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1.
Keisuke Nakata 《Researches on Population Ecology》1989,31(2):185-209
Summary Changes of the components of reproduction were analyzed quantitatively in a two-year cyclic population (which has two peaks
in alternate years during a five-year census) of the red-backed vole,Clethrionomys rufocanus bedfordiae, with reference to its regulatory mechanism: (1) Variation in sex ratios was not associated with population phase or density,
although a higher percentage of females in mature individuals was observed in the increase phase. (2) Females attained to
sexual maturity at younger age and at lighter body weight than did males. All the youngest mature individuals were found in
the low and the increase phases. Age and size at maturity became older and larger as the population went toward the peak phase.
(3) Maturation rate was strongly associated with population phase and density; this component is an important and good parameter
to predict population trend. Maturation rates were in the order, the low phase>the increase phase>the peak phase>the decline
phase; the differences in the rates among these phases were significant. Maturation rate was somewhat depressed when the population
density exceeded about 40 individuals/ha. Changes in age at maturity and in maturation rate are interpreted as derivative
phenomena related to the population density and the capacity of the number of mature voles per unit area. (4) The maximum
number of mature individuals were 26 males/ha and 29 females/ha; there was almost no increase of the number of mature voles
at higher population densities over about 40 individuals/ha. The number of exclusive home ranges per hectare calculated from
the observed range lengths did not differ much from the maximum number of mature voles of either sex. (5) Length of breeding
period was shorter in the high-density years than in the low-density years; the breeding started earlier and ended earlier
in the former than that in the latter. In the increase phase a few voles reproduced in winter. (6) The percentage of pregnant
females was significantly lower in the peak phase than those in the other phases. 相似文献
2.
3.
Population dynamics of humans and other animals 总被引:7,自引:1,他引:7
Ronald D. Lee 《Demography》1987,24(4):443-465
Human population dynamics, at least until the past century, have probably been governed by homeostasis and in this resembled those of other animals. Because human population homeostasis was probably substantially weaker than among large mammals, its operation has been less obvious. Nonetheless, the empirical evidence for advanced agriculturalists is compelling. Unlike animals, the human population has tended toward equilibria that have been tending upward at an accelerating rate. The acceleration might reflect long-run positive feedback between density and technological progress, as Boserup has suggested. Because homeostasis was weak, its role in shorter run historical explantation is limited; its force was gentle and easily overwhelmed by other particular influences. Malthusian oscillation, in the sense of distinctive medium-run dynamics arising from homeostasis, probably did not occur. And because homeostasis was weak, density dependence can in principle explain only a minute proportion of the annual variation in population growth rates. Yet homeostasis plays an essential role in demographic theory. Without it, we are incapable of explaining population size and change over time except by recounting a mindless chronology of events back to the beginning of humanity--whenever that was. Without it, we cannot explain the response of population growth to economic growth. Without it, we cannot explain recovery from catastrophe or the rapid natural increase in many frontier regions. Without it, we cannot properly analyze the influence of climatic variation and other partially density-independent factors. Our basic understanding of human history requires a grasp of what homeostasis can explain and what it cannot. A homeostatic approach to population dynamics also leads to questions about the roles of reproductive norms and institutions, not just whether they encourage high or low fertility, but whether they make natural increase responsive to resource abundance. And if they do, whether they strike the balance of population and the means of subsistence at a relatively prosperous or impoverished level. Such considerations may contribute to an understanding of broad preindustrial differences among the regions of the world in densities, average levels of vital rates, and living standards--which was very much how Malthus viewed the matter. Ordinary homeostatic tendencies essentially vanish in the course of economic development, and they were probably all but gone from much of Europe by the end of the 19th century.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
4.
Barry Edmonston 《Population research and policy review》2006,25(5-6):513-545
The effects of changes in rates of mortality, fertility, and migration depend not only on the age-specific patterns and levels
of these rates, but on the age structure of the population. In order to remove the influences of the age structure and concentrate
on the effects of the demographic rates themselves, a common practice is to analyze the influences of the rates for a standard
age structure. This paper analyzes current and future population changes in Germany, using a stationary population equivalent
model (SPE) that shows long-term effects of current fertility, mortality, and international migration patterns. Results indicate
that the German population will eventually decline because of below replacement fertility, if net immigration does not counteract
this decrease. This means, for instance, that the long-term stationary population levels for Germany will decrease by approximately
6.5 million during a decade in which current fertility, mortality, and international migration levels prevail. The paper also
reports how various other assumptions for mortality, fertility, and international migration affect the SPE model for Germany. 相似文献
5.
Summary The paper reports the results of demographic research in a rural village of about 1500 Hausaspeaking farmers in southern Niger, during the winter of 1973-74. The research site lies at the heart of the Sahel-sudanic zone just to the south of the Sahara, where drought, and in some areas, famine have exacted a heavy human, animal, and economic toll since 1968. The study was designed to measure and explain the change in the size and structure of the population during the years 1969-73. Social anthropological field techniques were used to ensure full and accurate reporting by community residents on all census topics. Data on rainfall and crop yields, on health and sanitary conditions, and on the political economy, social organization, and culture of the village were gathered in order to interpret the demographic situation The analysis of this data yields the following conclusions: 1. The population of the village appears younger (mean age: 15 years) and growing faster (mean doubling time: 23 years) than reported for Niger as a whole in 1972. 2. Contrary to what the researchers expected, the crude death rate, while relatively high to begin with, actually declined during the drought period (mean: 14.81); the crude birth rate remained very high (mean: 46.01), and the crude rate of increase rose from 1969 to 1973. 3. There was virtually no family out-migration from the target village during the drought, although the number of adult males participating in seasonal migrations to large West African towns rose from 35 per cent in 1969-70 to 75 per cent in 1973-74. 4. Problems of food production and distribution were acute, but thanks to the availability of donated foods, these were sufficiently short-lived during this drought cycle to make no discernible impact on population, although prolonged protein/calorie malnutrition among the very young may affect future fecundity. 相似文献
6.
7.
Takashi Saitoh 《Researches on Population Ecology》1995,37(1):49-57
The natal dispersal distance of the grey-sided vole,Clethrionomys rufocanus (Sundevall), was measured in a large outdoor enclosure (2.1 ha) in Hokkaido, Japan. Voles in about half of the enclosure
(1 ha) were fed. Distance from the natal site to the site of reproduction was significantly greater in males (64.9 m) than
in females (35.3 m). In males, 24.8% settled within one home range length of their natal site and 49.6% settled further than
two range lengths from their natal site. In femles, the respective percentages were reversed: 51.2% and 22.0%. The timing
of large movements (≥50 m) was related to body mass in both sexes. The population density was always higher on the fed grid
than on the control grid, which resulted in the frequency of large movements being greater on the fed grid that on the control
grid. Thus, the percentage of voles performing a large movement was not different between the grids in both sexes. 相似文献
8.
The purpose of this study is to analyse the mechanisms and effects of population pressure on rural livelihood system in South
central Ethiopia from 1950 to 2004. In Sub-Sahara Africa population pressure takes two different forms: (1) a pressure on
existing household to accommodate a growing number of children (change in household dependency ratio); (2) An increased demand
for new livelihood positions in a situation where the total resources available for households may be constrained (change
in density ratio). We blended the approaches of Boserup and Chayanov to understand how families make their living when dependency
and density ratios change over time. We collected data using a life course and cohort study approaches to capture the dynamics
and to compare the past with the present. We found out that livelihood strategies took different forms when both dependency
and density ratios were low and when they were on the increase. When both ratios were low livelihood strategies took the form
of agricultural extensification and this was due to the relative availability of land. When both ratios were on the increase,
livelihood strategies took the forms of agricultural intensification and diversification.
相似文献
Tsegaye TegenuEmail: |
9.
Ryo Tanaka 《Researches on Population Ecology》1972,13(2):127-151
Summary A substantial explication of the edge effect has been attempted by use of capture-recapture data for a vole population (Microtus montebelli), gathered intwo plots of 100×100 m or less during 12 days, cheked twice daily, in August 1970; the sample was quite sufficient
for the aim.
The edge effect as guessed by increased catch per trap is usually suspected to ensue from range-settlers in the outside boundary
strip of a plot and immigrants. But by a theoretical analysis I could attain a tentative conclusion that no increased catch
per trap will occur unless any invasion takes place. Then it follows that, apart from the effect of invasion, the role of
the adjoining outside settlers in the edge effect is essentially required to be studied in the light of knowledge on the truth
of size and shift in home range.
The variation in range behavior for 183 adult voles, captured 6 times or more, could be grouped into eight types, of which
the range-conservative type possessed 52% of the sample and the group of the type was justly utilized for giving averages
of range size. Besides, it was seen from the observed frequency of types that a considerable number of immigrants onto the
census plot were induced perhaps being allured by trap baits, but the majority of them proved to be assigned to the voles
that have their ranges inside the assessment line ofDice; the rest referable to effective immigrants was only a few (7%). I could perceive no reason such as disproves the idea ofDice’s additional boundary strip.
Viewed from maps of ingress shift of ranges, the effect of ingress must have been greater in the outer trap rows than in the
inner within the plot, so that it might well be called edge effect in general; such effect, however, is seen gradually diminishing
toward the center, and hence it is almost unlikely that one should find any clear-cut intra-plot assessment lines demarcating
such an inner square as quite free from edge effects.
Averages of observed range length and width (ORL and ORW), as reliable measures for the true range size, were determined from
the above group of specimens; as a result, the remarkable concept of elliptic range shape was established by regarding ORL
as long axis and ORW as short one, and, directly from these averages, the mean range sizes worked out at 0.04 for females
and 0.09 for males in acreage which proved to be surprisingly well agreeable with those of isotope-revealed ranges for voles
given byGodfrey (1954) andAmbrose (1969).
The catchability for marked voles (
) was estimated by the maximum likelihood method by use ofJolly’s formulae (1965), but that for unmarked ones (
) was made by the regression census formula; as a result it was shown that the population was clearly of π>p type and that the trap-experience that voles underwent one month or more ago can make them retain as high catchability as
π.
Contribution from JIBP-PT No. 110, carried out by the grant from the expenditure of Education Department to the specific study
on “Dynamics of Biosphere”. 相似文献
10.
Chobei Imai 《Researches on Population Ecology》1984,26(2):353-362
Summary The population dynamics of the housefly,Musca domestica, on patchy and unstable habitats consisting of refuse was investigated at a waste disposal site by using sticky flypaper
and mark-release-recapture technique (Jolly-Seber's method). The newly disposed garbage was favorable for breeding of the flies for about one month after being disposed, while
a mixture of garbage and ash from incinerated refuse was less favorable. On the garbage under favorable conditions, the rates
of population increase was 1.25–2.82 per day, and approximately 1300–1500 flies were produced per square meter within the
available period of one month. The rapid decrease in the fly density was observed just after the appearance of high density
peaks. The mark-release-recapture study suggested that this rapid decrease would be mainly due to the density-dependent emigration
of adult flies from the patchy habitats. The emigration was also activated when the time after garbage disposition became
long. 相似文献
11.
Summary A field work with two plots of grid, a snap trap being set on each station spaced 5 m apart, was executed in the summer of
1968 to evaluate prebaiting in census trapping by comparing the result in one plot, prebaited for three days, with that in
the other not prebaited. Since the population was as high as some 230 per acre on the average in density and formed of the
vole,Microtus montebelli, alone, sufficient samples were gathered irrespective of the plot size as small as 50×50 m.
Owning to the circumstances, multiple collisions inflicted so intense influence on sampling especially in the prebaited plot
thatz-equation for census adjusted to the effect was well applicable to the data in either plot. In sampling, the fact that small
voles are apt to be caught later than large voles was statistically evidenced in either sex, and yet any proof that males
tend to be caught prior to females was not offered. It was ascertained in either plot that the daily catch was realized according
to the same rule through the whole period of trapping in both external belt and internal square within the plot; hence it
follows that no considerable immigration occurred.
One of the beneficial effects of prebaiting is sure to be that the probability of capture was markedly enhanced in the prebaited
plot, and a second is supposed, though inconclusively, to be that a good sampling could be executed consistently through the
census period giving rise to no inordinate catches perhaps due to heterogeneous sampling as was seen in earlier days in the
not prebaited plot. The supposition has derived from the condition that most of the whole population is trappable, which is
established by interrelation among population density, size of home range and trap spacing. It was suggested that the effect
of prebaiting should be evaluated from the view-point of the interrelation, because the basic utility of prebaiting consists
in that it may help to our utlimate purpose to estimate the whole population.
Contribution from JIBP-PT No. 55, carried out by the grant from the expenditure of Education Department to the specific study
on “Dynamics of Biosphere” 相似文献
12.
人口安全是非传统安全中的重要组成部分,人口数量、人口结构、人口素质、人口迁移等均是影响人口安全的重要因素,而在这些因素内部也存在着相互影响、相互制约的关系,采用定量和定性相结合的研究方法,就影响人口安全的人口文化素质因素对人口数量和人口结构因素的作用分别进行纵向和横向的研究,并且在横向的实证研究中利用SPSS软件包将全国各省份的人口安全程度作聚类分析,以期更好地确定人口文化素质对人口数量和结构的影响程度。 相似文献
13.
Clark L. Erickson 《Population and environment》1992,13(4):285-300
The terrain within the Lake Titicaca Basin in the Andean highlands of Peru and Bolivia is a highly human-modified landscape. Archaeological investigations document that massive landscape modifications were undertaken throughout prehistory in order to intensively cultivate marginal lands. The paper focuses on raised fields, large earthen platforms which prevent waterlogging and flooding, increase soil fertility, conserve moisture, insure nutrient production and recycling, and improve crop microclimates. The environmental implications of the construction of over 82,000 hectares of raised fields for local vegetation, microclimate, soils, sedimentation, and hydrology are examined. The reuse of raised field agricultural technology to solve some problems of current land management is also discussed.The author would like to thank Virginia Abernethy, Dan A. Brinkmeier, Kay L. Candler, William M. Denevan, Timothy A. Kohler for constructive comments on this paper. I would especially like to thank Timothy Kohler for the opportunity to participate in the AAAS symposium and the other participants for a stimulating interchange of ideas on past environmental management. 相似文献
14.
Summary The population dynamics ofPryeria sinica was investigated in an undisturbed area in 1976–1979. We analyzed the process stabilizing the local population by the life
table approach for immature stages and the mark-recapture method for the adult stage. Females usually layed about 130 eggs
in an egg-mass. The shape of the survivorship curve was convex and was characterized by a relatively low mortality in the
egg and larval stages and by a relatively high mortality in the prepupal and pupal stages. The low mortality in the early
stage seemed to be not only due to the peculiar life cycle of this species (larvae develop in early spring when natural enemies
are not active) but due to their protective nest-webs, larval warning coloration and repellent smell. The high mortality after
cocooning was caused by severe parasitization byAgrothereutes minousubae. The number of adult in the population varied by 2.10-fold, which was less than that of other gregarious moths. The life
table data and field observations suggest that adult female dispersal would have acted as a stabilizing factor, andA. minousubae as a conditioning factor on the dynamics of the moth population. 相似文献
15.
Ryo Tanaka 《Researches on Population Ecology》1970,12(1):111-125
Summary Populations of the vole,Clethrionomys rufocanus, in a lowland woodlot of Hokkaido were studied for the presence of effects of prebaiting on censusing by the capture-recapture
method. A grid of 121 live-traps, spaced 5 m apart, was laid out on each of two plots, one of which alone was prebaited three
days long. Owing to very high densities and great trap-efficiency, sufficient and favourable samples could be available for
statistical analysis, except the trend of delayed catch for young in sampling. The population on either plot, however, proved
to be markedly variable in catchability of unmarked animals in the course of trapping; while the probability of recapture
was counted as invariable on the average from day to day, the recapture frequency was different between juveniles, subadults
and adults. Needless to say, the catchability was distinctly greater for marked voles than for unmarked ones, whether prebaited
or not, through the trapping period, except that the first-day catchability for unmarked ones on the prebaited plot seems
not to be significantly lower than that for marked ones.
Consequently, it turns out that the prebaiting has almost never helped to eliminate the important bias induced by differential
trap-response of marked and unmarked animals; its contribution is only that the catchability for unmarked ones is slightly
higher on the part of the prebaited plot on earlier days of the period.
In accordance with the heterogeneous catchability, the Γ-form distribution analogous to the geometric could be applied with
thorough fitness to the capture frequency in order to estimate the whole populations. The fact that the estimates are reliable,
being not at any rate underestimates, was further confirmed by the result of a follow-up work conducted by means of the removal
method with wider trap-spacing which brought forth distinct underestimation chiefly referable to unexposure to traps of the
partial populations. The subject of unexposure was discussed by laying stress on the relation between minimum range length
and trap-spacing.
Contribution from JIBP-PT No. 88, carried out by the grant from the expenditure of Education Department to the specific study
on “Dynamics of Biosphere”. 相似文献
16.
17.
Effects of population fluctuation of the gray-sided vole(Clethrionomys rufocanus) on the prevalence (infection rates) of the parasiteEchinococcus multilocularis in red fox(Vulpes vulpes) populations was investigated from 1985 to 1992 in eastern Hokkaido (Abashiri, Nemuro, and Kushiro area), Japan. This parasite
needs two hosts to complete its life cycle; the gray-sided vole as its intermediate host and the red fox as its final host.
We found that: (1) Infection rates in foxes depended on the current-year abundance of voles in all three study areas, particularly
in Abashiri. (2) In addition to this direct density-dependence, delayed density-dependence between the infection rate and
the prior-year abundance of voles was detected in Nemuro and in Kushiro. (3) The regional differences in density-dependence
pattern were related to regional differences in the winter food habits of red foxes: in Abashiri the proportion of voles in
the fox’s diet greatly decreases in winter, while the proportion remains high in winter in Nemuro and in Kushiro, probably
because of shallower snowpack. These results suggest that infection rates in foxes in Abashiri were less influenced by the
prior-year prevalence, since the infection cycle might be interrupted in winter, when voles became less important in fox’s
diet. In contrast, the state of the prevalence may carry over from year to year in Nemuro and in Kushiro, because red foxes
continue to eat a considerable amount of voles throughout year. The regionally contrasted results for the relationship between
infection rate in foxes and vole abundance were parallel to the regional difference in fluctuation pattern of vole populations,
which are highly variable in Abashiri area, but less variable in Kushiro-Nemuro area. Drastic change in vole populations appears
to affect the host-parasite system. 相似文献
18.
新世纪、新阶段人口研究和人口工作 总被引:2,自引:0,他引:2
文章分析了低生育水平下实现全面建设小康社会人口研究和人口工作的课题,总结了人口工作成功的主要经验,考察了新时期的人口新情况,质疑传统人口转变理论最后阶段的历程,提出从承载力、城市化、就业与社会保障、人口管理制度、低生育水平下的计划生育、老龄化、新的人口研究领域等方面进一步拓展人口和人口工作。 相似文献
19.
城镇化进程中的人口流动与城镇新增贫困人口问题分析 总被引:2,自引:0,他引:2
LUO Zuo-yan 《人口与经济》2007,(4):46-51
在城镇化的过程中,农村人口净流向城镇。这一方面推动城镇和农村的发展,另一方面带来城镇贫困人口的增加。由农村流入城镇的人口其贫困发生率大致在3%以上。为预防和保障人口流动中的城镇新增贫困人口,应该采取措施分类引导人口的城镇化,建立和完善进入城镇农民的社会保障体系,积极发展城镇服务业等第三产业,避免过度的城市化带来城镇贫困问题的扩大。 相似文献