Population Density Dynamics Research Articles

Оценка обеспеченности человеческим капиталом аграрного сектора экономики

Abstract. The formation and use of human capital in the agricultural economy must meet modern economic requirements and the level of development of agricultural production. The assessment of the efficiency of the use of human resources and the quality of products plays a key role in adapting to changing market conditions. Therefore, it is important to constantly strengthen human resources to ensure a prompt response to market challenges. At the same time, agricultural production is currently undergoing changes in all key areas. This article analyzes the availability and efficiency of the use of agricultural enterprises' labor resources, based on statistical data for the Russian Federation. In this regard, the purpose of this scientific study is to analyze the availability of human capital in agriculture. The objectives of the study include carrying out a qualitative and quantitative assessment of labor resources. Methods. The methodological basis is based on the general scientific principles of a systematic approach. The analysis uses logical, factorial, comparative and strategic methods, as well as methods of qualitative research of the main trends in the presence and use of human capital in agriculture. Results. The analysis of the formation and use of human capital in agriculture in its quantitative and qualitative assessment in the Russian Federation is carried out: the dynamics of rural population density and the number of workers, the growth rate of wages of agricultural workers, the grouping of those employed in agriculture by level of education, gender and age is given. Scientific novelty. As a result of the research, new theoretical and practical conclusions were obtained, including: 1) identification and classification of socio-economic conditions that promote or, conversely, hinder the effective use and preservation of human capital in the agricultural sector; 2) comprehensive schemes for the formation of human capital in the agricultural sector are proposed, taking into account internal and external factors; 3) the need for the formation of a comfortable socio-economic environment in rural areas is justified; 4) confirmed the need to provide special support measures to attract highly qualified specialists to rural areas.

An Autoregulatory Model of Forest Insect Population Dynamics and Forest Stand Damage Dynamics in Different Habitats: An Example of Lymantria dispar L.

This paper addresses the problem of constructing a mathematical model of population density dynamics and the dynamics of forest areas damaged by spongy moth (Lymantria dispar L.) outbreaks in the United States, Europe, Russia, and Japan. The key variable of the model is either the pest population density or the area of forests damaged by spongy moths during a season. This variable can be considered proportional to the total current pest abundance in the study area. For the purposes of modeling, data from a number of different authors was used (see bibliography), as well as data from surveys conducted at the egg or caterpillar stage. The complexity of modeling the dynamics of L. dispar abundance is largely due to the fact that, when studying the dynamics of spongy moth population density, the values of external factors such as parasites, predators, and the amount of available food are often unknown. A simple model was proposed using only two types of data: population density and monthly weather characteristics. Our analysis demonstrated that, even in the absence of knowledge regarding the characteristics of ecosystem components interacting with the spongy moth population (parasites, predators, and the state of forage trees), it is possible to introduce models that characterize the regulatory processes in the population in terms of (i) the presence of negative and positive feedbacks in the system and (ii) the influence of external weather factors. The system under investigation was described as an autoregressive system, whereby the current state of the population is dependent on its state in previous years. The order of autoregression in the system was estimated using the order of the maximum significant partial autocorrelation function. It was found that the regulation of spongy moth population density was characterized by the presence of two feedback loops: positive feedback between the current population density and the population density in the previous season and negative feedback between the current population density and the population density two years ago. To evaluate the model, its stability margin was calculated and found to be directly proportional to the positive feedback coefficient and inversely proportional to the negative feedback coefficient. The model was demonstrated to explain up to 90% of the observed variance of real data. Although the model coefficients for different local populations (North America, Europe, and Asia) differ, the general form of the equation describing both direct data on population densities and indirect data on pest dynamics characterized by areas of stand damage is consistent. Consequently, the form of the ADL model is general, irrespective of the location of the local population.

Crowd Analyzer using Trilateration and Keep Alive Signals

Tracking mobile phones in a specific area is crucial for assessing population density and understanding crowd dynamics. Traditional methods rely on Wi-Fi and GPS, but offline techniques like cell tower triangulation offer valuable insights even in areas with limited connectivity. By analyzing the number of mobile phones present, estimated through trilateration using signals from the phone's keep-alive signal, one can accurately estimate the crowd size. This information aids in urban planning, transportation management, event organization, and business strategies. Empowered with such data, decision-makers can optimize resource allocation, enhance safety measures, and improve overall societal well-being through informed decision-making.

Quantifying the trends and affecting factors of CO2 emissions under different urban development patterns: An econometric study on the Yangtze river economic belt in China

Environmental issues are rarely investigated within the framework of different urban development patterns, especially concerning CO2 emissions. This research works to reveal the trends and determining factors of urban CO2 emissions under different urban development patterns. Taking the cities in the Yangtze River Economic Belt (YREB) as an example, this study develops an identification system in light of the dynamics of urban population and population density to categorize urban development patterns as growth, potential shrinkage, smart shrinkage, and continuous shrinkage. Then, the Theil-sen medium analysis and spatial econometric modeling are applied to shed light on the trend and influencing factors of CO2 emissions, respectively. The findings indicate that urban growth and potential shrinkage are the main development patterns in the YREB, and the percentage of growing cities and potentially shrinking cities is more than 77 % across the different geographic areas of the YREB. CO2 emissions are remarkably heterogeneous under different urban development patterns. Over 90 % of cities show a growth trend or fluctuation in per capita CO2 emissions under the four development patterns during 2010∼2019. Only a few growing and potentially shrinking cities show a decreasing trend in per capita carbon emissions, suggesting a severe peak carbon challenge in the YREB. CO2 emissions in growing and shrinking cities are significantly influenced by their neighboring cities. Factors affecting CO2 emissions are different in shrinking and growing cities, and spatial spillover effects enhance the role of these factors. Compared with growing cities, improving population concentration, developing appropriate tertiary industries, strictly controlling land expansion, and developing green areas can pave the way for carbon emission reduction in shrinking cities. This study can support designing efficient carbon emission reduction measures for various cities.

Ecological characteristics of the siberian silkmoth (Dendrolimus sibiricus) (Insecta, Lasiocampidae) habitat in the Sayan montane conifer forests ecoregion

The article is devoted to studying the siberian silkmoth ( Dendrolimus sibiricus Tschetverikov, 1908) outbreaks, which is highly relevant today. The study was aimed at improving the system of forest pathology monitoring by revealing factors contributing to forest stand resistance to the pest attacks. We analyze the habitat conditions that are favorable for the siberian silkmoth in the early stages of its development and during the outbreak in dark coniferous taiga in the mountains of Southern Siberia (particularly, the Krasnoyarsk region). The research was based on remote sensing data combined with field data obtained in disturbed forests where we also con-ducted a pest population assessment. The habitat characteristics were based on the forest type and silvicultural and forest inventory details. We an alyzed environmental conditions and their influence on the pest reproduction. As a result, we divided the forest stands by their resistance to insect attacks. Primary habitats are stands with moss-covered forest floor, secondary habitats are stands with herbs-covered forest floor, and tertiary habitats are depressions with wet soils (forests along streams or swamp forests). We revealed the D. sibiricus population density dynamics related to the forest stands structure. The present research lets us determine forest sites vulnerable to pest attacks and conduct spatial monitoring of their dynamics and resistance.

Experimental Analysis of Diesel Engine Performance and Emissions with the Integration of Cyclonic Separator Device

The high population density and demographic dynamics have triggered a boom in the uptake of larger and more fuel-efficient diesel goods vehicles because diesel is cheaper than gasoline. Nevertheless, availability of diesel engines has lead to an increase of pollution especially in the urban area. This research examines whether a cyclonic separator which is an attachment device mounted on the vehicle exhaust system can sufficiently reduce particulate emissions from diesel engines. Thanks, the cyclonic separator is used to gather particles of size from 1μm to 50μm, to control the emission of diesel exhaust pollutants. Although we find that the utilization of the device decreases the pollution emission, our study shows that the installation of the device causes backpressure leading to a marginal reduction in thermal efficiency of between 0.8% to 1.01%. Nevertheless, the cyclonic separator can be considered one of the possible means to solve the problem of reduction of emissions of diesel engines and protect urban environment from pollution.

Mosquito larvae exposed to a sublethal dose of photosensitive insecticides have altered juvenile development but unaffected adult life history traits

BackgroundLarvicides are critical for the control of mosquito-borne diseases. However, even sublethal exposure to a larvicide can alter development and life history traits, which can then affect population density and disease transmission dynamics. Photosensitive insecticides (PSIs) are a promising class of larvicide that are toxic when ingested and activated by light. We investigated whether the time of day when exposure occurs, or the process of pupation, affects larval susceptibility to PSI phototoxicity in the mosquito Anopheles gambiae, and whether sublethal exposure to PSIs alters life history traits.MethodsLarvae were treated with lethal concentrations of the PSIs methylene blue (MB) and rose bengal (RB), and larval survival was measured at various times of day. Additionally, larvae were exposed to two concentrations of each PSI that resulted in low and medium mortality, and the life history traits of the surviving larvae were measured.ResultsPupation, which predominantly occurs in the evening, protected larvae from PSI toxicity, but the toxicity of PSIs against larvae that had yet to pupate was unaffected by time of day. Larval exposure to a sublethal concentration of MB, but not RB, shortened the time to pupation. However, larval exposure to a sublethal concentration of RB, but not MB, increased pupal mortality. Neither PSI had a meaningful effect on the time to eclosion, adult longevity, or adult melanization potential.ConclusionsPSIs are lethal larvicides. Sublethal PSI exposure alters mosquito development, but does not affect adult life history traits.Graphical

Spatiotemporal Dynamics of a Reaction Diffusive Predator-Prey Model: A Weak Nonlinear Analysis

In the realm of ecology, species naturally strive to enhance their own survival odds. This study introduces and investigates a predator-prey model incorporating reaction-diffusion through a system of differential equations. We scrutinize how diffusion impacts the model’s stability. By analysing the stability of the model’s uniform equilibrium state, we identify a condition leading to Turing instability. The study delves into how diffusion influences pattern formation within a predator-prey system. Our findings reveal that various spatiotemporal patterns, such as patches, spots, and even chaos, emerge based on species diffusion rates. We derive the amplitude equation by employing the weak nonlinear multiple scales analysis technique and the Taylor series expansion. A novel sinc interpolation approach is introduced. Numerical simulations elucidate the interplay between diffusion and Turing parameters. In a two-dimensional domain, spatial pattern analysis illustrates population density dynamics resulting in isolated groups, spots, stripes, or labyrinthine patterns. Simulation results underscore the method’s effectiveness. The article concludes by discussing the biological implications of these outcomes.

Investigation on Built-Up, Population, and Road Network Density Dynamics Using GIS, Regression, and Causation Analysis: A Case Study of Hyderabad City, India

Investigation on Built-Up, Population, and Road Network Density Dynamics Using GIS, Regression, and Causation Analysis: A Case Study of Hyderabad City, India

Возможное влияние летне-осенних сумм эффективных температур на динамику плотности популяции непарного шелкопряда Lymantria dispar (L.) в лесных насаждениях на северной границе ареала

Практически одновременно в 2016 г., вдоль северной границы ареала непарного шелкопряда Lymantria dispar (L.) на огромном пространстве более 1000 км в долготном направлении от Екатеринбурга (56,5° с.ш., 60,4° в.д.) до п. Кыштовка (Новосибирская область), 56,4°с.ш., 76,6°в.д. на сотнях тысяч гектар сформировались очаги непарного шелкопряда. Такая синхронность в возникновении очагов может указывать на воздействие единого модифицирующего фактора. Цель исследования - выявление общего модифицирующего фактора, который мог спровоцировать вспышку массового размножения непарного шелкопряда на основании анализа погодных условий в вегетационные сезоны, предшествующие формированию очагов и в период вспышки. На значительной территории, охватывающей зауральскую и западносибирскую популяции, в их северной части сценарии изменения погодных условий перед и в ходе реализации вспышки 2016-2018 гг. существенно различались по условиям влажности, но были схожи по теплообеспеченности. Два-три года теплообеспеченность была значительно ниже нормы, затем наступил сезон с теплообеспеченностью значительно выше нормы и резким возрастанием плотности популяции, приведшей к значительной дефолиации насаждений на следующий год при возвращении теплообеспеченности вегетационного сезона к норме. Это указывает на то, что на севере ареала вида модифицирующие факторы, провоцирующие вспышки массового размножения, отличаются от таковых в южных его частях. Возможно, вегетационные сезоны с низкой теплообеспеченностью приводят как к элиминации потомства особей популяции с большой длительностью развития до имагинальной стадии, так и к сокращению длительности развития личиночной стадии особей, получивших необходимую, но крайне небольшую сумму летне-осенних температур для завершения раннеэмбрионального развития и подготовки к зимовке. При наступлении вегетационного сезона с теплообеспеченностью значительно выше нормы снижается элиминация потомства особей с большей длительностью развития, что приводит к росту плотности популяции и значительной дефолиации на следующий год. Almost simultaneously in 2016, along the northern border of the range of spongy moth Lymantria dispar (L.) over a huge area of more than 1000 km in the longitude direction from Yekaterinburg (N 56.5 °, E 60.4°) to the village of Kyshtovka(Novosibirsk region), (N 56.4°, E 76.6°) the outbreaks of the spongy moth have formed on hundreds of thousands of hectares. Such synchronicity in the occurrence of outbreaks can indicate the impact of a single modifying factor. The purpose of the study is to identify a single modifying factor that could provoke an outbreak of the spongy moth, based on an analysis of weather conditions in the growing seasons preceding the formation of outbreaks and during their implementation. Over the large area covering the Trans-Ural and West Siberian populations, in their northern part, the scenarios of weather conditions changes before and during the implementation of the outbreak of 2016-2018 differed significantly in terms of humidity conditions but were similar in terms of heat availability. For two or three years, the heat availability was significantly lower than normal, then become the season with heat availability significantly higher than normal and a sharp increase in population density that provide the severe defoliation of stands for the next year when the heat availability of the growing season returns to normal. That indicates the differences in modifying factors provoking outbreaks at the north of the range of the spongy moth in comparison with southern parts of the range of this species. Possibly, growing seasons with low heat availability lead both to the elimination of the offspring of individuals in the population with a long duration of development till the imaginal stage, and to a reduction in the duration of development at the larval stage of individuals that have received the necessary, but an extremely small amount of summer-autumn temperatures to complete early embryonic development and preparation for wintering. With the onset of the growing season with a heat availability significantly higher than normal, the elimination of individuals with a longer duration of development decreases, which results in the population density increase and significant defoliation in the next year.

Spatial cumulant models enable spatially informed treatment strategies and analysis of local interactions in cancer systems

Theoretical and applied cancer studies that use individual-based models (IBMs) have been limited by the lack of a mathematical formulation that enables rigorous analysis of these models. However, spatial cumulant models (SCMs), which have arisen from theoretical ecology, describe population dynamics generated by a specific family of IBMs, namely spatio-temporal point processes (STPPs). SCMs are spatially resolved population models formulated by a system of differential equations that approximate the dynamics of two STPP-generated summary statistics: first-order spatial cumulants (densities), and second-order spatial cumulants (spatial covariances). We exemplify how SCMs can be used in mathematical oncology by modelling theoretical cancer cell populations comprising interacting growth factor-producing and non-producing cells. To formulate model equations, we use computational tools that enable the generation of STPPs, SCMs and mean-field population models (MFPMs) from user-defined model descriptions (Cornell et al. Nat Commun 10:4716, 2019). To calculate and compare STPP, SCM and MFPM-generated summary statistics, we develop an application-agnostic computational pipeline. Our results demonstrate that SCMs can capture STPP-generated population density dynamics, even when MFPMs fail to do so. From both MFPM and SCM equations, we derive treatment-induced death rates required to achieve non-growing cell populations. When testing these treatment strategies in STPP-generated cell populations, our results demonstrate that SCM-informed strategies outperform MFPM-informed strategies in terms of inhibiting population growths. We thus demonstrate that SCMs provide a new framework in which to study cell-cell interactions, and can be used to describe and perturb STPP-generated cell population dynamics. We, therefore, argue that SCMs can be used to increase IBMs’ applicability in cancer research.

External Factors Affecting the Pheromone Monitoring of the Spongy Moth

The method of pheromone monitoring in the pest density management system has gained wide popularity due to its relative simplicity. The aim of the study was to analyze the degree of conformity between the results of pheromone monitoring and population density dynamics of the spongy moth (Lymantria dispar (L.)), as well as external factors affecting the results of pheromone monitoring. The pheromone monitoring was carried out in the area of the Trans-Ural moth population in the Sverdlovsk region, in two areas – the one with a high population density and periodic outbreaks and other one with a very low density and no periodic outbreaks over the last 10 years. Simultaneously with the pheromone monitoring, population density was monitored based on autumn counts of egg masses. The results of long-term pheromone monitoring of the spongy moth allow us to come to the following conclusions. The catching capacity of traps is mainly influenced by weather conditions, including air temperature and the stability of air currents during the males’ flight. The masses’ density and the reproduction rate of the spongy moth population can influence the results of pheromone monitoring, but they are not the decisive factors. It is possible to make predictions of changes in the population density of this species only with detailed pheromone monitoring with accurate recording of main males’ flight period, using correction factors that take into account weather conditions. However, the authors doubt the economic feasibility of this kind of measures for the purpose of assessing the pest’s population’s density and monitoring its dynamics.

Birds of forest ecosystems of Southern Baikal in the conditions of modern climate warming: Dynamics of population density and structure in summer

On the basis of long-term works (2010-2022), the materials of studying the influence of climate warming on the bird population of forest ecosystems in the summer period are presented. The main indicators of the bird population were studied: population density and species composition. The dynamics of these indicators of the bird population structure and the features of their structure depending on the level of climate change on the ascending branch of the heat-dry phase of the centuries-old climate cycle, close to completion, are considered. The intensity of bird eviction is associated with the localization of very severe, prolonged and extensive droughts. It is the intensity of evictions that determines the new species composition of birds of the studied territories. They are characterized by very low numbers and therefore there is no clear link between the population density of birds and their species richness. At the same time, the general tendency to preserve this pattern (with an increase in the number of species, the population density of birds increases) is noted in some of their main categories. The obtained materials allow us to find out the peculiarities of the dynamics of the biodiversity of birds in Eastern Siberia during periods of severe climatic anomalies. Such materials are extremely important, as they allow us to find out the real role of natural and climatic factors in the evolution of natural ecosystems and the maintenance of the overall biodiversity of large zoogeographic regions of the Earth.

Diffusive size-structured population model with time-varying diffusion rate

<p style='text-indent:20px;'>This work is devoted to the study of a size-structured population model with a time-varying diffusion rate. Due to the seasonal variation, it is natural to consider the time-varying diffusion rate. Moreover, introducing the time-varying diffusion rate makes the model more challenging and requires the results of evolution operators for the analysis. Under some assumptions on the time-dependent diffusion coefficient, the existence and uniqueness of mild solution is shown. We apply the method of characteristics and evolution operators to derive our results. Positivity and boundedness of mild solution is also shown. Some examples are provided to illustrate the theoretical findings. We also solve our model numerically to study the size and spatial dynamics of population density.</p>

Demographic Spatialization Simulation under the Active “Organic Decentralization Population” Policy

A matter of considerable concern is managing rapid population growth in a growing megacity. After years of endeavor, the “decentralize and population cap” policy has finally been implemented and has achieved some success in Beijing, China. Before applying what has been learnt from this experience to other places, two questions remain to be addressed: “Can urbanization result in land-population harmony under the double effects of accessible guiding plans and invisible push-pull forces?” and “What will be the likely geo-simulation of population density resulting from a city decentralization process?” Under the guidance of “orderly city development” theory, our research (1) simulated the effects of the “organic population decentralization” policy on future population density dynamics; (2) proposed a new framework that coupled models of Verhulst logistic differential population and Cellular Auto-Markov; and (3) analyzed the steering effect of the policy toward a spatial population distribution that could be described as “spread through decentralization.” The results showed that Beijing is currently at the beginning of the “suburbanization” stage. This study can help geographers obtain an innovative method that couples the existing spatial population patterns and the potential population size, which is beneficial for urban planners in determining the spatial structure of a relative equilibrium status for urban development.

A haplodiploid mite adjusts fecundity and sex ratio in response to density changes during the reproductive period.

Population density is one of the main socio-environmental factors that have critical impacts on reproduction of animals. Consequently, they need to adjust their reproductive strategies in response to changes of local population density. In this study we used a haplodiploid spider mite, Tetranychus ludeni Zacher (Acari: Tetranychidae), to test how population density dynamics during the reproductive period altered female reproductive performance. We demonstrate that females produced fewer eggs with a significantly higher female-biased sex ratio in dense populations. Reducing fecundity and increasing daughter production in a dense environment could be an advantageous strategy to minimise the intensity of local food competition. However, females also reduced their fecundity after arrival in a new site of larger area from a dense population, which may be associated with higher web production costs because females need to produce more webs to cover the larger area. There was no trade-off between egg number and size, and egg size had little impact on reproductive fitness. Therefore, T. ludeni females could adapt to the shift of population density during their reproductive period by manipulating the fecundity and offspring sex ratio but not the egg size.

Dynamics of a pair of overlapping polar bright solitons in spin-1 Bose-Einstein condensates

We analyze the dynamics of both population and spin densities, emerging from the spatial overlap between two distinct polar bright solitons in Spin-1 Spinor Condensates. The dynamics of overlapping solitons in scalar condensates exhibits soliton fusion, atomic switching from one soliton to another and repulsive dynamics depending on the extent of overlap and the relative phase between the solitons. The scalar case also helps us understand the dynamics of the vector solitons. In the spinor case, non-trivial dynamics emerge in spatial and spin degrees of freedom. In the absence of spin changing collisions, we observe Josephson-like oscillations in the population dynamics of each spin component. In this case, the population dynamics is independent of the relative phase, but the dynamics of the spin-density vector depends on it. The latter also witnesses the appearance of oscillating domain walls. The pair of overlapping polar solitons emerge as four ferromagnetic solitons irrespective of the initial phase difference for identical spin-dependent and spin-independent interaction strengths. But the dynamics of final solitons depends explicitly on the relative phase. Depending on the ratio of spin-dependent and spin-independent interaction strengths, a pair of oscillatons can also emerge as the final state. Then, increasing the extent of overlap may lead to the simultaneous formation of both a stationary ferromagnetic soltion and a pair of oscillatons depending on the relative phase.

Features of population settlement in Orenburg oblast in the Ural River basin

One of the most topical problems of economic and geographical study of the regions of the Steppe belt in Russia is the development of a network of rural settlements. The territory of the Ural River basin within Orenburg oblast, where more than 75% of the region's population lives, was chosen by the authors as a model to assess the transformation of the population settlement system in the Steppe zone in recent decades. The paper gives municipal and territorial characteristics of the region, identifies specifics of the current system of population settlement, and classifies rural localities depending on the population and spatial distribution over the studied territory. The main areas of population concentration along transport, communication and landscape axes are identified and considered. About 20% of settlements are concentrated along 5 major highways; more than 30% of localities are confined to the valleys of 7 major rivers. Engel and Goltz coefficients, population concentration indices are calculated for municipalities, and indicators of the potential of the settlement field are identified for their centers. A cartographic diagram reflecting the spatial distribution of rural localities, the dynamics of rural population density and the level of transport development of municipalities, is constructed. In the territory under consideration, there has been a decrease in the density of the rural population by 4% for the past 10 years. The following large rural localities have the maximal potential of the fields of settlement: Saraktash, Akbulak, Novoorsk, Ilek, Sakmara, Oktyabrskoye and Tyulgan. Along with the compression of space and its polarization, the population continues to decline in urbanized areas too. The population decreased by almost 60 thousand inhabitants in seven cities. Conclusions and proposals on the sustainable development of the settlement network in close cooperation between the development of the supporting and natural-ecological frameworks are formulated.

Modeling weed community diversity based on species population density dynamics and herbicide use intensity

Herbicide programs change weed population density as well as weed community composition. The repeated use of a given program can result in a weed community that progressively becomes more difficult to manage or could lose its ability to provide ecosystem services. Simulation of those changes using stochastic models considering population dynamics of multiple species makes it possible to identify a priori potential community changes that might result from the use of a given herbicide program. The objectives of this work were to model the population dynamics of weed species under different herbicide programs and how those dynamics change weed community diversity over time. Weed population dynamics were stochastically modeled along ten years using population growth rate (lambda) for each species under different herbicide programs. Lambda values were obtained from an eight-year long, field experiment, and these were used to parameterize the stochastic ranges for the model for each weed species. Population trajectories were modeled for each individual species over ten years and the results were used to estimate richness, diversity, and evenness for each herbicide use scenario. The repeated use of glyphosate alone had a minimal effect on richness, but it caused a strong reduction in weed diversity and evenness. Programs with more mechanisms of action and the use of both preemergence and postemergence herbicides were slightly more likely to suffer the loss of weed species than programs with single or just a few herbicides. Conversely, the former had a higher probability of maintaining weed diversity and evenness than the latter. According to simulations, losses in weed community diversity are reversible, especially when highly competitive species were eradicated allowing other species with lower lambda to increase their populations. However, the eradication of species with low reproductive rates reduced diversity and evenness. The effects of herbicide programs on the weed community lasted for several years even after those programs were modified indicating that seed banks play a major buffering role in the rate of change of weed community composition. Thus, frequent changes in management interrupting the repeated use of specific weed control programs, even under high herbicide intensity use (i.e., number of applications and mechanisms of action), can help maintain weed diversity in agroecosystems.

Collisional radiative model for high-ionization-rate equilibrium argon plasma plume

An extensive collisional radiative model for the neutral argon and singly ionized argon plasma is developed to estimate the key properties of the high-ionization-rate equilibrium plasma plume. Major thirty-one argon atomic levels and ninety-five singly ionized argon levels are considered. The processes taken into account are radiative decay, electron impact ionization, excitation and deexcitation between all the levels, fast ion and atom impact excitation, and three body recombination. The model in conjunction with optical emission spectroscopy could be used to evaluate the electron temperature Te, the electron density ne, atom density ng and to investigate the dynamics of excitation population density. The local plasma spectrum in the plume region of an applied-field magnetoplasmadynamic thruster was measured with an optical immersion probe. The fundamental physical processes leading to W-shaped compound light variation in plume zone are explained based on the above plasma parameter distributions. A satisfactory agreement with the results measured by a Langmuir probe verifies the model's applicability to argon plasma plume.