The effect of genotypic diversity on the age structure and bud bank of the Leymus chinensis population has not yet been demonstrated.This experiment was designed to study the age structure of the tiller,rhizome,and bu...The effect of genotypic diversity on the age structure and bud bank of the Leymus chinensis population has not yet been demonstrated.This experiment was designed to study the age structure of the tiller,rhizome,and bud of L.chinensis at genotypic diversity levels of 1,2,4,8,and 12.A total of 64 communities were established in this experiment,following the principle of randomized block experimental design.The results indicated that genotypic diversity had a significant or obviously significant effect on the cumulative length of rhizomes of 2a and 4a,dry matter accumulation of rhizomes of 1a and 2a,tiller number of 1a,tiller productivity of 3a,but had no significant effect age structure of buds.As the levels of genotypic diversity increased,the proportion of the cumulative length of rhizomes with 4a decreased and then increased,and dry matter accumulation of rhizomes with 1a and 2a gradually increased while the number of tillers with 1a gradually decreased,when the gradient of genotypic diversity increased.At the 1,2,4,8,and 12 genotype diversity levels,the number of tillers,the cumulative length of rhizomes,and dry matter accumulation in rhizomes and buds were all age structures of expanding type.However,tiller productivity was an expanding or stable age structure at levels of 1,2,4,8 genotypic diversity,while it was a declining age structure at the 12 genotype diversity gradient.An appropriate genotypic diversity is conducive to maintaining the growth and stability of the age structure of L.chinensis population,but too high a gradient of genotypic diversity can have a negative impact on the population age structure.This study provided that an appropriate number of genotypic diversity contributes to the stability of the population.展开更多
Kalimeris integrifolia Turcz. is a root sucker form perennial herb of Compositae. In die late period of growing season, fresh fleshy radicels grow up above the soil surface to develop root-borne buds, which in turn gr...Kalimeris integrifolia Turcz. is a root sucker form perennial herb of Compositae. In die late period of growing season, fresh fleshy radicels grow up above the soil surface to develop root-borne buds, which in turn grow into ramets and taproot. On the basis of observation on numerous samples, methods to classify the age of ramets and buds for the root sucker herbaceous plant population and to estimate the ages of taproots were established according to their morphology. The age of ramets was classified based on the regeneration times of taproot buds. Ramets developed from new root sucker buds were classified as 1 a. After 1 a ramets died, the ramets reproduced from the taproots were 2 a, and so on. New buds from a root sucker were 0 a buds, other age classes of buds were consistent with that of ramets, i.e. buds produced from taproots of I a ramets were 1 a buds, and so on. In the hay clipping meadows of the Songnen Plains, for K. integrifolia population, there are three age classes of ramets, representing a steady age structure. The maximal age of taproots of ramets is 4 a. Among all age classes, the population productivity of 2 a ramets was the highest, and that of I a ramets was the lowest. The ramet productivity increased with ramet age. During the early period of growing season, the productivity of 3 a ramets was the highest, but after the middle of growing season, I a ramets showed the greatest relative growth rate. The population size and age structure in the next year could be accurately forecasted by the number of fresh roots with budlet and present population in late autumn. The potential population in the bud banks was more than two times of the present population, which may provide sufficient substitution in the future.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
Knowledge of life history is important for understanding possible connections to population declines. Here, we investigated the female age structure and fecundity of Echinotriton chinhaiensis, one of the most endanger...Knowledge of life history is important for understanding possible connections to population declines. Here, we investigated the female age structure and fecundity of Echinotriton chinhaiensis, one of the most endangered salamanders in the world, using skeletochronology based on specimens collected in 2008 and 2009 from a population in Ruiyansi, northeast of Ningbo, Zhejiang, China. The results showed that most female salamanders were between 5 and 6 years of age, with the minimal reproductive age, predicted to be 3 years, and the clutch size correlated to the body size. We argue that both delayed attainment of sexual maturity and low fecundity make this species more vulnerable to extinction.展开更多
The age structure of the natural Zoysia japonica clonal population at QipanMountain in Huishan Scenic Spot of Shenyang, Liaoning Province, China was studied using themorphological method in 2003 and 2004. The dynamics...The age structure of the natural Zoysia japonica clonal population at QipanMountain in Huishan Scenic Spot of Shenyang, Liaoning Province, China was studied using themorphological method in 2003 and 2004. The dynamics of leaves were recorded and the dynamics oftiller and rhizome in the growing season were observed. The results indicated that the rhizomesformed in different years changed in color and rigidity. Its internodes produced in autumn becameshorter. The number of naked nodes changed with the tiller age. Rhizome and tiller characters wereused as a foundation for judging the ages of modules in this study. The longevity of tiller andrhizome was 3 years at most. At the beginning of the growing season, 2-year-old tillers and rhizomespredominated. Then 1-year-old tillers and rhizomes increased rapidly and became dominant in July.The proportion of buds to tillers on quantity was stable at about 30% in the mid-phase of thegrowing season and rose to about 50% in autumn. The seasonal dynamics of tiller, rhizome and bud wasvery important to guarantee the sustained existence of the Zoysia japonica population. The turnoverof modules was the mechanism of sustaining the rejuvenation of the Zoysiajaponica clonalpopulation.展开更多
Age structure of a plant population carries important information on population dynamics. The traditional age classification of individuals by development phases could not explain the generation relationship neither b...Age structure of a plant population carries important information on population dynamics. The traditional age classification of individuals by development phases could not explain the generation relationship neither between individuals nor between modules, and it could not accurately predict the future of population or the tendency of peatland evolution. In a peatland of the Xiao Hinggan Mountains, China, at the middle of the growth season, the age structures of 3 modules, ramets, active buds and rhizomes of a Carex middendorffii clonal population were investigated, with the method of classifying age classes of ramets and active buds by counting generation quantity of tiller nodes, and classifying age classes of rhizomes by their real survival time. The quantity of vegetative ramets was dominant. Tiller nodes of ramets can propagate vegetatively for a maximum of 3 generations. The population of ramets consisted of 3 age classes of ramets at the middle of the growth season, and showed a stable age structure. In the two sampling events, there was no significant difference between quantities and age structure of the population. The maximum age of an excavated rhizome was 12 years old. Rhizomes were classified in 8 age classes, and age classes 4-6 contributed most to the total biomass. There was no significant difference in total length and total biomass per unit area, or in biomass per unit length in rhizomes between the two samplings. Four age classes of active buds were recognized, and their number increased from July to August. The Carex middendorffii clonal population achieved regeneration by budding from the tiller nodes of ramets. The age structures of the 3 modules suggested that the Carex middendorffii clonal population could persist in the early development phase of the oligotrophic peatland in the Xiao Hinggan Mountains, but it could not be dominant. It also faces the risk to disappear from the community as the peatland develops further.展开更多
We used skeletochronology to estimate age structure of the Omei Wood Frog, Rana omeimontis, from southwestern China.Average age differed significantly between males and females.Age at sexual maturity in both males and...We used skeletochronology to estimate age structure of the Omei Wood Frog, Rana omeimontis, from southwestern China.Average age differed significantly between males and females.Age at sexual maturity in both males and females was 1 year. Longevity was 6 and 7 years for males and females, respectively. Average body size differed significantly between the sexes, with females being larger than males. A non-significant correlation between age and body size was found within each sex in this population. The ANCOVA analysis revealed that females also had larger body size than males when the effect of age was controlled.展开更多
Using a theoretical model, this article concludes that age structures influence people＇s propensity to save and thereby influence their capital intensity. In the context that capital and labor are in a substitutional...Using a theoretical model, this article concludes that age structures influence people＇s propensity to save and thereby influence their capital intensity. In the context that capital and labor are in a substitutional relation, increased capital intensity may lead to a drop of labor income share. We perform empirical research with provincial-level data from 1990 to 2007 and have proved that the rising of the old dependency ratio and the decrease of the children dependency rate both contribute to the fall of labor income share. This assumption still holds true after the authors control the influences of other potential factors that may influence labor income share展开更多
Spatial pattern of trees, basal stem increment and height were examined in a 5.0 ha mixed deciduous/ Pinus koraiensis forest from October in 1984 to May in 1987. Conclusions arc as following: 1. Analysis of the age-st...Spatial pattern of trees, basal stem increment and height were examined in a 5.0 ha mixed deciduous/ Pinus koraiensis forest from October in 1984 to May in 1987. Conclusions arc as following: 1. Analysis of the age-structure of the korcan pine forest shows that it is different from general steady-state forest type. The lack of saplings and individuals in small-diameter class clearly indicates that regeneration is not continuous. Continuous regeneration depends on thinning of the canopy to form a gap. Similar-aged korcan pine seedings grow in these gaps. 2. The horizontal structure of the korcan pine is a mosaic of more or less even-aged groups of trees. The mosaic is a result of korcan pine by regeneration strategy. The aggregations of korcan pine of different ages overlaps to form a continuous population generation. As a results, the population is maintained in steady state.展开更多
Variation in age structure and body size benefits are identified to understand the evolution of life history.Here,we estimated the age structure and body size of two species of odorous frogs(Odorrana margaretae and Od...Variation in age structure and body size benefits are identified to understand the evolution of life history.Here,we estimated the age structure and body size of two species of odorous frogs(Odorrana margaretae and Odorrana grahami)by using skeletochronology.The ages at sexual maturity of O.grahami and O.margaretae in both sexes were 1 and 2 years,respectively.For both sexes,the maximum age observed in O.margaretae was six years.For O.grahami,the maximum age observed in males and females were 4 and 5 years,respectively.Males and females did not differ in mean age in the two species.The average body size of both species considerably differed between sexes,with females being larger than males.The body size of females was also larger than that of males when the effect of age was removed.We also found positive correlations between body size and age within each sex in O.margaretae,but only for female in O.grahami.The female-biased sexual size dimorphism of the two species suggested that fecundity selection for larger female size may increase the reproductive output.展开更多
In this paper the continuous solutions for an age-structured host-vector epidemic model are introduced and studied. The continuous solutions of the age-structured epidemic model are easy to investigate and use. The su...In this paper the continuous solutions for an age-structured host-vector epidemic model are introduced and studied. The continuous solutions of the age-structured epidemic model are easy to investigate and use. The sufficient conditions for existence and uniqueness of the continuous so lutions are established.展开更多
For a long time, China has large population, so the labor-intensive products become the comparative advantage.This paper analyzes the influences of population age structure＇s changes on the export commodity structure...For a long time, China has large population, so the labor-intensive products become the comparative advantage.This paper analyzes the influences of population age structure＇s changes on the export commodity structure of our country and draws conclusions.展开更多
Relict subtropical coniferous forests in China face severe fragmentation,resulting in declining populations,and some are under significant threat from invasive alien species.Despite the crucial importance of understan...Relict subtropical coniferous forests in China face severe fragmentation,resulting in declining populations,and some are under significant threat from invasive alien species.Despite the crucial importance of understanding forest dynamics,knowledge gaps persist,particularly regarding the impact of invasive plants on vulnerable natives like Keteleeria evelyniana.In this study,we investigated the impact of invasive plants on the regeneration of forests dominated by K.evelyniana,a subtropical relict species in southwestern China.For this purpose,we characterized forest dynamics of 160 forest plots featuring K.evelyniana as the primary dominant species and determined whether the presence of invasive plants was correlated with regeneration of K.evelyniana.We identified four distinct forest types in which K.evelyniana was dominant.We found that radial growth of K.evelyniana trees is faster in younger ageclasses today than it was for older trees at the same age.The population structure of K.evelyniana in each forest type exhibited a multimodal age-class distribution.However,three forest types lacked established saplings younger than 10 years old,a situation attributed to the dense coverage of the invasive alien Ageratina adenophora.This invasive species resulted in a reduction of understory species diversity.Additionally,our analysis uncovered a significant negative correlation in phylogenetic relatedness(net relatedness index)between native and invasive alien plant species in eastern Yunnan.This suggests closely related invasive species face heightened competition,hindering successful invasion.Taken together,our findings indicate that successful establishment and habitat restoration of K.evelyniana seedling/saplings require effective measures to control invasive plants.展开更多
This paper is concerned with the sustained periodic oscillation phenomenon in a threespecies delayed predation system with Holling type II functional response and age structure in top predator.The top predator fertili...This paper is concerned with the sustained periodic oscillation phenomenon in a threespecies delayed predation system with Holling type II functional response and age structure in top predator.The top predator fertility function is regarded as a piecewise continuous smooth function with regard to their maturation period T2.The complicated dynamic behavior is proved by integrated semigroup theory and Hopf bifurcation theorem for semilinear equations with non-dense domain.Through qualitative analysis and bifurcation study of the system,we yield that this system has a nontrivial periodic solution that bifurcates from the positive equilibrium age distribution when bifurcation parameter T passes through some critical values.Numerical simulations are also provided to illustrate theoretically analytical results.展开更多
Identifying the life-history strategies of fish and their associations with the surrounding environment is the basic foundation in the conservation and sustainable utilization of fish species.We examined the age,growt...Identifying the life-history strategies of fish and their associations with the surrounding environment is the basic foundation in the conservation and sustainable utilization of fish species.We examined the age,growth,and reproduction of Sarcocheilichthys nigripinnis using 352 specimens collected monthly from May 2009 to April 2010 in the Qingyi Stream.We found the sex ratio of this study population was 0.58:1(female:male),significantly different from expected 1:1.Females and males both comprised four age groups.The annuli on the scales were formed during February and March.No obvious between-sex difference was observed in length-weight and length-scale-radius relationships.The total length in back-calculation significantly increased with age for both sexes,but did not differ significantly at each age between the two sexes.An inflection point was observed in the growth curves given by the von Bertalanffy growth function for total weight.At this inflection point,fish were 3.95 years.Both sexes reach their 50% sex maturity at age 2,when females and males were 94.7 mm and 103.0 mm total length.The temporal pattern of the gonado-somatic index corresponded to a spawning period that occurred from April through July.The non-synchronicity of egg diameter in each mature ovary during the breeding period suggested these fish may be batch spawners.The absolute fecundity increased significantly with total length and weight,whereas no significant correlation was observed between the relative fecundity and body size.展开更多
A skeletochronological study was conducted for the age, longevity and growth of a Rana nigromaculata population in northeastern Sichuan, China. Of 139 specimens, 119(68 males and 51 females) exhibited distinct arreste...A skeletochronological study was conducted for the age, longevity and growth of a Rana nigromaculata population in northeastern Sichuan, China. Of 139 specimens, 119(68 males and 51 females) exhibited distinct arrested growth lines in phalanges. Age at first reproduction was found to be two years of age for males and three for females. Maximum longevity was estimated to be at least six years in males and seven years in females. Average age did not differ between males and females. Breeding females were significantly older than breeding males. Females were larger in body size and heavier in body mass than males. Age was not correlated with body size and body mass in males, but a significant correlation was found among age, body size and body mass in females. The growth curve appeared significantly different between the sexes, with a higher growth rate throughout life and a larger asymptotic size in females. Moreover, analysis of the growth model indicated that the population studied was relatively stable.展开更多
Age and body size a re critical for understanding life history evolution and ecology.In this study,the age and body size of the Shangcheng stout salamander,Pachyhynobius shangchengensis,from a population in Anhui Prov...Age and body size a re critical for understanding life history evolution and ecology.In this study,the age and body size of the Shangcheng stout salamander,Pachyhynobius shangchengensis,from a population in Anhui Province,China,were studied by skeletochronology.The mean age was 8.8±0.2(mean±SD)years in females and 9.6±0.2 in males and ranged 5-13 years for both sexes.The mean age was significantly different between sexes.The mean body size and mass were(100.21±0.91)mm and(31.76±0.73)g in females,and(105.31±1.23)mm and(37.14±1.12)g in males,respectively.Males were significantly larger and heavier than females,indicating sexual size dimorphism.There was a significant positive correlation among body size,body mass,and age,suggesting that the oldest individuals are larger and heavier.The growth rate in males was significantly higher than in females.The present study provides preliminary data on life-history traits which can be helpful for future studies of this species and other hynobiid salamanders.展开更多
Skeletochronology is a method commonly used for estimating the age of amphibians and reptiles in the wild. However, the number of lines of arrested growth （LAGs） does not necessarily reflect age in some species. We ...Skeletochronology is a method commonly used for estimating the age of amphibians and reptiles in the wild. However, the number of lines of arrested growth （LAGs） does not necessarily reflect age in some species. We validated the applicability of this method to an endangered eublepharid gecko, Goniurosaurus kuroiwae, then inferred its longevity and age structures in wild populations. We classified young geckos into three groups using previously published data for early growth： Group 1 contained hatchlings before the first winter, Group 2 contained hatchlings after the first win- ter, and Group 3 included yearlings after the second winter. LAG numbers in these groups were then compared. All individuals in Group 1 possessed a single LAG, which was considered as a hatching line. Most individuals in Groups 2 and 3 possessed one and two additional LAGs, respectively （LAG1 and LAG2）, corroborating the notion that LAGs are formed annually. A few geckos exhibited fewer LAGs than expected. Analysis of variations in LAG and marrow cavity diameter demonstrated that in animals with fewer LAGs, endosteal resorption or fusion of hatching line and LAG1 had occurred. LAG2 was never lost by endosteal resorption and was identifiable by its diameter. Thus, the age of adult geckos could be determined by counting LAGs outward from LAG2. Application of this method to wild populations re- vealed that the longevity of this species is not less than 83 months, but that almost all individuals in fragmented habitats die before 50 months, suggesting lower population sustainability in such habitats.展开更多
Background：Conceptual models of forest dynamics are powerful cognitive tools,which are indispensable for communicating ecological ideas and knowledge,and in developing strategic approaches and setting targets for for...Background：Conceptual models of forest dynamics are powerful cognitive tools,which are indispensable for communicating ecological ideas and knowledge,and in developing strategic approaches and setting targets for forest conservation,restoration and sustainable management.Forest development through time is conventionally described as a directional,or ＂linear＂,and predictable sequence of stages from ＂bare ground＂ to old forest representing the ＂climax-state＂.However,this simple view is incompatible with the current knowledge and understanding of intrinsic variability of forest dynamics.Hypothesis：Overly simple conceptual models of forest dynamics easily become transformed into biased mental models of how forests naturally develop and what kind of structures they display.To be able to communicate the essential features and diversity of forest dynamics,comprehensive conceptual models are needed.For this end,Kuuluvainen（2009） suggested a relatively simple conceptual model of forest dynamics,which separates three major modes of forest dynamics,and incorporates state changes and transitions between the forest dynamics modes depending on changes in disturbance regime.Conclusions：Conceptual models of forest dynamics should be comprehensive enough to incorporate both longterm directional change and short-term cyclic forest dynamics,as well as transitions from one dynamics mode to another depending on changes in the driving disturbance regime type.Models that capture such essential features of forest dynamics are indispensable for educational purposes,in setting reference conditions and in developing methods in forest conservation,restoration and ecosystem management.展开更多
基金supported by the National Natural Science Foundation of China(32071860).
文摘The effect of genotypic diversity on the age structure and bud bank of the Leymus chinensis population has not yet been demonstrated.This experiment was designed to study the age structure of the tiller,rhizome,and bud of L.chinensis at genotypic diversity levels of 1,2,4,8,and 12.A total of 64 communities were established in this experiment,following the principle of randomized block experimental design.The results indicated that genotypic diversity had a significant or obviously significant effect on the cumulative length of rhizomes of 2a and 4a,dry matter accumulation of rhizomes of 1a and 2a,tiller number of 1a,tiller productivity of 3a,but had no significant effect age structure of buds.As the levels of genotypic diversity increased,the proportion of the cumulative length of rhizomes with 4a decreased and then increased,and dry matter accumulation of rhizomes with 1a and 2a gradually increased while the number of tillers with 1a gradually decreased,when the gradient of genotypic diversity increased.At the 1,2,4,8,and 12 genotype diversity levels,the number of tillers,the cumulative length of rhizomes,and dry matter accumulation in rhizomes and buds were all age structures of expanding type.However,tiller productivity was an expanding or stable age structure at levels of 1,2,4,8 genotypic diversity,while it was a declining age structure at the 12 genotype diversity gradient.An appropriate genotypic diversity is conducive to maintaining the growth and stability of the age structure of L.chinensis population,but too high a gradient of genotypic diversity can have a negative impact on the population age structure.This study provided that an appropriate number of genotypic diversity contributes to the stability of the population.
文摘Kalimeris integrifolia Turcz. is a root sucker form perennial herb of Compositae. In die late period of growing season, fresh fleshy radicels grow up above the soil surface to develop root-borne buds, which in turn grow into ramets and taproot. On the basis of observation on numerous samples, methods to classify the age of ramets and buds for the root sucker herbaceous plant population and to estimate the ages of taproots were established according to their morphology. The age of ramets was classified based on the regeneration times of taproot buds. Ramets developed from new root sucker buds were classified as 1 a. After 1 a ramets died, the ramets reproduced from the taproots were 2 a, and so on. New buds from a root sucker were 0 a buds, other age classes of buds were consistent with that of ramets, i.e. buds produced from taproots of I a ramets were 1 a buds, and so on. In the hay clipping meadows of the Songnen Plains, for K. integrifolia population, there are three age classes of ramets, representing a steady age structure. The maximal age of taproots of ramets is 4 a. Among all age classes, the population productivity of 2 a ramets was the highest, and that of I a ramets was the lowest. The ramet productivity increased with ramet age. During the early period of growing season, the productivity of 3 a ramets was the highest, but after the middle of growing season, I a ramets showed the greatest relative growth rate. The population size and age structure in the next year could be accurately forecasted by the number of fresh roots with budlet and present population in late autumn. The potential population in the bud banks was more than two times of the present population, which may provide sufficient substitution in the future.
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supported by the National Natu-ral Science Foundation of China(30770316)
文摘Knowledge of life history is important for understanding possible connections to population declines. Here, we investigated the female age structure and fecundity of Echinotriton chinhaiensis, one of the most endangered salamanders in the world, using skeletochronology based on specimens collected in 2008 and 2009 from a population in Ruiyansi, northeast of Ningbo, Zhejiang, China. The results showed that most female salamanders were between 5 and 6 years of age, with the minimal reproductive age, predicted to be 3 years, and the clutch size correlated to the body size. We argue that both delayed attainment of sexual maturity and low fecundity make this species more vulnerable to extinction.
基金This study was supported by Doctor Startup Foundation of Liaoning Province (20031029), Doctor Startup Foundation of Shenyang Normal University and Director Foundation of Shenyang Normal University (sy200513).
文摘The age structure of the natural Zoysia japonica clonal population at QipanMountain in Huishan Scenic Spot of Shenyang, Liaoning Province, China was studied using themorphological method in 2003 and 2004. The dynamics of leaves were recorded and the dynamics oftiller and rhizome in the growing season were observed. The results indicated that the rhizomesformed in different years changed in color and rigidity. Its internodes produced in autumn becameshorter. The number of naked nodes changed with the tiller age. Rhizome and tiller characters wereused as a foundation for judging the ages of modules in this study. The longevity of tiller andrhizome was 3 years at most. At the beginning of the growing season, 2-year-old tillers and rhizomespredominated. Then 1-year-old tillers and rhizomes increased rapidly and became dominant in July.The proportion of buds to tillers on quantity was stable at about 30% in the mid-phase of thegrowing season and rose to about 50% in autumn. The seasonal dynamics of tiller, rhizome and bud wasvery important to guarantee the sustained existence of the Zoysia japonica population. The turnoverof modules was the mechanism of sustaining the rejuvenation of the Zoysiajaponica clonalpopulation.
文摘Age structure of a plant population carries important information on population dynamics. The traditional age classification of individuals by development phases could not explain the generation relationship neither between individuals nor between modules, and it could not accurately predict the future of population or the tendency of peatland evolution. In a peatland of the Xiao Hinggan Mountains, China, at the middle of the growth season, the age structures of 3 modules, ramets, active buds and rhizomes of a Carex middendorffii clonal population were investigated, with the method of classifying age classes of ramets and active buds by counting generation quantity of tiller nodes, and classifying age classes of rhizomes by their real survival time. The quantity of vegetative ramets was dominant. Tiller nodes of ramets can propagate vegetatively for a maximum of 3 generations. The population of ramets consisted of 3 age classes of ramets at the middle of the growth season, and showed a stable age structure. In the two sampling events, there was no significant difference between quantities and age structure of the population. The maximum age of an excavated rhizome was 12 years old. Rhizomes were classified in 8 age classes, and age classes 4-6 contributed most to the total biomass. There was no significant difference in total length and total biomass per unit area, or in biomass per unit length in rhizomes between the two samplings. Four age classes of active buds were recognized, and their number increased from July to August. The Carex middendorffii clonal population achieved regeneration by budding from the tiller nodes of ramets. The age structures of the 3 modules suggested that the Carex middendorffii clonal population could persist in the early development phase of the oligotrophic peatland in the Xiao Hinggan Mountains, but it could not be dominant. It also faces the risk to disappear from the community as the peatland develops further.
基金Financial support was provided by the National Natural Science Foundation of China (31101633)the Foundation of Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education)+1 种基金China West Normal UniversityChina (XNYB01-3).
文摘We used skeletochronology to estimate age structure of the Omei Wood Frog, Rana omeimontis, from southwestern China.Average age differed significantly between males and females.Age at sexual maturity in both males and females was 1 year. Longevity was 6 and 7 years for males and females, respectively. Average body size differed significantly between the sexes, with females being larger than males. A non-significant correlation between age and body size was found within each sex in this population. The ANCOVA analysis revealed that females also had larger body size than males when the effect of age was controlled.
文摘Using a theoretical model, this article concludes that age structures influence people＇s propensity to save and thereby influence their capital intensity. In the context that capital and labor are in a substitutional relation, increased capital intensity may lead to a drop of labor income share. We perform empirical research with provincial-level data from 1990 to 2007 and have proved that the rising of the old dependency ratio and the decrease of the children dependency rate both contribute to the fall of labor income share. This assumption still holds true after the authors control the influences of other potential factors that may influence labor income share
文摘Spatial pattern of trees, basal stem increment and height were examined in a 5.0 ha mixed deciduous/ Pinus koraiensis forest from October in 1984 to May in 1987. Conclusions arc as following: 1. Analysis of the age-structure of the korcan pine forest shows that it is different from general steady-state forest type. The lack of saplings and individuals in small-diameter class clearly indicates that regeneration is not continuous. Continuous regeneration depends on thinning of the canopy to form a gap. Similar-aged korcan pine seedings grow in these gaps. 2. The horizontal structure of the korcan pine is a mosaic of more or less even-aged groups of trees. The mosaic is a result of korcan pine by regeneration strategy. The aggregations of korcan pine of different ages overlaps to form a continuous population generation. As a results, the population is maintained in steady state.
基金Financial support was provided by the National Natural Sciences Foundation of China(Nos.31772451,31970393)the Science and Technology Youth Innovation Team of Sichuan Province(2019JDTD0012)。
文摘Variation in age structure and body size benefits are identified to understand the evolution of life history.Here,we estimated the age structure and body size of two species of odorous frogs(Odorrana margaretae and Odorrana grahami)by using skeletochronology.The ages at sexual maturity of O.grahami and O.margaretae in both sexes were 1 and 2 years,respectively.For both sexes,the maximum age observed in O.margaretae was six years.For O.grahami,the maximum age observed in males and females were 4 and 5 years,respectively.Males and females did not differ in mean age in the two species.The average body size of both species considerably differed between sexes,with females being larger than males.The body size of females was also larger than that of males when the effect of age was removed.We also found positive correlations between body size and age within each sex in O.margaretae,but only for female in O.grahami.The female-biased sexual size dimorphism of the two species suggested that fecundity selection for larger female size may increase the reproductive output.
文摘In this paper the continuous solutions for an age-structured host-vector epidemic model are introduced and studied. The continuous solutions of the age-structured epidemic model are easy to investigate and use. The sufficient conditions for existence and uniqueness of the continuous so lutions are established.
文摘For a long time, China has large population, so the labor-intensive products become the comparative advantage.This paper analyzes the influences of population age structure＇s changes on the export commodity structure of our country and draws conclusions.
基金funded by the Major Program for Basic Research Project of Yunnan Province,China,grant number 202101BC070002the Special Foundation for National Science and Technology Basic Resources Investigation of China,grant number 2019FY202300.
文摘Relict subtropical coniferous forests in China face severe fragmentation,resulting in declining populations,and some are under significant threat from invasive alien species.Despite the crucial importance of understanding forest dynamics,knowledge gaps persist,particularly regarding the impact of invasive plants on vulnerable natives like Keteleeria evelyniana.In this study,we investigated the impact of invasive plants on the regeneration of forests dominated by K.evelyniana,a subtropical relict species in southwestern China.For this purpose,we characterized forest dynamics of 160 forest plots featuring K.evelyniana as the primary dominant species and determined whether the presence of invasive plants was correlated with regeneration of K.evelyniana.We identified four distinct forest types in which K.evelyniana was dominant.We found that radial growth of K.evelyniana trees is faster in younger ageclasses today than it was for older trees at the same age.The population structure of K.evelyniana in each forest type exhibited a multimodal age-class distribution.However,three forest types lacked established saplings younger than 10 years old,a situation attributed to the dense coverage of the invasive alien Ageratina adenophora.This invasive species resulted in a reduction of understory species diversity.Additionally,our analysis uncovered a significant negative correlation in phylogenetic relatedness(net relatedness index)between native and invasive alien plant species in eastern Yunnan.This suggests closely related invasive species face heightened competition,hindering successful invasion.Taken together,our findings indicate that successful establishment and habitat restoration of K.evelyniana seedling/saplings require effective measures to control invasive plants.
文摘This paper is concerned with the sustained periodic oscillation phenomenon in a threespecies delayed predation system with Holling type II functional response and age structure in top predator.The top predator fertility function is regarded as a piecewise continuous smooth function with regard to their maturation period T2.The complicated dynamic behavior is proved by integrated semigroup theory and Hopf bifurcation theorem for semilinear equations with non-dense domain.Through qualitative analysis and bifurcation study of the system,we yield that this system has a nontrivial periodic solution that bifurcates from the positive equilibrium age distribution when bifurcation parameter T passes through some critical values.Numerical simulations are also provided to illustrate theoretically analytical results.
基金supported by National Basic Research Program of China(2009CB119200)Natural Science Foundation of China(31172120)Anhui Provincial Natural Science Foundation(090413080)
文摘Identifying the life-history strategies of fish and their associations with the surrounding environment is the basic foundation in the conservation and sustainable utilization of fish species.We examined the age,growth,and reproduction of Sarcocheilichthys nigripinnis using 352 specimens collected monthly from May 2009 to April 2010 in the Qingyi Stream.We found the sex ratio of this study population was 0.58:1(female:male),significantly different from expected 1:1.Females and males both comprised four age groups.The annuli on the scales were formed during February and March.No obvious between-sex difference was observed in length-weight and length-scale-radius relationships.The total length in back-calculation significantly increased with age for both sexes,but did not differ significantly at each age between the two sexes.An inflection point was observed in the growth curves given by the von Bertalanffy growth function for total weight.At this inflection point,fish were 3.95 years.Both sexes reach their 50% sex maturity at age 2,when females and males were 94.7 mm and 103.0 mm total length.The temporal pattern of the gonado-somatic index corresponded to a spawning period that occurred from April through July.The non-synchronicity of egg diameter in each mature ovary during the breeding period suggested these fish may be batch spawners.The absolute fecundity increased significantly with total length and weight,whereas no significant correlation was observed between the relative fecundity and body size.
基金Financial support was provided by the Foundation of Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education)
文摘A skeletochronological study was conducted for the age, longevity and growth of a Rana nigromaculata population in northeastern Sichuan, China. Of 139 specimens, 119(68 males and 51 females) exhibited distinct arrested growth lines in phalanges. Age at first reproduction was found to be two years of age for males and three for females. Maximum longevity was estimated to be at least six years in males and seven years in females. Average age did not differ between males and females. Breeding females were significantly older than breeding males. Females were larger in body size and heavier in body mass than males. Age was not correlated with body size and body mass in males, but a significant correlation was found among age, body size and body mass in females. The growth curve appeared significantly different between the sexes, with a higher growth rate throughout life and a larger asymptotic size in females. Moreover, analysis of the growth model indicated that the population studied was relatively stable.
基金supported by the National Natural Science Foundation of China(NSFC 31471971)to Jianli XIONGgrants from the National Natural Science Foundation of China(NSFC 31272332)to Baowei ZHANG。
文摘Age and body size a re critical for understanding life history evolution and ecology.In this study,the age and body size of the Shangcheng stout salamander,Pachyhynobius shangchengensis,from a population in Anhui Province,China,were studied by skeletochronology.The mean age was 8.8±0.2(mean±SD)years in females and 9.6±0.2 in males and ranged 5-13 years for both sexes.The mean age was significantly different between sexes.The mean body size and mass were(100.21±0.91)mm and(31.76±0.73)g in females,and(105.31±1.23)mm and(37.14±1.12)g in males,respectively.Males were significantly larger and heavier than females,indicating sexual size dimorphism.There was a significant positive correlation among body size,body mass,and age,suggesting that the oldest individuals are larger and heavier.The growth rate in males was significantly higher than in females.The present study provides preliminary data on life-history traits which can be helpful for future studies of this species and other hynobiid salamanders.
基金supported by the Zoshinkai Fund for Protection of Endangered Animals and the Grant from the Japan Society for the Promotion of Science (JSPS KAKENHI Grant number 22510244)
文摘Skeletochronology is a method commonly used for estimating the age of amphibians and reptiles in the wild. However, the number of lines of arrested growth （LAGs） does not necessarily reflect age in some species. We validated the applicability of this method to an endangered eublepharid gecko, Goniurosaurus kuroiwae, then inferred its longevity and age structures in wild populations. We classified young geckos into three groups using previously published data for early growth： Group 1 contained hatchlings before the first winter, Group 2 contained hatchlings after the first win- ter, and Group 3 included yearlings after the second winter. LAG numbers in these groups were then compared. All individuals in Group 1 possessed a single LAG, which was considered as a hatching line. Most individuals in Groups 2 and 3 possessed one and two additional LAGs, respectively （LAG1 and LAG2）, corroborating the notion that LAGs are formed annually. A few geckos exhibited fewer LAGs than expected. Analysis of variations in LAG and marrow cavity diameter demonstrated that in animals with fewer LAGs, endosteal resorption or fusion of hatching line and LAG1 had occurred. LAG2 was never lost by endosteal resorption and was identifiable by its diameter. Thus, the age of adult geckos could be determined by counting LAGs outward from LAG2. Application of this method to wild populations re- vealed that the longevity of this species is not less than 83 months, but that almost all individuals in fragmented habitats die before 50 months, suggesting lower population sustainability in such habitats.
文摘Background：Conceptual models of forest dynamics are powerful cognitive tools,which are indispensable for communicating ecological ideas and knowledge,and in developing strategic approaches and setting targets for forest conservation,restoration and sustainable management.Forest development through time is conventionally described as a directional,or ＂linear＂,and predictable sequence of stages from ＂bare ground＂ to old forest representing the ＂climax-state＂.However,this simple view is incompatible with the current knowledge and understanding of intrinsic variability of forest dynamics.Hypothesis：Overly simple conceptual models of forest dynamics easily become transformed into biased mental models of how forests naturally develop and what kind of structures they display.To be able to communicate the essential features and diversity of forest dynamics,comprehensive conceptual models are needed.For this end,Kuuluvainen（2009） suggested a relatively simple conceptual model of forest dynamics,which separates three major modes of forest dynamics,and incorporates state changes and transitions between the forest dynamics modes depending on changes in disturbance regime.Conclusions：Conceptual models of forest dynamics should be comprehensive enough to incorporate both longterm directional change and short-term cyclic forest dynamics,as well as transitions from one dynamics mode to another depending on changes in the driving disturbance regime type.Models that capture such essential features of forest dynamics are indispensable for educational purposes,in setting reference conditions and in developing methods in forest conservation,restoration and ecosystem management.
