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Stratified resampling of phytosociological databases : Some strategies for obtaining more representative data sets for classification studies / Ilona Knollová in Journal of Vegetation Science, vol. 16, n°4 (Année 2005)
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Titre : Stratified resampling of phytosociological databases : Some strategies for obtaining more representative data sets for classification studies Type de document : Livre Auteurs : Ilona Knollová, Auteur ; Milan Chytrý, Auteur ; Lubomír Tichý, Auteur ; Ondrej Hájek, Auteur Année de publication : 2005 Article en page(s) : pp. 479-486 Langues : Anglais Catégories : [Thèmes] SIG - Télédétection Mots-clés : indicateur d'Ellenberg stratification géographique stratification de l'habitat donnée phytosociologique communauté végétale relevé phytosociologique conception d'échantillonnage Résumé : "Random resampling of the initial data set and geographically stratified resampling resulted in similar classifications. By contrast, classifications of the resampled data sets that were based on habitat stratifications (2–5) differed from each other and from the initial data set. Stratification 2 resulted in classifications that strongly reflected environmental factors with a coarse grain of spatial heterogeneity (e.g. macroclimate), whereas stratification 5 resulted in classifications emphasizing fine-grained factors (e.g. soil nutrient status). Stratification 3 led to the most deviating results, possibly due to the subjective nature of the traditional phytosociological classifications." (source : auteurs) Type de publication : périodique Référence biblio : Knollová I., Chytrý M., Tichý L., Hájek O., 2005 - Stratified resampling of phytosociological databases : Some strategies for obtaining more representative data sets for classification studies. Journal of Vegetation Science, 16 (4) : 479-486. ID PMB : 71035 DOI : 10.1111/j.1654-1103.2005.tb02388.x Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=71035
in Journal of Vegetation Science > vol. 16, n°4 (Année 2005) . - pp. 479-486[article]Exemplaires
Cote Localisation Disponibilité aucun exemplaire Addressing species turnover and community changes in vegetation resurvey studies / Elsa Alfonsi in Applied Vegetation Science, vol. 20, n°2 (Année 2017)
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Titre : Addressing species turnover and community changes in vegetation resurvey studies Type de document : Livre Auteurs : Elsa Alfonsi, Auteur ; Marie-Lise Benot, Auteur ; Virgil Fievet, Auteur ; Didier Alard, Auteur Année de publication : 2017 Article en page(s) : pp. 172-182 Langues : Anglais Catégories : [habitats/milieux] ZH - Zones humides Mots-clés : changement communautaire base de données donnée phytosociologique végétation classification Résumé : "Our study suggests that the resurvey strategy influences our ability to detect the degree and characteristics of vegetation changes in time. The plot-specific approach allows detection of species turnover and real trajectories but may over-emphasize community changes. The community-specific approach offers another way to interpret community changes that could be relevant for habitat conservation issues, especially at a regional level. For the community-specific approach, the detection and interpretation of vegetation change is influenced by the grain of community classification." (source : auteurs) Type de publication : périodique Référence biblio : Alfonsi E., Benot M.-L., Fievet V., Alard D., 2017 - Addressing species turnover and community changes in vegetation resurvey studies. Applied Vegetation Science, 20 (2) : 172-182. ID PMB : 65442 DOI : 10.1111/avsc.12258 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=65442
in Applied Vegetation Science > vol. 20, n°2 (Année 2017) . - pp. 172-182[article]Exemplaires
Cote Localisation Disponibilité aucun exemplaire A new measure of fidelity and its application to defining species groups / Heide Bruelheide in Journal of Vegetation Science, vol. 11, n°2 (Année 2000)
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Titre : A new measure of fidelity and its application to defining species groups Type de document : Livre Auteurs : Heide Bruelheide, Auteur Année de publication : 2000 Article en page(s) : pp. 167-178 Langues : Anglais Mots-clés : distribution binomiale COCKTAIL unité de végétation espèce différentielle distribution hypergéométrique méthode numérique base de données donnée phytosociologique classification de la végétation Résumé : "The first objective of this paper is to define a new measure of fidelity of a species to a vegetation unit, called u. The value of u is derived from the approximation of the binomial or the hypergeometric distribution by the normal distribution. It is shown that the properties of u meet the requirements for a fidelity measure in vegetation science, i.e. (1) to reflect differences of a species’relative frequency inside a certain vegetation unit and its relative frequency in the remainder of the data set; (2) to increase with increasing size of the data set. Additionally (3), u has the property to be dependent on the proportion of the vegetation unit's size to the size of the whole data set.
The second objective is to present a method of how to use the value of u for finding species groups in large data bases and for defining vegetation units. A species group is defined by possession of species that show the highest value of u among all species in the data set with regard to the vegetation unit defined by this species group. The vegetation unit is defined as comprising all relevés that include a minimum number of the species in the species group. This minimum number is derived statistically in such a way that fewer relevés always belong to a species group than would be expected if the differential species were distributed randomly among the relevés. An iterative algorithm is described for detecting species groups in data bases. Starting with an initial species group, species composition of this group and the vegetation unit defined by this group are mutually optimized. With this algorithm species groups are formed in a data set independently of each other. Subsequently, these species groups can be combined in such a way that they are suited to define commonly known syntaxa a posteriori." (source : auteur)Type de publication : périodique Référence biblio : Bruelheide H., 2000 - A new measure of fidelity and its application to defining species groups. Journal of Vegetation Science, 11 (2) : 167-178. ID PMB : 65719 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=65719
in Journal of Vegetation Science > vol. 11, n°2 (Année 2000) . - pp. 167-178[article]Exemplaires
Cote Localisation Disponibilité aucun exemplaire