Diversité bêta

Résumé

La diversité bêta (diversité-β) est une mesure de la biodiversité qui consiste à comparer la diversité des espèces entre écosystèmes ou le long de gradients environnementaux. Cela suppose de comparer le nombre de taxons qui sont uniques à chacun des écosystèmes. C'est le taux de variation en composition d'espèces dans l'ensemble des habitats ou parmi des communautés. Cela donne une mesure quantitative de la diversité des communautés des environnements changeants. Indices

Indice de similitude de Sørensen \beta=\frac{2c}{S_1+S_2}

Où, S1= le nombre total d'espèces enregistrées dans la première communauté, S2= le nombre total d'espèces enregistrées dans la deuxième communauté, et c= le nombre d'espèces communes aux deux communautés. L'indice de Sørensen est une mesure très simple de la biodiversité bêta, variant de 0 quand il n'y a pas d'espèces communes entre les deux communautés, à la valeur 1 lorsque les mêmes espèces existent dans les deux communautés.

Source officielle

https://fr.wikipedia.org/wiki/Diversit%C3%A9_b%C3%AAta

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées (16)

Publications associées

Chargement

Personnes associées

Chargement

Unités associées

Chargement

Concepts associés (4)

Concepts associés

Chargement

Cours associés (3)

Cours associés

Chargement

Séances de cours associées (5)

Séances de cours associées

Chargement

Vegetation-environment relationships in alpine mires of the West Carpathians and the Alps

Lucia Sekulova

QuestionsHow do two distant mountain ranges differ in their vegetation-environment relationships, overall species composition and its variability and species richness of vascular plants and bryophytes in alpine fens and bogs? Is the floristic difference consistent along the acidity-alkalinity gradient? LocationWest Carpathians (Poland, Slovakia) and Swiss Alps. MethodsVascular plant and bryophyte species compositions and environmental characteristics were sampled along the large acidity-alkalinity gradient within the alpine belts. PERMANOVA was used for testing floristic differences between the regions, DCA for the patterns description, CCA for testing the vegetation-environment relationships and linear models for testing the local species richness determinants. Compositional -diversity (rate of compositional turnover) and regional species pool were compared using PERMDISP and sample-based rarefaction curves. ResultsMost floristic variation was explained by water pH in both regions. Macroclimate was the second most important gradient in the Alps, correlating with the second DCA axis delimiting the moderately poor brown-moss fens from the Sphagnum bogs. The species composition differed significantly between the regions in all three pH classes, expect for bryophytes in the middle pH class. Bryophytes exhibited higher similarities between the regions, except in acidic mires. Vascular plant composition differed most in the middle pH class. The local species richness was predominantly determined by pH, except for bryophytes in the Alps. As compared to bryophytes, vascular plant local species richness was affected by more factors and showed a clear linear response to pH. Within the particular pH classes, there were few differences in local species richness, compositional -diversity and regional species pool between the two mountain ranges. ConclusionsThe pattern in inter-regional floristic dissimilarities differs between bryophytes and vascular plants, probably because of better dispersal ability of bryophytes, and different causes of these dissimilarities: lower mass effect at extreme ends of the acidity-alkalinity gradient in the case of vascular plants and higher compositional -diversity of acidic mires in the case of bryophytes. Contrary to previously explored alpine springs of the same regions, local species richness and composition were determined rather by pH than mineral richness, and all patterns were more consistent between the regions and the taxonomic groups.

Wiley-Blackwell2013

Chargement

Patterns of bryophyte and vascular plant richness in European subalpine springs

Alexandre Buttler, Lucia Sekulova

The diversity of spring habitats can be determined not only by local environmental conditions, but also by large-scale biogeographical effects. The effects can differ across various groups of organisms. We compared alpha-, beta- and gamma-diversity patterns of bryophytes and vascular plants of (sub)alpine springs in three contrasting mountain ranges: Alps (Switzerland), Balkans (Bulgaria), Western Carpathians (Slovakia, Poland). We used univariate and multivariate statistics to test for the effects of pH, conductivity, altitude, slope, mean annual temperature and annual precipitation on diversity patterns of both taxonomic groups and compared diversity patterns among the regions for particular pH and conductivity classes. We identified acidophyte and basiphyte, calcifuge and calcicole species using species response modelling. All regions displayed significant relationship between conductivity and alpha-diversity of vascular plants. Bulgaria showed the highest alpha-diversity of vascular plants for the middle part of the conductivity gradient. For both taxonomic groups, the beta-diversity in the middle part of gradient was highest in Swiss Alps. The total species pool was lowest in Bulgaria. The percentage of basiphyte and calcicole species was highest in the Alps. In (sub)alpine springs, mineral richness was a better determinant of vascular plant alpha-diversity than pH, and the extent of the alpine area did not coincide with alpha-diversity. Observed inter-regional differences in diversity patterns could be explained by the different proportion of limestone bedrock and different biogeographic history. The differences in alpha-diversity between both taxonomic groups are presumably result of the different rates of adaptation processes.

Springer Netherlands2012

Chargement

Tropical forests are major repositories of biodiversity, but are fast disappearing as land is converted to agriculture. Decision-makers need to know which of the remaining forests to prioritize for conservation, but the only spatial information on forest biodiversity has, until recently, come from a sparse network of ground-based plots. Here we explore whether airborne hyperspectral imagery can be used to predict the alpha diversity of upper canopy trees in a West African forest. The abundance of tree species were collected from 64 plots (each 1250 m(2) in size) within a Sierra Leonean national park, and Shannon-Wiener biodiversity indices were calculated. An airborne spectrometer measured reflectances of 186 bands in the visible and near-infrared spectral range at 1 m(2) resolution. The standard deviations of these reflectance values and their first-order derivatives were calculated for each plot from the c. 1250 pixels of hyperspectral information within them. Shannon-Wiener indices were then predicted from these plot-based reflectance statistics using a machine-learning algorithm (Random Forest). The regression model fitted the data well (pseudo-R-2 = 84.9%), and we show that standard deviations of green-band reflectances and infra-red region derivatives had the strongest explanatory powers. Our work shows that airborne hyperspectral sensing can be very effective at mapping canopy tree diversity, because its high spatial resolution allows within-plot heterogeneity in reflectance to be characterized, making it an effective tool for monitoring forest biodiversity over large geographic scales.

Public Library of Science2014

Chargement

Vegetation-environment relationships in alpine mires of the West Carpathians and the Alps

Lucia Sekulova

Wiley-Blackwell2013