不同水稻生育期对稻粉虱种群动态的影响

本主要研究了不同水稻生育期对稻粉虱Aleurocybotus indicus种群动态的影响。研究结果表明,水稻分蘖期至拔节期最容易受稻粉虱为害,卵孵化率为88．1％,拟蛹的羽化率为82．9％,孵化率和羽化率均高于水稻其它生育期。     

螳螂种群增长制约因素分析

在自然界中,螳螂种群数量的增长受到多种因素的制约。作者通过野外调查和实验室饲养观察,以及对国内外相关资料的查阅,对这些主要制约因素逐一进行了分析和归纳。在影响螳螂分布与制约种群数量增长的这些因素中,自然条件中的温度是关键的制约因素,食物、天敌、自残行为、人类活动等是重要的制约因素。     

Impact factors of purse seine net and dip net fisheries on a chub mackerel population

There are two major kinds of fisheries for the chub mackerel in Japan. The purse seine net fishery exploits young and adult fish during the foraging season, while the dip net fishery exploits fish before and during the spawning season. To compare the damage to the chub mackerel stock caused by purse seine net and dip net fisheries, we introduced impact factors of the two kinds of fisheries on the two kinds of fisheries and estimated number of eggs spawned in 1982. We defined the impact factor as the ratio of the average reproductive value of individuals caught by each fishery to the reproductive value at maturity. The number of individuals caught by the purse seine net fishery was 66 times larger than the number caught by the dip net fishery, while the impact factor of the former was 84% of that of the latter. Thus, the total damage caused by the purse seine net fishery was much higher than the damage caused by the dip net fishery. We can evaluate the damage caused by mortality factors on endangered species using this method.     

Human population growth and the demographic transition

The world and most regions and countries are experiencing unprecedentedly rapid demographic change. The most obvious example of this change is the huge expansion of human numbers: four billion have been added since 1950. Projections for the next half century expect a highly divergent world, with stagnation or potential decline in parts of the developed world and continued rapid growth in the least developed regions. Other demographic processes are also undergoing extraordinary change: women''s fertility has dropped rapidly and life expectancy has risen to new highs. Past trends in fertility and mortality have led to very young populations in high fertility countries in the developing world and to increasingly older populations in the developed world. Contemporary societies are now at very different stages of their demographic transitions. This paper summarizes key trends in population size, fertility and mortality, and age structures during these transitions. The focus is on the century from 1950 to 2050, which covers the period of most rapid global demographic transformation.     

苹果全爪螨在不同温度下的实验种群生命表

在5种不同温度和16h/d光照长度的条件下组建苹果全爪螨Panonychus ulmi(Koch)实验种群生命表,在此基础上进行该实验种群的一些特征和生命参数分析。结果表明,适于苹果全爪螨实验种群增长的温度在26~30℃。     

Global evaluation of growth in a rural population: comparative analysis of shape and size

In this work the analogies and differences in shape and size between a rural school population (6–14 aged) of the Lozoya-Somosierra region (Madrid) and several recent and past Spanish populations from different environments have been studied. The results show the growth trend as well as the influences of ecological and socioeconomical factors. Paper presented at the 4^th congress of the European Anthropology Association (Florence, Sept. 1984).     

A novel approach for estimating growth phases and parameters of bacterial population in batch culture

Using mathematical analysis, a new method has been developed for studying the growth kinetics of bacterial populations in batch culture. First, sampling data were smoothed with the spline interpolation method. Second, the instantaneous rates were derived by numerical differential techniques and finally, the derived data were fitted with the Gaussian function to obtain growth parameters. We named this the Spline-Numerical-Gaussian or SNG method. This method yielded more accurate estimates of the growth rates of bacterial populations and new parameters. It was possible to divide the growth curve into four different but continuous phases based on changes in the instantaneous rates. The four phases are the accelerating growth phase, the constant growth phase, the decelerating growth phase and the declining phase. Total DNA content was measured by flow cytometry and varied depending on the growth phase. The SNG system provides a very powerful tool for describing the kinetics of bacterial population growth. The SNG method avoids the unrealistic assumptions generally used in the traditional growth equations.     

斑苦竹无性系种群克隆生长格局动态的研究

采用“例逐龄级累加法”（ＲＡＡ）研究了缙云山斑苦竹无性系种群的克隆生长格局动态,以及无性系分株克隆生长型的动态趋势．结果表明,作为复轴型的斑苦竹,其无性系种群随时间进程表现为聚集程度逐渐降低的集群分布格局．在自然条件下,斑苦竹更多地表现出单轴型的繁殖趋势．应用ＲＡＡ分析植物种群,尤其是竹类植物种群前期的克隆生长格局的动态,结果可靠,具有重要的应用价值．     

On the global stability of the logistic age-dependent population growth

We study an age-dependent population equation with a nonlinear death rate of logistic type. The global asymptotic stability of the null solution is investigated when R(0)<1. If R(0)>1 we get the existence of a nontrivial steady state that becomes asymptotically stable itself, while the null solution is unstable. The rate of decay is estimated.Supported in part by CNR-GNAFA     

Host-specificity of AM fungal population growth rates can generate feedback on plant growth

While the mutualistic interaction between plants and AM fungi is of obvious importance to ecosystem processes, the factors influencing the ecological and evolutionary dynamics within this interaction are poorly understood. The mutual interdependence of plant and AM fungal relative growth rates could generate complex dynamics in which the composition of the AM fungal community changes due to association with host and this change in fungal composition then differentially feeds back on plant growth. I first review evidence for feedback dynamics and then present an approach to evaluating such complex dynamics. I specifically present evidence of host-specific differences in the population growth rates of AM fungi. Pure cultures of AM fungi were mixed to produce the initial fungal community. This community was then distributed into replicate pots and grown with one of four co-occurring plant species. Distinct compositions of AM fungal spores were produced on different host species. The AM fungal communities were then inoculated back onto their own host species and grown for a second growing season. The differentiation observed in the first generation was enhanced during this second generation, verifying that the measure of spore composition reflects host-specific differences in AM fungal population growth rates. In further work on this system, I have found evidence of negative feedback through two pairs of plant species. The dynamic within the AM fungal community can thereby contribute to the coexistence of plant species.     

基于营养供需动态平衡考虑的种群生物量增长模型

本文在种群实际增长是限制性营养供需动态平衡所导致的结果这一假定下,推导出了一个单种群生物量增长数学模型。该模型在形式上与崔-Lawson模型相一致。但其3个参数的生物学意义与崔-Lawson模型有不同的内涵。该模型概括了崔-Lawson模型所不能概括的一类单种群物量增长方式,并给出了不同类型生物量增长方式与种群自身特征和营养再循环的分解条件的关系。本模型的建立和解释具有直观性。     

Natural enemy ravine revisited: the importance of sample size for determining population growth

Abstract. 1. The population growth of three aphid species, Metopolophium dirhodum (Walker), Rhopalosiphum padi (L.), and Sitobion avenae (F.), on winter wheat, was analysed by regression. The calculations were based on censuses of aphids made in 268 plots at 3- or 7-day intervals for 10 years on leaves and 6 years on ears. The calculations were made separately for each plot each year, then repeated on the pooled data from all plots monitored in a year.
2. At the level of individual plots, no population growth was detected at very low densities. At high densities, the populations grew exponentially and the growth rates did not decrease with increasing aphid density.
3. Significant growth was always detected in the pooled data. These growth rates decreased significantly at the highest densities. Field estimates of the intrinsic rate of increase derived from these data ranged from 0.010 to 0.026 for M. dirhodum , 0.0071–0.011 for R. padi , and 0.00078–0.0061 and 0.0015–0.13 for S. avenae , on leaves and ears respectively .
4. The apparent lack of growth in the individual plots at low densities is attributable to small sample size. It is concluded that the natural enemy ravine in the population dynamics of cereal aphids, identified by Southwood and Comins (1976), is a consequence of low population densities at which population increase is undetectable unless very large samples are taken.     

温度对水螅种群增长和个体大小的影响

应用群体累积培养法,以枝角类为食物,在10℃、20℃和30℃三种温度下,研究了温度对水螅(Hydra sp．)种群密度、种群增长率和个体大小的影响。结果表明温度对水螅种群密度和个体体积由极显著影响。在培养初期,30℃下的水螅种群密度最大;而在培养后期,20℃下的水螅种群密度则显著大于30℃下的值;10℃下的值则始终最小。在同一温度下,种群增长率均与时间呈曲线相关,10℃、20℃、30℃的回归方程分别为：Y=0．000433X^2-0．00262X 0．00332、Y=-0．003367X^2 0．068335X-0．066489、Y=-0．018469X^2 0．188952X-0．030933。在研究范围内,30℃的水螅个体最小。     

Decomposing variation in population growth into contributions from environment and phenotypes in an age-structured population

Evaluating the relative importance of ecological drivers responsible for natural population fluctuations in size is challenging. Longitudinal studies where most individuals are monitored from birth to death and where environmental conditions are known provide a valuable resource to characterize complex ecological interactions. We used a recently developed approach to decompose the observed fluctuation in population growth of the red deer population on the Isle of Rum into contributions from climate, density and their interaction and to quantify their relative importance. We also quantified the contribution of individual covariates, including phenotypic and life-history traits, to population growth. Fluctuations in composition in age and sex classes ((st)age structure) of the population contributed substantially to the population dynamics. Density, climate, birth weight and reproductive status contributed less and approximately equally to the population growth. Our results support the contention that fluctuations in the population's (st)age structure have important consequences for population dynamics and underline the importance of including information on population composition to understand the effect of human-driven changes on population performance of long-lived species.