Modifying the t Test for Assessing the Correlation Between Two Spatial Processes

Dutilleul, Pierre; Clifford, Peter; Richardson, Sylvia; Hémon, Denis

doi:10.2307/2532625

Cited by 818 publications

(713 citation statements)

References 10 publications

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“…4B, linear regression model: F 1,924 = 110.3, p < 0.001, R 2 = 0.1057), with large number of ducks in areas where there is no second crop harvest. We verified the significance of these associations in presence of spatial autocorrelation using the modified t-test (Dutilleul, 1993), and both associations were found to be significant (p < 0.001, and p = 0.0039, respectively).…”

Section: Resultsmentioning

confidence: 83%

Avian influenza, domestic ducks and rice agriculture in Thailand

Gilbert

Xiao

Chaitaweesub

et al. 2007

Agriculture, Ecosystems & Environment

118

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Highly pathogenic avian influenza (HPAI) caused by H5N1 viruses has become a global scale problem which first emerged in southern China and from there spread to other countries in Southeast and East Asia, where it was first confirmed in end 2003. In previous work, geospatial analyses demonstrated that free grazing ducks played critical role in the epidemiology of the disease in Thailand in the winter 2004/2005, both in terms of HPAI emergence and spread. This study explored the geographic association between free grazing duck census counts and current statistics on the spatial distribution of rice crops in Thailand, in particular the crop calendar of rice production. The analysis was carried out using both district level rice statistics and rice distribution data predicted with the aid of remote sensing, using a rice-detection algorithm. The results indicated a strong association between the number of free grazing ducks and the number of months during which second-crop rice harvest takes place, as well as with the rice crop intensity as predicted by remote sensing. These results confirmed that free grazing duck husbandry was strongly driven by agricultural land use and rice crop intensity, and that this later variable can be readily predicted using remote sensing. Analysis of rice cropping patterns may provide an indication of the location of populations of free grazing ducks in other countries with similar mixed duck and rice production systems and less detailed duck census data. Apart from free ranging ducks and rice cropping, the role of hydrology and seasonality of wetlands and water bodies in the HPAI risk analysis is also discussed in relation to the presumed dry season aggregation of wild waterfowl and aquatic poultry offering much scope for virus transmission.

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Section: Resultsmentioning

confidence: 83%

Avian influenza, domestic ducks and rice agriculture in Thailand

Gilbert

Xiao

Chaitaweesub

et al. 2007

Agriculture, Ecosystems & Environment

118

View full text Add to dashboard Cite

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“…In order to determine the accuracy of the species richness models, the percentage of explained deviance was calculated for each model (see Dobson 1999). We evaluated the models' accuracy by fitting it to the evaluation set and compared the predicted and observed species richness using Spearman's rank correlation (Heikkinen and Neuvonen 1997;Maes et al 2005).…”

Section: Modelling Species Richnessmentioning

confidence: 99%

Determinants of species richness patterns in the Netherlands across multiple taxonomic groups

et al. 2008

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We examined the species richness patterns of five different species groups (mosses, reptiles and amphibians, grasshoppers and crickets, dragonflies, and hoverflies) in the Netherlands (41,500 km 2 ) using sampling units of 5 9 5 km. We compared the spatial patterns of species richness of the five groups using Spearman's rank correlation and used a stepwise multiple regression generalized linear modelling (GLM) approach to assess their relation with a set of 36 environmental variables, selected because they can be related to the several hypotheses on biodiversity patterns. Species richness patterns of the five groups were to a certain extent congruent. Our data suggest that environmental heterogeneity (in particular habitat heterogeneity) is one of the major determinants of variation in species richness within these five groups. We found that for taxonomic groups comprising a low number of species, our regression model explained more of the variability in species richness than for taxonomic groups with a large number of species.

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“…We used Dutilleul's method for corrected, 'geographically effective', degrees of freedom (d.f. *) to adjust for the amount of spatial autocorrelation (Dutilleul, 1993;Hawkins et al, 2005).…”

Section: Environmental Correlates Of Avian Diversitymentioning

confidence: 99%

Environmental correlates of avian diversity in lowland Panama rain forests

Rompré

Robinson

Desrochers

et al. 2007

Journal of Biogeography

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Aim The composition of communities is known to be influenced by biogeographical history, but also by local environmental conditions. Yet few studies have evaluated the relative importance of the direct and indirect effects of multiple factors on species diversity in rich Neotropical forests. Our study aims to assess drivers of change in local bird species richness in lowland tropical rain forests.Location Thirty-two physiographic subregions along the corridor of the Panama Canal, Panama.Methods We mapped the distributions of all forest-dwelling bird species and quantified the environmental characteristics of all subregions, including mean annual rainfall, topographic complexity, elevational variability, forest age and forest area. Plant species richness, believed to be correlated with structural complexity, was estimated by interpolation through kriging for subregions where data were unavailable.Results The study region has a strong rainfall gradient across a short distance (65 km), which is also accompanied by steep gradients in plant and bird species diversity. Path analysis showed that precipitation strongly affected plant species diversity, which in turn affected avian diversity. Forest age and topography affected bird diversity independently of plant diversity. Forest area and its proportion occurring in the largest two fragments of each subregion (habitat configuration) were also positive correlates of bird species richness.Main conclusions Our results suggest that plant species richness, known to be influenced in part by biogeographical history and geology, also affects bird species assemblages locally. We provide support for the hypothesis that bird species richness increases with structural complexity of the habitat. Our analysis of the distributions of the region's most disturbance-sensitive bird species showed that subregions with more rainfall, more complex topography and older forests harboured not only richer communities but also more sensitive species; while subregions with the opposite characteristics usually lacked large fractions of the regional forest bird community and hosted only common, widely distributed species. Results also emphasize the importance of preserving forest diversity from habitat loss and fragmentation, and confirm that larger, continuous forest tracts are necessary to maintain the rich avian diversity in the region.

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Modifying the t Test for Assessing the Correlation Between Two Spatial Processes

Cited by 818 publications

References 10 publications

Avian influenza, domestic ducks and rice agriculture in Thailand

Avian influenza, domestic ducks and rice agriculture in Thailand

Determinants of species richness patterns in the Netherlands across multiple taxonomic groups

Environmental correlates of avian diversity in lowland Panama rain forests

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