Influence des caractères pédologiques sur la répartition spatiale de deux espèces du genre Eperua (Caesalpiniaceae) en forêt guyanaise

An attempt is made to assess the relationships between soil conditions and the spatial distribution of two sympa trie species of rain forest trees belonging to genus Eperua (Caesalpiniaceae). The study was carried out at the Paracou study site, French Guiana, on the domed hills of precambrian basement rock, locally schistose or migmatic. The relationships between the distribution of individuals of both species and soil variables (126 samples) were studied using factor analysis and hierarchical classification. Eperua falcata is mostly found on hydromorphic or shallow vertically drained soils, often with a high exchangeable aluminium content. This tree appears to be well adapted to unfavourable soil conditions, but it can also be found in other situations. Eperua grandiflora is also adapted to shallow soils, but it does not withstand hydromorphic conditions as well as E. falcata ; it is also very sensitive to the high aluminium content of the soil. The two Eperua species are therefore complementary to one another, except on shallow soils, thus allowing genus Eperua to fill different edaphic niches.Barthès Bernard. Influence des caractères pédologiques sur la répartition spatiale de deux espèces du genre Eperua (Caesalpiniaceae) en forêt guyanaise. In: Revue d'Écologie (La Terre et La Vie), tome 46, n°4, 1991. pp. 303-320

Etude agropédologique sur une parcelle en manioc à Mana, Guyane (projet UTAP) : rapport de terrain

Dans le cadre du projet régional de développement de la culture mécanisée du manioc en Guyane, on a achevé de caractériser les aptitudes de différents terrains pour cette culture. Le site d'étude, à Mana (Nord-Ouest du pays), montre des sols sur socle et sur série détritique de base (S.D.B. = matériau détritique issu du socle). Les facteurs physico-hydriques qui déterminent une production élevée sont : une bonne aération en surface, ce qui pénalise principalement les zones basses, engorgées plusieurs mois par an, mais aussi les zones de replat, où l'on observe des stagnations d'eau à faible profondeur, liées au compactage/lissage à la base de l'horizon cultivé ; d'importantes réserves hydriques, ce qui favorise les sols profonds de la S.D.B. au détriment de ceux moins épais sur socle. (Résumé d'auteur

On the opportunistic use of geostationary satellite signals to estimate rain rate in the purpose of radar calibration

International audienceRain gauge networks are often used for radar calibration. However, the deployment of such networks is relatively complex and expensive. The present study deals with the development of a new low cost microwave device devoted to radar calibration. The principle of this device is to use rain atmospheric attenuation along microwave links to deduce the path averaged rain rate. In order to perform a feasibility study of such a device, a measurement campaign is performed for two years near Paris. Measurements of atmospheric attenuation over an earth-space link have been carried out by receiving TV channels from different geostationary satellites in Ku-band. These links are characterized by an aperture angle of 2° and a 30° elevation angle corresponding more or less to a 6 km path length through troposphere. The aim of this paper is to propose an algorithm to retrieve rain rate from the measured signal and to quantify the expected averaged rain rate accuracy along the earth-space link. In practice, the received signal is sensitive to rain as well as to many other fluctuations due to atmospheric scintillations, clouds, water vapor, small changes in the satellite orbit, power fluctuations