scholarly journals Niche-based process and neutral dynamics emerge the per capita ecological difference and equivalence among species at different spatio-temporal-environmental scales

2020 ◽  
Author(s):  
takayuki yunoki
Keyword(s):  
Initial Conditions ◽  
Variation Partitioning ◽  
Species Pool ◽  
Open Boundary ◽  
Relative Role ◽  
Evolutionary Mechanisms ◽  
Regional Species Pool ◽  
Per Capita ◽  
Spatio Temporal ◽  
Ecological Difference

Reconciling niche-based process and neutral dynamics in a portion of an infinite system, the regional species pool may be already not free parameter, and the divergent ecological-evolutionary mechanisms may operate consistently. The individual-based model was implemented in the two-dimensional grid with periodic boundary condition. The model was explored using a fixed speciation rate, and a range of system sizes, dispersal rates, environmental structures and initial conditions of regional species pool. The model communities in the center of system had a fixed population size, and approximated from an area encompassing independent biogeographic units to an area packed in a biogeographic unit with open boundary conditions, and presented the three environmental structures; four humps, linear and random. Across scenarios, the number of guilds in system achieved first to a stationary state; then, the species richness converged eventually to a dynamical equilibrium through speciation-extinction balance. In simulations, the per capita ecological difference among species only contributed to the probabilities of immigration success, so the weighted lottery process was more efficient and immediate at higher dispersal rates. The increase of functional redundancy in model communities suggested that the relative role of neutral dynamics increased in an area encompassing independent biogeographic units. The variation partitioning based on canonical analysis inferred that not only the neutral dynamics among the species of single guild, but also the competition-colonization trade-off among the species of more than two guilds with similar environmental optimum and different levels of specialization operated in the spatial structures found within and among patchy habitats. Ecologist to disentangle the influence of alternative processes must shift focus from the contribution of local competitions and regional dispersals to detecting the spatio-temporal-environmental scales on which the per capita ecological difference and equivalence among species are emerged through divergent ecological-evolutionary mechanisms.

scholarly journals Species ethnobotanical values rather than regional species pool determine plant diversity in agroforestry systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daniel K. N’Woueni ◽  
Orou G. Gaoue
Keyword(s):  
Species Diversity ◽  
Plant Species ◽  
Plant Diversity ◽  
Agroforestry Systems ◽  
Natural Vegetation ◽  
Species Pool ◽  
Higher Plant ◽  
Natural Habitats ◽  
Natural Systems ◽  
Regional Species Pool

AbstractThe conversion of natural systems into farms and agroecosystems is the main cause of biodiversity loss. In human-dominated landscapes, understanding the interactions between agroforestry systems and adjacent natural vegetation is fundamental to developing sustainable agricultural systems. Species can move between these two systems with natural systems providing the regional pool of species that shape the agricultural values and conservation value of the agroforestry systems. We investigated the influence of neighboring natural habitats on traditional agroforestry systems in the buffer zone of Pendjari Biosphere Reserve in Benin to understand the contribution of regional processes on the quality of agroforestry systems. We expected that agroforestry parklands adjacent to natural vegetation with high species diversity will also have higher plant species diversity. We found no similarity in plant species composition between agroforestry systems and adjacent natural habitats. A small proportion of species in adjacent natural habitats were found in agroforestry systems. The proportion of shared species was not significantly influenced by plant diversity in adjacent natural habitats or the distance from the agroforestry systems to the natural adjacent habitat. However, plant diversity in agroforestry systems was strongly associated with site ethnobotanical values indicating that farmers act as a supplemental but severe environmental filter of the regional species pool. Our study suggests that promoting the plantation of plants with high ethnobotanical use-value is a potentially viable strategy for sustainable agriculture and ecological restoration in Biosphere reserves.

scholarly journals Forecasting circulation in the Cilician Basin of the Levantine Sea

2006 ◽  
Vol 3 (5) ◽  
pp. 1481-1514 ◽  
Author(s):  
E. Özsoy ◽  
A. Sözer
Keyword(s):  
Boundary Conditions ◽  
Initial Conditions ◽  
Eastern Mediterranean ◽  
Model Performance ◽  
Surface Flux ◽  
Mediterranean Coast ◽  
Open Boundary ◽  
Surface Boundary ◽  
Open Boundary Conditions ◽  
Levantine Sea

Abstract. The Cilician Basin/Shelf Model is adapted for studying the shelf circulation in the Cilician Basin – Gulf of İskenderun region of the Levantine Basin of the Eastern Mediterranean between the Turkish Mediterranean coast, Syria and the island of Cyprus. The model initial conditions and open boundary conditions are supplied by the ALERMO regional model of the Levantine Sea, while interactive surface flux boundary conditions are specified by an atmospheric boundary layer sub-model using calculated water properties and surface atmospheric variables supplied by the Skiron atmospheric model, within the nested modelling approach of the MFSTEP (Mediterranean Forecasting System: Towards Environmental Predictions) project. Sensitivity tests are performed for alternative surface boundary conditions. Model performance for shelf/meso-scale forecasts is demonstrated.

Entrainment and growth of vortical disturbances in the channel-entrance region

2021 ◽  
Vol 927 ◽  
Author(s):  
Pierre Ricco ◽  
Claudia Alvarenga
Keyword(s):  
Initial Conditions ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Analytical Description ◽  
Reynolds Numbers ◽  
Boundary Region ◽  
Shear Layers ◽  
Base Flow ◽  
Open Boundary ◽  
Classical Stability

The entrainment of free-stream unsteady three-dimensional vortical disturbances in the entry region of a channel is studied via matched asymptotic expansions and by numerical means. The interest is in flows at Reynolds numbers where experimental studies have documented the occurrence of intense transient growth, despite the flow being stable according to classical stability analysis. The analytical description of the vortical perturbations at the channel mouth reveals how the oncoming disturbances penetrate into the wall-attached shear layers and amplify downstream. The effects of the channel confinement, the streamwise pressure gradient and the viscous/inviscid interplay between the oncoming disturbances and the boundary-layer perturbations are discussed. The composite perturbation velocity profiles are employed as initial conditions for the unsteady boundary-region perturbation equations. At a short distance from the channel mouth, the disturbance flow is mostly confined within the shear layers and assumes the form of streamwise-elongated streaks, while farther downstream the viscous disturbances permeate the whole channel although the base flow is still mostly inviscid in the core. Symmetrical disturbances exhibit a more significant growth than anti-symmetrical disturbances, the latter maintaining a nearly constant amplitude for several channel heights downstream before growing transiently, a unique feature not reported in open boundary layers. The disturbances are more intense as the frequency decreases or the bulk Reynolds number increases. We compute the spanwise wavelengths that cause the most intense downstream growth and the threshold wall-normal wavelengths below which the perturbations are damped through viscous dissipation.

Community assembly and species traits

2019 ◽  
pp. 231-246
Author(s):  
Gary G. Mittelbach ◽  
Brian J. McGill
Keyword(s):  
Functional Traits ◽  
Community Assembly ◽  
Species Traits ◽  
Fundamental Question ◽  
Species Pool ◽  
Environmental Filters ◽  
Abiotic Environment ◽  
Local Site ◽  
Powerful Approach ◽  
Regional Species Pool

There is perhaps no more fundamental question in ecology than what determines the number and kinds of species found in a community and their relative abundances. This chapter lays out a powerful approach to answering this question, based on the concepts of a regional species pool and environmental filters. The species pool is the set of species that could potentially colonize a local site or community. Of these potential colonists, some species are limited in their ability to disperse to site, some are limited by their ability to survive the abiotic environment, and some are limited by their interactions with other species. These “filters” act individually or in concert, and the functional traits of species determine their success in passing through these filters to colonize a local site. There is growing empirical evidence that both abiotic and biotic processes select for specific functional traits. Focusing on the functional traits of species may lead to rules of community assembly that are general and help unify a variety of more specific theories.

Can long-distance dispersal shape the local and regional species pool?

2005 ◽  
Vol 40 (1) ◽  
pp. 35-44 ◽  
Author(s):  
Martin Zobel ◽  
Merit Otsus ◽  
Kai Rünk ◽  
Jaan Liira
Keyword(s):  
Species Pool ◽  
Long Distance Dispersal ◽  
Long Distance ◽  
Regional Species Pool

Spatio-temporal variations in agricultural diversification in India

2019 ◽  
Vol 9 (5) ◽  
pp. 476-502 ◽  
Author(s):  
Md Ejaz Anwer ◽  
Bimal Kishore Sahoo ◽  
Simantini Mohapatra
Keyword(s):  
Capita Income ◽  
Temporal Variations ◽  
Primary Study ◽  
Per Capita Income ◽  
Indian States ◽  
Price Inflation ◽  
Content Type ◽  
Agricultural Diversification ◽  
Per Capita ◽  
Spatio Temporal

Purpose Agriculture diversification acts as income enhancing as well as distress mitigating strategy. India has witnessed rise in per-capita income which in turn has increased the demand for food particularly high-valued food items but agricultural production has failed to keep pace with the growing demand. The purpose of this paper is to examine spatio-temporal variations in agricultural diversification (AD) in India. Second, the authors try to identify the determinants of AD. Third, the authors examine the convergence hypothesis with reference to agriculture diversification across Indian states. Design/methodology/approach The study is based on the panel data constituting 20 major states of India during 1990–1991 to 2013–2014. It uses Simpson Diversification Index to measure AD. The heteroskedasticity-corrected panel regression model is applied to find out the determinants of AD. The fixed-effects model is used to examine β-convergence in AD across the sample states. Alternative time series models are applied to examine σ-convergence in AD. Findings The rising per-capita income and urbanization are driving dietary diversity towards high-valued crops and providing ample opportunity for AD. But poor and inadequate cold storage facility and rising cost of cultivation are posing major hindrance to it. Small land holding and road length have negatively influenced AD which is contrary to the traditional wisdom. The study found divergence in diversification and rising inequality in diversification. Research limitations/implications The study is based on secondary data. A primary study to complement this could have been better. It is only based on one country. Social implications Food inflation has serious adverse effect on the society at large. It is necessary to promote AD for controlling food price inflation. Minimum support price provided by the government should be extended to all crops; otherwise, it will fuel inflation. Given the fact fragmentation of land holding is adversely affecting AD, community based farming and consolidation of farm land should be the way forward to improve farmers’ income as well as reduce risk. Originality/value To best of the authors’ study, this is the first study that examines determinants of AD and convergence in AD during the high growth period of India.

scholarly journals Effects of Initial Epidemic Conditions, Sporulation Rate, and Spore Dispersal Gradient on the Spatio-Temporal Dynamics of Plant Disease Epidemics

1998 ◽  
Vol 88 (10) ◽  
pp. 1000-1012 ◽  
Author(s):  
X.-M. Xu ◽  
M. S. Ridout
Keyword(s):  
Spatial Pattern ◽  
Power Law ◽  
Temporal Dynamics ◽  
Initial Conditions ◽  
Disease Incidence ◽  
Disease Status ◽  
Spatio Temporal ◽  
Disease Epidemics ◽  
Sporulation Rate ◽  
The Relationship

A stochastic model that simulates the spread of disease over space and time was developed to study the effects of initial epidemic conditions (number of initial inocula and their spatial pattern), sporulation rate, and spore dispersal gradient on the spatio-temporal dynamics of plant disease epidemics. The spatial spread of disease was simulated using a half-Cauchy distribution with median dispersal distance μ (units of distance). The rate of temporal increase in disease incidence (βI, per day) was influenced jointly by μ and by the sporulation rate λ (spores per lesion per day). The relationship between βI and μ was nonlinear: the increase in βI with increasing μ was greatest when μ was small (i.e., when the dispersal gradient was steep). The rate of temporal increase in disease severity of diseased plants (βS) was affected mainly by λ: βS increased directly with increasing λ. Intraclass correlation (κt), the correlation of disease status of plants within quadrats, increased initially with disease incidence, reached a peak, and then declined as disease incidence approached 1.0. This relationship was well described by a power-law model that is consistent with the binary form of the variance power law. The amplitude of the model relating κt to disease incidence was affected mainly by μ: κt decreased with increasing μ. The shape of the curve was affected mainly by initial conditions, especially the spatial pattern of the initial inocula. Generally, the relationship of spatial autocorrelation (ρt,k), the correlation of disease status of plants at various distances apart, to disease incidence and distance was well described by a four-parameter power-law model. ρt,k increased with disease incidence to a maximum and then declined at higher values of disease incidence, in agreement with a power-law relationship. The amplitude of ρt,k was determined mainly by initial conditions and by μ: ρt,k decreased with increasing μ and was lower for regular patterns of initial inocula. The shape of the ρt,k curve was affected mainly by initial conditions, especially the spatial pattern of the initial inocula. At any level of disease incidence, autocorrelation declined exponentially with spatial lag; the degree of this decline was determined mainly by μ: it was steeper with decreasing μ.

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