Population growth rates of weed species in response to herbicide programme intensity and their impact on weed community

Weed Research ◽  
2021 ◽  
Author(s):  
Fernando H. Oreja ◽  
Matthew D. Inman ◽  
David L. Jordan ◽  
Ramon G. Leon
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Weed Species ◽  
Population Growth Rates

Identifying Critical Control Points in the Wild Oat (Avena fatua) Life Cycle and the Potential Effects of Harvest Weed-Seed Control

Weed Science ◽  
2016 ◽  
Vol 64 (3) ◽  
pp. 463-473 ◽  
Author(s):  
Breanne D. Tidemann ◽  
Linda M. Hall ◽  
K. Neil Harker ◽  
Brendan C. S. Alexander
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Seedling Survival ◽  
Integrated Weed Management ◽  
Wild Oat ◽  
Weed Seed ◽  
Weed Species ◽  
Population Growth Rates ◽  
Critical Control Points ◽  
Management Techniques

Wild oat is a problematic weed species that requires new management techniques in the face of herbicide resistance; harvest weed-seed control (HWSC) may be an option. Wild oat demographic information was collected in long-term, rotational field studies in Lacombe, AB, Canada, in 2006 and 2007, and a periodic matrix model was parameterized using management extremes (no IPM, no herbicide to high IPM, and full herbicide). Population growth rates were calculated for each treatment and year. Prospective (elasticity) and retrospective (LTRE) analyses were conducted alongside a rearrangement of the model equation in which population growth rates were designated and the required proportion of newly shed seed survival that gives that growth rate was solved for. All populations had λ > 1 or increasing populations. Elasticity analyses indicated that λ was most-highly elastic to the overwinter seedbank (Esw = 1), followed by seedling survival, fecundity, and survival of newly shed seed (0.63 to 0.86 across treatments). The latter may be the most-accessible vital rate for management of herbicide resistant populations. LTRE exposed the stochasticity of wild oat population growth rates between years and their ability to take advantage of lapses in control. Decreasing the proportion of newly shed seeds (snew) that survives was the most-effective and available control strategy until reduced to 0.1 to 0.3 when the summer seedbank becomes more critical. When averaged across treatments, > 80% of newly shed seed must be eliminated to stop the population from growing, resulting in a stable population, but not a decline. Because of preharvest shattering, HWSC will likely not be effective enough alone to cause wild oat populations to decline. New management techniques for wild oat control that can be used in combination with HWSC and integrated weed management strategies are needed.

scholarly journals Estimates of regional annual abundance and population growth rates of white sharks off central California

2021 ◽  
Vol 257 ◽  
pp. 109104
Author(s):  
Paul E. Kanive ◽  
Jay J. Rotella ◽  
Taylor K. Chapple ◽  
Scot D. Anderson ◽  
Timothy D. White ◽  
...  
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Central California ◽  
Population Growth Rates

scholarly journals ATIVIDADE ACARICIDA DE ÓLEOS ESSENCIAIS SOBRE Tetranychus ludeni (Zacher) (Acari: Tetranychidae) EM DUAS CULTIVARES DE ALGODOEIRO

Nativa ◽  
2019 ◽  
Vol 7 (5) ◽  
pp. 469
Author(s):  
Yasmin Bruna de Siqueira Bezerra ◽  
José Vargas de Oliveira ◽  
Taciana Keila dos Anjos Ramalho ◽  
Douglas Rafael e Silva Barbosa ◽  
Carlos Romero Ferreira de Oliveira ◽  
...  
Keyword(s):  
Population Growth ◽  
Essential Oils ◽  
Growth Rates ◽  
Ocimum Basilicum ◽  
Alternative Control ◽  
Population Growth Rates ◽  
Colored Cotton ◽  
Potential Alternative ◽  
Tetranychus Ludeni ◽  
Corymbia Citriodora

O presente trabalho teve como objetivo avaliar os efeitos repelentes e as taxas de crescimento populacional de óleos essenciais de Corymbia citriodora, Ocimum basilicum e Myracroduon urundeuva sobre o ácaro vermelho Tetranychus ludeni (Zacher) em algodoeiro de fibra colorida. Para o teste de repelência, óleos de Corymbia citriodora, Ocimum basilicum e Myracroduon urundeuva foram testados em diferentes concentrações sobre fêmeas adultas de T. ludeni, assim como para o teste de crescimento populacional, onde as cultivares foram tratadas com óleos essenciais.  O efeito repelente foi verificado para todos os óleos testados nas duas cultivares de algodão colorida. As taxas instantâneas de crescimento populacional para T. ludeni nas cultivares de algodoeiro BRS Verde e BRS Rubi foram todas positivas (ri> 0), indicando que a população está em estado ascendente, no entanto, a população cresceu a uma taxa menor quando comparada ao controle. Os óleos essenciais de C. citriodora, O. basilicum e M. urundeuva apresentam efeito acaricida e potencial controle alternativo de T. ludeni em algodoeiro de fibras coloridas sem causar danos ao algodoeiro.Palavras-chave: ácaro vermelho; algodão colorido; controle alternativo; taxa instantânea de crescimento; repelência. ACARICIDAL ACTIVITY OF ESSENTIAL OILS ON RED MITETetranychus ludeni (Zacher) (Acari: Tetranychidae) IN TWO COTTON CULTIVARS ABSTRACT: The objective of this work was to evaluate the repellent and population growth rates of essential oils of Corymbia citriodora, Ocimum basilicum and Myracroduon urundeuva on the red mite Tetranychus ludeni (Zacher) in cotton fiber. For the repellency test, oils of Corymbia citriodora, Ocimum basilicum and Myracroduon urundeuva were tested in different concentrations on adult females of T. ludeni, as well as for the population growth test, where the cultivars were treated with essential oils. The repellent effect was verified for all tested oils the two cultivars of colored cotton. The instant population growth rates for T. ludeni in the cultivars BRS Verde and BRS Rubi were all positive (ri> 0), indicating that the population is in an upward, however, the population grew at a lower rate when compared to the control. The essential oils of C. citriodora, O. basilicum and M. urundeuva have an acaricidal effect and potential alternative control of T. ludeni in cotton from colored fibers without causing damage to the cotton.Keywords: Red mite; colored cotton; essential oils; instant growth rate; repellency.

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.

Life history and environmental influences on population dynamics in sockeye salmon

2014 ◽  
Vol 71 (8) ◽  
pp. 1198-1208 ◽  
Author(s):  
Douglas C. Braun ◽  
John D. Reynolds
Keyword(s):  
Population Dynamics ◽  
Life History ◽  
Population Growth ◽  
Growth Rates ◽  
Environmental Conditions ◽  
Sockeye Salmon ◽  
Life History Traits ◽  
Relative Importance ◽  
Population Growth Rates ◽  
Habitat Variables

Understanding linkages among life history traits, the environment, and population dynamics is a central goal in ecology. We compared 15 populations of sockeye salmon (Oncorhynchus nerka) to test general hypotheses for the relative importance of life history traits and environmental conditions in explaining variation in population dynamics. We used life history traits and habitat variables as covariates in mixed-effect Ricker models to evaluate the support for correlates of maximum population growth rates, density dependence, and variability in dynamics among populations. We found dramatic differences in the dynamics of populations that spawn in a small geographical area. These differences among populations were related to variation in habitats but not life history traits. Populations that spawned in deep water had higher and less variable population growth rates, and populations inhabiting streams with larger gravels experienced stronger negative density dependence. These results demonstrate, in these populations, the relative importance of environmental conditions and life histories in explaining population dynamics, which is rarely possible for multiple populations of the same species. Furthermore, they suggest that local habitat variables are important for the assessment of population status, especially when multiple populations with different dynamics are managed as aggregates.

Past, Present and Future Population Growth and Urban Management in Zimbabwe

2018 ◽  
pp. 1197-1214
Author(s):  
Innocent Chirisa ◽  
Aaron Maphosa ◽  
Lazarus Zanamwe ◽  
Elmond Bandauko ◽  
Liaison Mukarwi
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Urban Population ◽  
Urban Infrastructure ◽  
Natural Increase ◽  
Urban Migration ◽  
Urban Management ◽  
Population Growth Rates ◽  
Secondary Sources ◽  
Urban Population Growth

The central focus of this chapter is to analyse the urban population growth–urban management nexus in Zimbabwean cities. These cities are registering rapid population growth rates, due mainly to massive rural to urban migration and natural increase. Ideally, rapid urban population growth rates should be proportionate to urban infrastructure, facilities and services. This is not in the case in Zimbabwean cities, where the development of informal settlements, rising urban poverty, dilapidated urban infrastructure and other urban developmental challenges are rampant. Drawing from Malthusian theory, the current conditions in Zimbabwean cities represents that stage where the positive and negative checks are expected. In putting together this chapter, we used archival sources such as newspapers, government reports and other secondary sources. We conclude that planning initiatives and population control measures need to be used in Zimbabwean cities to address inefficiency and urban management challenges, which may be compromising urban sustainability. This study provides evidence-based information that urban local authorities may use to formulate policies to manage urban problems.

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