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Accurate modelling of canopy traits from seasonal Sentinel-2 imagery based on the vertical distribution of leaf traits / Tawanda W. Gara in ISPRS Journal of photogrammetry and remote sensing, vol 157 (November 2019)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 157 (November 2019) . - pp 108 - 123 Titre : Accurate modelling of canopy traits from seasonal Sentinel-2 imagery based on the vertical distribution of leaf traits Type de document : Article/Communication Auteurs : Tawanda W. Gara, Auteur ; Roshanak Darvishzadeh, Auteur ; Andrew K. Skidmore, Auteur ; et al., Auteur Année de publication : 2019 Article en page(s) : pp 108 - 123 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes descripteurs IGN] Bavière (Allemagne) [Termes descripteurs IGN] canopée [Termes descripteurs IGN] classification par forêts aléatoires [Termes descripteurs IGN] écosystème forestier [Termes descripteurs IGN] hétérogénéité spatiale [Termes descripteurs IGN] image Sentinel-MSI [Termes descripteurs IGN] indice foliaire [Termes descripteurs IGN] Leaf mass per area [Termes descripteurs IGN] photosynthèse [Termes descripteurs IGN] variation saisonnière Résumé : (Auteur) Leaf traits at canopy level (hereinafter canopy traits) are conventionally expressed as a product of total canopy leaf area index (LAI) and leaf trait content based on samples collected from the exposed upper canopy. This traditional expression is centered on the theory that absorption of incident photosynthetically active radiation (PAR) follow a bell-shaped function skewed to the upper canopy. However, the validity of this theory has remained untested for a suite of canopy traits in a temperate forest ecosystem across multiple seasons using multispectral imagery. In this study, we examined the effect of canopy traits expression in modelling canopy traits using Sentinel-2 multispectral data across the growing season in Bavaria Forest National Park (BFNP), Germany. To achieve this, we measured leaf mass per area (LMA), chlorophyll (Cab), nitrogen (N) and carbon content and LAI from the exposed upper and shaded lower canopy respectively over three seasons (spring, summer and autumn). Subsequently, we estimated canopy traits using two expressions, i.e. the traditional expression-based on the product of LAI and leaf traits content of samples collected from the sunlit upper canopy (hereinafter top-of-canopy expression) and the weighted expression - established on the proportion between the shaded lower and sunlit upper canopy LAI and their respective leaf traits content. Using a Random Forest machine-learning algorithm, we separately modelled canopy traits estimated from the two expressions using Sentinel-2 spectral bands and vegetation indices. Our results showed that dry matter related canopy traits (LMA, N and carbon) estimated based on the weighted canopy expression yield stronger correlations and higher prediction accuracy (NRMSECV  0.48 µg/cm2) across all seasons. We also developed a generalized model that explained 52.57–67.82% variation in canopy traits across the three seasons. Using the most accurate Random Forest model for each season, we demonstrated the capability of Sentinel-2 data to map seasonal dynamics of canopy traits across the park. Results presented in this study revealed that canopy trait expression can have a profound effect on modelling the accuracy of canopy traits using satellite imagery throughout the growing seasons. These findings have implications on model accuracy when monitoring the dynamics of ecosystem functions, processes and services. Numéro de notice : A2019-493 Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2019.09.005 date de publication en ligne : 11/09/2019 En ligne : https://doi.org/10.1016/j.isprsjprs.2019.09.005 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93725 [article]

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Testing spatial heterogeneity in geographically weighted principal components analysis / Javier Roca-Pardiñas in International journal of geographical information science IJGIS, vol 31 n° 3-4 (March-April 2017)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 31 n° 3-4 (March-April 2017) . - pp 676 - 693 Titre : Testing spatial heterogeneity in geographically weighted principal components analysis Type de document : Article/Communication Auteurs : Javier Roca-Pardiñas, Auteur ; Celestino Ordóñez, Auteur ; Tomás R. Cotos-Yáñez, Auteur ; Rubén Pérez-Álvarez, Auteur Année de publication : 2017 Article en page(s) : pp 676 - 693 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale [Termes descripteurs IGN] analyse en composantes principales [Termes descripteurs IGN] données localisées [Termes descripteurs IGN] hétérogénéité spatiale [Termes descripteurs IGN] interpolation par pondération de zones [Termes descripteurs IGN] vecteur propre Résumé : (Auteur) We propose a method to evaluate the existence of spatial variability in the covariance structure in a geographically weighted principal components analysis (GWPCA). The method, that is extensive to locally weighted principal components analysis, is based on performing a statistical hypothesis test using the eigenvectors of the PCA scores covariance matrix. The application of the method to simulated data shows that it has a greater statistical power than the current statistical test that uses the eigenvalues of the raw data covariance matrix. Finally, the method was applied to a real problem whose objective is to find spatial distribution patterns in a set of soil pollutants. The results show the utility of GWPCA versus PCA. Numéro de notice : A2017-079 Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/13658816.2016.1224886 En ligne : http://dx.doi.org/10.1080/13658816.2016.1224886 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84342 [article]

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Exposure-related forest-steppe: A diverse landscape type determined by topography and climate / Martin Hais in Journal of Arid Environments, vol 135 (December 2016)  

Public [article]  inJournal of Arid Environments > vol 135 (December 2016) . - pp 75 - 84 Titre : Exposure-related forest-steppe: A diverse landscape type determined by topography and climate Type de document : Article/Communication Auteurs : Martin Hais, Auteur ; Milan Chytrý, Auteur ; Michal Horsak, Auteur Année de publication : 2016 Article en page(s) : pp 75 - 84 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes descripteurs IGN] climat continental [Termes descripteurs IGN] hétérogénéité spatiale [Termes descripteurs IGN] image Landsat [Termes descripteurs IGN] modèle numérique de surface [Termes descripteurs IGN] occupation du sol [Termes descripteurs IGN] pente [Termes descripteurs IGN] précipitation [Termes descripteurs IGN] Sibérie [Termes descripteurs IGN] steppe [Termes descripteurs IGN] topographie locale [Vedettes matières IGN] Ecologie forestière Résumé : (auteur) Topographic heterogeneity under dry continental climate can create a landscape mosaic called “exposure-related forest-steppe”, characterized by a regular pattern of forest on the north- and steppe on the south-facing slopes. Here we identify the climatic and topographic determinants of this landscape type, using a model of the Altai Mountains in southern Siberia because they (1) contain large areas of forest-steppe together with forested and steppe landscapes, and (2) possess well-preserved natural land-cover. Based on the Landsat land-cover classification and digital elevation model we identified areas containing exposure-related forest-steppe and modeled their climatic and topographic thresholds using regression trees. The models showed that in the Altai exposure-related forest-steppe is most common in topographically heterogeneous areas with May–September precipitation of 226–377 mm and a mean July temperature of 13.8–15.6 °C. Its existence is jointly determined by hilly topography and a climate that is moist enough to support tree growth on north-facing slopes, but insufficiently so to support woodland development on south-facing slopes. This is consistent with the concept of effective topographic heterogeneity, suggesting that topographic heterogeneity on the landscape level is translated into high habitat diversity and species diversity only within a certain range of climatic conditions. Numéro de notice : A2016--158 Thématique : FORET Nature : Article En ligne : https://doi.org/10.1016/j.jaridenv.2016.08.011 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86984 [article]

Combined effects of area, connectivity, history and structural heterogeneity of woodlands on the species richness of hoverflies (Diptera: Syrphidae) / Pierre-Alexis Herrault in Landscape ecology, vol 31 n° 4 (May 2016)

Public [article]  inLandscape ecology > vol 31 n° 4 (May 2016) . - pp 877 - 893 Titre : Combined effects of area, connectivity, history and structural heterogeneity of woodlands on the species richness of hoverflies (Diptera: Syrphidae) Type de document : Article/Communication Auteurs : Pierre-Alexis Herrault, Auteur ; Laurent Larrieu, Auteur ; S. Cordier, Auteur ; U. Gimmi, Auteur ; T. Lachat, Auteur ; Annie Ouin, Auteur ; Jean-Pierre Sarthou, Auteur ; David Sheeren , Auteur Année de publication : 2016 Article en page(s) : pp 877 - 893 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes descripteurs IGN] analyse spatio-temporelle [Termes descripteurs IGN] connexité (topologie) [Termes descripteurs IGN] hétérogénéité spatiale [Termes descripteurs IGN] ilot boisé [Termes descripteurs IGN] indicateur biologique [Termes descripteurs IGN] microhabitat [Termes descripteurs IGN] syrphidae [Vedettes matières IGN] Ecologie forestière Résumé : (auteur) Context : Hoverflies are often used as bio-indicators for ecosystem conservation, but only few studies have actually investigated the key factors explaining their richness in woodlands. Objectives : In a fragmented landscape in southwest France, we investigated the joint effects of woodland area, structural heterogeneity, connectivity and history on the species richness of forest-specialist hoverflies, and whether there was a time lag in the response of hoverflies to habitat changes, and tested the effect of spatiotemporal changes. Methods : Current species richness was sampled in 48 woodlands using 99 Malaise traps. Structural variables were derived from a rapid habitat assessment protocol. Old maps and aerial photographs were used to extract past and present spatial patterns of the woodlands since 1850. Relationships between species richness and explanatory variables were explored using generalized linear models. Results : We show that current habitat area, connectivity, historical continuity and the average density of tree-microhabitats explained 35 % of variation in species richness. Species richness was affected differently by changes in patch area between 1979 and 2010, depending on woodland connectivity. In isolated woodlands, extinction debt and colonization credit were revealed, showing that even several decades are not sufficient for hoverflies to adapt to landscape-scale habitat conditions. Conclusions : These findings emphasise the importance of maintaining connectedness between woodlands, which facilitates the dispersion in a changing landscape. Our results also highlight the benefits of using a change-oriented approach to explain the current distribution patterns of species, especially when several spatial processes act jointly. Numéro de notice : A2016-359 Thématique : BIODIVERSITE/FORET Nature : Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81093 [article]

Mapping the value of ecosystem services: A case study from the Austrian Alps / Alessandro Paletto in Annals of forest research, vol 58 n° 1 (January 2015)  

Public [article]  inAnnals of forest research > vol 58 n° 1 (January 2015) . - pp 157 - 175 Titre : Mapping the value of ecosystem services: A case study from the Austrian Alps Type de document : Article/Communication Auteurs : Alessandro Paletto, Auteur ; Clemens Geitner, Auteur ; Gianluca Grilli, Auteur ; Richard Hastik, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 157 - 175 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Economie [Termes descripteurs IGN] aide à la décision [Termes descripteurs IGN] alpes orientales [Termes descripteurs IGN] carte thématique [Termes descripteurs IGN] distribution spatiale [Termes descripteurs IGN] forêt alpestre [Termes descripteurs IGN] hétérogénéité spatiale [Termes descripteurs IGN] indicateur de service écosystémique [Termes descripteurs IGN] ressources naturelles [Termes descripteurs IGN] service écosystémique [Termes descripteurs IGN] valeur économique [Termes descripteurs IGN] Vorarlberg (Autriche) Résumé : (auteur) Ecosystem services (ES) are considered the conditions and processes through which natural ecosystems sustain and fulfil human life. In the decision making process related to the natural resources management, two key-aspects must be taken into account: the economic value of the benefits provided by ES (provisioning, regulating and cultural services) and the spatial distribution of these benefits. The purpose of the paper is to develop a method aimed to capture the economic value of the benefits provided by ES, in order to support the decision makers in the natural resources management. ES are not homogeneous across landscapes nor in space. Consequently, gaining knowledge on the spatial distribution of the economic relevance of ES is a fundamental information to target management actions. This method was tested in a case study in the Austrian Alps (Leiblachtal area in Vorarlberg region), characterized by a high importance of forests and grasslands. The results show that the highest economic values could be achieved for the provisioning services with a range between 200 €/ha year and 1,400€/ha year. The regulating services have also important economic values, but strongly localized in specific areas (i.e. protective forests against natural hazards). The economic values of the cultural services are influenced by the preferences of tourists and varies between 5 €/ha year to 60 €/ha year. The method allowed us to reveal the spatial heterogeneity of provisioning, regulating and cultural ES, depending on the ecological characteristics of the site. Numéro de notice : A2015-716 Thématique : FORET Nature : Article En ligne : http://www.afrjournal.org/index.php/afr/article/view/335 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=78360 [article]

Spatial chromatic model in high-dimensional spaces and the uniqueness of chromatic code: a new perspective of geographic entity–space relationship / Weining Zhu in International journal of geographical information science IJGIS, vol 29 n° 1 (January 2015)  

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La construction d'une matrice de flux à partir de traces de téléphones portables / Françoise Bahoken in Cartes & Géomatique, n° 217 (septembre 2013) 

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Estimation of imprecision in length and area computation in vector databases including production processes description / Jean-François Girres (26/05/2010) 

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Formal specifications to automatically identify heterogeneities [diaporama] / Nathalie Abadie (02/06/2009)

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Quantifying spatial heterogeneity at the landscape scale using variogram models / S. Garrigues in Remote sensing of environment, vol 103 n° 1 (15 July 2006)

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Approche numérique de l'espace agricole / J.P. Rogala (1982)

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