期刊文献+
共找到2,293篇文章
< 1 2 115 >
每页显示 20 50 100
Contemporary Asymmetric Genetic Introgression Between Two Pelophylax Species in Shanghai
1
作者 Xu WEI Wenli LIU +12 位作者 Gang WANG Rui MA Meiling HUANG Jiaxin ZHENG Tingwei DONG Changqing YUAN Shunqi BO Xiao YUAN Ben LI Shuo MA Qu YUE Youzhong DING Zhenghuan WANG 《Asian Herpetological Research》 SCIE CSCD 2024年第1期1-11,共11页
Human disturbances are considered to break reproduction barriers among species.Significant increases in hybridization events have been reported among a large number of taxonomic groups in anthropogenic environments,pr... Human disturbances are considered to break reproduction barriers among species.Significant increases in hybridization events have been reported among a large number of taxonomic groups in anthropogenic environments,providing novel insights into species evolution mechanisms and conservation management in the Anthropocene.The Eastern Golden Frog(Pelophylax plancyi)and BlackSpotted Frog(P.nigromaculatus)are two sympatric anuran species with a long history of mitochondrial genome introgression in highly urbanized continental East Asia.However,there is only limited understanding of the pattern of their contemporary hybridization and factors influencing their interspecific relationship under anthropogenic disturbances.Here,interspecific hybridization between P.plancyi and P.nigromaculatus at the population level was investigated in Shanghai.All except two haplotypes obtained from both species in Shanghai were mixed together,and located in the introgression clade,implying multiple ancient mitochondrial introgression events occurred in the populations of our study area.Asymmetric genetic introgression was detected by microsatellite markers,with 0.7%of P.plancyi and 14.6%of P.nigromaculatus identified as contemporary admixed individuals.Consistent with the trend of population density,higher genetic diversity of neutral microsatellite loci was found in the more abundant P.plancyi;however,variation in mitochondrial(Cyt-b)and nuclear(POMC)genes was higher in relatively rare P.nigromaculatus.The population density of P.plancyi and number of water patches within local habitats were significantly positively correlated with both occurrences and proportions of admixed individuals in the populations of P.plancyi and P.nigromaculatus.Considering the prevalent transformation of habitats in urbanized areas,these results imply that a high population density in isolated artificially altered habitats is likely to increase interspecific hybridization.Thus,population monitoring and improvement of landscape connectivity between habitats would be needed to control the intensity of interspecific hybridization between P.plancyi and P.nigromaculatus in anthropogenic-disturbed environments. 展开更多
关键词 anthropogenic disturbances interspecific hybridization Pelophylax species abundance urban landscape URBANIZATION
下载PDF
A new species of Discostella guiyangensis sp.nov.(Bacillariophyta,Stephanodiscales)from Guiyang,China:morphology and phylogeny
2
作者 Yandan XIANG Fangru NAN +3 位作者 Xudong LIU Shulian XIE John Patrick KOCIOLEK Qi LIU 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2024年第4期1312-1324,共13页
We describe a new species of Discostella from Guiyang based on light and scanning electron microscopic observations,as well as molecular analysis.This species is morphologically distinguished from other species by a r... We describe a new species of Discostella from Guiyang based on light and scanning electron microscopic observations,as well as molecular analysis.This species is morphologically distinguished from other species by a relatively smooth and slightly recessed central area with marginal striae of unequal lengths forked near the margin.Marginal fultoportulae and a single rimoportula are situated between every two costae or on the costae.Both morphological characters and the concatenated data of rbc L and SSU rDNA indicate that Discostella guiyangensis is a unique and new species.According to divergence time estimation analysis,Discostella guiyangensis is the oldest species among the Discostella species sequenced currently.In addition,we complement molecular data of Discostella asterocostata and Discostella stelligera. 展开更多
关键词 Discostella MORPHOLOGY molecular analysis divergence time estimation new species
下载PDF
Assessment of plant diversity of endemic species of the Saharo-Arabian region in Egypt
3
作者 Asmaa S ABO HATAB Yassin M AL-SODANY +2 位作者 Kamal H SHALTOUT Soliman A HAROUN Mohamed M EL-KHALAFY 《Journal of Arid Land》 SCIE CSCD 2024年第7期1000-1021,I0002-I0044,共65页
Savanna, semi-deserts, and hot deserts characterize the Saharo-Arabian region, which includes Morocco, Mauretania, Algeria, Tunisia, Libya, Egypt, Palestine, Kuwait, Saudi Arabia, Qatar, Bahrain, the United Arab Emira... Savanna, semi-deserts, and hot deserts characterize the Saharo-Arabian region, which includes Morocco, Mauretania, Algeria, Tunisia, Libya, Egypt, Palestine, Kuwait, Saudi Arabia, Qatar, Bahrain, the United Arab Emirates, Oman, Yemen, southern Jordan, Syria, Iraq, Iran, Afghanistan, Pakistan, and northern India. Its neighboring regions, the Sudano-Zambezian region belonging to the Paleotropical Kingdom and the Mediterranean and Irano-Turanian regions included in the Holarctic Kingdom, share a large portion of their flora with the Saharo-Arabian region. Despite the widespread acknowledgment of the region's global importance for plant diversity, an up to date list of the Saharo-Arabian endemics is still unavailable. The available data are frequently insufficient or out of date at both the whole global and the national scales. Therefore, the present study aims at screening and verifying the Saharo-Arabian endemic plants and determining the phytogeographical distribution of these taxa in the Egyptian flora. Hence, a preliminary list of 429 Saharo-Arabian endemic plants in Egypt was compiled from the available literature. Indeed, by excluding the species that were recorded in any countries or regions outside the Saharo-Arabian region based on different literature, database reviews, and websites, the present study has reduced this number to 126 taxa belonging to 87 genera and 37 families. Regarding the national geographic distribution, South Sinai is the richest region with 83 endemic species compared with other eight phytogeographic regions in Egypt, followed by the Isthmic Desert(the middle of Sinai Peninsula, 53 taxa). Sahara regional subzone(SS1) distributes all the 126 endemic species, Arabian regional subzone(SS2) owns 79 taxa, and Nubo-Sindian subzone(SS3) distributes only 14 endemics. Seven groups were recognized at the fourth level of classification as a result of the application of the two-way indicator species analysis(TWINSPAN) to the Saharo-Arabian endemic species in Egypt, i.e., Ⅰ Asphodelus refractus group, Ⅱ Agathophora alopecuroides var. papillosa group, Ⅲ Anvillea garcinii group, Ⅳ Reseda muricata group, V Agathophora alopecuroides var. alopecuroides group, Ⅵ Scrophularia deserti group, and Ⅶ Astragalus schimperi group. It's crucial to clearly define the Saharo-Arabian endemics and illustrate an updated verified database of these taxa for a given territory for providing future management plans that support the conservation and sustainable use of these valuable species under current thought-provoking devastating impacts of rapid anthropogenic and climate change in this region. 展开更多
关键词 ENDEMISM phytogeographical regions Saharo-Arabian floristic region Egyptian flora plant diversity two-way indicator species analysis(TWINSPAN)
下载PDF
Investigation and Analysis of Main Diseases of Landscape Plants in the Main Urban Area of Lu'an City
4
作者 Gao LIU Hao SONG Juanjuan HU 《Plant Diseases and Pests》 2024年第1期18-21,共4页
To figure out the disease occurrence of landscape plants in the main urban area of Lu'an City,the author investigated the disease occurrence of landscape plants in park green space,residential green space,unit att... To figure out the disease occurrence of landscape plants in the main urban area of Lu'an City,the author investigated the disease occurrence of landscape plants in park green space,residential green space,unit attached green space and main road in the area under administration.The survey results showed that there were 29 species of urban landscape plant diseases,mainly powdery mildew and spot diseases.According to the characteristics of the diseases,the causes and problems of the diseases were analyzed,and the corresponding prevention and control measures were put forward. 展开更多
关键词 Landscape plant Disease species INVESTIGATION Status analysis Lu'an City
下载PDF
Calculations and Sensitivity Analysis of Chlorine-,NO_(x)-,and Bromine-Depleting Cycles of Stratospheric Ozone
5
作者 Ibraheem Alelmi Sen Nieh 《Journal of Environmental Science and Engineering(B)》 CAS 2024年第2期53-69,共17页
This paper presents an engineering system approach using a 2D model of conservation of mass to study the dynamics of ozone and concerned chemical species in the stratosphere.By considering all fourteen photolysis,ozon... This paper presents an engineering system approach using a 2D model of conservation of mass to study the dynamics of ozone and concerned chemical species in the stratosphere.By considering all fourteen photolysis,ozone-generating,and-depleting chemical reactions,the model calculated the transient,spatial changes of ozone under different physical-chemical-radiative conditions.Validation against the measured data demonstrated good accuracy,close match of our model with the observed ozone concentrations at both 20°S and 90°N locations.The deviation in the average concentration was less than 1% and in ozone profiles less than 17%.The impacts of various chlorine-(Cl),nitrogen oxides-(NO_(x)),and bromine-(Br)depleting cycles on ozone concentrations and distribution were investigated.The chlorine catalytic depleting cycle was found to exhibit the most significant impact on ozone dynamics,confirming the key role of chlorine in the problem of ozone depletion.Sensitivity analysis was conducted with levels of 25%,50%,100%,200%,and 400% of the baseline value.The combined cycles(Cl+NO_(x)+Br)showed the most significant influence on ozone behavior.The total ozone abundance above the South Pole could decrease by a small 3%,from 281 DU(Dubson Units)to 273 DU for the 25% level,or by a huge thinning of 60%to 114 DU for the 400% concentration level.When the level of chlorine gases increased beyond 200%,it would cause ozone depletion to a level of ozone hole(below 220 DU).The 2D Ozone Model presented in this paper demonstrates robustness,convenience,efficiency,and executability for analyzing complex ozone phenomena in the stratosphere. 展开更多
关键词 Ozone depletion 2-D model CHLORINE BROMINE nitrogen oxides sensitivity analysis total ozone abundance DU
下载PDF
Fish Assemblage and Abundance Distribution in Nanji Islands Marine Nature Reserve in Relation to Season Change
6
作者 Cheikh Sarr Cungen Yu +2 位作者 Ousmane Ndiaye Hamet Diadhiou Ngor Ndour 《Journal of Agricultural Chemistry and Environment》 2024年第1期13-32,共20页
The fishing survey station located in the warm waters of the East China Sea is one of the abundant fishery resources of waters;with a large number of economic fish breeding grounds and economic juvenile feeding ground... The fishing survey station located in the warm waters of the East China Sea is one of the abundant fishery resources of waters;with a large number of economic fish breeding grounds and economic juvenile feeding grounds. Several fish species according to this bottom trawl survey results which appear in the annual survey from winter to autumn give us a total of 58 species, which have appeared throughout the year. But the vast majority of species appears only in certain seasons, according to the sea fish survey and based on seasonal migratory species or species mainly small endemic species. The survey of fish is tropical and subtropical warm water species and warm temperate species, and the history of the area has several types of 397 different species. There are many reasons, in addition to recent years, human disturbance and adverse consequences of environmental changes brought about, but also with the relevant sampling methods and sampler time, the survey sampled only trawl based, from Ping yang Ocean and Fisheries Bureau, the waters are still other jobs method net, gill nets, fishing industry, etc. Survey results show that the type of fish in the summer (58 species) > spring (55 species) > winter (51 species) > autumn (42 species). The type of season was among spring to summer rose, summer to autumn decline. The survey found that in the reef area of the Nanji Islands, no one species of fish is the dominant species throughout the year (according to the dominant species, each species is dominant only in one season). From the dominant species turnover accounting for the four seasons, in winter it has 53.72% of the total biomass or annual biomass, spring it has 41.53% of the overall biomass, summer it has 31.85% and autumn it has 38.56% of total biomass. Visible, seasonal succession of dominant species of fish phenomenon is very obvious, especially in the spring and winter, summer transfers dominate species at this stage show the greatest change, but winter, the transfer of this dominant species changes in minimal. Seasonal changes from biomass and the average annual marine fish survey biomass were 4832.25 g/h. From different seasons, the average biomass in winter (10779.88 g/h) > of the average biomass in spring (3624.1 g/hour) > of the mean biomass in autumn (3158 g/h) > the average Biomass in summer (1767 g/h). All of them show significant seasonal variation of the biomass, in winter and spring, the biomass is generally not high, but significantly higher than in the summer and autumn seasons. Each season, around the coast of southern Zhejiang, is less than the biomass and other catches off, which involves investigating sea location, size range, and the survey ship different network related tools. Another change from the area of biomass, some studies found that the survey of four-season fish of waters above the biological capacity of several kilograms only in some stations, namely stations and the highest biomass in summer appeared in stations 3, 7 and 11. In autumn the highest biomass appeared in stations 3, 6, 20 and 23. 展开更多
关键词 Nanji Islands species Composition abundance Distribution SEASONS
下载PDF
Species distribution of polymeric aluminium ferrum——timed complexation colorimetric analysis method of Al-Fe-Ferron 被引量:8
7
作者 Hu, YY Tu, CQ Wu, HH 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2001年第4期418-421,共4页
The effects of the calorimetric buffer solutions were investigated while the two colorimetric reactions of AI-ferron complex and Fe-ferron complex occurred individually, and the effects of the testing wavelength and t... The effects of the calorimetric buffer solutions were investigated while the two colorimetric reactions of AI-ferron complex and Fe-ferron complex occurred individually, and the effects of the testing wavelength and the pH of the solutions were also investigated. A timed complexatian colorimetric analysis method of Al-Fe-ferron in view of the total concentration of {AI + Fe} was then established to determine the species distribution of polymeric Al-Fe. The testing wavelength was recommended at 362 net and the testing pH value was 5. With a comparison of the ratios of n(Al)/n(Fe), the standard adsorption curves of the polymeric Al-Fe solutions were derived from the experimental results. Furthermore, the solutions' composition were carious in both the molar n(Al)/n(Fe) ratios, i.e. 0/0, 5/5, 9/1 and 0/10, and the concentrations associated with the total ( Al + Fe which ranged from 10(-5) to 10(-4) mol/L.. 展开更多
关键词 polymeric aluminum-ferrum species distribution timed complexation colarimetric analysis method Al-Fe-ferron
下载PDF
Multi-scale analysis on species diversity within a 40-ha old-growth temperate forest 被引量:2
8
作者 Jie Gao Peng Zhang +1 位作者 Xing Zhang Yanhong Liu 《Plant Diversity》 SCIE CAS CSCD 2018年第2期45-49,共5页
In order to better explore the maintenance mechanisms of biodiversity, data collected from a 40-ha undisturbed Pinus forest were applied to the Individual Species-Area Relationship model(ISAR) to determine distributio... In order to better explore the maintenance mechanisms of biodiversity, data collected from a 40-ha undisturbed Pinus forest were applied to the Individual Species-Area Relationship model(ISAR) to determine distribution patterns for species richness. The ecological processes influencing species abundance distribution patterns were assessed by applying the same data set to five models: a LogNormal Model(LNM), a Broken Stick Model(BSM), a Zipf Model(ZM), a Niche Preemption Model(NPM), and a Neutral Model(NM). Each of the five models was used at six different sampling scales(10 m×10 m, 20 m×20 m, 40 m×40 m, 60 m×60 m, 80 m×80 m, and 100 m×100 m). Model outputs showed that:(1) Accumulators and neutral species strongly influenced species diversity, but the relative importance of the two types of species varied across spatial scales.(2) Distribution patterns of species abundance were best explained by the NPM at small scales(10 m-20 m), whereas the NM was the best fit model at large spatial scales.(3) Species richness and abundance distribution patterns appeared to be driven by similar ecological processes. At small scales, the niche theory could be applied to describe species richness and abundance, while at larger scales the neutral theory was more applicable. 展开更多
关键词 species richness species abundance Spatial scales Niche theory Neutral theory
下载PDF
Species abundance distribution models of Toona ciliata communities in Hubei Province,China 被引量:4
9
作者 Yang Wang Huoming Zhou +2 位作者 Jingyong Cai Congwen Song Linzhao Shi 《Journal of Forestry Research》 SCIE CAS CSCD 2021年第1期103-117,共15页
The study of plant species abundance distribution(SAD)in natural communities is of considerable importance to understand the processes and ecological rules of community assembly.With the distribution of tree,shrub and... The study of plant species abundance distribution(SAD)in natural communities is of considerable importance to understand the processes and ecological rules of community assembly.With the distribution of tree,shrub and herb layers of eight natural communities of Toona ciliata as research targets,three diff erent ecological niche models were used:broken stick model,overlapping niche model and niche preemption model,as well as three statistical models:log-series distribution model,log-normal distribution model and Weibull distribution model,to fi t SAD of the diff erent vegetation layers based on data collected.Goodness-of-fi t was compared with Chi square test,Kolmogorov–Smirnov(K–S)test and Akaike Information Criterion(AIC).The results show:(1)based on the criteria of the lowest AIC value,Chi square value and K–S value with no signifi cant diff erence(p>0.05)between theoretic and observed SADs.The suitability and goodness-of-fi t of the broken stick model was the best of three ecological niche models.The log-series distribution model did not accept the fi tted results of most vegetation layers and had the lowest goodness-of-fi t.The Weibull distribution model had the best goodness-of-fi t for SADs.Overall,the statistical SADs performed better than the ecological ones.(2)T.ciliata was the dominant species in all the communities;species richness and diversity of herbs were the highest of the vegetation layers,while the diversities of the tree layers were slightly higher than the shrub layers;there were fewer common species and more rare species in the eight communities.The herb layers had the highest community evenness,followed by the shrub and the tree layers.Due to the complexity and habitat diversity of the diff erent T.ciliata communities,comprehensive analyses of a variety of SADs and tests for optimal models together with management,are practical steps to enhance understanding of ecological processes and mechanisms of T.ciliata communities,to detect disturbances,and to facilitate biodiversity and species conservation. 展开更多
关键词 Toona ciliata community Tree-shrubherb layers Niche models Statistical models species abundance distribution(SAD) Model fi t
下载PDF
Population Viability Analysis of Gloydius shedaoensis from Northeastern China:A Contribution to the Assessment of the Conservation and Management Status of an Endangered Species 被引量:2
10
作者 LIU Peng SUN Lixin +3 位作者 LI Jianli WANG Li ZHAO Wenge JIA Jingbo 《Asian Herpetological Research》 SCIE 2010年第1期48-56,共9页
Shedao pit-vipers(Gloydius shedaoensis) on Snake Island in the Liaoning Province, China, are among the most imperiled species in China. The isolated and unique populations are crucial in the recovery of this endangere... Shedao pit-vipers(Gloydius shedaoensis) on Snake Island in the Liaoning Province, China, are among the most imperiled species in China. The isolated and unique populations are crucial in the recovery of this endangered species by providing a way for conservation and management. Research based on the ecological simulation tools can evaluate alternative mitigation strategies in terms of their benefits to the populations, which are vital for informed decision-making. In this paper, using the program VORTEX 9.42, we developed a population viability analysis(PVA) for the Shedao pit-viper to:(1) address the extinction likelihood of the population;(2) simulate population dynamics under various environment events, and(3) evaluate the efficacy of current protection and management strategies. Overall, we found the population to be susceptible to the factors of catastrophic events, mortality and environment capacity. The population is recovering slowly at present on account of improvement of habitat and greater food availability. Under the current conditions, the probability of extinction in 100 years is approximately zero. These data coincide with the evidence that the wild population may be arriving at K. Our results strengthen the view that protection and management can create a pronounced effect on populations of this endangered species. 展开更多
关键词 Gloydius shedaoensis VORTEX simulation model sensitivity analysis model veracity test species conservation
下载PDF
A New Species of Cupressinocladus from the Lower Cretaceous of Guyang Basin,Inner Mongolia,China and Cluster Analysis 被引量:1
11
作者 JIN Peihong MAO Teng +5 位作者 DONG Junling WANG Zixi SUN Mingxuan XU Xiaohui DU Baoxia SUN Bainian 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2017年第4期1200-1214,共15页
Cupressinocladus Seward is a fossil genus of conifers and conifer fossils with reproductive organs are very rare. In general, it is difficult to understand the natural affinities with other conifers. In this paper, a ... Cupressinocladus Seward is a fossil genus of conifers and conifer fossils with reproductive organs are very rare. In general, it is difficult to understand the natural affinities with other conifers. In this paper, a new species, Cupressinocladus guyangensis P.H. Jin et B.N. Sun sp. nov., is reported based on branches with immature female cones from the Lower Cretaceous Guyang Formation of the Guyang Basin in Inner Mongolia, northern China. The foliage shoots are decussate. Leaves are decussate, imbricate, scale-like, weakly dimorphic, and bear longitudinal glands on the abaxial view. Stomata complexes are haplocheilic, monocyclic, irregularly arranged, and spread along the leaf margin. Immature female cones are subglobose with 6-8 cone scales, and three subglobose ovules arranged in a row at the base of the cone scales. Moreover, we performed cluster analysis using a statistics and machine learning toolbox for 23 fossils and extant species based on 16 morphological characters. The result implies that the new species bears a close resemblance to the extant Cupressusfunebris Endl. and might have nearest systematic affinities to it. 展开更多
关键词 Cupressinocladus Immature female cone Lower Cretaceous Cluster analysis New species
下载PDF
Abundance quantification by independent component analysis of hyperspectral imagery for oil spill coverage calculation 被引量:2
12
作者 韩仲志 万剑华 +1 位作者 张杰 张汉德 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2017年第4期978-986,共9页
The estimation of oil spill coverage is an important part of monitoring of oil spills at sea.The spatial resolution of images collected by airborne hyper-spectral remote sensing limits both the detection of oil spills... The estimation of oil spill coverage is an important part of monitoring of oil spills at sea.The spatial resolution of images collected by airborne hyper-spectral remote sensing limits both the detection of oil spills and the accuracy of estimates of their size.We consider at-sea oil spills with zonal distribution in this paper and improve the traditional independent component analysis algorithm.For each independent component we added two constraint conditions:non-negativity and constant sum.We use priority weighting by higher-order statistics,and then the spectral angle match method to overcome the order nondeterminacy.By these steps,endmembers can be extracted and abundance quantified simultaneously.To examine the coverage of a real oil spill and correct our estimate,a simulation experiment and a real experiment were designed using the algorithm described above.The result indicated that,for the simulation data,the abundance estimation error is 2.52% and minimum root mean square error of the reconstructed image is 0.030 6.We estimated the oil spill rate and area based on eight hyper-spectral remote sensing images collected by an airborne survey of Shandong Changdao in 2011.The total oil spill area was 0.224 km^2,and the oil spill rate was 22.89%.The method we demonstrate in this paper can be used for the automatic monitoring of oil spill coverage rates.It also allows the accurate estimation of the oil spill area. 展开更多
关键词 oil spill hyperspectral imagery endmember extraction abundance quantification independent component analysis (ICA)
下载PDF
Analysis of Energetic Species Caused by Contact Glow Discharge Electrolysis in Aqueous Solution 被引量:1
13
作者 高锦章 王爱香 +5 位作者 付燕 吴建林 马东平 郭晓 李岩 杨武 《Plasma Science and Technology》 SCIE EI CAS CSCD 2008年第1期30-38,共9页
Contact glow discharge electrolysis is a non-Faradaic electrochemical process with an abnormal relationship between the current and voltage. Hydroxyl radicals, hydrogen radicals and hydrogen peroxide can be produced u... Contact glow discharge electrolysis is a non-Faradaic electrochemical process with an abnormal relationship between the current and voltage. Hydroxyl radicals, hydrogen radicals and hydrogen peroxide can be produced under the glow discharge, which are often used to degrade organic contaminants in aqueous solution. In this study, with 4-nitrophenol taken as an example of contaminants and tert-butanol as a scavenger of hydroxyl radicals, the role of energetic species in degrading organic compounds was examined in detail. Moreover, the effects of the applied voltage, solution conductivity and pH on the formation of three energetic species were also observed. The formation rate constants of the three energetic species were calculated based on the experimental data. 展开更多
关键词 contact glow discharge electrolysis analysis energetic species formation rate constant
下载PDF
Selection of tree species by principal component analysis for abandoned farmland in southeastern Horqin Sandy Land,China 被引量:1
14
作者 Peng Meng Jing Liu Xuefeng Bai 《Journal of Forestry Research》 SCIE CAS CSCD 2022年第2期475-486,共12页
With changes in global climate and land use,the area of desertified farmland in southeastern Horqin Sandy Land(HSL)has increased in recent years,and farmlands are being abandoned.These abandoned farmlands(AFs)nega-tiv... With changes in global climate and land use,the area of desertified farmland in southeastern Horqin Sandy Land(HSL)has increased in recent years,and farmlands are being abandoned.These abandoned farmlands(AFs)nega-tively impact the local ecology.Therefore,the aim of the present study was to select suitable trees and shrubs for those AFs to prevent and control the desertification tendency.In this study,three AFs were fenced for 2 years,then 37 arbor and shrub species or varieties of 21 families were planted in the fenced AFs and grown for 10 years.The ecological adaptability of the species was evaluated and ranked using a principal component analysis.The results showed that the biodiversity of the AFs significantly improved after 2 years of fencing;the Shannon-Wiener index and species rich-ness of perennial grasses and forbs were 1.45 and 3.6 times higher,respectively,than for the unfenced AF.Among all species planted in fenced AFs,nine tree species had posi-tive comprehensive F(CF)values;Pinus sylvestris(Russian Shira steppe provenance),Populus alba‘Berolinensis’and Gleditsia triacanthos had CF greater than 1,and the first(PC1),second(PC2)and third(PC3)principal component values(F_(1),F_(2),F_(3))were all positive.Among the shrubs,only Lespedeza bicolor and Rosa xanthina f.normalis had CF greater than 0.All these results suggest that fencing improves biodiversity and that planting trees and shrubs that have higher CF values on the basis of fencing is an effective way to green and beautify AFs in HSL. 展开更多
关键词 Horqin Sandy Land Fenced abandoned farmland Principal component analysis Tree species selection
下载PDF
The biogeographical distribution of tree species-abundance and its relation to climatic factors in mass islands 被引量:2
15
作者 LI Xiaoming WU Chengzhen +7 位作者 GU Wu YE Ran ZHANG Haibo QI Ping WANG Shengqiang ZHOU Siying WEI Yongjie CAI Yanhong 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2017年第9期87-90,共4页
Tree species-abundance in forests is a function of geographical area and climate, although it is not clear whether such relationships apply to mass islands. We examined the spatial pattern of tree species in mass isla... Tree species-abundance in forests is a function of geographical area and climate, although it is not clear whether such relationships apply to mass islands. We examined the spatial pattern of tree species in mass islands along the coast of Zhejiang, East China Sea using the Preston model, to identify the relationships between tree communities and climatic conditions. The results show that:(1) the biogeographical distribution of tree species-abundance conformes to Preston's log-normal pattern, and is in accordance with the findings in both tropical rainforests and estuarine forests;(2) the climatic factors related to tree communities in mass islands are similar to that of the subtropical zone, including the major species of evergreen needle-leaf, broad-leaf and deciduous broad-leaf forests. We conclude that the Preston model can be applied to the trees of mass islands and thus facilitate the systematic ecological researches of vegetation species' composition in subtropical zone. 展开更多
关键词 mass islands species-abundance spatial pattern log-normal model
下载PDF
Determination of Inorganic Antimony Species Conversions during Its Speciation Analysis in Soil Using Isotope Dilution Techniques 被引量:1
16
作者 Sameer Amereih Thomas Meisel +1 位作者 Zaher Barghouthi Wolfhard Wegscheider 《Journal of Analytical Sciences, Methods and Instrumentation》 2013年第2期130-136,共7页
A new method was developed in this work to account for inorganic Sb species interconversion during soil sample preparation and subsequent separation steps. The Sb(III) and Sb(V) concentrations at each investigated ste... A new method was developed in this work to account for inorganic Sb species interconversion during soil sample preparation and subsequent separation steps. The Sb(III) and Sb(V) concentrations at each investigated step in the analytical procedure were determined using species specific spikes (121Sb(III) with 81.18% and 123Sb(V) with 74.04% enrichment). The spiking of these enriched isotopes species solutions was done separately before soil sample extraction and before HPLC separation. Simply by subtracting the final concentration of each species done by on-line isotope dilution (ID) from its concentration at different stages of the analytical procedure done by species specific ID, the influence of each step on species transformation can be estimated. After optimization, the extraction procedure for inorganic Sb species 6% Sb(III) (1.3 RSD, n = 3) and 43.2% Sb(V) (2.9% RSD, n = 3) as percent of total Sb were detected in the examined soil sample using online ID. Using the above described methodology we found that there was no reduction of Sb(V) to Sb(III) during sample preparation or species separation. While about 9.3% of extractable Sb (4.6% of total) was converted from Sb(III) to Sb(V) during the extraction step, no conversion during HPLC separation step was observed. By compensating for Sb(III) transformation during the sample preparation step;the extractable Sb(III) and Sb(V) as percent of total Sb yielded 10.6% and 38.7%, respectively. 展开更多
关键词 ANTIMONY speciATION analysis species Interconversions ISOTOPE DILUTION TECHNIQUES
下载PDF
Estimation of Natural Mortality Coefficient from Fish Abundance and Catch Data Using Virtual Population Analysis(VPA)
17
作者 WANG Yingbin LIU Qun WANG Yanjun 《Journal of Ocean University of China》 SCIE CAS 2007年第1期53-59,共7页
Natural mortality coefficient (M) was estimated from fish abundance (N) and catch (C) data using a Virtual Population Analysis (VPA) model. Monte Carlo simulations were used to evaluate the impact of different error d... Natural mortality coefficient (M) was estimated from fish abundance (N) and catch (C) data using a Virtual Population Analysis (VPA) model. Monte Carlo simulations were used to evaluate the impact of different error distributions for the simulated data on the estimates of M. Among the four error structures (normal, lognormal, Poisson and gamma), simulations of normally dis-tributed errors produced the most viable estimates for M, with the lowest relative estimation errors (REEs) and median mean absolute deviations (MADs) for the ratio of the true to the estimated Ms. In contrast, the lognormal distribution had the largest REE value. Errors with different coefficients of variation (CV) were added to N and C. In general, when CVs in the data were less than 10%, reliable estimates of M were obtained. For normal and lognormal distributions, the estimates of M were more sensitive to the CVs in N than in C; when only C had error the estimates were close to the true. For Poisson and gamma distributions, opposite results were obtained. For instance, the estimates were more sensitive to the CVs in C than in N, with the largest REE from the scenario of error only in C. Two scenarios of high and low fishing mortality coefficient (F) were generated, and the simulation results showed that the method performed better for the scenario with low F. This method was also applied to the published data for the anchovy (Engraulis japonicus) of the Yellow Sea. Viable estimates of M were obtained for young groups, which may be explained by the fact that the great uncertainties in N and C observed for older Yellow Sea anchovy introduced large variation in the corresponding estimates of M. 展开更多
关键词 natural mortality COEFFICIENT FISH abundance CATCH DATA virtual population analysis
下载PDF
STUDY ON THE TEN MAJOR TREE SPECIES OCCUPYING GEOGRAPHICAL SPACE IN NATURAL SECONDARY FOREST USING SPACE ANALYSIS
18
作者 Li RuxiuNortheast Forestry University 《Journal of Northeast Forestry University》 SCIE CAS CSCD 1993年第2期51-56,共6页
The paper studies ten major tree species occupying the space in naturalsecondary forests in Mao Er mountain area.The space is divided into horizon,elevation,slope,aspect and topographic position layer.The features of ... The paper studies ten major tree species occupying the space in naturalsecondary forests in Mao Er mountain area.The space is divided into horizon,elevation,slope,aspect and topographic position layer.The features of the species of trees areexamined using the concept of distribution width and the method of space statistics.Theconclusions of analysis indicate that Aspen and Asian White Birch community of forests inthe area would become failing,and the distribution of Mongolian Oak and Mongolian Lidenand Manchurian Walnut are Limited by the slope and aspect and topographic position.Elm,Maple,Manchurian Ash would become the major species constituting naturalsecondary forests in future in this area. 展开更多
关键词 species of TREE GEOGRAPHIC SPACE Distribution SPACE analysis
下载PDF
Distribution of dominant species and abundance of nannofossils in surface sediments of the central and northern partsof the South China Sea──Comparison and discussion
19
作者 Cheng Xinrong 《Acta Oceanologica Sinica》 SCIE CAS CSCD 1995年第4期525-535,共11页
The distributional trends and their controlling factors of dominant species and nannofossil abundance in sur face sediments of marginal and coastal seas in low to middle latitudes and high latitudes are discussed on t... The distributional trends and their controlling factors of dominant species and nannofossil abundance in sur face sediments of marginal and coastal seas in low to middle latitudes and high latitudes are discussed on the basis of theanalysis of 146 samples from the nothern and central parts of the South China Sea and of comparison between the resultsof current work and data from other seas.Despite significant variations in taxonomic composition between seas or between areas within one sea, there are somegeneral trends in nannofossil distribution of marginal and coastal seas. All those nannofossil assemblages in middle and lowlatitudes are dominated by two species: Gephyrocapsa oceanica and Emiliania huxleyi. Although the relative abundanceof these species may vary greatly from area to area, Gephyrocapsa oceanica in general prevails in nearshore or semiclosedenvironments, increasing in number towards the shoreline, while Emiliania huxleyi increases in relative abundance to wards continental slope and open ocean environments, decreasing in abundance again only in very deep-water, i. e., nearthe CCD. Similarly, the abundance of calcareous nannofossils, as a whole, is lower nearshore, increasing with water depthtowards the continental slope, and then decreasing again towards and near the CCD. In high latitudes, the dominantspecies are Emiliania huxleyi and Coccolithus pelagicus.There are two groups of factors controlling the nannofossil distribution in surface sediments: ecological factors, in cluding particularly water temperature, supply of nutrients; and sedimentological factors, including influx of terrigenousmaterials and deep-water carbonate dissolution. 展开更多
关键词 Dominant species nannofossil abundance
下载PDF
Abundance Analysis of HD131023
20
作者 ZHANG Hua-Wei ZHAO Gang 《Chinese Physics Letters》 SCIE CAS CSCD 2001年第3期461-462,共2页
Based on high resolution and high signal-to-noise ratio spectra,we determine the chemical abundances of nearby star HD131023 by using the differential analysis.Abundances of total 24 elements are presented.Some heavy ... Based on high resolution and high signal-to-noise ratio spectra,we determine the chemical abundances of nearby star HD131023 by using the differential analysis.Abundances of total 24 elements are presented.Some heavy elements,such as Sr,Y,Ba,La,Nd,are found to be overabundant relative to the sun. 展开更多
关键词 analysis. Abu abundant
下载PDF
上一页 1 2 115 下一页 到第
使用帮助 返回顶部