Search results for "changes"

The role of slabs and oceanic plate geometry in the net rotation of the lithosphere, trench motions, and slab return flow

2012

International audience; [1] Absolute plate motion models with respect to a deep mantle reference frame (e.g., hot spots) typically contain some net rotation (NR) of the lithosphere. Global mantle flow models for the present-day plate setting reproduce similarly oriented NRs but with amplitudes significantly smaller than those found in some high NR Pacific hot spot reference frames. It is therefore important to understand the mechanisms of NR excitation, which we attempt here with two-dimensional cylindrical models of an idealized Pacific domain. We study the influence of slab properties, oceanic ridge position, continental keels, and a weak asthenospheric layer on NR and trench migration. F…

Impacts of Integrated Weed management in cropping systems on N2O emissions from soils

2014

International audience

Cropping system dynamics, climate variability, and seed losses among East African smallholder farmers: a retrospective survey.

2014

Abstract Climate variability directly affects traditional low input and rain-fed farming systems, but few studies have paid attention retrospectively to the cropping system’s ability to mitigate climate risk. This study analyzes the impacts of rainfall variability on farmers’ seed variety losses over time, considering changes in smallholder farming systems. The cropping system dynamics, in favoring maize at the expense of sorghum and pearl millet, have induced an increasing risk of seed loss during drought. Combining ecological anthropology and climatology, a retrospective survey asking farmers about the period 1961–2006 was carried out at three altitudinal levels (750, 950, and 1100 m) on …

The Mistigri Thermal Infrared Project: Scientific Objectives And Mission Specifications

2013

ISI Document Delivery No.: 147NI Times Cited: 4 Cited Reference Count: 117 Cited References: Abrams M, 2000, INT J REMOTE SENS, V21, P847, DOI 10.1080/014311600210326 Agam N, 2007, J GEOPHYS RES-ATMOS, V112, DOI 10.1029/2007JD008407 Allen RG, 2007, J IRRIG DRAIN E-ASCE, V133, P380, DOI 10.1061/(ASCE)0733-9437(2007)133:4(380) Alletto L, 2006, CHEMOSPHERE, V64, P1053, DOI 10.1016/j.chemosphere.2005.12.004 Arnfield AJ, 2003, INT J CLIMATOL, V23, P1, DOI 10.1002/joc.859 Baschek B., 2010, 2010 OC SCI M PORTL Bastiaanssen WGM, 1998, J HYDROL, V212, P198, DOI 10.1016/S0022-1694(98)00253-4 Bastiaanssen WGM, 2005, J IRRIG DRAIN E-ASCE, V131, P85, DOI 10.1061/(ASCE)0733-9437(2005)131:1(85) Beck LR, 2…

Quelles échelles pertinentes de temps et d’espace pour prédire l’occurrence des espèces adventices ?

2013

National audience; L’identification des déterminants de la distribution spatiale des espèces adventices dans les agro-écosystèmes et la compréhension des processus écologiques sous-jacents sont un prérequis au développement d’une gestion intégrée de ces espèces. Les modèles statistiques de distribution d’espèces sont des outils potentiellement intéressant pour avancer dans cette compréhension. Néanmoins, un problème récurrent de ce genre d’approche est l’identification des échelles appropriées de temps et d’espace pour la modélisation. Dans le cas des adventices, si les facteurs déterminant leur distribution spatiale ont généralement été étudiés à l’échelle de la parcelle, de récentes étude…

Modélisation du cycle du carbone et de l'azote

1996

International audience

Widespread diminishing anthropogenic effects on calcium in freshwaters

2019

Calcium (Ca) is an essential element for almost all living organisms. Here, we examined global variation and controls of freshwater Ca concentrations, using 440 599 water samples from 43 184 inland water sites in 57 countries. We found that the global median Ca concentration was 4.0 mg L−1 with 20.7% of the water samples showing Ca concentrations ≤ 1.5 mg L−1 , a threshold considered critical for the survival of many Ca-demanding organisms. Spatially, freshwater Ca concentrations were strongly and proportionally linked to carbonate alkalinity, with the highest Ca and carbonate alkalinity in waters with a pH around 8.0 and decreasing in concentrations towards lower pH. However, on a temporal…

La Bourgogne entre les bassins rhénan, rhodanien et parisien : carrefour ou frontière ?

1996

International audience; Au coeur même de son territoire, la région de Bourgogne a accueilli pour quelques jours, à l'occasion de son 18e colloque, la communauté des néolithiciens. Bien des congressistes, venus du Nord, de l'Ouest ou du Sud pour se rendre à Dijon, n'auront pas manqué de percevoir le relatif obstacle au franchissement que constitue le massif bourguignon.Mais le frein partiel engendré par la topographie ne saurait masquer l'ouverture vers l'extérieur de la Bourgogne, naturellement échancrée par trois bassins alluviaux. La Seine, l'Yonne et leurs affluents constituent des vallées propices aux échanges avec le Bassin parisien. Le couloir de la Saône, prolongé par celui du Rhône,…

Magnetic survey on Chupicuaro archaeological sites (late pre-classic period, Middle Lerma Valley, Guanajuato, Mexico)

2009

Les versants du Petit Saint-Bernard de la Préhistoire à l'Antiquité : nouvelles données sur les premières occupations de la montagne autour d'un pass…

2006

The Petit Saint-Bernard mountain pass is one of the main transalpine passages at the south of Mont Blanc. Within the context of an Interreg programme, archaeological research is being done on the two sides of the pass. This work aims to develop knowledge of the first populating of the mountain and of its interaction with transalpine circulations. The method is based on a vast series of manual excavations carried out in areas prone to sedimentary trappings. The study area, which is quite large, covers the entire height of the sides and makes it possible to study the relations between the different biogeographical steps. The collected data are presented in chronological order, from Prehistory…