CONSTRUCTION D'INDICATEURS SPATIAUX POUR L'AIDE A LA DECISION : INTERET D'UNE DEMARCHE PARTICIPATIVE LE CAS DU PERIURBAIN LANGUEDOCIEN

N° ISBN - 978-2-7380-1284-5International audiencePopulation growth in the Languedoc coastal region is very high since few decades. This phenomenon produces a rapid and uncontrolled urban sprawl at agricultural lands expense. While these lands are often high agronomical potential, they are most often permanently lost. To better understand the dynamics of consumption of these agricultural lands by artificial surfaces and to have spatial tools to argue the risk of permanent loss of agronomical potential heritage, the Regional Direction of Food, Agriculture and Forestry of Languedoc-Roussillon has commissioned a study from research institutions: INRA for the agronomical theme and Cemagref for the spatial information and analysis. In order to quantify and qualify agricultural land changes, a methodology intended to build a system of spatial and spatialized indicators is being developed. The appropriation of indicators by users is the guarantee of their use. Research has therefore relied on an iterative participatory approach for the co-construction and the co-evaluation of indicators by stakeholders. The paper aims to present and discuss the approach and methods used for the production of indicators. More generally, it's a contribution to analyze process of consultation intended to develop measurement and decision-making tools

Reconnaissance du patrimoine agronomique des sols : une démarche novatrice en Languedoc-Roussillon.

En Languedoc-Roussillon, depuis les années 1960, l’afflux de population se traduit par une urbanisation rapide et mal maîtrisée de la plaine littorale, notamment sur les terres les plus productives. La perte de ces terres est au cœur des préoccupations des institutions et des acteurs agricoles qui s’interrogent sur les conditions à réunir pour conserver ce patrimoine productif à long terme. Cet article présente la démarche novatrice conduite avec les instances agricoles régionales et départementales pour contribuer à la reconnaissance et à la préservation du patrimoine agronomique des sols. La démarche s’appuie sur la construction d’un indice de qualité des sols spatialisé et sur la mise en place d’une méthode de traitement d’images satellitaires pour suivre la progression des espaces artificialisés dans le temps. L’application de ces méthodologies, à l’échelle des quatre départements littoraux du Languedoc-Roussillon, permet d’estimer la quantité et la qualité des terres perdues par artificialisation de 1997 à 2009. Les résultats de cette étude révèlent les besoins en connaissance qui permettraient d’identifier et de mesurer les enjeux liés à la protection des espaces agricoles en zone périurbaine. La production de données spatiales nouvelles a permis de répondre en partie aux besoins des acteurs, en revanche d’importants efforts restent à faire pour accompagner la diffusion et assurer l’opérationnalité des données produites.Population growth in the Languedoc coastal region has been very high for several decades. This phenomenon has spawned rapid and uncontrolled urban sprawl at the expense of agricultural lands. While these lands have often high agronomical potential, they are most often permanently lost. This paper presents an innovative approach with the agricultural institutions of Languedoc-Roussillon and is intended to contribute to the acknowledgement and preservation of our agronomical land heritage. The proposed approach is based on the construction of a spatialized soil quality index and on the application of a satellites images treatment process in order to follow the evolution of artificialized spaces in time. The application of those methodologies, scalled to the four coastal Departements of Languedoc-Roussilon, allow to estimate the quantity and the quality of lost lands by artificialization, from 1997 to 2009. The results of this study reveals the importance of needs remaining to be given to produce a fine knowledge that would allow to identify and to measure the goals linked to the protection of agricultural lands in periurban area. The production of new spatial data has allowed a partial response to the needs of stakeholders, however significant efforts are needed to ensure operational capability of the produced data

Estimating spatial and temporal variations in solar radiation within Bordeaux winegrowing region using remotely sensed data

International audienceAims: This paper presents a study solar radiation spatial and temporal variations in Bordeaux winegrowing area, for a 20 year period (1986-2005). Methods and results: Solar radiation data was retrieved from the HelioClim-1 database, elaborated from Meteosat satellite images, using the Heliosat-2 algorithm. Daily data was interpolated using ordinary kriging to produce horizontal solar radiation maps at a 500 m resolution. Using a digital elevation model, high resolution daily solar radiation maps with terrain integration were then produced for the period 2001-2005, at a 50 m resolution. The long term (20 years) analysis of solar radiation at low spatial resolution (500 m) showed a west to east decreasing gradient within Bordeaux vineyards. Mean August-to-September daily irradiation values, on horizontal surface, were used to classify Bordeaux winegrowing areas in three zones: low, medium, and high solar radiation areas. This initial zoning was upscaled at 50 m resolution, applying a local correction ratio, based on 2001-2005 solar radiation on inclined surface analysis. Grapevine development and maturation potential of the different zones of appellation of origin of Bordeaux winegrowing area are discussed in relation with this zoning. 2 Conclusions: Solar radiation variability within Bordeaux winegrowing area is mainly governed by terrain slopes and orientations, which induce considerable variations within the eastern part of Bordeaux vineyards. Significance and impact of the study: Solar radiation has a major impact on vineyard water balance, grapevine development and berry ripening. However, irradiation data is seldom available in weather stations records. This paper underline the interest of high resolution cartography of solar radiation, using satellite sensing and terrain effect integration, for agroclimatic studies in viticulture

Chapitre 3 - Consommation des terres agricoles en Languedoc-Roussillon : système d’indicateurs et démarche participative

Introduction Dans l’ancienne région Languedoc-Roussillon, comme dans toutes les zones à forte croissance urbaine, les acteurs du secteur agricole doivent convaincre les élus et l’ensemble de la société de l’intérêt de préserver les sols aux meilleures potentialités productives. En effet, ces potentialités sont peu prises en compte dans les politiques d’aménagement et les procédures d’urbanisme. Cela peut s’expliquer en partie pa..

Copper contamination in vineyard soils of Bordeaux: spatial risk assessment for the replanting of vines and crops

Copper (Cu) is widely and historically used in viticulture as a fungicide against mildew. Cu has a strong affinity for soil organic matter and accumulates in topsoil horizons. Thus, Cu may negatively affect soil organisms and plants, consequently reducing soil fertility and productivity. The Bordeaux vineyards have the largest vineyard surfaces (26%) within French controlled appellation and a great proportion of French wine production (around 5 million hl per year). Considering the local context of vineyard surfaces decreasing (vine uprooting) and possible new crop plantation, the issue of Cu potential toxicity rises. Therefore, the aims of this work are firstly to evaluate the Cu contamination in vineyard soils of Bordeaux, secondly to produce a risk assessment map for new vine or crop plantation. We used soil analyses from several local studies to build a database with 4496 soil horizon samples. The database was enhanced by means of pedotransfer functions in order to estimate the bioaccessible (EDTA-extractable) Cu in soils of samples without measurements. From this database, 1797 georeferenced samples with CuEDTA concentrations in the topsoil (0-50 cm depth) were used for kriging interpolation in order to produce the spatial distribution map of CuEDTA in vineyard soils. Then, the spatial distribution of Cu was crossed with vine uprooting surfaces and municipality boundaries. CuEDTAconcentrations ranged from 0.52 to 459 mg/kg and showed clear anomalies. Our results from spatial analysis showed that almost 50% of vineyard soil surfaces have CuEDTA concentrations higher than 30 mg/kg (moderate risk for new plantation) and 20% with concentrations higher than 50 mg/kg (high risk for new plantation). A decision-support map based on municipalities was realised to provide a simple tool to stakeholders concerned by land use management

Dynamics and sources of last glacial aeolian deposition in southwest France derived from dune patterns, grain-size gradients and geochemistry, and reconstruction of efficient wind directions

Dune pattern, grain-size gradients and geochemistry were used to investigate the sources and dynamics of aeolian deposition during the last glacial in southwest France. The coversands form widespread fields of low-amplitude ridges (zibars), whereas Younger Dryas parabolic dunes mainly concentrate in corridors and along rivers. Spatial modelling of grain-size gradients combined with geochemical analysis points to a genetic relationship between coversands and loess, the latter resulting primarily from dust produced by aeolian abrasion of the coversands. The alluvium of the Garonne river provided also significant amounts of dust at a more local scale. The geochemical composition of loess shows much lower scattering than that of coversands, due to stronger homogenisation during transport in the atmosphere. Overall, sandy loess and loess deposits decrease in thickness away from the coversands. Dune orientation and grain-size gradients suggest that the efficient winds blew respectively from the W to the NW during the glacial, and the W-SW during the Younger Dryas. A comparison between the wind directions derived from the proxy data and those provided by palaeoclimatic simulations suggests a change of the main transport season. Ground surface conditions and their evolution throughout the year, i.e. the length of the season with snow and frozen or moist topsoil, and the seasonal distribution of wind speeds able to cause deflation are thought to have been the main factors that controlled the transport season in the study area

Present-day uplift of the western Alps

International audienceCollisional mountain belts grow as a consequence of continental plate convergence and eventuallydisappear under the combined effects of gravitational collapse and erosion. Using a decade ofGPS data, we show that the western Alps are currently characterized by zero horizontal velocityboundary conditions, offering the opportunity to investigate orogen evolution at the time ofcessation of plate convergence. We find no significant horizontal motion within the belt, but GPS andlevelling measurements independently show a regional pattern of uplift reaching ~2.5 mm/yr in thenorthwestern Alps. Unless a low viscosity crustal root under the northwestern Alps locally enhancesthe vertical response to surface unloading, the summed effects of isostatic responses to erosion andglaciation explain at most 60% of the observed uplift rates. Rock-uplift rates corrected from transientglacial isostatic adjustment contributions likely exceed erosion rates in the northwestern Alps. In theabsence of active convergence, the observed surface uplift must result from deep-seated processes

Les terres agricoles face à l’urbanisation

La perte de terres agricoles liées à l’urbanisation constitue l’une des facettes de la consommation des terres. Commencé dans les années 1970, ce phénomène — essentiellement dû à l’étalement urbain — prend des proportions jusque-là inégalées. Les conséquences de ces processus d’artificialisation sont multiples et portent à la fois sur la production et sur la sécurité alimentaire ainsi que sur la perte de biodiversité. Ces processus interrogent aussi les formes de solidarité territoriale entre les villes et les espaces péri-urbains et ruraux. Issu d’une collaboration scientifique lancée au début des années 2010 entre l’Université de technologie de Sydney (University of Technology Sydney, UTS) et l’Institut national de recherche en sciences et technologies pour l’environnement et l’agriculture (Irstea), cet ouvrage aborde des points clés de la problématique de la consommation des terres en se focalisant sur les terres agricoles en France et en Australie. Plutôt que d’offrir une analyse comparative approfondie de la planification des terres agricoles périurbaines entre les deux pays, il propose une exploration des « boîtes à outils » de l’ingénierie territoriale développées et mobilisées pour faire face à l’enjeu de la perte de terres agricoles liée à l’urbanisation. Il offre également un « arrêt sur image » dans un panorama de champs de recherche en pleine évolution, autant du point de vue théorique que méthodologique

Cinématique actuelle et dynamique de l'Iran (GPS et modélisation numérique)

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Ice cap melting and low-viscosity crustal root explain the narrow geodetic uplift of the Western Alps

International audienceMore than 10 years of geodetic measurements demonstrate an uplift rate of 1–3 mm/yr of the high topography region of the Western Alps. By contrast, no significant horizontal motion has been detected. Two uplift mechanisms have been proposed: (1) the isostatic response to denudation responsible for only a fraction of the observed uplift and (2) the rebound induced by the Wurmian ice cap melting which predicts a broader uplifting region than the one evidenced by geodetic observations. Using a numerical model to fit the geodetic data, we show that a crustal viscosity contrast between the foreland and the central part of the Alps, the latter being weaker with a viscosity of 1021 Pa s, is needed. The vertical rates are enhanced if the strong uppermost mantle beneath the Moho is interrupted across the Alps, therefore allowing a weak vertical rheological anomaly over the entire lithosphere