Why do traditional dispersion indices used for analysis of spatial distribution of plants tend to become obsolete?

2021 ◽  
Author(s):  
Gabriella Freitas Alves ◽  
Denise Garcia Santana
Keyword(s):  
Spatial Distribution ◽  
Dispersion Indices

Can rational sampling maximise isolation and fix distribution measure of entomopathogenic nematodes?

Nematology ◽  
2020 ◽  
Vol 22 (8) ◽  
pp. 907-916 ◽  
Author(s):  
Mahfouz M.M. Abd-Elgawad
Keyword(s):  
Spatial Distribution ◽  
Distribution Pattern ◽  
Entomopathogenic Nematodes ◽  
Insect Pests ◽  
Tree Canopy ◽  
Systematic Sampling ◽  
Infested Soil ◽  
Wide Range ◽  
Dispersion Indices ◽  
Rational Sampling

Summary Entomopathogenic nematodes (EPN) can infect and kill a wide range of insect pests and are used as safe alternatives to chemical insecticides. Hence, a hypothesis was tested for obtaining EPN with high recovery frequency value and accurate distribution pattern based on combining four factors: favourable sampling method, time and site targeting and use of multiple extraction technique. As the extreme diversity of EPN sampling makes any generalisation from a given case study difficult, this functional sampling was limited to recovering EPN from citrus trees only in Egypt. It could both detect more EPN isolates and allow the application of different indices of dispersion to study their spatial distribution pattern. Therefore, stratified random and systematic sampling from weed-infested soil under tree canopy during the season of abundant insect pests was done, followed by multiple cycles of Galleria-baiting technique. Consequently, the nematodes were recovered from the seven surveyed groves (100%) and from 37 of 60 (61.7%) soil samples. The spatial distribution of these EPN isolates, previously identified as Heterorhabditis indica, was characterised using five dispersion indices, which were mainly a random rather than an over-dispersed distribution.

scholarly journals Population structure and spatial distribution of Copaifera langsdorffii Desf.

2020 ◽  
pp. 3000-3005
Author(s):  
Priscila Bezerra de Souza ◽  
Bruno Aurélio Campos Aguiar ◽  
Giuseppe Varaschim Neto ◽  
Euclides Figueredo Fonseca ◽  
Bárbara Maria Martins Santos ◽  
...  
Keyword(s):  
Population Structure ◽  
Spatial Distribution ◽  
Sensu Stricto ◽  
Dispersion Index ◽  
Cerrado Biome ◽  
J Curve ◽  
Dispersion Indices ◽  
Copaifera Langsdorffii ◽  
Morisita Index ◽  
Index Calculation

The aim of this work was to analyze the population structure and the spatial distribution of Copaifera langsdorffii Desf. in two areas of the Cerrado biome. The study was carried out in two physiognomies of the Cerrado biome: cerrado sensu stricto and cerradão, both located in the southern region of the state of Tocantins. The spatial distribution was evaluated using Morisita and dispersion indices, as well as the population structure of C. langsdorffii. We quantified 318 individuals of C. langsdorffii in the two studied areas. There were 200 individuals sampled in the cerrado sensu stricto and 118 in the area of cerradão. Regarding the type of spatial distribution of individuals of C. langsdorffii, the value found for the Morisita index was 2.67 in the physiognomy of cerrado sensu stricto, suggesting grouped spatial distribution (I >1). The dispersion index calculation showed that, in fact, the spatial distribution of the individuals sampled in the two areas was the grouped type; for the area of cerrado sensu stricto, the variance (S2) found was 24.21 and for the cerradão it was 9.67, higher than their means 10.00 and 9.67 respectively. By analyzing the age structure of the population of C. langsdorffii, we found a typical trend of the inverted-J curve, suggesting that the areas studied are self-regenerating communities composed of young and developing individuals.

Analysis of Spatial Distribution of Common Lambsquarters (Chenopodium album) in No-Till Soybean (Glycine max)

Weed Science ◽  
1995 ◽  
Vol 43 (2) ◽  
pp. 258-268 ◽  
Author(s):  
John Cardina ◽  
Denise H. Sparrow ◽  
Edward L. McCoy
Keyword(s):  
Spatial Distribution ◽  
Spatial Statistics ◽  
Large Scale ◽  
Chenopodium Album ◽  
Spherical Model ◽  
Rational Approach ◽  
Common Lambsquarters ◽  
Contour Maps ◽  
Classical Statistics ◽  
Dispersion Indices

The nonuniform spatial distribution of weeds complicates sampling, modeling, and management of weed populations. Principles of a rational approach to analysis of weed spatial distribution, combining classical and spatial statistics, are presented using data for cumulative emergence of common lambsquarters in no-tillage soybean fields in 1990 and 1993. Classical statistics, dispersion indices, mean/variance relationships, and frequency histograms confirmed that raw and loge-transformed data were not normally distributed, that populations were aggregated, and that large-scale trends in population means violated assumptions of spatial statistics. Detrending was accomplished by median polishing loge-transformed data and confirmed by evaluation of standardized residuals and frequency histograms. Detrended residuals were used to construct omni-directional and uni-directional semivariograms to describe the spatial structure of the populations. A spherical model fit to the data was verified by cross validation. Semivariograms showed that common lambsquarters density was spatially autocorrelated at distances to 16 m, with more than 30% of the variance in density due to distance between field locations. Comparisons of kriged estimates and their standard deviations with and without detrending indicated that estimates using detrended data were more appropriate and more precise. Kriged estimates of common lambsquarters density were used to draw contour maps of the populations.

scholarly journals Population dynamics and spatial distribution of Abaris basistriata Chaudoir, 1873 (Coleoptera: Carabidae)

2016 ◽  
Vol 40 (1) ◽  
pp. 57-66 ◽  
Author(s):  
Ivan Carlos Fernandes Martins ◽  
Francisco Jorge Cividanes ◽  
José Carlos Barbosa ◽  
Joaquim Alves de Lima Junior ◽  
Lourival Dias Campos
Keyword(s):  
Population Dynamics ◽  
Spatial Distribution ◽  
Probabilistic Models ◽  
Large Population ◽  
Linear Interpolation ◽  
Distribution Data ◽  
Distribution Analysis ◽  
Natural Habitats ◽  
Refuge Area ◽  
Dispersion Indices

ABSTRACT Abaris basistriata, a beetle species dominant in agroecosystems and natural habitats, may benefit from the establishment of nearby refuge areas or crop field centers. To confirm this hypothesis, we analyzed the spatial distribution of the species and verified the population dynamics of this predator in a soybean/corn rotation crop and a central refuge area. The 1-ha experimental area was divided in half by a range of herbaceous plants (2 m in width and 80 m in length). Beetle samples were collected using pitfall traps every fortnight during the in-season and every month during the off-season (a total of 27 sampling occurrences). Population fluctuation was analyzed by correlating the total number of specimens with plant phenology. We used multiple regression analysis with variable (stepwise) selection to examine the influence of meteorological factors on species occurrence. To determine the spatial distribution, data were analyzed using dispersion indices and probabilistic models based on the Coleoptera frequency distribution. Distribution visualization was assessed using a linear interpolation map. A total of 143 A. basistriata specimens were collected, with 83 from the soybean/corn area and 60 from the refuge area. Periods of large population size occurred during a season with high rainfall and high maximum and minimum temperatures. On the basis of the spatial distribution analysis of A. basistriata, it is likely that the beetles occur in an aggregate form, preferably in the refuge area.

scholarly journals Spatial distribution of Diaphorina citri Kuwayama (Hemiptera: Psyllidae) in citrus orchards

2010 ◽  
Vol 67 (5) ◽  
pp. 546-554 ◽  
Author(s):  
Marilia Gregolin Costa ◽  
José Carlos Barbosa ◽  
Pedro Takao Yamamoto ◽  
Renata Moreira Leal
Keyword(s):  
Spatial Distribution ◽  
Negative Binomial Distribution ◽  
Binomial Distribution ◽  
Negative Binomial ◽  
Sweet Orange ◽  
Central Area ◽  
Diaphorina Citri ◽  
Paulo State ◽  
Dispersion Indices ◽  
Citrus Orchards

The psyllid Diaphorina citri Kuwayama is one of the most important pests of citrus, mainly because it is the vector of the bacterium that causes huanglongbing (HLB) or 'Greening' disease. To study the spatial distribution of nymphs and adults of this pest, an experiment was carried out in two 'Valencia' sweet orange orchards, four and 12 years of age, established in Matão, central area of São Paulo state, Brazil. The following dispersion indices were used to study pest aggregation in the citrus plants: variance/mean relationship (I), index of Morisita (Iδ), coefficient of Green (Cx), the <img border=0 width=16 height=16 src="../../../../../img/revistas/sa/v67n5/a08form10.gif" align=absmiddle>exponent of negative binomial distribution, common k (<img border=0 width=16 height=16 src="../../../../../img/revistas/sa/v67n5/a08form10.gif" align=absmiddle>c) and Taylor's Power Law for each sampling. The negative binomial distribution was more representative of the spatial distribution of this psyllid, for both nymphs and adults. For most samplings, psyllid nymphs found in branches and adults caught in traps had an aggregated distribution.

Lithography below 100 nm

1983 ◽  
Vol 41 ◽  
pp. 96-99
Author(s):  
L. D. Jackel
Keyword(s):  
Spatial Distribution ◽  
Electron Beam ◽  
Electron Scattering ◽  
Electron Beam Lithography ◽  
Substrate Material ◽  
Local Electron ◽  
Electron Dose ◽  
Positive Resist ◽  
Exposure Process

Most production electron beam lithography systems can pattern minimum features a few tenths of a micron across. Linewidth in these systems is usually limited by the quality of the exposing beam and by electron scattering in the resist and substrate. By using a smaller spot along with exposure techniques that minimize scattering and its effects, laboratory e-beam lithography systems can now make features hundredths of a micron wide on standard substrate material. This talk will outline sane of these high- resolution e-beam lithography techniques.We first consider parameters of the exposure process that limit resolution in organic resists. For concreteness suppose that we have a “positive” resist in which exposing electrons break bonds in the resist molecules thus increasing the exposed resist's solubility in a developer. Ihe attainable resolution is obviously limited by the overall width of the exposing beam, but the spatial distribution of the beam intensity, the beam “profile” , also contributes to the resolution. Depending on the local electron dose, more or less resist bonds are broken resulting in slower or faster dissolution in the developer.

SEM evaluation of the TEM cold-stage double-film specimen

1984 ◽  
Vol 42 ◽  
pp. 272-273
Author(s):  
Jayesh Bellare
Keyword(s):  
Spatial Distribution ◽  
Sample Preparation ◽  
Sample Thickness ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Liquid Sample ◽  
Thin Specimen ◽  
Sample Preparation Technique ◽  
Cold Stage ◽  
Film Specimen

Seeing is believing, but only after the sample preparation technique has received a systematic study and a full record is made of the treatment the sample gets.For microstructured liquids and suspensions, fast-freeze thermal fixation and cold-stage microscopy is perhaps the least artifact-laden technique. In the double-film specimen preparation technique, a layer of liquid sample is trapped between 100- and 400-mesh polymer (polyimide, PI) coated grids. Blotting against filter paper drains excess liquid and provides a thin specimen, which is fast-frozen by plunging into liquid nitrogen. This frozen sandwich (Fig. 1) is mounted in a cooling holder and viewed in TEM.Though extremely promising for visualization of liquid microstructures, this double-film technique suffers from a) ireproducibility and nonuniformity of sample thickness, b) low yield of imageable grid squares and c) nonuniform spatial distribution of particulates, which results in fewer being imaged.

Macroprobe Mode for the Study of Segregation in Steels

1990 ◽  
Vol 48 (2) ◽  
pp. 260-261
Author(s):  
Auclair Gilles ◽  
Benoit Danièle
Keyword(s):  
Mechanical Properties ◽  
Spatial Distribution ◽  
High Performance ◽  
Volume Fraction ◽  
Sheet Steel ◽  
Acquisition Time ◽  
Chemical Information ◽  
X Ray ◽  
Accurate Quantitative Analysis ◽  
Optical Micrographs

During these last 10 years, high performance correction procedures have been developed for classical EPMA, and it is nowadays possible to obtain accurate quantitative analysis even for soft X-ray radiations. It is also possible to perform EPMA by adapting this accurate quantitative procedures to unusual applications such as the measurement of the segregation on wide areas in as-cast and sheet steel products.The main objection for analysis of segregation in steel by means of a line-scan mode is that it requires a very heavy sampling plan to make sure that the most significant points are analyzed. Moreover only local chemical information is obtained whereas mechanical properties are also dependant on the volume fraction and the spatial distribution of highly segregated zones. For these reasons we have chosen to systematically acquire X-ray calibrated mappings which give pictures similar to optical micrographs. Although mapping requires lengthy acquisition time there is a corresponding increase in the information given by image anlysis.

Ultrastructural analysis of the spatial distribution of MRNA

1992 ◽  
Vol 50 (1) ◽  
pp. 552-553
Author(s):  
Gary Bassell ◽  
Robert H. Singer
Keyword(s):  
Electron Microscopy ◽  
Spatial Distribution ◽  
In Situ Hybridization ◽  
High Resolution ◽  
Nucleic Acids ◽  
Colloidal Gold ◽  
Dna Probe ◽  
Nucleotide Analogs ◽  
Gold Particles

We have been investigating the spatial distribution of nucleic acids intracellularly using in situ hybridization. The use of non-isotopic nucleotide analogs incorporated into the DNA probe allows the detection of the probe at its site of hybridization within the cell. This approach therefore is compatible with the high resolution available by electron microscopy. Biotinated or digoxigenated probe can be detected by antibodies conjugated to colloidal gold. Because mRNA serves as a template for the probe fragments, the colloidal gold particles are detected as arrays which allow it to be unequivocally distinguished from background.

Sign in / Sign up

Export Citation Format

Share Document