Nicolas Delbart - Academia.edu (original) (raw)

Papers by Nicolas Delbart

Bulletin de l'association de géographes français

Influence des surfaces enneigées sur les débits de cours d'eau du piémont andin argentin Implicat... more Influence des surfaces enneigées sur les débits de cours d'eau du piémont andin argentin Implications pour la gestion du risque de pénurie d'eau Impact of snow-covered surfaces on river discharge in the Argentinian Andean piedmont. Implications for the management of the water scarcity risk Nicolas Delbart, Émilie Lavie et Régis Goma Édition électronique RÉSUMÉ -Le risque de pénurie en eau pour les oasis de la diagonale aride sudaméricaine est étudié depuis longtemps, notamment en ce qui concerne la fonte des glaciers andins, ressource à long terme pour les espaces irrigués du piémont. L'étude menée ici présente l'originalité de s'intéresser à la ressource à court et moyen termes : la neige annuelle, qui représente la plus grande part des écoulements. En observant conjointement la saisonnalité de la couverture neigeuse par télédétection et

Agu Fall Meeting Abstracts, Dec 1, 2008

The global ecosystem model SEIB-DGVM was adapted for an eastern Siberian larch forest through inc... more The global ecosystem model SEIB-DGVM was adapted for an eastern Siberian larch forest through incorporation of empirical rules of allometry, allocation, and phenology developed for a larch stand at the Spasskaya-pad tower site, Yakutsk, Russia. After calibration, the model reconstructed post-fire successional patterns of forest structure and carbon cycling. It also reconstructed seasonal changes in carbon, water, and energy cycling in a mature larch forest. Sensitivity analysis showed that simulated functional properties of forest (LAI, NPP, carbon pools, and water runoff) are mainly determined by climatic environment, and population dynamic parameters (i.e., parameters for establishment and mortality) plays only minor role on them. Sensitivity analysis also showed that plant productivity and biomass were mainly limited by available water at Spasskaya-pad, where mean annual precipitation is only 257 mm. In the model, higher air temperature increases plant productivity via extension of growing season, and decreases plant productivity via causing drought and higher respiration. We found that the net effect is reduction of productivity, suggesting a possibility that global warming induces decrement of plant productivity in eastern Siberian larch forests. ß

Supplement to Ottle Catherine Lescure Julie Maignan Fabienne Poulter Benjamin Wang Tao Delbart Nicolas Use of Various Remote Sensing Land Cover Products For Plant Functional Type Mapping Over Siberia Earth System Science Data 5 331 348 Doi 10 5194 Essd 5 331 2013, Apr 26, 2013

Revue de géographie alpine, 2015

Cuadernos de Investigación Geográfica, 2013

Correo electrónico de contacto: svicen@ipe.csic.es RESUMEN. En este trabajo se analiza la distrib... more Correo electrónico de contacto: svicen@ipe.csic.es RESUMEN. En este trabajo se analiza la distribución espacial de la actividad vegetal en Siberia central y su relación con la variabilidad en la circulación atmosférica. Para ello se han utilizado imágenes NOAA-AVHRR a partir de la base de datos Pathfinder a una resolución espacial de 1 grado. A partir de esta base de datos se calculó la actividad vegetal anual en cada píxel (aNDVI) entre 1982 y 2001. Se realizó un Análisis de Componentes Principales para determinar los principales patrones espaciales en la variabilidad interanual de la actividad vegetal. Los tres principales modos explican más del 50% de la varianza total, y cada uno corresponde a una amplia región. Mediante valores de presión atmosférica se analizó la circulación atmosférica en esta región y se investigó el papel de la estacionalidad en los patrones de circulación sobre la actividad vegetal. En general, se ha comprobado que la principal relación entre la variabilidad en la circulación atmosférica, las condiciones climáticas y la variabilidad del aNDVI se localiza en aquellas áreas con condiciones climáticas más limitantes para el desarrollo de la vegetación, como es el caso de las regiones de tundra del norte. Esto puede explicarse por el importante papel de la circulación atmosférica sobre las temperaturas estivales, que tienen un peso directo sobre el desarrollo de la vegetación.

Climate change in Siberia and more generally in high latitudes, is impacting strongly the environ... more Climate change in Siberia and more generally in high latitudes, is impacting strongly the environment and the societies. If the present climate warming evolves as projected, these impacts are likely to increase, greatly affecting ecosystems, cultures, lifestyles and economies. The CLASSIQUE French research project is focused on these questions, with a special attention to land cover evolution, forest vulnerability and permafrost reduction in Siberia. It mobilizes climatologists, hydrologists, agronomists, demographers, geographers and specialists of scientific mediation in a trans-disciplinary effort to better quantify (1) future changes of climate and vegetation properties in Siberia; (2) the consecutive evolution of the agricultural potential of the region; (3) the demographic and societal effects of these changes; and (4) the interactions and feedbacks induced. The chosen approach aims to develop integrated models able to predict the evolution of land cover and hydrology and the ...

ABSTRACT Poster : EGU General Assembly .

Remote Sensing of Environment, 2015

ABSTRACT Annual maps of the remote sensing green-up date derived from SPOT-VEGETATION data were c... more ABSTRACT Annual maps of the remote sensing green-up date derived from SPOT-VEGETATION data were compared to the phenological observations collected by the PlantWatch citizen science project across Canada between 1998 and 2012. Green-up dates were found to relate to the leaf-out dates for four woody species (Populus tremuloides, Acer rubrum, Syringa vulgaris, Larix laricina), with a RMSE from 13.6 to 15.6 days. This was true for all landcover types except in pixels where agriculture or water bodies were dominant. This is less accurate than the results from previous studies for boreal Eurasia (RMSE = 8.7 days), with phenology data from an operational network. When data were aggregated at a regional level, the remote sensing green-up date matched well with the interannual variations in leafing and also in flowering of most of the recorded species. These included spring events for trees, shrubs and non-woody plants which were either native to Canada or introduced. For most plants, spring flowering and leafing times are functions of accumulated temperature. For this reason, plant species develop in a predictable sequence, and interannual variations in this cohort of species leafing and flowering are correlated. This explains the correlation with remote sensing green-up. Data from this volunteer PlantWatch network proved consistent with independent satellite data, suggesting that combining the two will strengthen the future capacity to monitor vegetation changes.

Earth System Science Data Discussions, 2013

High-latitude ecosystems play an important role in the global carbon cycle and in regulating the ... more High-latitude ecosystems play an important role in the global carbon cycle and in regulating the climate system and are presently undergoing rapid environmental change. Accurate land cover data sets are required to both document these changes as well as to provide land-surface information for benchmarking and initializing Earth system models. Earth system models also require specific land cover classification systems based on plant functional types (PFTs), rather than species or ecosystems, and so post-processing of existing land cover data is often required. This study compares over Siberia, multiple land cover data sets against one another and with auxiliary data to identify key uncertainties that contribute to variability in PFT classifications that would introduce errors in Earth system modeling. Land cover classification systems from GLC 2000, GlobCover 2005 and 2009, and MODIS collections 5 and 5.1 are first aggregated to a common legend, and then compared to high-resolution land cover classification systems, vegetation continuous fields (MODIS VCFs) and satellite-derived tree heights (to discriminate against sparse, shrub, and forest vegetation). The GlobCover data set, with a lower threshold for tree cover and taller tree heights and a better spatial resolution, tends to have better distributions of tree cover compared to high-resolution data. It has therefore been chosen to build new PFT maps for the ORCHIDEE land surface model at 1 km scale. Compared to the original PFT data set, the new PFT maps based on GlobCover 2005 and an updated cross-walking approach mainly differ in the characterization of forests and degree of tree cover. The partition of grasslands and bare soils now appears more realistic compared with ground truth data. This new vegetation map provides a framework for further development of new PFTs in the ORCHIDEE model like shrubs, lichens and mosses, to represent the water and carbon cycles in northern latitudes better. Updated land cover data sets are critical for improving and maintaining the relevance of Earth system models for assessing climate and human impacts on biogeochemistry and biophysics.

International Journal of Applied Earth Observation and Geoinformation, 2015

ABSTRACT This paper combines participatory activities (PA) with remote sensing analysis into an i... more ABSTRACT This paper combines participatory activities (PA) with remote sensing analysis into an integrated methodology to describe and explain land-cover changes. A remote watershed on Mindanao (Philippines) is used to showcase the approach, which hypothesizes that the accuracy of expert knowledge gained from remote sensing techniques can be further enhanced by inputs from vernacular knowledge when attempting to understand complex land mosaics and past land-use changes. Six participatory sessions based on focus-group discussions were conducted. These were enhanced by community-based land-use mapping, resulting in a final total of 21 participatory land-use maps (PLUMs) co-produced by a sample of stakeholders with different sociocultural and ecological perspectives. In parallel, seven satellite images (Landsat MSS, Landsat TM, Landsat ETM+, and SPOT4) were classified following standard techniques and provided snapshots for the years 1976, 1996, and 2010. Local knowledge and collective memory contributed to define and qualify relevant land-use classes. This also provided information about what had caused the land-use changes in the past. Results show that combining PA with remote-sensing analysis provides a unique understanding of land-cover change because the two methods complement and validate one another. Substantive qualitative information regarding the chronology of land-cover change was obtained in a short amount of time across an area poorly covered by scientific literature. The remote sensing techniques contributed to test and to quantify verbal reports of land-use and land-cover change by stakeholders. We conclude that the method is particularly relevant to data-poor areas or conflict zones where rapid reconnaissance work is the only available option. It provides a preliminary but accurate baseline for capturing land changes and for reporting their causes and consequences. A discussion of the main challenges encountered (i.e. how to combine different systems of knowledge), and options for further methodological improvements, are also provided.

IEEE International Geoscience and Remote Sensing Symposium, 2002

Page 1. Forest Biomass Retrieval using L-band polarimetric measurements Nicolas Delbart, Pierre M... more Page 1. Forest Biomass Retrieval using L-band polarimetric measurements Nicolas Delbart, Pierre Melon, Géraldine Florsch, Thuy Le Toan, Jean-Michel Martinez ... The HV backscattering coefficient was selected for inversion up to 70 m3/ha. ...

In the Sahel, interannual variability of rainfall is known to be strong, from meso- to continenta... more In the Sahel, interannual variability of rainfall is known to be strong, from meso- to continental spatial scales. This is associated with changes in surface radiative fluxes. The actual role played by surface fluxes on the interannual variability of rainfall has been much debated, especially within the context of the major regional scale, multi-decadal West African drought which started at

According to several studies, the onset of spring has tended to get earlier in the last few decad... more According to several studies, the onset of spring has tended to get earlier in the last few decades. However, most studies analyze the phenological variations either for a short time period (since 1982 with satellite observations), or for a restricted region using ground observations. Ground observations, satellite observations and modeling were analysed jointly to study phenological variations in boreal Eurasia in 1936-2005, and 1920-2005 in Central Siberia. The results show that the trend that is observed by remote sensing is essentially due to a shift at the end of the 1980's, related to a shift in the spring temperature. In West Siberia and European Russia, the trend to an earlier spring has existed since as early as 1940. In contrast, the central and eastern parts of Siberia display successive trends with opposite signs, and the trend observed by remote sensing is due to both very early leaf appearance in the 1990's and to very late leaf appearance in 1983-1984, showi...