Éditeur(s) : HAL CCSD Society for Range Management
Résumé : Grasslands and agroecosystems occupy one-third of the terrestrial area, but their contribution to the global carbon cycle remains uncertain. We used a set of 316 site-years of CO(2) exchange measurements to quantify gross primary productivity, respiration, and light-response parameters of grasslands, shrublands/savanna, wetlands, and cropland ecosystems worldwide. We analyzed data from 72 global flux-tower sites partitioned into gross photosynthesis and ecosystem respiration with the use of the light-response method (Gilmanov, T. G., D. A. Johnson, and N. Z. Saliendra. 2003. Growing season CO(2) fluxes in a sagebrushsteppe ecosystem in Idaho: Bowen ratio/energy balance measurements and modeling. Basic and Applied Ecology 4:167-183) from the RANGEFLUX and WORLDGRASSAGRIFLUX data sets supplemented by 46 sites from the FLUXNET La Thuile data set partitioned with the use of the temperature-response method (Reichstein, M., E. Falge, D. Baldocchi, D. Papale, R. Valentini, M. Aubinet, P. Berbigier, C. Bernhofer, N. Buchmann, M. Falk, T. Gilmanov, A. Granier, T. Grunwald, K. Havrankova, D. Janous, A. Knohl, T. Laurela, A. Lohila, D. Loustau, G. Matteucci, T. Meyers, F. Miglietta, J.M. Ourcival, D. Perrin, J. Pumpanen, S. Rambal, E. Rotenberg, M. Sanz, J. Tenhunen, G. Seufert, F. Vaccari, T. Vesala, and D. Yakir. 2005. On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm. Global Change Biology 11: 1.424-1439). Maximum values of the quantum yield (alpha = 75 mmol.mol(-1)), photosynthetic capacity (A(max) = 3.4 mg CO(2) . m(-2).s-1), gross photosynthesis (P(g,max) = 1.16 g CO(2) . m(-2).d(-1)), and ecological light-use efficiency (epsilon(ecol) = 59 mmol . mol(-1)) of managed grasslands and high-production croplands exceeded those of most forest ecosystems, indicating the potential of nonforest ecosystems for uptake of atmospheric CO(2). Maximum values of gross primary production (8 600 g CO(2) . m(-2).yr(-1)), total ecosystem respiration (7 900 g CO(2) . m(-2).yr(-1)), and net CO(2) exchange (2 400 g CO(2) . m(-2).yr(-1)) were observed for intensively managed grasslands and high-yield crops, and are comparable to or higher than those for forest ecosystems, excluding some tropical forests. On average, 80% of the nonforest sites were apparent sinks for atmospheric CO(2), with mean net uptake of 700 g CO(2) . m(-2).yr(-1) for intensive grasslands and 933 g CO(2) . m(-2).d(-1) for croplands. However, part of these apparent sinks is accumulated in crops and forage, which are carbon pools that are harvested, transported, and decomposed off site. Therefore, although agricultural fields may be predominantly sinks for atmospheric CO(2), this does not imply that they are necessarily increasing their carbon stock.
ISSN: 1550-7424

hal-01190754
https://hal.archives-ouvertes.fr/hal-01190754
DOI : 10.2111/rem-d-09-00072.1
PRODINRA : 214043

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : International audience
Antisynthetase syndrome is an inflammatory myopathy frequently associated with pulmonary manifestations, especially interstitial lung diseases, and uncommonly pulmonary hypertension. In the context of a suggestive clinical and radiological picture, positive anti-RNA synthetase antibodies confirm the diagnosis. Anti-Jo1, anti-PL7, and anti-PL12 antibodies are the more commonly encountered. The presence of a number of extra-thoracic manifestations in association with pulmonary disease may suggest the diagnosis. These include: myalgia or muscular deficit, Raynaud's phenomenon, polyarthritis, fever, mechanics hands. Serum creatine kinase levels are usually increased. Electromyogram, muscular magnetic resonance imaging or muscle pathology are not mandatory to make the diagnosis. There is a high variability in symptoms and severity, between patients but also during the course of the disease in the same patient. The presence of an interstitial lung disease is a major prognostic factor and an indication for more intensive treatment, principally with systemic corticosteroids with or without immunosuppressive drugs. Improving respiratory physicians’ knowledge of this disease, which is often revealed by its pulmonary manifestations, should help diagnosis, therapeutic management, and possibly prognosis.
Le syndrome des antisynthétases correspond à une myopathie inflammatoire fréquemment associée à une atteinte pulmonaire, surtout parenchymateuse (pneumopathie infiltrante diffuse) et plus rarement vasculaire (hypertension pulmonaire). Devant un tableau clinique et radiologique évocateur, la présence d’anticorps anti-ARNt synthétases signe le diagnostic. Les plus fréquents de ces auto-anticorps sont les anti-Jo1, les anti-PL7 et les anti-PL12. De nombreuses manifestations cliniques extrathoraciques associées à l’atteinte pulmonaire peuvent orienter le diagnostic : myalgies ou déficit musculaire, phénomène de Raynaud, polyarthrite, fièvre et « mains de mécaniciens ». Une augmentation des créatine-phospho-kinases est quasi constante. Le recours à l’électromyogramme, à l’imagerie musculaire par résonance magnétique ou à l’histologie n’est pas systématique. Néanmoins, il existe une grande variabilité des symptômes et de leur sévérité d’un patient à l’autre ou au long de l’évolution de la maladie. L’atteinte pulmonaire est un facteur pronostic majeur et incite à traiter de manière intensive les patients, principalement par corticothérapie systémique, voire d’emblée par association corticoïdes et immunosuppresseurs. Mieux connaître cette pathologie qui est souvent de révélation pneumologique permettrait d’améliorer le diagnostic et la prise en charge thérapeutique, voire même le pronostic.
ISSN: 0761-8425

hal-01085369
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01085369
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01085369/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01085369/file/Manifestations%20pulmonaires%20du%20syndrome%20des%20antisynth%C3%A9tases_accepted.pdf
DOI : 10.1016/j.rmr.2014.07.013