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Forest vegetation in western Romania in relation to climate variables: Does community composition reflect modelled tree species distribution? / S. Heinrichs in Annals of forest research, vol 59 n° 2 (July - December 2016)
[article]
Titre : Forest vegetation in western Romania in relation to climate variables: Does community composition reflect modelled tree species distribution? Type de document : Article/Communication Auteurs : S. Heinrichs, Auteur ; Helge Walentowski, Auteur ; E. Bergmeier, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 219 - 236 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] changement climatique
[Termes IGN] composition floristique
[Termes IGN] Europe centrale
[Termes IGN] Fagus sylvatica
[Termes IGN] forêt thermophile
[Termes IGN] phytosociologie
[Termes IGN] Quercus sessiliflora
[Termes IGN] Roumanie
[Termes IGN] unité phytosociologique
[Vedettes matières IGN] Végétation et changement climatiqueRésumé : (auteur) European beech (Fagus sylvatica L.) is the prevailing tree species of mesic forests in Central Europe. Increasing summer temperatures and decreasing precipitation, as climate change scenarios predict, may, however, negatively influence beech growth and induce a shift to more thermophilous forest communities. Temperatures as expected in the future for western Central Europe are currently found in parts of western Romania. In light of this climate analogy we investigated forest vegetation as an indicator for future vegetation changes in five regions of western Romania representing a climatic gradient. We related species composition to climate variables and examined if tree and understorey species composition respond similarly to the climatic gradient. We further analysed if tree species occurrences correspond with their modelled distance to the rear niche edge. We found evidence for climatic effects on vegetation composition among regions as well as within deciduous and pine forests, respectively. This underlines that vegetation composition is a useful indicator for environmental change. Tree and understorey species compositions were closely linked showing that community-based characterization of forest stands can provide additional information on tree species suitability along environmental gradients. Both, vegetation composition and a climatic marginality index demonstrate the rear niche edge occurrence of beech in the studied sites of Romania and can predict the site suitability for different tree species. While vegetation surveys indicate Quercus petraea to be associated to moderately mesic forests, the marginality index suggested an inner niche position of sessile oak along the climatic gradient. Phytosociological relevés that differentiate between subspecies (or microspecies) of sessile oak with differing habitat requirements should be considered to complement national forest inventories and species distribution maps when modelling rear distribution edges. We conclude that climate driven forest vegetation composition in western Romania is a suitable analogon and may indicate future forest development in western Central Europe. Numéro de notice : A2016--094 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 10.15287/afr.2016.692 En ligne : http://doi.org/10.15287/afr.2016.692 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84646
in Annals of forest research > vol 59 n° 2 (July - December 2016) . - pp 219 - 236[article]A simple method for detecting phenological change from time series of vegetation index / Jin Chen in IEEE Transactions on geoscience and remote sensing, vol 54 n° 6 (June 2016)
[article]
Titre : A simple method for detecting phenological change from time series of vegetation index Type de document : Article/Communication Auteurs : Jin Chen, Auteur ; Yuhan Rao, Auteur ; Miaogen Shen, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 3436 - 3449 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection
[Termes IGN] changement climatique
[Termes IGN] Chine
[Termes IGN] Enhanced vegetation index
[Termes IGN] image Aqua-MODIS
[Termes IGN] image Terra-MODIS
[Termes IGN] indice de végétation
[Termes IGN] phénologie
[Termes IGN] série temporelleRésumé : (Auteur) Remote sensing is a valuable way to retrieve spatially continuous information on vegetation phenological changes, which are widely used as an indicator of climate change. We propose a simple method called weighted cross-correlogram spectral matching-phenology (CCSM-P), which combines CCSM and a weighted correlation system, for detecting vegetation phenological changes by using multiyear vegetation index (VI) time series. In experiments with simulated enhanced VI (EVI) for various scenarios, CCSM-P exhibited high accuracy and robustness to noise and the potential to capture long-term phenological change trends. For a temperate grassland in northern China, CCSM-P retrieved more reasonable vegetation spring phenology from Moderate Resolution Imaging Spectroradiometer (MODIS) EVI images than the MODIS phenology product (MCD12Q2). When validated against field phenological observations in five of the AmeriFlux Network sites in the U.S. (four deciduous broadleaf forest sites and a closed shrublands site), and a cropland site in China, CCSM-P exhibited mean absolute differences (MADs) ranging from 2 to 10 days (median: 4.2 days), whereas MAD of non-CCSM methods showed larger variations, ranging from 5 to 58 days (median: 21.3 days). This is because CCSM-P integrates field phenological observations. Compared with non-CCSM methods, which are widely used to identify phenological events, CCSM-P is more accurate and less dependent on prior knowledge (thresholds or predefined functions), which indicates its effectiveness and applicability for detecting year-to-year variations and long-term change trends in phenology, and should facilitate more reliable assessments of phenological changes in climate change studies. Numéro de notice : A2016-854 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2016.2518167 En ligne : http://dx.doi.org/10.1109/TGRS.2016.2518167 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=82992
in IEEE Transactions on geoscience and remote sensing > vol 54 n° 6 (June 2016) . - pp 3436 - 3449[article]Single-frequency precise point positioning using multi-constellation GNSS: GPS, Glonass, Galileo and Beidou / Mahmoud Abd Rabbou in Geomatica, vol 70 n° 2 (June 2016)
[article]
Titre : Single-frequency precise point positioning using multi-constellation GNSS: GPS, Glonass, Galileo and Beidou Type de document : Article/Communication Auteurs : Mahmoud Abd Rabbou, Auteur ; Ahmed El-Rabbany, Auteur Année de publication : 2016 Article en page(s) : pp 113 - 122 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement
[Termes IGN] constellation GNSS
[Termes IGN] modèle ionosphérique
[Termes IGN] positionnement par GNSS
[Termes IGN] positionnement ponctuel précisRésumé : (auteur) Single-frequency precise point positioning (PPP) presents a cost-effective positioning technique for a large number of users. However, it possesses low positioning accuracy and convergence time compared with the dual-frequency PPP. Single-frequency PPP commonly employs GPS satellite systems that suffer from poor satellite geometry, especially in dense urban areas. We develop a new single-frequency PPP model that combines the observations of current GNSS constellations, including GPS, GLONASS, Galileo and Beidou. The MGEX IGS final precise products are utilized to account for the orbital and clock errors, while the IGS final global ionospheric maps (GIM) model is used to correct for the ionospheric delay. The GNSS inter-system biases are treated as additional unknowns in the estimation process. The contribution of the additional GNSS observations to single-frequency PPP is assessed through solution comparison with its traditional GPS-only counterpart. Various GNSS combinations are considered in the assessment, including GPS/GLONASS, GPS/Galileo, GPS/BeiDou and all-constellation GNSS. It is shown that the additional GNSS observations enhance the PPP solution accuracy and convergence time in comparison with the traditional GPS-only solution. Except for stations with a sufficient number of tracked BeiDou satellites, both Galileo and BeiDou have marginal effects on the positioning accuracy due to their limited number of satellites. However, for stations with a sufficient number of visible BeiDou satellites, an average of 40% PPP accuracy improvement is obtained. The major contribution to the PPP accuracy enhancement is obtained from GLONASS satellite observations. Numéro de notice : A2016-679 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.5623/cig2016-203 En ligne : http://dx.doi.org/10.5623/cig2016-203 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81933
in Geomatica > vol 70 n° 2 (June 2016) . - pp 113 - 122[article]There's an app for that : using a smartphone for GNSS ionospheric data collection / Andrew Kennedy in GPS world, vol 27 n° 6 (June 2016)
[article]
Titre : There's an app for that : using a smartphone for GNSS ionospheric data collection Type de document : Article/Communication Auteurs : Andrew Kennedy, Auteur ; Ryan Kingsbury, Auteur ; Anthea Coster, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 58 - 65 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement
[Termes IGN] acquisition de données
[Termes IGN] Androïd
[Termes IGN] application informatique
[Termes IGN] ionosphère
[Termes IGN] récepteur GNSS
[Termes IGN] téléphone intelligent
[Termes IGN] teneur totale en électronsRésumé : (éditeur) [...] In this month’s column, we take a look at the use of a smartphone app to collect GNSS ionospheric data. Why would you want to do that? In the experience of the developers of the app, GNSS receivers are often characterized by a complex, proprietary data interface that differs for each manufacturer. In practice, this leads to significant investments in understanding interfaces and software tools. Human operators must familiarize themselves with the commands used to configure each receiver as well as with proprietary graphical user interfaces and tools specific to each receiver. The authors’ app-centric approach provides a software framework and output format that remain the same for different receivers. Receiver-specific commands are configurable within the app, so users can easily attach new receivers while reusing the existing infrastructures for data collection and processing. And smartphones have more than enough power and connectivity to do the job and can be easily moved from site to site. The smartphone as a handheld device to help scientists study the ionosphere? Probably not even Clive Sinclair foresaw that. Numéro de notice : A2016-333 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans En ligne : http://gpsworld.com/innovation-theres-an-app-for-that/ Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=80984
in GPS world > vol 27 n° 6 (June 2016) . - pp 58 - 65[article]Wavelet analysis of low-frequency variability in oak tree-ring chronologies from east Central Europe / Asok K. Sen in Open geosciences, vol 8 n° 1 (January - July 2016)
[article]
Titre : Wavelet analysis of low-frequency variability in oak tree-ring chronologies from east Central Europe Type de document : Article/Communication Auteurs : Asok K. Sen, Auteur ; Zoltan Kern, Auteur Année de publication : 2016 Article en page(s) : pp 478 - 483 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Végétation
[Termes IGN] analyse diachronique
[Termes IGN] dendrochronologie
[Termes IGN] Europe centrale
[Termes IGN] ondelette
[Termes IGN] précipitation
[Termes IGN] Quercus (genre)
[Termes IGN] série temporelle
[Termes IGN] variabilitéRésumé : (auteur) This study investigates the low-frequency (interannual and longer period) variability in three hydroclimatic records from east Central Europe. Two of these records consist of climate proxies derived from oak-tree rings in Bakta forest, and Balaton Highlands in Hungary, for the time interval 1783-2003. The third record consists of homogenized instrumental precipitation data from Budapest, Hungary, from 1842 to 2003. Using wavelet analysis, the three time series are analyzed and compared with one another. It is found that all three time series exhibit strong interannual variability at the 2-4 years timescales, and these variations occur intermittently throughout the length of each record. Significant variability is also observed in all the records at decadal timescales, but these variations persist for only two to three cycles. Wavelet coherence among the various time series is used to explore their time-varying correlation. The results reveal significant coherence at the 2-4 years band. At these timescales, the climatic variations are correlated to the tree-ring signal over different time intervals with changing phase. Increased (decreased) contribution of large-scale stratiform precipitation offers a potential explanation for enhanced (faded) coherence at the interannual timescale. Strong coherence was also observed occasionally at decadal timescales, however these coherences did not appear uniformly. These results reinforce the earlier assertion that neither the strength nor the rank of the similarity of the local hydroclimate signals is stable throughout the past two centuries. Numéro de notice : A2016--070 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 10.1515/geo-2016-0044 En ligne : https://doi.org/10.1515/geo-2016-0044 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84416
in Open geosciences > vol 8 n° 1 (January - July 2016) . - pp 478 - 483[article]Evaluation of single frequency GPS precise point positioning assisted with external ionosphere sources / Reza Ghoddousi-Fard in Advances in space research, vol 57 n° 10 (May 2016)PermalinkReconstruction of the vertical electron density profile based on vertical TEC using the simulated annealing algorithm / Chunhua Jiang in Advances in space research, vol 57 n° 10 (May 2016)Permalinkvol 30 n° 5-6 - May - June 2016 - Analysis of movement data (Bulletin de International journal of geographical information science IJGIS) / Robert WeibelPermalinkAssessing regulating and provisioning ecosystem services in a contrasting tropical forest landscape / Mohammed Alamgir in Ecological indicators, vol 64 (May 2016)PermalinkL'essor soudain du "vivre avec" le risque / Pierre Clergeot in Géomètre, n° 2136 (mai 2016)PermalinkGlobal sensitivity analysis of the L-MEB model for retrieving soil moisture / Zengyan Wang in IEEE Transactions on geoscience and remote sensing, vol 54 n° 5 (May 2016)PermalinkStorm event representation and analysis based on a directed spatiotemporal graph model / W. Liu in International journal of geographical information science IJGIS, vol 30 n° 5-6 (May - June 2016)PermalinkComparative analysis of real-time precise point positioning zenith total delay estimates / F.A. Ahmed in GPS solutions, vol 20 n° 2 (April 2016)PermalinkTowards sustainable mobility behavior: research challenges for location-aware information and communication technology / Paul Weiser in Geoinformatica, vol 20 n° 2 (April - June 2016)Permalink14 years of GPS tropospheric delays in the French–Italian border region : comparisons and first application in a case study / Domenico Sguerso in Applied geomatics, vol 8 n° 1 (March 2016)Permalink