时间比对(尚未进行精密星历表改正),精度可以达到±4.79ns (GPS C/A码)和±2.27ns (GLONASS P码).  相似文献   

福建前汛期区域暴雨客观预报模型研究   总被引：5，自引：4，他引：1       下载免费PDF全文

刘爱鸣 潘宁邹燕  张明席 《应用气象学报》2003,14(4):419-429

利用滑动分区切比雪夫展开方法,求取高度场特征分布的展开系数及其时间变量,通过相关分析,从中提取物理意义明确和相关性好的预报因子集和消空因子集,再通过预报因子的多形态组合分析,提炼出物理图像清晰的福建省前汛期区域暴雨预报模型。研究结果表明:以高度场的滑动分区切比雪夫展开系数做为研制前汛期的区域性暴雨预报模型的信息源是合理且可行的。切比雪夫正交多项式能够对要素场的内在特征信息进行定量化提取,生成彼此相互独立的场量因子;滑动分区展开技术可对场信息做极限化的开发,产生多种尺度的特征信息,从而获得对预报对象成因更完备的认识。  相似文献   

Functional feeding groups of a macroinvertebrate community in a northern German lake outlet (Lake Belau, Schleswig-Holstein)     

Rainer Poepperl   《Limnologica》1999,29(2):137

At four typical sections of the stream Kossau Diptera were caught by emergence traps. Two of the sections can be regarded as to a great degree undisturbed due to their morphology and vegetation at the banks. Two sections have undergone various anthropogenic changes. Representatives of the families Chironomidae, Ceratopogonidae, Psychodidae, Limoniidae, Ptychopteridae, Dixidae, Culicidae, Simuliidae, and Empididae were collected. Altogether, 106 species were identified. The majority of species belong to the family Chironomidae (74), followed by the Ceratopogonidae (8), Psychodidae, and Empididae (7 each). The numbers of species collected at each stream section ranged from 56 to 69. At the undisturbed and shaded sections 69 and 66 species were found, at the meadow sections 56 and 68 species. Hence, a general connection between the loss of a state close to the natural environment and the number of species can not be stated.A total of 29,349 Diptera emerged. The highest number of individuals was found at a stream section covered with aquatic macrophytes (16,797 ind.), the lowest at a forest section without macrophytes (2,554 ind.). The Chironomidae make up for more than 82% of all Diptera. The Simuliidae rank second accounting for 3 to 17%, followed by the Ceratopogonidae. Like the Ceratopogonidae, all other families comprise less than 1% of the individuals collected.Only a few species demonstrated a distinct preference for the two forest sections of the stream, whereas about 50% of the species occurred in at least three of the four sections. Regarding the species represented by more than two individuals per emergence trap, it became apparent that the correspondence between the forst and the meadow sections is rather small.A comparison of the emergence of individual families revealed that many species found in the Kossau also occur in another lowland stream, similar to the Kossau concerning width, current velocity, and water level. Furthermore, the ecological demands of several species turned out to be not as high as they were considered to be, mainly referring to the temperature: Species proven in the Kossau and in other summer-warm streams may no longer be regarded as ‘cold-stenothermic’.  相似文献