National Population Health Data Center(NPHDC)is one of China's 20 national-level science data centers,jointly designated by the Ministry of Science and Technology and the Ministry of Finance.Operated by the Chines...National Population Health Data Center(NPHDC)is one of China's 20 national-level science data centers,jointly designated by the Ministry of Science and Technology and the Ministry of Finance.Operated by the Chinese Academy of Medical Sciences under the oversight of the National Health Commission,NPHDC adheres to national regulations including the Scientific Data Management Measures and the National Science and Technology Infrastructure Service Platform Management Measures,and is committed to collecting,integrating,managing,and sharing biomedical and health data through openaccess platform,fostering open sharing and engaging in international cooperation.展开更多
The four-color three-step selective photoionization process of atom is very important in laser isotope separation technology.The population trapping phenomena and their influences are studied theoretically in monochro...The four-color three-step selective photoionization process of atom is very important in laser isotope separation technology.The population trapping phenomena and their influences are studied theoretically in monochromatic and non-monochromatic laser fields based on the density matrix theory in this work.Time evolutions of the photoionization properties of the four-color,three-step process are given.The population trapping effects occur intensely in monochromatic excitation,while it gradually turns weak as the laser bandwidth increases.The effects of bandwidth,Rabi frequency,time delay,and frequency detuning on the population trapping effect are investigated in monochromatic and non-monochromatic laser fields.The effects of laser process parameters and atomic parameters on the effective selective photoionization are also discussed.The ionization probability and selectivity factors,as evaluation indexes,are difficult to improve synchronously by adjusting systematic parameters.Besides,the existence of metastable state may play a negative role when its population is low enough.展开更多
In evolutionary games,most studies on finite populations have focused on a single updating mechanism.However,given the differences in individual cognition,individuals may change their strategies according to different...In evolutionary games,most studies on finite populations have focused on a single updating mechanism.However,given the differences in individual cognition,individuals may change their strategies according to different updating mechanisms.For this reason,we consider two different aspiration-driven updating mechanisms in structured populations:satisfied-stay unsatisfied shift(SSUS)and satisfied-cooperate unsatisfied defect(SCUD).To simulate the game player’s learning process,this paper improves the particle swarm optimization algorithm,which will be used to simulate the game player’s strategy selection,i.e.,population particle swarm optimization(PPSO)algorithms.We find that in the prisoner’s dilemma,the conditions that SSUS facilitates the evolution of cooperation do not enable cooperation to emerge.In contrast,SCUD conditions that promote the evolution of cooperation enable cooperation to emerge.In addition,the invasion of SCUD individuals helps promote cooperation among SSUS individuals.Simulated by the PPSO algorithm,the theoretical approximation results are found to be consistent with the trend of change in the simulation results.展开更多
The atomic-vapor cell is a vital component for Rydberg atomic microwave sensors,and impacts on overall capability of Rydberg sensors.However,the conventional analysis approach on effect of vapor-cell length contains t...The atomic-vapor cell is a vital component for Rydberg atomic microwave sensors,and impacts on overall capability of Rydberg sensors.However,the conventional analysis approach on effect of vapor-cell length contains two implicit assumptions,that is,the same atomic population density and buffer gas pressure,which make it unable to accurately capture actual response about effect of Rydberg-atom-based sensor performance on different Rydberg atom populations.Here,utilizing a stepped cesium atomic-vapor cell with five different dimensions at the same atomic population density and buffer gas pressure,the height and full width at half maximum of electromagnetically induced transparency(EIT)signal,and the sensitivity of the atomic superheterodyne sensor are comprehensively investigated under conditions of the same Rabi frequencies(saturated laser power).It is identified that EIT signal height is proportional to the cell length,full width at half maximum and sensitivity grow with the increment of cell length to a certain extent.Employing the coherent integration signal theory and atomic linear expansion coefficient method,theoretical analysis of the EIT height and sensitivity are further investigated.The results could shed new light on understanding and design of ultrahigh-sensitivity Rydberg atomic microwave sensors and find promising applications in quantum measurement,communication,and imaging.展开更多
We present an optimal and robust quantum control method for efficient population transfer in asymmetric double quantum-dot molecules.We derive a long-duration control scheme that allows for highly efficient population...We present an optimal and robust quantum control method for efficient population transfer in asymmetric double quantum-dot molecules.We derive a long-duration control scheme that allows for highly efficient population transfer by accurately controlling the amplitude of a narrow-bandwidth pulse.To overcome fluctuations in control field parameters,we employ a frequency-domain quantum optimal control theory method to optimize the spectral phase of a single pulse with broad bandwidth while preserving the spectral amplitude.It is shown that this spectral-phase-only optimization approach can successfully identify robust and optimal control fields,leading to efficient population transfer to the target state while concurrently suppressing population transfer to undesired states.The method demonstrates resilience to fluctuations in control field parameters,making it a promising approach for reliable and efficient population transfer in practical applications.展开更多
Population connectivity through seed and pollen dispersal determines the genetic diversity,adaptive potential,and demography of plant metapopulations.In wind-pollinated trees,population connectivity is typically maint...Population connectivity through seed and pollen dispersal determines the genetic diversity,adaptive potential,and demography of plant metapopulations.In wind-pollinated trees,population connectivity is typically maintained by long-distance pollen flow,counteracting the genetic differentiation generated by drift and restricted seed dispersal.Although strong population fragmentation is theoretically expected to disrupt connectivity in forest trees,empirical evidence remains scarce and inconclusive.We investigated contemporary connectivity within a network of small remnant populations of a declining conifer(Taxus baccata L.),which have been hypothesized to be largely isolated from each other.We tested this hypothesis using molecular data for adult trees and naturally recruited seedlings from all known remnants across a fragmented landscape spanning a length of 20 km,and a specifically designed statistical approach to quantify contemporary pollen and seed migration rates between populations.We additionally assessed dispersal potential using a spatially explicit parentage analysis to estimate seed and pollen dispersal kernels within one of the remnants.Estimated pairwise migration rates between populations were barely detectable for seeds,while they were larger(up to 1.1%)and significant for pollen.Both seed and pollen migration rates decreased with geographic distance between populations,more steeply in the case of pollen migration.According to parentage-based dispersal kernels,51.8% of seeds and 11.4% of pollen travel less than 25 m,whereas 0.2% of seeds and 36.1%of pollen travel more than 250 m from a source tree.In addition,1.2% of pollen can travel more than 2.5 km.We showed that strong present-day population fragmentation,with separation distances over a few kilometers between small fragments,can substantially limit the connectivity of a wind-pollinated declining tree,leading to low pollen-mediated contemporary gene flow and null or virtually null demographic connectivity via seed dispersal.展开更多
The Random Amplified Polymorphism DNA (RAPD) markers were used to stu dy the intra-specific diversity and regional differentiation of the Chinese fore st frogs (Rana chensinensis), which were sampled from the fields o...The Random Amplified Polymorphism DNA (RAPD) markers were used to stu dy the intra-specific diversity and regional differentiation of the Chinese fore st frogs (Rana chensinensis), which were sampled from the fields of 8 regions in Heilongjiang Province. Totally 78 polymorphic DNA loci were amplified by 10 RAP D primers. By genetic distance analysis and phylogenetic tree reconstruction wit h the Neighbor-Joining (NJ) method the results showed that the populations of Ch inese forest frogs distributed in 8 regions existed great differentiation (Avera ge Fst=0.347, SD=0.235) while there was the paradox between geographic distances and genetic distances. Based on geographic and geological data, a hypothesis wa s posed that it is very possible that the hilly lands in the downstream of the S onghua River and the Heilong River were the center of the origin of the Chinese forest frogs in Heilongjiang Province. And mainly through the Songhua River syst em, the Chinese forest frogs dispersed into the Songneng Plain from the Sanjiang Plain whereas the Fangzheng region became a sub-center for the western dispersi on.展开更多
Genetic diversity and genetic differentiation of natural populations of Pinus kesiya var. langbinanensis were examined by means of electrophoresis technique. Analysis of 9 enzyme systems including 16 loci showed that ...Genetic diversity and genetic differentiation of natural populations of Pinus kesiya var. langbinanensis were examined by means of electrophoresis technique. Analysis of 9 enzyme systems including 16 loci showed that all the three natural popu-lations of the pine were high in genetic diversity but low in inter-population genetic differentiation. The proportion of polymorphic loci is 0.667, with each locus holding 2.13 alleles, averagely. The average expected and observed heterozygosity was 0.288 and 0.197, respectively. The gene differentiation among populations was 0.052, but the mean genetic distance was only 0.015.展开更多
A new breeding population of Mandarin Duck （Aix gaIericulata, Linnaeus） was first recorded in 2003 in Jiao- tanzhuang-Hehekou region of Pingshan county, Hebei Province, China. Recently, the gradually increasing popu...A new breeding population of Mandarin Duck （Aix gaIericulata, Linnaeus） was first recorded in 2003 in Jiao- tanzhuang-Hehekou region of Pingshan county, Hebei Province, China. Recently, the gradually increasing population indicates that there are suitable breeding habitats （such as foraging habitats and nesting sites） for Mandarin Duck. However, these habitats are always close to human disturbances, which are the potential risk for their population. Therefore, it is urgent to put forward an applicable protection strategy, in order to strengthen the public awareness for this unprotected population.展开更多
We used sequences of mitochondrial control region （807bp） in 75 samples from three breeding colonies and one wintering population to investigate the genetic diversity and population structure of Marsh Grassbird （Lo...We used sequences of mitochondrial control region （807bp） in 75 samples from three breeding colonies and one wintering population to investigate the genetic diversity and population structure of Marsh Grassbird （Locustella pryeri sinensis） in different regions of China. Marsh Grassbird retained a moderate amount of haplotype （0.759 ± 0.056） and nucleotide diversity （0.002）. The results of FST among 3 phy-logeographic units and ФST between breeding and wintering sites revealed little evidence of genetic distinction between different colonies. Neither UPGMA tree structure analysis nor Network picture analysis showed obvious divergence between populations at different locations. Analysis of molecular variance also showed a lack of regional subdivision within Locustella pryeri sinesis, 98.5% of source of variation within populations and only 1.5% among populations. The neutrality test showed negative Fu’s FS value, which, in combination with detection of the mismatch distribution, suggested that population expansion occurred in the evolu-tionary history of this species. This hypothesis was further supported by Tajima’s D test and Fu’s test （D = -1.80, p = 0.02; Fs = -22.11, p = 0.001）, this expansion was estimated to occur about 28,700 years ago.展开更多
The competition-density effect of plant populations is of significance in theory and practice of forest management and has been studied for long time. The differences between the two reciprocal equations of the compet...The competition-density effect of plant populations is of significance in theory and practice of forest management and has been studied for long time. The differences between the two reciprocal equations of the competition-density effect in nonself-thinning populations and self-thinning populations were analyzed theoretically. This supplies a theoretical basis for analyzing the dynamics of forest populations and evaluating the effect of forest management.展开更多
The age-structure of natural population of Zoysia japonica in Xiuyan County of Liaoning Province was studied by generational method. The results showed that the highest tiller age class was three, but 1st age class ti...The age-structure of natural population of Zoysia japonica in Xiuyan County of Liaoning Province was studied by generational method. The results showed that the highest tiller age class was three, but 1st age class tillers held dominant posi-tion with proportions over 95% in each month during the growing seasons. The 2nd age class and 3rd age class tillers were minority in the population. So Z. japonica population was an expanding population. The zero age class buds on the rhizomes were dominant in buds age structures. The proportion of buds to tillers on quantity in each month was about 30% to 40% and reached the highest at the end of September. The increasing of buds proportion before dormancy guaranteed the quantity of tillers in the next spring. The biomass of 1st age class tillers changed with time. The biomass kept increasing from April to July and reached the highest at the end of July and then decreased.展开更多
The scalar of Japanese yew （Taxus cuspidata） population and the relationship between individual distribution and site factors were analyzed according to investigating data in 74 sample belts with a total sampled are...The scalar of Japanese yew （Taxus cuspidata） population and the relationship between individual distribution and site factors were analyzed according to investigating data in 74 sample belts with a total sampled area of 436.872 hm2 in Muling Nature Reserve. The result showed that the distribution rules of Japanese yew population were correlated to elevation, slope position, slope aspect and slope gradient. The optimal distribution range in elevation for the natural Japanese yew population is at the attitudes of 700-800 m. The amounts of Japanese yew individuals on shady slope were more than those on sunny slope. On top slope and mid-slope, the individual amounts of Japanese yew are more than those on toe slope. Most of Japanese yew individuals occurred on slope gradient of less than 15. The scalar of the population was decreased with the slope gradient increasing.展开更多
From 700 m to 1900 m on the northern slope of Changbai Mountain, 13 plots with an interval of 100 m in elevation were investigated to study the variations of population structure and important value of the main edific...From 700 m to 1900 m on the northern slope of Changbai Mountain, 13 plots with an interval of 100 m in elevation were investigated to study the variations of population structure and important value of the main edificators along the elevation gradient. In their core distribution areas, most of the edificators had healthy population structure and could regenerate smoothly except Larix olgensis, but important value of Larix olgensis had no obvious variations with elevation changes, which showed that Larix olgensis had its own particularity and strong adaptability. At high elevation above 1800 m, Betula ermanii was the only species that could form a mono-dominant community. Important values of Pinus koraiensis and Acer mono had similar changing trends, and they had the similar ecological adaptabilities.展开更多
Phoebe bournei（Hemsl.） Yang is a rare and protected plant in China. This study was conducted to determine the phenotypic variation in this species and to document phenotypic variation within and among populations of...Phoebe bournei（Hemsl.） Yang is a rare and protected plant in China. This study was conducted to determine the phenotypic variation in this species and to document phenotypic variation within and among populations of P. bournei. Nested analysis of variance, coefficient of variation, multiple comparisons, principal component analysis（PCA） and correlation analysis were used to analyze ten phenotypic traits in ten natural populations of P.bournei from both the northeastern and the primary region of the range of this species. Significant differences among and within populations were observed in leaf and seed phenotypic traits. Variation among populations（34.92%）was greater than that within populations（26.19%）. The mean phenotypic differentiation coefficient was 53.77% among populations, indicating that variation among populations comprised the majority of the phenotypic variation of P. bournei. The coefficient of variance（CV） of ten traits varied from 6.44 to 18.45%, with an average of 12.03%.The CV of leaf traits among populations（15.64%） was higher than that of seed traits（8.60%）, indicating that seed traits were more stable. The results from CV and PCA indicated that leaf area, leaf length and thousand seed weight were the main factors accounting for the observed phenotypic variations. Significant or highly significant correlations were observed among most leaf and/or in seed phenotypic traits, whereas no significant correlations were observed between phenotypic traits and geographic factors.Based on cluster analysis, the ten populations can be divided into three clusters. These clusters were not a result of geographic distances.展开更多
Comparing with an affinity and widespread species Adenophora potaninii the age structures of A. loboPhylla population, an endangered plant species were studied. 29 sample plots were investigated in the centered distri...Comparing with an affinity and widespread species Adenophora potaninii the age structures of A. loboPhylla population, an endangered plant species were studied. 29 sample plots were investigated in the centered distribution area, Jinchuan county from altitude 2 300 m to 3 400 m. The main factors which influence the population age structures of A. lobophylla were analyzed. The principal characteristics of A. lobophylla populations are that the number of seedling and the density of population are much less than these of A. potaninii population. Below aititude of 2 700 m, the age structures of most A. lobophylla populations show the declining status, only above altitude of 2 700 m they are stable, while age structures of all populations of A. potaninll populations at corresponding altitude perform stable and developing features. The age structure patterns, relations between age (X) and number of individual (y) of stable populations of A. lobophylla can be expressed by equation : y =e(a-bx), and the longest life spah is 25a. Whereas A. potaninii populations can be expressed by the equationf y =ax-b, and the longest life span of individual is 21a. The external factors, which constrain the extension of A. lobophylla population, are extreme environmental conditions such as serious drought, external disturbance and low temperature.展开更多
The Tibet Shannan Red Deer Nature Reserve is the center of the geographic distribution of Tibetan red deer. This paper presents the results of DNA analysis of 199 red deer fecal pellet groups collected during 2013 and...The Tibet Shannan Red Deer Nature Reserve is the center of the geographic distribution of Tibetan red deer. This paper presents the results of DNA analysis of 199 red deer fecal pellet groups collected during 2013 and 2014 during the green-plant period. We successfully extracted DNA from 87 DNA pellet groups and determined individual identification with 12 microsatellite loci. We evaluated the genetic diversity of the population and various population estimates with Capwire in R software. The87 successfully extracted pellet groups were from 50 individuals. In the population, the average number of alleles was 7.58 ± 0.18, the average effective number of alleles was 4.58 ± 0.15, and average polymorphism information content was 0.67 ± 0.01. Among the 12 loci,only T123 was moderately polymorphic; the other 11 loci were highly polymorphic. Expected heterozygosity ranged from 0.45 to 0.91, with an average of 0.72 ± 0.01, and average observed heterozygosity was 0.52 ± 0.11.Although Tibetan red deer remains endangered, the high genetic diversity indicates that this population has a good chance of recovery. This study provided insight that could be used by the local forestry department to develop programs to protect Tibetan red deer.展开更多
Research on chip-scale atomic clocks （CSACs） based on coherent population trapping （CPT） is reviewed. The back- ground and the inspiration for the research are described, including the important schemes proposed t...Research on chip-scale atomic clocks （CSACs） based on coherent population trapping （CPT） is reviewed. The back- ground and the inspiration for the research are described, including the important schemes proposed to improve the CPT signal quality, the selection of atoms and buffer gases, and the development of micro-cell fabrication. With regard to the re- liability, stability, and service life of the CSACs, the research regarding the sensitivity of the CPT resonance to temperature and laser power changes is also reviewed, as well as the CPT resonance＇s collision and light of frequency shifts. The first generation CSACs have already been developed but its characters are still far from our expectations. Our conclusion is that miniaturization and power reduction are the most important aspects calling for further research.展开更多
An investigation was conducted on distribution pattern, site condition and population structure of yew Taxus cuspidata Sieb. et Zucc. in Muling Forest Bureau of Heilongjiang Province, China in April, 2005. Results sho...An investigation was conducted on distribution pattern, site condition and population structure of yew Taxus cuspidata Sieb. et Zucc. in Muling Forest Bureau of Heilongjiang Province, China in April, 2005. Results showed that yew is mainly distributed under the main storey of natural mixed forest of conifer and broadleaf, the soil moisture content of the yew site is high （40%-60%）, the pH value of soil is relatively lower （4.7-5.5）, and that the population structure of wild yew is not rational, belonging to the degeneration population, which is one of the reasons leading to the population decline. Although the site conditions of Muling area are suitable for the growth of wild yew, the population of wild yew shows a decline tendency, due to the fact that the middle-sized adult yew trees have been cut, young yews are often grazed by wildlife, and that the trunks of adult yew tend to be hollow.展开更多
We investigated the plant population structure and the phy- tosociological and regeneration status in two disturbed tropical forests in Assam Province, the Hojai Reserve Forest and Kumorakata Reserve Forest. A total o...We investigated the plant population structure and the phy- tosociological and regeneration status in two disturbed tropical forests in Assam Province, the Hojai Reserve Forest and Kumorakata Reserve Forest. A total of 166 species （80 trees, 20 shrubs and 66 herbs） of 136 genera and 63 families were recorded in both study sites. The disturbance index at the two sites, Kumorakata Reserve Forest and Hojai Reserve Forest, were recorded at 11.4% and 3.70% respectively. Reverse J-shaped population curve and exploitation of tree species in higher girth classes were recorded at both study sites. In the girth classes （10-30 cm, 30-60 cm, 60-90 cm and 90-120 cm in size） the percentage of cut stump density was higher than the percentage of individual living trees. The 18% （Kumorakata Reserve Forest） and 7% （Hojai Reserve Forest） spe- cies were recorded as not regenerating. Illegal felling and over-exploitation of forest resources may lead to species-specific changes in the population structure and can alter the future structure and composi- tion of the forests.展开更多
文摘National Population Health Data Center(NPHDC)is one of China's 20 national-level science data centers,jointly designated by the Ministry of Science and Technology and the Ministry of Finance.Operated by the Chinese Academy of Medical Sciences under the oversight of the National Health Commission,NPHDC adheres to national regulations including the Scientific Data Management Measures and the National Science and Technology Infrastructure Service Platform Management Measures,and is committed to collecting,integrating,managing,and sharing biomedical and health data through openaccess platform,fostering open sharing and engaging in international cooperation.
文摘The four-color three-step selective photoionization process of atom is very important in laser isotope separation technology.The population trapping phenomena and their influences are studied theoretically in monochromatic and non-monochromatic laser fields based on the density matrix theory in this work.Time evolutions of the photoionization properties of the four-color,three-step process are given.The population trapping effects occur intensely in monochromatic excitation,while it gradually turns weak as the laser bandwidth increases.The effects of bandwidth,Rabi frequency,time delay,and frequency detuning on the population trapping effect are investigated in monochromatic and non-monochromatic laser fields.The effects of laser process parameters and atomic parameters on the effective selective photoionization are also discussed.The ionization probability and selectivity factors,as evaluation indexes,are difficult to improve synchronously by adjusting systematic parameters.Besides,the existence of metastable state may play a negative role when its population is low enough.
基金Project supported by the Doctoral Foundation Project of Guizhou University(Grant No.(2019)49)the National Natural Science Foundation of China(Grant No.71961003)the Science and Technology Program of Guizhou Province(Grant No.7223)。
文摘In evolutionary games,most studies on finite populations have focused on a single updating mechanism.However,given the differences in individual cognition,individuals may change their strategies according to different updating mechanisms.For this reason,we consider two different aspiration-driven updating mechanisms in structured populations:satisfied-stay unsatisfied shift(SSUS)and satisfied-cooperate unsatisfied defect(SCUD).To simulate the game player’s learning process,this paper improves the particle swarm optimization algorithm,which will be used to simulate the game player’s strategy selection,i.e.,population particle swarm optimization(PPSO)algorithms.We find that in the prisoner’s dilemma,the conditions that SSUS facilitates the evolution of cooperation do not enable cooperation to emerge.In contrast,SCUD conditions that promote the evolution of cooperation enable cooperation to emerge.In addition,the invasion of SCUD individuals helps promote cooperation among SSUS individuals.Simulated by the PPSO algorithm,the theoretical approximation results are found to be consistent with the trend of change in the simulation results.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61901495 and 12104509)
文摘The atomic-vapor cell is a vital component for Rydberg atomic microwave sensors,and impacts on overall capability of Rydberg sensors.However,the conventional analysis approach on effect of vapor-cell length contains two implicit assumptions,that is,the same atomic population density and buffer gas pressure,which make it unable to accurately capture actual response about effect of Rydberg-atom-based sensor performance on different Rydberg atom populations.Here,utilizing a stepped cesium atomic-vapor cell with five different dimensions at the same atomic population density and buffer gas pressure,the height and full width at half maximum of electromagnetically induced transparency(EIT)signal,and the sensitivity of the atomic superheterodyne sensor are comprehensively investigated under conditions of the same Rabi frequencies(saturated laser power).It is identified that EIT signal height is proportional to the cell length,full width at half maximum and sensitivity grow with the increment of cell length to a certain extent.Employing the coherent integration signal theory and atomic linear expansion coefficient method,theoretical analysis of the EIT height and sensitivity are further investigated.The results could shed new light on understanding and design of ultrahigh-sensitivity Rydberg atomic microwave sensors and find promising applications in quantum measurement,communication,and imaging.
基金This work was supported by the National Natural Science Foundations of China(Grant Nos.12275033,61973317,and 12274470)the Natural Science Foundation of Hunan Province for Distinguished Young Scholars(Grant No.2022JJ10070)+1 种基金the Natural Science Foundation of Hunan Province(Grant No.2022JJ30582)the Scientific Research Fund of Hunan Provincial Education Department(Grant No.20A025).
文摘We present an optimal and robust quantum control method for efficient population transfer in asymmetric double quantum-dot molecules.We derive a long-duration control scheme that allows for highly efficient population transfer by accurately controlling the amplitude of a narrow-bandwidth pulse.To overcome fluctuations in control field parameters,we employ a frequency-domain quantum optimal control theory method to optimize the spectral phase of a single pulse with broad bandwidth while preserving the spectral amplitude.It is shown that this spectral-phase-only optimization approach can successfully identify robust and optimal control fields,leading to efficient population transfer to the target state while concurrently suppressing population transfer to undesired states.The method demonstrates resilience to fluctuations in control field parameters,making it a promising approach for reliable and efficient population transfer in practical applications.
基金supported by the National Science Centre,Poland(the grant UMO-2018/31/B/NZ8/01808 to IJC).
文摘Population connectivity through seed and pollen dispersal determines the genetic diversity,adaptive potential,and demography of plant metapopulations.In wind-pollinated trees,population connectivity is typically maintained by long-distance pollen flow,counteracting the genetic differentiation generated by drift and restricted seed dispersal.Although strong population fragmentation is theoretically expected to disrupt connectivity in forest trees,empirical evidence remains scarce and inconclusive.We investigated contemporary connectivity within a network of small remnant populations of a declining conifer(Taxus baccata L.),which have been hypothesized to be largely isolated from each other.We tested this hypothesis using molecular data for adult trees and naturally recruited seedlings from all known remnants across a fragmented landscape spanning a length of 20 km,and a specifically designed statistical approach to quantify contemporary pollen and seed migration rates between populations.We additionally assessed dispersal potential using a spatially explicit parentage analysis to estimate seed and pollen dispersal kernels within one of the remnants.Estimated pairwise migration rates between populations were barely detectable for seeds,while they were larger(up to 1.1%)and significant for pollen.Both seed and pollen migration rates decreased with geographic distance between populations,more steeply in the case of pollen migration.According to parentage-based dispersal kernels,51.8% of seeds and 11.4% of pollen travel less than 25 m,whereas 0.2% of seeds and 36.1%of pollen travel more than 250 m from a source tree.In addition,1.2% of pollen can travel more than 2.5 km.We showed that strong present-day population fragmentation,with separation distances over a few kilometers between small fragments,can substantially limit the connectivity of a wind-pollinated declining tree,leading to low pollen-mediated contemporary gene flow and null or virtually null demographic connectivity via seed dispersal.
基金the Natural Science Foundation of Heilongjiang Province (C9726).
文摘The Random Amplified Polymorphism DNA (RAPD) markers were used to stu dy the intra-specific diversity and regional differentiation of the Chinese fore st frogs (Rana chensinensis), which were sampled from the fields of 8 regions in Heilongjiang Province. Totally 78 polymorphic DNA loci were amplified by 10 RAP D primers. By genetic distance analysis and phylogenetic tree reconstruction wit h the Neighbor-Joining (NJ) method the results showed that the populations of Ch inese forest frogs distributed in 8 regions existed great differentiation (Avera ge Fst=0.347, SD=0.235) while there was the paradox between geographic distances and genetic distances. Based on geographic and geological data, a hypothesis wa s posed that it is very possible that the hilly lands in the downstream of the S onghua River and the Heilong River were the center of the origin of the Chinese forest frogs in Heilongjiang Province. And mainly through the Songhua River syst em, the Chinese forest frogs dispersed into the Songneng Plain from the Sanjiang Plain whereas the Fangzheng region became a sub-center for the western dispersi on.
基金his article was supported by the Natural Science Founda-tion of Yunnan Province (No.98C017Q).
文摘Genetic diversity and genetic differentiation of natural populations of Pinus kesiya var. langbinanensis were examined by means of electrophoresis technique. Analysis of 9 enzyme systems including 16 loci showed that all the three natural popu-lations of the pine were high in genetic diversity but low in inter-population genetic differentiation. The proportion of polymorphic loci is 0.667, with each locus holding 2.13 alleles, averagely. The average expected and observed heterozygosity was 0.288 and 0.197, respectively. The gene differentiation among populations was 0.052, but the mean genetic distance was only 0.015.
基金supported by Natural Science Foun-dation of Hebei Province (D2006000701, C2007000247)Doctoral Fund of Hebei Normal University (L2008B11)
文摘A new breeding population of Mandarin Duck （Aix gaIericulata, Linnaeus） was first recorded in 2003 in Jiao- tanzhuang-Hehekou region of Pingshan county, Hebei Province, China. Recently, the gradually increasing population indicates that there are suitable breeding habitats （such as foraging habitats and nesting sites） for Mandarin Duck. However, these habitats are always close to human disturbances, which are the potential risk for their population. Therefore, it is urgent to put forward an applicable protection strategy, in order to strengthen the public awareness for this unprotected population.
基金supported by National Natural Science Foundation of China (No. 130370221 and No. 30770309)
文摘We used sequences of mitochondrial control region （807bp） in 75 samples from three breeding colonies and one wintering population to investigate the genetic diversity and population structure of Marsh Grassbird （Locustella pryeri sinensis） in different regions of China. Marsh Grassbird retained a moderate amount of haplotype （0.759 ± 0.056） and nucleotide diversity （0.002）. The results of FST among 3 phy-logeographic units and ФST between breeding and wintering sites revealed little evidence of genetic distinction between different colonies. Neither UPGMA tree structure analysis nor Network picture analysis showed obvious divergence between populations at different locations. Analysis of molecular variance also showed a lack of regional subdivision within Locustella pryeri sinesis, 98.5% of source of variation within populations and only 1.5% among populations. The neutrality test showed negative Fu’s FS value, which, in combination with detection of the mismatch distribution, suggested that population expansion occurred in the evolu-tionary history of this species. This hypothesis was further supported by Tajima’s D test and Fu’s test （D = -1.80, p = 0.02; Fs = -22.11, p = 0.001）, this expansion was estimated to occur about 28,700 years ago.
文摘The competition-density effect of plant populations is of significance in theory and practice of forest management and has been studied for long time. The differences between the two reciprocal equations of the competition-density effect in nonself-thinning populations and self-thinning populations were analyzed theoretically. This supplies a theoretical basis for analyzing the dynamics of forest populations and evaluating the effect of forest management.
基金This study was supported by the NKBRSF (G1999043407-1) Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-406+3 种基金 SCXZD0101) NKTRDP (2001BA510B-07 2002BA516A20) and Education Committee Projects of Liaong Province (990121400
文摘The age-structure of natural population of Zoysia japonica in Xiuyan County of Liaoning Province was studied by generational method. The results showed that the highest tiller age class was three, but 1st age class tillers held dominant posi-tion with proportions over 95% in each month during the growing seasons. The 2nd age class and 3rd age class tillers were minority in the population. So Z. japonica population was an expanding population. The zero age class buds on the rhizomes were dominant in buds age structures. The proportion of buds to tillers on quantity in each month was about 30% to 40% and reached the highest at the end of September. The increasing of buds proportion before dormancy guaranteed the quantity of tillers in the next spring. The biomass of 1st age class tillers changed with time. The biomass kept increasing from April to July and reached the highest at the end of July and then decreased.
基金This work was supported by Northeast Forestry University fund Program from Science and Technology Department of Heilongjiang Province (LC05C14)
文摘The scalar of Japanese yew （Taxus cuspidata） population and the relationship between individual distribution and site factors were analyzed according to investigating data in 74 sample belts with a total sampled area of 436.872 hm2 in Muling Nature Reserve. The result showed that the distribution rules of Japanese yew population were correlated to elevation, slope position, slope aspect and slope gradient. The optimal distribution range in elevation for the natural Japanese yew population is at the attitudes of 700-800 m. The amounts of Japanese yew individuals on shady slope were more than those on sunny slope. On top slope and mid-slope, the individual amounts of Japanese yew are more than those on toe slope. Most of Japanese yew individuals occurred on slope gradient of less than 15. The scalar of the population was decreased with the slope gradient increasing.
基金This research was supported by Chinese Academy of Sciences '100 people'project National Natural Science Foundation of China (39970123) and Changbai Mountain Open Research Station.
文摘From 700 m to 1900 m on the northern slope of Changbai Mountain, 13 plots with an interval of 100 m in elevation were investigated to study the variations of population structure and important value of the main edificators along the elevation gradient. In their core distribution areas, most of the edificators had healthy population structure and could regenerate smoothly except Larix olgensis, but important value of Larix olgensis had no obvious variations with elevation changes, which showed that Larix olgensis had its own particularity and strong adaptability. At high elevation above 1800 m, Betula ermanii was the only species that could form a mono-dominant community. Important values of Pinus koraiensis and Acer mono had similar changing trends, and they had the similar ecological adaptabilities.
基金financially supported by the Major Science and Technology Project(No.2010C12009)Agricultural New Varieties Breeding Project(No.2012C12908-4)Key Research and Development Plan(No.2017C02028)of Zhejiang Province,China
文摘Phoebe bournei（Hemsl.） Yang is a rare and protected plant in China. This study was conducted to determine the phenotypic variation in this species and to document phenotypic variation within and among populations of P. bournei. Nested analysis of variance, coefficient of variation, multiple comparisons, principal component analysis（PCA） and correlation analysis were used to analyze ten phenotypic traits in ten natural populations of P.bournei from both the northeastern and the primary region of the range of this species. Significant differences among and within populations were observed in leaf and seed phenotypic traits. Variation among populations（34.92%）was greater than that within populations（26.19%）. The mean phenotypic differentiation coefficient was 53.77% among populations, indicating that variation among populations comprised the majority of the phenotypic variation of P. bournei. The coefficient of variance（CV） of ten traits varied from 6.44 to 18.45%, with an average of 12.03%.The CV of leaf traits among populations（15.64%） was higher than that of seed traits（8.60%）, indicating that seed traits were more stable. The results from CV and PCA indicated that leaf area, leaf length and thousand seed weight were the main factors accounting for the observed phenotypic variations. Significant or highly significant correlations were observed among most leaf and/or in seed phenotypic traits, whereas no significant correlations were observed between phenotypic traits and geographic factors.Based on cluster analysis, the ten populations can be divided into three clusters. These clusters were not a result of geographic distances.
文摘Comparing with an affinity and widespread species Adenophora potaninii the age structures of A. loboPhylla population, an endangered plant species were studied. 29 sample plots were investigated in the centered distribution area, Jinchuan county from altitude 2 300 m to 3 400 m. The main factors which influence the population age structures of A. lobophylla were analyzed. The principal characteristics of A. lobophylla populations are that the number of seedling and the density of population are much less than these of A. potaninii population. Below aititude of 2 700 m, the age structures of most A. lobophylla populations show the declining status, only above altitude of 2 700 m they are stable, while age structures of all populations of A. potaninll populations at corresponding altitude perform stable and developing features. The age structure patterns, relations between age (X) and number of individual (y) of stable populations of A. lobophylla can be expressed by equation : y =e(a-bx), and the longest life spah is 25a. Whereas A. potaninii populations can be expressed by the equationf y =ax-b, and the longest life span of individual is 21a. The external factors, which constrain the extension of A. lobophylla population, are extreme environmental conditions such as serious drought, external disturbance and low temperature.
基金supported by National Natural Science Foundation of China(31500328)Project of State Forestry Administration:Population Monitoring and Habitat Maintenance of Tibetan Red Deer(2015419)
文摘The Tibet Shannan Red Deer Nature Reserve is the center of the geographic distribution of Tibetan red deer. This paper presents the results of DNA analysis of 199 red deer fecal pellet groups collected during 2013 and 2014 during the green-plant period. We successfully extracted DNA from 87 DNA pellet groups and determined individual identification with 12 microsatellite loci. We evaluated the genetic diversity of the population and various population estimates with Capwire in R software. The87 successfully extracted pellet groups were from 50 individuals. In the population, the average number of alleles was 7.58 ± 0.18, the average effective number of alleles was 4.58 ± 0.15, and average polymorphism information content was 0.67 ± 0.01. Among the 12 loci,only T123 was moderately polymorphic; the other 11 loci were highly polymorphic. Expected heterozygosity ranged from 0.45 to 0.91, with an average of 0.72 ± 0.01, and average observed heterozygosity was 0.52 ± 0.11.Although Tibetan red deer remains endangered, the high genetic diversity indicates that this population has a good chance of recovery. This study provided insight that could be used by the local forestry department to develop programs to protect Tibetan red deer.
基金Project support by the National Natural Science Foundation of China(Grant No.11074012)
文摘Research on chip-scale atomic clocks （CSACs） based on coherent population trapping （CPT） is reviewed. The back- ground and the inspiration for the research are described, including the important schemes proposed to improve the CPT signal quality, the selection of atoms and buffer gases, and the development of micro-cell fabrication. With regard to the re- liability, stability, and service life of the CSACs, the research regarding the sensitivity of the CPT resonance to temperature and laser power changes is also reviewed, as well as the CPT resonance＇s collision and light of frequency shifts. The first generation CSACs have already been developed but its characters are still far from our expectations. Our conclusion is that miniaturization and power reduction are the most important aspects calling for further research.
文摘An investigation was conducted on distribution pattern, site condition and population structure of yew Taxus cuspidata Sieb. et Zucc. in Muling Forest Bureau of Heilongjiang Province, China in April, 2005. Results showed that yew is mainly distributed under the main storey of natural mixed forest of conifer and broadleaf, the soil moisture content of the yew site is high （40%-60%）, the pH value of soil is relatively lower （4.7-5.5）, and that the population structure of wild yew is not rational, belonging to the degeneration population, which is one of the reasons leading to the population decline. Although the site conditions of Muling area are suitable for the growth of wild yew, the population of wild yew shows a decline tendency, due to the fact that the middle-sized adult yew trees have been cut, young yews are often grazed by wildlife, and that the trunks of adult yew tend to be hollow.
文摘We investigated the plant population structure and the phy- tosociological and regeneration status in two disturbed tropical forests in Assam Province, the Hojai Reserve Forest and Kumorakata Reserve Forest. A total of 166 species （80 trees, 20 shrubs and 66 herbs） of 136 genera and 63 families were recorded in both study sites. The disturbance index at the two sites, Kumorakata Reserve Forest and Hojai Reserve Forest, were recorded at 11.4% and 3.70% respectively. Reverse J-shaped population curve and exploitation of tree species in higher girth classes were recorded at both study sites. In the girth classes （10-30 cm, 30-60 cm, 60-90 cm and 90-120 cm in size） the percentage of cut stump density was higher than the percentage of individual living trees. The 18% （Kumorakata Reserve Forest） and 7% （Hojai Reserve Forest） spe- cies were recorded as not regenerating. Illegal felling and over-exploitation of forest resources may lead to species-specific changes in the population structure and can alter the future structure and composi- tion of the forests.
