Population Dynamics of the Australian Plague Locust, Chortoicetes Terminifera (Walker) in Central Western New South Wales Iii. Analysis of Population Processes.

1982 ◽  
Vol 30 (4) ◽  
pp. 569 ◽  
Author(s):  
RA Farrow
Keyword(s):  
Large Scale ◽  
Local Population ◽  
Population Fluctuations ◽  
Density Dependent ◽  
Delayed Effects ◽  
South Wales ◽  
Key Factor ◽  
Population Processes ◽  
The Times ◽  
Australian Plague Locust

An analysis of population processes in the Australian plague locust showed that the key factor determining local population fluctuations was net migration. The density-disturbing effects of migration were over-compensated by the delayed effects of natural enemies on immature survival. There was no evidence that the amplitude of fluctuations was controlled at any stage by density-dependent processes, even at the highest densities encountered. Gregarization, although density-dependent and leading to daytime emigration: rarely stabilized population peaks because swarming populations remained relatively static. Densities never reached the carrying capacity of the habitats, even locally, because of the frequency of emigration at night. Local population extinctions due to emigration and low productivity were compensated by eventual immigration at night in favourable weather. In neither situation was the size of night migration shown to be density-dependent, although a spurious effect was detected. Variations in natality and survival had little influence on local population trends but, when synchronized over large areas by unusually favourable weather, influenced the course of large-scale fluctuations. Regional populations were more stable than local ones, due to spatial and temporal differences in reproductive success in a heterogeneous environment, and to peripheral emigration losses. Variations in the synoptic circulation and rainfall at the times of migration and reproduction cause stochastic processes to exert a major control of regional population fluctuations in the Australian plague locust.

Offshore Migration and the Collapse of Outbreaks of the Australian Plague Locust (Chortoicetes Terminifera Walk.) In South-East Australia.

1975 ◽  
Vol 23 (4) ◽  
pp. 569 ◽  
Author(s):  
RA Farrow
Keyword(s):  
Special Reference ◽  
Large Scale ◽  
New South ◽  
South Australia ◽  
Migration Patterns ◽  
South Wales ◽  
Nocturnal Migration ◽  
The Relationship ◽  
Synoptic Circulation ◽  
Australian Plague Locust

High levels of night-flight activity of the Australian plague locust, Chortoicetes terminifera Walker, occurred on at least five separate occasions during the 1973-74 plague in south-east Australia and resulted in episodic, large-scale invasions at night of parts of southern New South Wales, Victoria and South Australia from more northerly breeding areas. The plague did not, however, reach the severe and damaging levels expected in the areas invaded, since on at least three out of five occasions nocturnal migration continued offshore and resulted in extensive mortality. The relationship between migration patterns and synoptic circulation is shown for each of the five situations, with special reference to the use and limitations of wind trajectories for estimating high-altitude displacement of locusts at night.

Origin and Decline of the 1973 Plague Locust Outbreak in Central Western New South Wales.

1977 ◽  
Vol 25 (3) ◽  
pp. 455 ◽  
Author(s):  
RA Farrow
Keyword(s):  
New South ◽  
New South Wales ◽  
Population Fluctuations ◽  
Green Food ◽  
Synoptic Weather ◽  
South Wales ◽  
Southern Central ◽  
Slow Moving ◽  
And Migration ◽  
Australian Plague Locust

An important outbreak of the Australian plague locust, Chortoicetes terminifera (Wlk.), occurred in 1973 in central western New South Wales. The dynamics of the outbreak could be resolved into a sequence of five principal interacting events: (1) Sustained population increases in low-density populations in northern central western New South Wales during three successive breeding periods in 1972. The increases were a result of successful, local multiplication, immigration from more northerly breeding areas and restricted opportunities for dispersal. The continuing concentration of locusts in the northern central west led to local gregarisation and swarm formation in autumn and spring 1972. (2) Massive southward displacements at night during an intense tropical disturbance between 29 January and 4 February 1973, which resulted in an invasion and concentration of infestations in southern central western New South Wales. (3) Substantial multiplication increases (10- to 30-fold), as a result of the drought-breaking rainfall in the autumn and spring of 1973 in the central-west. This resulted in an intensification of the plague with the production of numerous, slow-moving swarms. (4) Massive southward displacements during several periods of disturbed weather in spring 1973, which led to the disappearance of adult infestations from the central west and a dispersal of infestations in areas invaded further south. (5) Heavy mortality in residual populations of hoppers and eggs. The combined effects of parasites, predators and a reduced viability of eggs and hoppers resulted in a complete collapse of the plague in the central west by December 1973.Although displacement by adults at night is shown to be the principal factor regulating both population fluctuations in specific localities and the spread of plagues through southward invasions, outbreaks are ultimately determined by initial multiplication increases in relatively sedentary recession populations. Both multiplication and migration were influenced more by variations in synoptic weather than by any other factor. Diurnal swarm movements, although conspicuous, did not significantly influence the overall spread of the outbreak studied.The quality and quantity of available fresh green food did not appear to limit further successful breeding during the decline of the plague. Although influxes of locusts into the central-west continued during disturbed weather in 1974, none remained to breed and densities fell to levels (<1/ha) lower than those of drought seasons. It appears unlikely, therefore, that plagues can be sustained in any one area, even when environmental conditions remain favourable for breeding, because of: (1) mass emigration during disturbed weather; (2) increased effectiveness of natural enemies; and (3) declines in viability and fecundity in moist conditons.

scholarly journals Behavioural phase polyphenism in the Australian plague locust ( Chortoicetes terminifera )

2009 ◽  
Vol 5 (3) ◽  
pp. 306-309 ◽  
Author(s):  
Lindsey J. Gray ◽  
Gregory A. Sword ◽  
Michael L. Anstey ◽  
Fiona J. Clissold ◽  
Stephen J. Simpson
Keyword(s):  
Population Density ◽  
Phase Change ◽  
Local Population ◽  
Density Dependent ◽  
Behavioural Changes ◽  
Highly Active ◽  
Phase Polyphenism ◽  
Australian Plague Locust

Swarming and the expression of phase polyphenism are defining characteristics of locust species. Increases in local population density mediate morphological, physiological and behavioural changes within individuals, which correlate with mass marching of juveniles in migratory bands and flying swarms of adults. The Australian plague locust ( Chortoicetes terminifera ) regularly forms migratory bands and swarms, but is claimed not to express phase polyphenism and has accordingly been used to argue against a central role for phase change in locust swarming. We demonstrate that juvenile C. terminifera express extreme density-dependent behavioural phase polyphenism. Isolated-reared juveniles are sedentary and repelled by conspecifics, whereas crowd-reared individuals are highly active and are attracted to conspecifics. In contrast to other major locust species, however, behavioural phase change does not accumulate across generations, but shifts completely within an individual's lifetime in response to a change in population density.

POPULATION DYNAMICS OF LEPTINOTARSA DECEMLINEATA (SAY) IN EASTERN ONTARIO: III. MAJOR POPULATION PROCESSES

1971 ◽  
Vol 103 (7) ◽  
pp. 1049-1061 ◽  
Author(s):  
D. G. Harcourt
Keyword(s):  
Population Dynamics ◽  
Leptinotarsa Decemlineata ◽  
Food Resource ◽  
Weather Conditions ◽  
Density Dependent ◽  
Natural Agents ◽  
Potato Beetle ◽  
Key Factor ◽  
Leptinotarsa Decemlineata Say ◽  
Population Processes

AbstractAn appraisal of population processes in the Colorado potato beetle, Leptinotarsa decemlineata (Say), on its principal host plant showed that the insect has no natural agents that act in a manner that prevent it from overshooting its food supply. It is little affected by weather conditions or predators, and its only parasite, the tachinid Doryphorophaga doryphorae (Riley), is inversely density dependent in its action. Once the beetle has exploited its food resource, the larvae starve and the adults emigrate in quest of other hosts.The analysis of age interval survivals showed that populations are both regulated and disturbed by the principal key factor, adult migration, which is density dependent but overcompensating. A predictive model based on density relationships explained 94% of the variance in population trend.

A key-factor analysis of population fluctuations in Andraca bipunctata Walker (Lepidoptera: Bombycidae)

1979 ◽  
Vol 69 (1) ◽  
pp. 195-201 ◽  
Author(s):  
B. Banerjee
Keyword(s):  
Factor Analysis ◽  
Statistical Tests ◽  
Population Fluctuations ◽  
Female Mortality ◽  
Mortality Factors ◽  
Density Dependent ◽  
Key Factor ◽  
Key Factor Analysis ◽  
Insect Populations ◽  
Sampling Procedures

AbstractThe causes of fluctuation and stabilisation in a population of Andraca bipunctata Wlk. on tea in India were assessed over three years using the technique of key-factor analysis. Failure to produce the maximum complement of eggs, together with female mortality and adult migration, is shown to be the key-factor. Other mortality factors include non-viability of eggs and parasitism of the caterpillars by the tachinid Cylindromyia sp. Mortality of the female pupae tends to stabilise the population by compensating for losses due to the key-factor, but neither this nor any other mortality factors appear to be significantly density-dependent. The need for devising specialised sampling procedures and statistical tests for tropical insect populations is discussed.

Population Dynamics of the Australian Plague Locust, Chortoicetes Terminifera (Walker), in Central Western New South Wales. I. Reproduction and Migration in Relation to Weather.

1979 ◽  
Vol 27 (5) ◽  
pp. 717 ◽  
Author(s):  
RA Farrow
Keyword(s):  
New South ◽  
New South Wales ◽  
Population Fluctuations ◽  
Relative Importance ◽  
Net Migration ◽  
South Wales ◽  
Reproductive Rates ◽  
And Migration ◽  
Australian Plague Locust

On three adjacent experimental plots in central western New South Wales, from 1971 to 1974, population fluctuations of the Australian plague locust were interpreted in terms of the interactions between reproductive rates (Ro) between generations and net migration losses or gains (M plus or minus ) within generations. Changes due to variations in net migration fluctuated over a greater range than those due to variations in reproductive rates, and were the major cause of the population fluctuations during the 16 generations studied. Variations in rainfall during breeding accounted for nearly 90% of the variance in reproductive rates, provided rain followed relatively dry periods. Changes caused by migration resulted from episodic, often long-range and generally southward displacements of adults at night in the gradient wind during disturbed weather. The frequency and intensity of migration depended primarily on the availability of potential emigrants and secondarily on the incidence of weather favourable for takeoff and prolonged flight. The incidence of rainfall before periods of migration was higher than expected. Adults thus migrated into areas already favourable for successful breeding. Long-term median rainfall during breeding at Trangie gave mean reproductive rates greater than 1 per generation. Hence, population surpluses tend to be produced and generally disperse south to areas less favourable for breeding. There was close correspondence between the occurrence of heavy drought-breaking rains, leading to substantial population increases and migrations, and the observed incidence of outbreaks in this area. Changes in the relative importance of reproduction and migration in the drier breeding areas further inland are discussed in relation to historical changes in the distribution and abundance of the plague locust.

Going the Distance

2020 ◽  
Author(s):  
Ron Harris
Keyword(s):  
Large Scale ◽  
Western Europe ◽  
Family Firms ◽  
Global Trade ◽  
Long Distance ◽  
Business Corporation ◽  
Modern Economy ◽  
Key Factor ◽  
Silk Route ◽  
Passive Investors

Before the seventeenth century, trade across Eurasia was mostly conducted in short segments along the Silk Route and Indian Ocean. Business was organized in family firms, merchant networks, and state-owned enterprises, and dominated by Chinese, Indian, and Arabic traders. However, around 1600 the first two joint-stock corporations, the English and Dutch East India Companies, were established. This book tells the story of overland and maritime trade without Europeans, of European Cape Route trade without corporations, and of how new, large-scale, and impersonal organizations arose in Europe to control long-distance trade for more than three centuries. It shows that by 1700, the scene and methods for global trade had dramatically changed: Dutch and English merchants shepherded goods directly from China and India to northwestern Europe. To understand this transformation, the book compares the organizational forms used in four major regions: China, India, the Middle East, and Western Europe. The English and Dutch were the last to leap into Eurasian trade, and they innovated in order to compete. They raised capital from passive investors through impersonal stock markets and their joint-stock corporations deployed more capital, ships, and agents to deliver goods from their origins to consumers. The book explores the history behind a cornerstone of the modern economy, and how this organizational revolution contributed to the formation of global trade and the creation of the business corporation as a key factor in Europe's economic rise.

scholarly journals Introducing Twitter Daily Estimates of Residents and Non-Residents at the County Level

2021 ◽  
Vol 10 (6) ◽  
pp. 227
Author(s):  
Yago Martín ◽  
Zhenlong Li ◽  
Yue Ge ◽  
Xiao Huang
Keyword(s):  
Large Scale ◽  
Local Population ◽  
External Validation ◽  
Population Estimates ◽  
County Level ◽  
Internal Validation ◽  
Population Movements ◽  
Dynamic Component ◽  
Home Location ◽  
Non Local

The study of migrations and mobility has historically been severely limited by the absence of reliable data or the temporal sparsity of available data. Using geospatial digital trace data, the study of population movements can be much more precisely and dynamically measured. Our research seeks to develop a near real-time (one-day lag) Twitter census that gives a more temporally granular picture of local and non-local population at the county level. Internal validation reveals over 80% accuracy when compared with users’ self-reported home location. External validation results suggest these stocks correlate with available statistics of residents/non-residents at the county level and can accurately reflect regular (seasonal tourism) and non-regular events such as the Great American Solar Eclipse of 2017. The findings demonstrate that Twitter holds the potential to introduce the dynamic component often lacking in population estimates. This study could potentially benefit various fields such as demography, tourism, emergency management, and public health and create new opportunities for large-scale mobility analyses.

scholarly journals Trace element catalyses mineral replacement reactions and facilitates ore formation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yanlu Xing ◽  
Joël Brugger ◽  
Barbara Etschmann ◽  
Andrew G. Tomkins ◽  
Andrew J. Frierdich ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Trace Elements ◽  
Fluid Flow ◽  
Large Scale ◽  
Metal Accumulation ◽  
Nucleation And Growth ◽  
Reaction Interface ◽  
Ore Formation ◽  
Key Factor ◽  
Mineral Replacement

AbstractReaction-induced porosity is a key factor enabling protracted fluid-rock interactions in the Earth’s crust, promoting large-scale mineralogical changes during diagenesis, metamorphism, and ore formation. Here, we show experimentally that the presence of trace amounts of dissolved cerium increases the porosity of hematite (Fe2O3) formed via fluid-induced, redox-independent replacement of magnetite (Fe3O4), thereby increasing the efficiency of coupled magnetite replacement, fluid flow, and element mass transfer. Cerium acts as a catalyst affecting the nucleation and growth of hematite by modifying the Fe2+(aq)/Fe3+(aq) ratio at the reaction interface. Our results demonstrate that trace elements can enhance fluid-mediated mineral replacement reactions, ultimately controlling the kinetics, texture, and composition of fluid-mineral systems. Applied to some of the world’s most valuable orebodies, these results provide new insights into how early formation of extensive magnetite alteration may have preconditioned these ore systems for later enhanced metal accumulation, contributing to their sizes and metal endowment.

scholarly journals Threat of arsenic contamination, salinity and water pollution in agricultural practices of Sundarban Delta, India, and mitigation strategies

2021 ◽  
Vol 3 (5) ◽  
Author(s):  
Anirban Nath ◽  
Sourav Samanta ◽  
Saon Banerjee ◽  
Anamitra Anurag Danda ◽  
Sugata Hazra
Keyword(s):  
Plant Breeding ◽  
Rural Population ◽  
Large Scale ◽  
Local Population ◽  
Agricultural Practices ◽  
Mitigation Strategies ◽  
Saline Stress ◽  
Freshwater Resources ◽  
Catchment Areas ◽  
The Sundarbans

AbstractThe paper through a critical appraisal of the agricultural practices in the Indian Sundarban deltaic region explores the tripartite problems of arsenic biomagnification, salinity of arable lands and ingress of agrochemical pollutants into the freshwater resources, which endanger the health, livelihood and food security of the rural population inhabiting the delta. The threefold problem has rendered a severe blow to the agrarian economy consequently triggering large-scale outmigration of the rural population from the region. Although recent studies have addressed these issues separately, the inter-connectivity among these elements and their possible long-term impact upon sustainability in the Sundarbans are yet to be elucidated. In the current scenario, the study emphasizes that the depleting freshwater resources is at the heart of the threefold problems affecting the Sundarbans. Owing to the heavy siltation of the local river systems, freshwater resources from the local ravines have salinized beyond the point of being used for agricultural purposes. At the same time, increasing salinity levels resulting from fluctuation of pre- and post-monsoon rainfall, frequent cyclones and capillary movement of salinized groundwater (primarily during the Rabi season) have severely hampered the agricultural practices. Salinization of above groundwater reserves has forced the farmers toward utilization of groundwater, which are lifted using STWs, especially for rice and other cultivations in the Rabi season. The Holocene aquifers of the region retain toxic levels of arsenic which are lifted during the irrigation process and are deposited on to the agricultural fields, resulting in bioaccumulation of As in the food products resourced from the area. The compound effect of consuming arsenic-contaminated food and drinking water has resulted in severe health issues recorded among the local population in the delta. Furthermore, due to the sub-optimal conditions for sustaining agriculture under saline stress, farmers often opt for the cultivation of post-green revolution high-yielding varieties, which require additional inputs of nitrogen-based fertilizers, organophosphate herbicides and pesticides that are frequently washed away by runoff from the watershed into the low-lying catchment areas of the biosphere reserve. Such practices have endangered the vulnerable conditions of local flora and fauna. In the present situation, the study proposes mitigation strategies which necessitate the smart use of locally obtainable resources like water, adaptable cultivars and sustainable agronomic practices like organic farming. The study also suggests engaging of conventional plant breeding strategies such as “Evolutionary plant breeding” for obtaining cultivars adapted to the shifting ecological conditions of the delta in the long run.

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