scholarly journals Timescale Analyses of Fluctuations in Coexisting Populations of a Native and Invasive Tree Squirrel

2021 ◽  
Author(s):  
Robert Desharnais ◽  
Alan Muchlinski ◽  
Janel Ortiz ◽  
Ruby Alvidrez ◽  
Brian Gatza
Keyword(s):  
Spectral Power ◽  
Volterra Model ◽  
Population Fluctuations ◽  
Competing Species ◽  
Risk Of Extinction ◽  
Invasive Tree ◽  
Tree Squirrels ◽  
Western Gray Squirrel ◽  
Long Timescales ◽  
The Impact

1. Competition from invasive species is an increasing threat to biodiversity. In Southern California, the western gray squirrel (Sciurus griseus, WGS) is facing increasing competition from the fox squirrel (Sciurus niger, FS), an invasive congener. 2. We used spectral methods to analyze 140 consecutive monthly censuses of WGS and FS within a 11.3 ha section of the California Botanic Garden. Variation in the numbers for both species and their synchrony was distributed across long timescales (> 15 months). 3. After filtering out annual changes, concurrent mean monthly temperatures from nearby Ontario Airport (ONT) yielded a spectrum with a large semiannual peak and significant spectral power at long timescales (> 30 months). Squirrel-temperature cospectra showed significant negative covariation at long timescales (> 35 months) for WGS and smaller significant negative peaks at 6 months for both species. 4. Simulations from a Lotka-Volterra model of two competing species indicates that the risk of extinction for the weaker competitor increases quickly as environmental noise shifts from short to long timescales. 5. We analyzed the timescales of fluctuations in detrended mean annual temperatures for the time period 1915-2014 from 1218 locations across the continental USA. In the last two decades, significant shifts from short timescales to long timescales have occurred, changing from less than 3 years to 4-6 years. 6. Our results indicate that (i) population fluctuations in co-occurring native and invasive tree squirrels are synchronous, occur over long timescales, and may be driven by fluctuations in environmental conditions; (ii) long timescale population fluctuations increase the risk of extinction in competing species, especially for the inferior competitor; and (iii) the timescales of interannual environmental fluctuations may be increasing from recent historical values. These results have broad implications for the impact of climate change on the maintenance of biodiversity.

scholarly journals Timescale Analyses of Fluctuations in Coexisting Populations of a Native and Invasive Tree Squirrel

2021 ◽  
Author(s):  
Robert Desharnais ◽  
Alan Muchlinski ◽  
Janel Ortiz ◽  
Ruby Alvidrez ◽  
Brian Gatza
Keyword(s):  
Spectral Power ◽  
Volterra Model ◽  
Population Fluctuations ◽  
Competing Species ◽  
Risk Of Extinction ◽  
Invasive Tree ◽  
Tree Squirrels ◽  
Western Gray Squirrel ◽  
Long Timescales ◽  
The Impact

1. Competition from invasive species is an increasing threat to biodiversity. In Southern California, the western gray squirrel (Sciurus griseus, WGS) is facing increasing competition from the fox squirrel (Sciurus niger, FS), an invasive congener. 2. We used spectral methods to analyze 140 consecutive monthly censuses of WGS and FS within a 11.3 ha section of the California Botanic Garden. Variation in the numbers for both species and their synchrony was distributed across long timescales (> 15 months). 3. After filtering out annual changes, concurrent mean monthly temperatures from nearby Ontario Airport (ONT) yielded a spectrum with a large semiannual peak and significant spectral power at long timescales (> 30 months). Squirrel-temperature cospectra showed significant negative covariation at long timescales (> 35 months) for WGS and smaller significant negative peaks at 6 months for both species. 4. Simulations from a Lotka-Volterra model of two competing species indicates that the risk of extinction for the weaker competitor increases quickly as environmental noise shifts from short to long timescales. 5. We analyzed the timescales of fluctuations in detrended mean annual temperatures for the time period 1915-2014 from 1218 locations across the continental USA. In the last two decades, significant shifts from short timescales to long timescales have occurred, changing from less than 3 years to 4-6 years. 6. Our results indicate that (i) population fluctuations in co-occurring native and invasive tree squirrels are synchronous, occur over long timescales, and may be driven by fluctuations in environmental conditions; (ii) long timescale population fluctuations increase the risk of extinction in competing species, especially for the inferior competitor; and (iii) the timescales of interannual environmental fluctuations may be increasing from recent historical values. These results have broad implications for the impact of climate change on the maintenance of biodiversity.

AN OVERVIEW OF THE IMPACT OF STRAY LIGHT FROM COMMERCIAL GREENHOUSES

2021 ◽  
Author(s):  
K. Bertin ◽  
G. Zissis ◽  
G. Salas ◽  
P.M. Raynham ◽  
A. Moutsi ◽  
...  
Keyword(s):  
Power Distribution ◽  
Spectral Power ◽  
Stray Light ◽  
Significant Problem ◽  
Light Sources ◽  
Spectral Power Distribution ◽  
Outdoor Work ◽  
Local Residents ◽  
The Impact ◽  
Current Standards

Stray light from commercial greenhouses is becoming a significant problem causing disruption to wildlife activity and annoyance for local residents. To quantify the amount of stray light from a typical large greenhouse the authors have modelled several lighting installations based on a range of generic horticultural light sources. The impact of the stray light is dependent on the spectral power distribution of the sources employed, the intensity and distribution. Current standards for obtrusive light from outdoor work places do not seem to be suitable when applied to greenhouses.

Evaluating the predictability of central Indian rainfall on short and long timescales using theory of nonlinear dynamics

2019 ◽  
Vol 11 (4) ◽  
pp. 1134-1149 ◽  
Author(s):  
Uday Pratap Singh ◽  
Ashok Kumar Mittal ◽  
Suneet Dwivedi ◽  
Anurag Tiwari
Keyword(s):  
Finite Size ◽  
Coupled Model ◽  
India Meteorological Department ◽  
Rapid Decrease ◽  
Error Growth ◽  
Indian Rainfall ◽  
Low Dimensional ◽  
Projected Changes ◽  
Long Timescales ◽  
The Impact

Abstract The theoretical and practical understanding of projected changes in rainfall is desirable for planning and adapting to climate change. In this study, finite size Lyapunov exponents (FSLE) are used to study error growth rates of the system at different timescales. This is done to quantify the impact of enhanced anthropogenic greenhouse gas emissions on the predictability of fast and slow varying components of central Indian rainfall (CIR). The CIR time series for this purpose is constructed using the daily gridded high-resolution India Meteorological Department (IMD) dataset and Coupled Model Inter-comparison Project phase 5 (CMIP5) output for historical run and three representative concentration pathways (RCP2.6, RCP4.5, and RCP8.5) from the HadGEM2-ES, IPSL-CM5A-LR, CCSM4, BCC-CSM1.1, and MPI-ESM-LR models. The analyzed CIR dataset reveals a low dimensional chaotic attractor, suggesting that CIR requires a minimum of 5 and maximum of 11 variables to describe the state of the system. FSLE analysis shows a rapid decrease in the Lyapunov exponent with increasing timescales. This analysis suggests a predictability of about 2–3 weeks for fast varying components at short timescale of the CIR and about 5–9 years for slow varying components at long timescales.

scholarly journals Eco-evolutionary dynamics: disentangling phenotypic, environmental and population fluctuations

2009 ◽  
Vol 364 (1523) ◽  
pp. 1491-1498 ◽  
Author(s):  
Thomas H.G. Ezard ◽  
Steeve D. Côté ◽  
Fanie Pelletier
Keyword(s):  
Population Growth ◽  
Evolutionary Dynamics ◽  
Environmental Variability ◽  
Phenotypic Variability ◽  
Ecological Change ◽  
Population Fluctuations ◽  
Rapid Responses ◽  
Evolutionary Response ◽  
Anthropogenic Threats ◽  
The Impact

Decomposing variation in population growth into contributions from both ecological and evolutionary processes is of fundamental concern, particularly in a world characterized by rapid responses to anthropogenic threats. Although the impact of ecological change on evolutionary response has long been acknowledged, the converse has predominantly been neglected, especially empirically. By applying a recently published conceptual framework, we assess and contrast the relative importance of phenotypic and environmental variability on annual population growth in five ungulate populations. In four of the five populations, the contribution of phenotypic variability was greater than the contribution of environmental variability, although not significantly so. The similarity in the contributions of environment and phenotype suggests that neither is worthy of neglect. Population growth is a consequence of multiple processes, which strengthens arguments advocating integrated approaches to assess how populations respond to their environments.

Small spate disturbance and the complexity of habitat architecture in Mountain River, Tasmania

1996 ◽  
Vol 47 (6) ◽  
pp. 851 ◽  
Author(s):  
BJ Robson
Keyword(s):  
Benthic Invertebrates ◽  
Base Flow ◽  
Temporal Context ◽  
Population Fluctuations ◽  
Mountain River ◽  
Similar Magnitude ◽  
Short Term ◽  
Before And After ◽  
Study Sites ◽  
The Impact

Densities of benthic invertebrates were counted over several weeks before and after a small winter spate (15.5 times base flow) in two riffle types of contrasting architectural complexity in Mountain River, Tasmania. Complex benthic architecture reduced the impact of this spate on invertebrate densities over the short term (seven days). Longer-term recovery (several weeks) was unaffected by riffle architecture, with one of the riffles recovering much more slowly than the others. Refuges from small spates in Mountain River may exist in mid channel in complex boulder-cobble riffles. Within its temporal context, the effects of the spate on the study sites were of a similar magnitude to other unexplained population fluctuations.

scholarly journals Physical behaviour of anthropogenic light propagation into the nocturnal environment

2015 ◽  
Vol 370 (1667) ◽  
pp. 20140117 ◽  
Author(s):  
Martin Aubé
Keyword(s):  
Radiative Transfer ◽  
Natural Environment ◽  
Spectral Power ◽  
Radiative Transfer Model ◽  
City Centre ◽  
Light Pollution ◽  
Transfer Model ◽  
Light Sources ◽  
Night Time ◽  
The Impact

Propagation of artificial light at night (ALAN) in the environment is now known to have non negligible consequences on fauna, flora and human health. These consequences depend on light levels and their spectral power distributions, which in turn rely on the efficiency of various physical processes involved in the radiative transfer of this light into the atmosphere and its interactions with the built and natural environment. ALAN can affect the living organisms by direct lighting and indirect lighting (scattered by the sky and clouds and/or reflected by local surfaces). This paper mainly focuses on the behaviour of the indirect light scattered under clear sky conditions. Various interaction processes between anthropogenic light sources and the natural environment are discussed. This work mostly relies on a sensitivity analysis conducted with the light pollution radiative transfer model, Illumina (Aubé et al . 2005 Light pollution modelling and detection in a heterogeneous environment: toward a night-time aerosol optical depth retrieval method. In Proc. SPIE 2005, vol. 5890, San Diego, California, USA). More specifically, the impact of (i) the molecular and aerosol scattering and absorption, (ii) the second order of scattering, (iii) the topography and obstacle blocking, (iv) the ground reflectance and (v) the spectrum of light devices and their angular emission functions are examined. This analysis considers different behaviour as a function of the distance from the city centre, along with different zenith viewing angles in the principal plane.

The impact of R&D on GDP study based on grey delay Lotka-Volterra model

2015 ◽  
Vol 5 (1) ◽  
pp. 74-88 ◽  
Author(s):  
Shuhua Mao ◽  
Mingyun Gao ◽  
Min Zhu
Keyword(s):  
Design Methodology ◽  
Actual Data ◽  
Volterra Model ◽  
Grey Theory ◽  
Content Type ◽  
Lag Effects ◽  
Relation Analysis ◽  
Analytic Expression ◽  
The Impact ◽  
Practical Implications

Purpose – The purpose of this paper is to elevate the accuracy when predicting the gross domestic product (GDP) on research and development (R&D) and to develop the grey delay Lotka-Volterra model. Design/methodology/approach – Considering the lag effects between input in R&D and output in GDP, this paper estimated the delay value via grey delay relation analysis. Taking the delay into original Lotka-Volterra model and combining with the thought of grey theory and grey transform, the authors proposed grey delay Lotka-Volterra model, estimated the parameter of model and gave the discrete time analytic expression. Findings – Collecting the actual data of R&D and GDP in Wuhan China from 1995 until 2008, this paper figure out that the delay between R&D and GDP was 2.625 year and found the dealy time would would gradually be reduced with the economy increasing. Practical implications – Constructing the grey delay Lotka-Volterra model via above data, this paper shown that the precision was satisfactory when fitting the data of R&D and GDP. Comparing the forecasts with the actual data of GDP in Wuhan from 2009 until 2012, the error was small. Social implications – The result shows that R&D and GDP would be both growing fast in future. Wuhan will become a city full of activity. Originality/value – Considering the lag between R&D and GDP, this work estimated the delay value via a grey delay relation analysis and constructed a novel grey delay Lotka-Volterra model.

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