Search results for "végétation"
showing 10 items of 15 documents
sPlotOpen – An environmentally balanced, open‐access, global dataset of vegetation plots
2021
Datos disponibles en https://github.com/fmsabatini/sPlotOpen_Code
Interannual memory effects for spring NDVI in semi-arid South Africa
2008
[1] Almost 20 years of Normalized Difference Vegetative Index (NDVI) and precipitation (PPT) data are analysed to better understand the interannual memory effects on vegetation dynamics observed at regional scales in Southern Africa (SA). The study focuses on a semi-arid region (25°S–31°S; 21°E–26°E) during the austral early summer (September–December). The memory effects are examined using simple statistical approaches (linear correlations and regressions) which require the definition of an early summer vegetation predictand (December NDVI minus September NDVI) and a consistent set of potential predictors (rainfall amount, number of rainy days, rainfall intensity, NDVI and Rain-Use-Efficie…
Vegetation structure and greenness in Central Africa from Modis multi-temporal data.
2013
African forests within the Congo Basin are generally mapped at regional scale as broad-leaved evergreen forests, with a main distinction between terra-firme and swamp forests types. At the same time, commercial forest inventories, as well as national maps, have highlighted a strong spatial heterogeneity of forest types. A detailed vegetation map generated using consistent methods is needed to inform decision makers about spatial forest organisation and theirs relationships with environmental drivers in the context of global change. We propose a multi-temporal remotely sensed data approach to characterize vegetation types using vegetation index annual profiles. The classifications identified…
Timing and patterns of the ENSO signal in Africa over the last 30 years: insights from normalized difference vegetation index data.
2014
Abstract A more complete picture of the timing and patterns of the ENSO signal during the seasonal cycle for the whole of Africa over the three last decades is provided using the normalized difference vegetation index (NDVI). Indeed, NDVI has a higher spatial resolution and is more frequently updated than in situ climate databases, and highlights the impact of ENSO on vegetation dynamics as a combined result of ENSO on rainfall, solar radiation, and temperature. The month-by-month NDVI–Niño-3.4 correlation patterns evolve as follows. From July to September, negative correlations are observed over the Sahel, the Gulf of Guinea coast, and regions from the northern Democratic Republic of Congo…
Distribution de la végétation au Svalbard
2016
International audience
A Simple Fusion Method for Image Time Series Based on the Estimation of Image Temporal Validity
2015
High-spatial-resolution satellites usually have the constraint of a low temporal frequency, which leads to long periods without information in cloudy areas. Furthermore, low-spatial-resolution satellites have higher revisit cycles. Combining information from high- and low- spatial-resolution satellites is thought a key factor for studies that require dense time series of high-resolution images, e.g., crop monitoring. There are several fusion methods in the bibliography, but they are time-consuming and complicated to implement. Moreover, the local evaluation of the fused images is rarely analyzed. In this paper, we present a simple and fast fusion method based on a weighted average of two in…
Cycle saisonnier du NDVI dans le Nord-Cameroun et relations avec la pluviométrie (1982-2002)
2008
National audience; Résumé : Dans ce travail, il est question, de juger de la pertinence de l'indice de végétation normalisé (NDVI) pour l'étude de l'évolution du couvert végétal à petite échelle spatiale. Le choix de notre zone d'étude est porté dans le Nord-Cameroun qui, comparativement à la partie méridionale du pays, présente une végétation plus dépendante des conditions pluviométriques. Il en ressort que l'utilisation du NDVI est plus appropriée dans la région située au-dessus du 9e parallèle où la végétation démarre avec un retard de 3 à 9 décades par rapport au début de la saison des pluies. Dans la région soudanienne située au sud de cette latitude, le NDVI est plus représentatif des…
Les impacts du campagnol terrestre sur les systèmes fourragers : le cas de l’élevage bovin allaitant en Bourgogne
2014
EAAgroSupECOLDUR; Do vole outbreaks have the same effects on suckler beef farms in Burgundy as they do on daily farms in Auvergne and Franche-Comte? Semi-structured interviews were carried out with 19 farmers from Burgundy who had been affected by a water vole outbreak in 2011. The results indicate that, just like farmers in Auvergne and Franche-Comte, farmers in Burgundy witnessed a decrease in forage quantity and quality. Farmers used diverse measures to deal with the outbreak (e.g., avoidance strategies or the use of bromadiolone). Farmers that described water voles as pests were more likely to have used bromadiolone, while those who described water voles in morphological terms or in ter…
Impacts d’une meilleure description de la végétation urbaine sur des simulations du climat urbain avec SURFEX-TEB.
2022
Le réseau MUSTARDijon offre la possibilité de procéder à une cartographie fine des températureshoraires sur Dijon Métropole. La méthode proposée ici repose sur des régressions linéaires multiplesmobilisant deux familles de prédicteurs : des descripteurs du relief et des descripteurs de l’occupation dusol. L’application porte sur la canicule de l’été 2020 (6-9 août). Deux configurations sont comparées. L’une,en mode recherche, laisse la possibilité aux descripteurs de varier dynamiquement en fonction de leurpertinence statistique, l’autre, en mode opérationnel, impose les 5 mêmes descripteurs en entrée. Entermes de performance statistique ou de structure spatiale, l’impact de la méthode n’es…
Différenciation isotopique (13C) du carbone organique dissous (COD) au cours de la dégradation des matières organiques dans les sols forestiers : inf…
2008
National audience