Genotypic Diversity Affects Age Structure of Tiller and Rhizome of Leymus chinensis Population,But Not Age Structure of Bud

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.

Age Structure of Females in a Breeding Population of Echinotriton chinhaiensis(Caudata:Salamandridae) and Its Conservation Implication

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.

Skeletochronological Study of Age,Longevity and Growth in a Population of Rana nigromaculata(Amphibia:Anura) in Sichuan,China

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.

Age structure and dynamics of Zoysia japonica module population

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.

Age and Body Size of the Shangcheng Stout Salamander Pachyhynobius shangchengensis(Caudata:Hynobiidae)from Southeastern China

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.

Validation and Application of Skeletochronology for Age Determination of the Ryukyu Ground Gecko, Goniurosaurus kuroiwae(Squamata: Eublepharidae)

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.

Skeletochronological Study on Age Structure of a Chinese Endemic Frog(Rana omeimontis)

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.

Conceptual models of forest dynamics in environmental education and management:keep it as simple as possible,but no simpler

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.

Age,growth and reproduction of Sarcocheilichthys nigripinnis from the Qingyi Stream in the Huangshan Mountains

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.

AGE STRUCTURE AND SPATIAL PATTERN OF OLD-GROWTH KOREAN PINE FOREST IN XIAOXING'ANLING MOUNTAIN

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.

Effect of shading treatment on stomatal behavior of Adenophora lobophylla at different ages

The stomatal behavior of Adenophora lobophylla of different age structures was studied in July 1995 in greenhouse of the Harbin Forest Farm of Northeast Forestry University by means of shading experiment. The effects of different shading treatments on the stomatal physiological character and ecological adaptation of A. lobophylla of different ages were compared. The results showed that the morphological characters of annual A. lobophylla were more obvious than that of the perennial, but the stomatal density of annual was less than that of perennial. Growth of annual A. lobophylla was more sensitive to the change of environment than that of the perennial. The ecological adaptation of annual was weak, which was one of the main causes of endangered population.

Age Structure of Two Species of Odorous Frogs(Odorrana margaretae and Odorrana grahami)

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.

Population dynamics and protection strategies of Litsea coreana Levl.var.sinensis with Guizhou Province in China as an example

Studying the dynamics of plant populations is crucial to the conservation and management of endangered plants.The diameter at breast height(DBH),tree height,crown width,and environmental factors of a total of 15 plots in five populations in Guizhou Province,China were measured in this study.The method of substituting diameter at breast height for age was used to divide the population into 7 age classes.The age structure,static life table,and relationship between the population characteristics and environmental factors of the Litsea coreana Levl.var.sinensis population were studied.Moreover,the time series model was used to predict the population dynamics.Results showed that the age structure of population in Zhengan County(Population ZA)had an inverted Jshape with abundant seedlings and insufficient middle-aged and elderly individuals.The age structures of populations in Daozhen County(Population DZ),Kaiyang County(KY),Meitan County(Population MT),and Xishui County(Population XS)were spindle-shaped with few young individuals and many middle-aged and elderly individuals.The mortality rate of each population fluctuated with the increase in age class,and the populations were extremely unstable.The survival curve was close to the Deevey III type,and the degree of deviation was related to the lack of young individuals.After the age stages II,IV,and VI,the number of aged plants in the different populations initially increased then decreased,and population stability was difficult to maintain.Redundancy analysis showed that the DBH,tree height and crown width of the population decreased with the increase of annual mean temperature,and the population density was restricted by soil nutrient conditions to a certain extent.The results of this work provide scientific basis for the conservation and sustainable utilization of natural populations of L.coreana var.sinensis in Guizhou Province,China.

Well-Posedness and a Finite Difference Approximation for a Mathematical Model of HPV-Induced Cervical Cancer

We present a first-order finite difference scheme for approximating solutions of a mathematical model of cervical cancer induced by the human papillomavirus (HPV), which consists of four nonlinear partial differential equations and a nonlinear first-order ordinary differential equation. The scheme is analyzed and used to provide an existence-uniqueness result. Numerical simulations are performed in order to demonstrate the first-order rate of convergence. A sensitivity analysis was done in order to compare the effects of two drug types, those that increase the death rate of HPV-infected cells, and those that increase the death rate of the precancerous cell population. The model predicts that treatments that affect the precancerous cell population by directly increasing the corresponding death rate are far more effective than those that increase the death rate of HPV-infected cells.

Assess Medical Screening and Isolation Measures Based on Numerical Method for COVID-19 Epidemic Model in Japan

This study aims to improve control schemes for COVID-19 by a numerical model with estimation of parameters.We established a multi-level and multi-objective nonlinear SEIDR model to simulate the virus transmission.The early spread in Japan was adopted as a case study.The first 96 days since the infection were divided into five stages with parameters estimated.Then,we analyzed the trend of the parameter value,age structure ratio,and the defined PCR test index(standardization of the scale of PCR tests).It was discovered that the self-healing rate and confirmed rate were linear with the age structure ratio and the PCR test index using the stepwise regression method.The transmission rates were related to the age structure ratio,PCR test index,and isolation efficiency.Both isolation measures and PCR test medical screening can effectively reduce the number of infected cases based on the simulation results.However,the strategy of increasing PCR test medical screening would encountered a bottleneck effect on the virus control when the index reached 0.3.The effectiveness of the policy would decrease and the basic reproduction number reached the extreme value at 0.6.This study gave a feasible combination for isolation and PCR test by simulation.The isolation intensity could be adjusted to compensate the insufficiency of PCR test to control the pandemic.

Temporal dynamics and spatial variations of forest vegetation carbon stock in Liaoning Province, China

There are many uncertainties in the estimation of forest carbon sequestration in China, especially in Liaoning Province where various forest inventory data have not been fully utilized. By using forest inventory data, we estimated forest vegetation carbon stock of Liaoning Province between 1993 and 2005. Results showed that forest biomass carbon stock increased from 68.91 Tg C in 1993 to 97.51 Tg C in 2005, whereas mean carbon density increased from 18.48 Mg·ha^-1 C to 22.33 Mg·ha^-1 C. The carbon storage of young- and middle-aged forests increased by 22.1 Tg C and 5.95 Tg C, but that of mature forests has decreased by 0.25 Tg C. The carbon stock and density of forests in Liaon- ing Province varied greatly in space： larger carbon storage and higher carbon density were primarily found in the east area. The spatial distribution of carbon density was determined by many factors, of which human activities played an important role. The forests in Liaoning Province played a positive role as a sink of atmospheric carbon dioxide. The carbon fixation ability of forests in this area was primarily derived from forest plantation and the total forest carbon sequestration can be enhanced by expanding young- and middle-aged forests.

Age-structured model for COVID-19: Effectiveness of social distancing and contact reduction in Kenya

Coronavirus disease 2019 is caused by severe acute respiratory syndrome coronavirus 2.Kenya reported its first case on March 13,2020 and by March 16,2020 she instituted physical distancing strategies to reduce transmission and flatten the epidemic curve.An age-structured compartmental model was developed to assess the impact of the strategies on COVID-19 severity and burden.Contacts between different ages are incorporated via contact matrices.Simulation results show that 45%reduction in contacts for 60-days period resulted to 11.5e13%reduction of infections severity and deaths,while for the 190-days period yielded 18.8e22.7%reduction.The peak of infections in the 60-days mitigation was higher and happened about 2 months after the relaxation of mitigation as compared to that of the 190-days mitigation,which happened a month after mitigations were relaxed.Low numbers of cases in children under 15 years was attributed to high number of asymptomatic cases.High numbers of cases are reported in the 15e29 years and 30e59 years age bands.Two mitigation periods,considered in the study,resulted to reductions in severe and critical cases,attack rates,hospital and ICU bed demands,as well as deaths,with the 190-days period giving higher reductions.

Dynamics of Betula ermanni population in subalpine vegetation in Changbai Mountain, Northeast China

Betula ermanni population was divided into three groups: the upper population (2 000–2 200 m), the middle population (1 700–2 000 m), and the down population (1 400–1 700 m) in Changbai Mountain. The dynamics ofBetula ermanni populations in subalpine vegetation are studied and the population life table, fecundity schedule, survival curves, age structure, and fecundity curves were established. The results showed that the, middle population is obviously, the transition from the upper population to the down population.

Changes in Natural Mortality of Atlantic Cod(Gadus morhua) on Eastern Georges Bank

The assessment of Eastern Georges Bank cod with the assumption of a constant natural mortality of 0.2 has over-estimated stock productivity, resulting in a severe retrospective pattern since the late 2000 s. Comparing relative exploitation rate(ratio of fishery catch at age to survey abundance indices at age) with total mortality calculated from the age distribution in surveys indicated a conflict when constant natural mortality was assumed. This inconsistency implies an increase in natural mortality since the mid-1990 s. In this paper, natural mortality estimated by Virtual Population Analysis(VPA) indicated that natural mortality for this stock has increased to 0.8 since the mid-1990 s for ages 6+. Potential factors contributing to this elevated natural mortality, including poor fish conditions and increased losses due to seal predation were discussed.