scholarly journals Population Trends and Urbanization: Simulating Density Effects Using a Local Regression Approach

2020 ◽  
Vol 9 (7) ◽  
pp. 454 ◽  
Author(s):  
Gloria Polinesi ◽  
Maria Cristina Recchioni ◽  
Rosario Turco ◽  
Luca Salvati ◽  
Kostas Rontos ◽  
...  
Keyword(s):  
Population Density ◽  
Population Growth ◽  
Growth Rates ◽  
European Regions ◽  
Density Dependent ◽  
Metropolitan Growth ◽  
Dependent Processes ◽  
Demographic Growth ◽  
Over Time

Density-dependent population growth regulates long-term urban expansion and shapes distinctive socioeconomic trends. Despite a marked heterogeneity in the spatial distribution of the resident population, Mediterranean European countries are considered more homogeneous than countries in other European regions as far as settlement structure and processes of metropolitan growth are concerned. However, rising socioeconomic inequalities among Southern European regions reflect latent demographic and territorial transformations that require further investigation. An integrated assessment of the spatio-temporal distribution of resident populations in more than 1000 municipalities (1961–2011) was carried out in this study to characterize density-dependent processes of metropolitan growth in Greece. Using geographically weighted regressions, the results of our study identified distinctive local relationships between population density and growth rates over time. Our results demonstrate that demographic growth rates were non-linearly correlated with other variables, such as population density, with positive and negative impacts during the first (1961–1971) and the last (2001–2011) observation decade, respectively. These findings outline a progressive shift over time from density-dependent processes of population growth, reflecting a rapid development of large metropolitan regions (Athens, Thessaloniki) in the 1960s, to density-dependent processes more evident in medium-sized cities and accessible rural regions in the 2000s. Density-independent processes of population growth have been detected in the intermediate study period (1971–2001). This work finally discusses how a long-term analysis of demographic growth, testing for density-dependent mechanisms, may clarify the intrinsic role of population concentration and dispersion in different phases of the metropolitan cycle in Mediterranean Europe.

scholarly journals La población rural en España: un enfoque a escala municipal

2011 ◽  
Vol 10 (1) ◽  
pp. 35 ◽  
Author(s):  
Ignacio Atance ◽  
María Teresa Martínez Jávega ◽  
Rogelio Pujol ◽  
Julio Urruela
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Rural Areas ◽  
Rural Population ◽  
Population Data ◽  
Demographic Variables ◽  
Rural Depopulation ◽  
Demographic Growth

Population in Spain has grown significantly during the last decade; however, population growth has not increased evenly across the country. High demographic growth rates in costal and urbaninfluenced rural areas can lead to errors when considering added rural population data. This research depicts Spanish rural population’s evolution using a municipal scale approach and analyzes classic demographic variables and their explanatory capacity on rural population’s evolution. Results show that rural depopulation is still increasing in wide areas of the country. Classical demographic variables have been tested significant although they are not deciding factors in explaining rural population’s evolution

An Evaluation of RNA–DNA Ratio as a Measure of Long-Term Growth in Fish Populations

1973 ◽  
Vol 30 (2) ◽  
pp. 195-199 ◽  
Author(s):  
Terry A. Haines
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Growth Rates ◽  
Population Growth Rate ◽  
Environmental Changes ◽  
Age Distribution ◽  
Smallmouth Bass ◽  
Fish Populations ◽  
Population Growth Rates

The value of RNA–DNA ratio as a measure of long-term growth of fish populations under semi-natural conditions and when subjected to environmental manipulations was determined. Populations of carp and smallmouth bass of known age distribution were established in artificial ponds maintained at two fertility levels. After 15 months, population growth rates (as percent increase in weight) and RNA–DNA ratios of muscle tissue from selected fish were measured. Each species exhibited a range of population growth rates. The relation between population growth rate and individual fish RNA–DNA ratio for each species was significant. When reproduction occurred, the relation was not significant unless young-of-the-year fish were excluded from population growth rate calculations. Age of fish was also found to have an important effect on RNA–DNA ratio, with the ratio being higher in younger fish.RNA–DNA ratio can be a reliable indicator of long-term population growth in fish when population age structure is known and recruitment is controlled. The method has potential for use in detecting response to environmental changes before growth rate changes become severe.

Density-Dependent Population Growth

2020 ◽  
pp. 29-46
Author(s):  
Michael J. Fogarty ◽  
Jeremy S. Collie
Keyword(s):  
Population Density ◽  
Population Growth ◽  
Density Dependence ◽  
Multiple Equilibria ◽  
Dynamical Behavior ◽  
Logistic Growth ◽  
Density Dependent ◽  
Per Capita ◽  
Discrete Time Models ◽  
Complex Dynamical Behavior

The observation that no population can grow indefinitely and that most populations persist on ecological timescales implies that mechanisms of population regulation exist. Feedback mechanisms include competition for limited resources, cannibalism, and predation rates that vary with density. Density dependence occurs when per capita birth or death rates depend on population density. Density dependence is compensatory when the population growth rate decreases with population density and depensatory when it increases. The logistic model incorporates density dependence as a simple linear function. A population exhibiting logistic growth will reach a stable population size. Non-linear density-dependent terms can give rise to multiple equilibria. With discrete time models or time delays in density-dependent regulation, the approach to equilibrium may not be smooth—complex dynamical behavior is possible. Density-dependent feedback processes can compensate, up to a point, for natural and anthropogenic disturbances; beyond this point a population will collapse.

The Railways, Urbanization, and Local Demography in England and Wales, 1825–1911

2010 ◽  
Vol 34 (2) ◽  
pp. 199-228
Author(s):  
Ian N. Gregory ◽  
Jordi Martí Henneberg
Keyword(s):  
World War I ◽  
Population Growth ◽  
World War ◽  
England And Wales ◽  
Rail Network ◽  
Level Data ◽  
Integrate Data ◽  
Single Set ◽  
Over Time

This article uses geographic information systems (GIS) to explore the growth of the rail network in England and Wales in the period before World War I. It uses two major GIS databases, one containing data on the growth of the rail network, including both lines and stations, and one containing parish-level populations. The parish-level data are particularly important for two reasons: they give an unparalleled level of spatial detail, and they are interpolated onto a single set of boundaries over time, which allows direct long-term comparisons. GIS's ability to integrate data allows the article to shed new light on how quickly the railways spread into the country's population. It then explores whether gaining a station made it more likely for a parish's population growth to increase and whether gaining one early was an advantage compared to gaining one relatively late. The article explores this impact at a variety of urban levels.

Using population dynamics modelling to evaluate potential success of restoration: a case study of a Hawaiian vine in a changing climate

2014 ◽  
Vol 42 (1) ◽  
pp. 20-30 ◽  
Author(s):  
TAMARA M. WONG ◽  
TAMARA TICKTIN
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Key Management ◽  
Demographic Data ◽  
Population Decline ◽  
Management Strategies ◽  
Survival Rates ◽  
Population Modelling ◽  
Population Growth Rates

SUMMARYDemographic comparisons between wild and restored populations of at-risk plant species can reveal key management strategies for effective conservation, but few such studies exist. This paper evaluates the potential restoration success ofAlyxia stellata, a Hawaiian vine. Stage-structured matrix projection models that compared long-term and transient dynamics of wild versus restoredA. stellatapopulations, and restored populations under different levels of canopy cover, were built from demographic data collected over a four year period. Stochastic models of wild populations projected stable or slightly declining long-term growth rates depending on frequency of dry years. Projected long-term population growth rates of restored populations were significantly higher in closed than open canopy conditions, but indicated population decline under both conditions. Life table response experiments illustrated that lower survival rates, especially of small adults and juveniles, contributed to diminished population growth rates in restored populations. Transient analyses for restored populations projected short-term decline occurring even faster than predicted by asymptotic dynamics. Restored populations will not be viable over the long term under conditions commonly found in restoration projects and interventions will likely be necessary. This study illustrates how the combination of long-term population modelling and transient analyses can be effective in providing relevant information for plant demographers and restoration practitioners to promote self-sustaining native populations, including under future climates.

scholarly journals Effect of mutualist partner identity on plant demography

2014 ◽  
Author(s):  
Emilio M Bruna ◽  
Thiago J Izzo ◽  
Brian D Inouye ◽  
Heraldo L Vasconcelos
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Census Data ◽  
Interspecific Variation ◽  
Multiple Partner ◽  
Population Growth Rates ◽  
Crematogaster Laevis ◽  
Asymptotic Growth Rate ◽  
Demographic Effects

Mutualisms play a central role in the origin and maintenance of biodiversity. Because many mutualisms have strong demographic effects, interspecific variation in partner quality could have important consequences for population dynamics. Nevertheless, few studies have quantified how a mutualist partner influences population growth rates, and still fewer have compared the demographic impacts of multiple partner species. We used integral projection models parameterized with three years of census data to compare the demographic effects of two ant species – Crematogaster laevis and Pheidole minutula – on populations of the Amazonian ant-plant Maieta guianensis. Estimated population growth rates were positive (i.e., λ>1) for all ant-plant combinations. However, populations with only Pheidole minutula had the highest asymptotic growth rate (λ=1.23), followed by those colonized by Crematogaster laevis (λ=1.16), and in which the partner ant alternated between C. laevis and P. minutula at least once during our study (λ=1.15). Our results indicate that the short-term superiority of a mutualist partner – in this system P. minutula is a better defender of plants against herbivores than C. laevis – can have long-term demographic consequences. Furthermore, the demographic effects of switching among alternative partners appear to be context-dependent, with no benefits to plants hosting C. laevis but a major cost of switching to plants hosting P. minutula. Our results underscore the importance of expanding the study of mutualisms beyond the study of pair-wise interactions to consider the demographic costs and benefits of interacting with different, and multiple, potential partners.

Meta-analysis reveals declines in terrestrial but increases in freshwater insect abundances

Science ◽  
2020 ◽  
Vol 368 (6489) ◽  
pp. 417-420 ◽  
Author(s):  
Roel van Klink ◽  
Diana E. Bowler ◽  
Konstantin B. Gongalsky ◽  
Ann B. Swengel ◽  
Alessandro Gentile ◽  
...  
Keyword(s):  
Land Use ◽  
North America ◽  
Protected Areas ◽  
Meta Analysis ◽  
Spatiotemporal Patterns ◽  
European Regions ◽  
Insect Abundance ◽  
Abundance Trends ◽  
Over Time

Recent case studies showing substantial declines of insect abundances have raised alarm, but how widespread such patterns are remains unclear. We compiled data from 166 long-term surveys of insect assemblages across 1676 sites to investigate trends in insect abundances over time. Overall, we found considerable variation in trends even among adjacent sites but an average decline of terrestrial insect abundance by ~9% per decade and an increase of freshwater insect abundance by ~11% per decade. Both patterns were largely driven by strong trends in North America and some European regions. We found some associations with potential drivers (e.g., land-use drivers), and trends in protected areas tended to be weaker. Our findings provide a more nuanced view of spatiotemporal patterns of insect abundance trends than previously suggested.

Growth rates of black caiman (Melanosuchus niger) and spectacled caiman (Caiman crocodilus) from two different Amazonian flooded habitats

2013 ◽  
Vol 34 (4) ◽  
pp. 437-449 ◽  
Author(s):  
Ronis Da Silveira ◽  
Zilca Campos ◽  
John Thorbjarnarson ◽  
William E. Magnusson
Keyword(s):  
Growth Rates ◽  
Biotic Interactions ◽  
Alligator Mississippiensis ◽  
Growth And Survival ◽  
Density Dependent ◽  
Demographic Models ◽  
Caiman Crocodilus ◽  
Dependent Growth ◽  
Rates Of Growth ◽  
Dependent Processes

Rates of growth and survival in wild populations are affected by the physical environment, biotic interactions, and density-dependent processes, such as growth and fecundity. However, the relative importance of these factors in long-lived reptiles is poorly understood. We analyzed growth rates of Melanosuchus niger and Caiman crocodilus coexisting in two areas of the Brazilian Amazon with very different environmental characteristics. Growth rates of Caiman crocodilus at the two sites were similar, but M. niger grew more slowly in the area with higher productivity and higher density of caimans. Growth rates of the same species from other sites and of the temperate-zone Alligator mississippiensis indicate large differences among sites, but little evidence that these differences are primarily due to differences in productivity or temperature. Demographic models used to estimate sustained yields from caiman harvests should take into account the likely importance of density-dependent growth.

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