A partir de cette page vous pouvez :
Retourner au premier écran avec les dernières notices... |
Journal of Vegetation Science / Association Internationale pour l'étude de la végétation . vol. 13, n°1Mention de date : Année 2002Paru le : 01/02/2002 |
Dépouillements
Ajouter le résultat dans votre panierDetermination of diagnostic species with statistical fidelity measures / Milan Chytrý in Journal of Vegetation Science, vol. 13, n°1 (Année 2002)
[article]
Titre : Determination of diagnostic species with statistical fidelity measures Type de document : Livre Auteurs : Milan Chytrý, Auteur ; Lubomír Tichý, Auteur ; Jason Holt, Auteur ; Zoltan Botta-Dukat, Auteur Année de publication : 2002 Article en page(s) : pp. 79-90 Langues : Anglais Résumé : "Statistical measures of fidelity, i.e. the concentration of species occurrences in vegetation units, are reviewed and compared. The focus is on measures suitable for categorical data which are based on observed species frequencies within a vegetation unit compared with the frequencies expected under random distribution. Particular attention is paid to Bruelheide's u value. It is shown that its original form, based on binomial distribution, is an asymmetric measure of fidelity of a species to a vegetation unit which tends to assign comparatively high fidelity values to rare species. Here, a hypergeometric form of u is introduced which is a symmetric measure of the joint fidelity of species to a vegetation unit and vice versa. It is also shown that another form of the binomial u value may be defined which measures the asymmetric fidelity of a vegetation unit to a species. These u values are compared with phi coefficient, chi‐square, G statistic and Fisher's exact test. Contrary to the other measures, phi coefficient is independent of the number of relevés in the data set, and like the hypergeometric form of u and the chi‐square it is little affected by the relative size of the vegetation unit. It is therefore particularly useful when comparing species fidelity values among differently sized data sets and vegetation units. However, unlike the other measures it does not measure any statistical significance and may produce unreliable results for small vegetation units and small data sets. The above measures, all based on the comparison of observed/expected frequencies, are compared with the categorical form of the Dufrêne‐Legendre Indicator Value Index, an index strongly underweighting the fidelity of rare species.
These fidelity measures are applied to a data set of 15 989 relevés of Czech herbaceous vegetation. In a small subset of this data set which simulates a phytosociological table, we demonstrate that traditional table analysis fails to determine diagnostic species of general validity in different habitats and large areas. On the other hand, we show that fidelity calculations used in conjunction with large data sets can replace expert knowledge in the determination of generally valid diagnostic species. Averaging positive fidelity values for all species within a vegetation unit is a useful approach to measure quality of delimination of the vegetation unit. We propose a new way of ordering species in synoptic species‐by‐relevé tables, using fidelity calculations."Type de publication : périodique Référence biblio : Chytrý M., Tichý L., Holt J., Botta-Dukat Z., 2002 - Determination of diagnostic species with statistical fidelity measures. Journal of Vegetation Science, 13 (1) : 79-90. Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=66163
in Journal of Vegetation Science > vol. 13, n°1 (Année 2002) . - pp. 79-90[article]Exemplaires
Cote Localisation Disponibilité aucun exemplaire Patterns of plant species and community diversity at different organization levels in a forested riparian landscape / Guillaume Decocq in Journal of Vegetation Science, vol. 13, n°1 (Année 2002)
[article]
Titre : Patterns of plant species and community diversity at different organization levels in a forested riparian landscape Type de document : Livre Auteurs : Guillaume Decocq, Auteur Année de publication : 2002 Article en page(s) : pp. 91-106 Langues : Anglais Mots-clés : paysage riverain boisé contrôle environnemental phytosociologie diversité végétale dépendance à l'échelle organisation spatio-temporelle Résumé : "Integrated synusial phytosociology combined with traditional measures of diversity is used to describe the structure of vascular vegetation diversity along the forested riparian landscape of the upper Oise valley (Belgium and France). The two dimensions (longitudinal and lateral) of the geomorphological complex are examined at four scales: synusia, phytocoenosis, tesela and catena. The results support the following hypotheses: (1) the environmental gradients observed, particularly the lateral ones, are very complex; (2) there is a clear lack of coupling between the tree, shrub and herb layers, which indicates a differential response to the underlying influence of environmental controls; (3) moderate flooding‐induced disturbance enhances herb species richness; (4) stressful environments support a low plant species diversity but a high synusial richness; (5) natural factors (substrate, climate, disturbance) are more important at the synusia and phytocoenose scales, but (6) anthropogenic disturbances, mainly through forest and river management, are more important at the landscape level. By considering plant communities as structural‐dynamic entities of ecosystems in a landscape context, integrated synusial phytosociology provides a basis for decomposing a complex system since the different hierarchical levels are both nested and thus strongly relational and process‐based." (source : auteur) Type de publication : périodique Référence biblio : Decocq G., 2002 - Patterns of plant species and community diversity at different organization levels in a forested riparian landscape. Journal of Vegetation Science, 13 (1) : 91-106. ID PMB : 68945 DOI : 10.1111/j.1654-1103.2002.tb02026.x Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=68945
in Journal of Vegetation Science > vol. 13, n°1 (Année 2002) . - pp. 91-106[article]Exemplaires
Cote Localisation Disponibilité aucun exemplaire
Exemplaires
Cote | Localisation | Disponibilité |
---|---|---|
aucun exemplaire |