Réflexions d'un écologue.

Réflexions d'un écologue qui pendant 30 ans a étudié et regardé la dynamique de la végétation après incendie dans la région méditerranéenne

Tentative d'analyse logique des recherches sur les feux de végétation entreprises au département d'écologie générale du C.E.P.E. Louis Emberger

Les recherches sur les feux ont trait aux conditions climatiques et végétales qui déterminent l'apparition des feux, au comportement du feu et à son impact sur les milieux. L'article donne quelques résultats concernant l'application

Réponses des végétaux ligneux méditerranéens à l'action du feu

The response of different Mediterranean wood species to fire action is studied in the neiglibourhood of Montpellier (France). Along 19 years (1969-1987), the author follows the evolution of 35 experimental plots undergoing artificial fires in the spring and fallow, and with different frequencies: 2,3 a 6 years. He controls moreover 52 areas burned from natural fires, for ten years after the burning. Concluding remarks show that woody species of Mediterranean region are, in general, rather fire-resistant. Some of them, however, such as Cistus monspeliensis, Juniperus oxycedrus and Rhamnus alaternus, con be eliminated if the fires are too frequent. Other, such as Quercus coccifera, Q. ilex or Q. pubescens, show, importance for the regeneration capability of the species, mainly for those being very sensitive to frequent fires.[fr] On étudie les réponses des végétaux ligneux méditerranéens l'action du feu dans une zone autour de Montpellier (France). L'auteur suit sur 19 ans (1969-1987) l'évolution de 35parcelles expérimentales, soumises au feu pendant le printemps ou l'automne et avec différentes fréquences: 2, 3 et 6 ans. Par ailleurs, étudie 52 zones d'observation brûlées par des feux sauvages pendant les dix premières années après l'incendie. L'auteur conclut en montrant que dans l'ensemble, les végétaux ligneux du bassin méditerranéen résistent au feu. Toutefois, certains (p. ex. Cistus monspeliensis, Juniperus oxycedrus, Rhamnus alaternus) peuvent être éliminés lorsque les feux sont trop fréquents. En revanche, d'autres (p. ex. Quercus coccifera, Q. ilex et Q. pubescens) montrent une résistance très forte. La saison des feux a une grande importance sur les capacités de régénération des espèces, et plus particulièrement celles qui sont extrêmement sensibles à la fréquence des incendies. [es] Se estudia la respuesta de diferentes especies leñosas mediterráneas a la acción del fuego en los alrededores de Montpellier (Francia). El autor sigue durante 19 años (1969-1987) la evolución de 35 parcelas experimentales sometidas a fuegos provocados en primavera o en otoño y con distintas frecuencias: 2, 3 y 6 años. Además controla 52 áreas quemadas con fuegos naturales durante los 10 años posteriores al incendio. Concluye señalando que en conjunto las especies leñosas de la cuenca mediterránea son bastante resistentes al fuego. Sin embargo, algunas como Cistus monspeliensis, Juniperus oxycedrus y Rhamnus alaternus llegan a ser eliminadas cuando los fuegos son muy frecuentes. Por el contrario, otras (Quercus coccifera, Q. ilex y Q. pubescens, por ejemplo) muestran una resistencia muy fuerte. La estación en que se quema tiene gran importancia en la capacidad de regeneración de las especies, especialmente en las extremadamente sensibles a los incendios repetidos

Réponses du chêne vert et du chêne blanc à l'action du feu

L'influence du feu a été étudié, dans le Bas Languedoc, de façon diachronique sur la dynamique de la composition floristique et de la structure des chênaies incendiées de Quercus ilex. De la même façon, la croissance post incendie a été suivie sur des individus de Quercus ilex et Quercus pubescens. Leur résistance aux incendies répétés a été mesurée expérimentalement

Cross-resistance to elvitegravir and dolutegravir in 502 patients failing on raltegravir: a French national study of raltegravir-experienced HIV-1-infected patients

OBJECTIVES: The objectives of this study were to determine the prevalence and patterns of resistance to integrase strand transfer inhibitors (INSTIs) in patients experiencing virological failure on raltegravir-based ART and the impact on susceptibility to INSTIs (raltegravir, elvitegravir and dolutegravir). PATIENTS AND METHODS: Data were collected from 502 treatment-experienced patients failing a raltegravir-containing regimen in a multicentre study. Reverse transcriptase, protease and integrase were sequenced at failure for each patient. INSTI resistance-associated mutations investigated were those included in the last ANRS genotypic algorithm (v23). RESULTS: Among the 502 patients, at failure, median baseline HIV-1 RNA (viral load) was 2.9 log10 copies/mL. Patients had been previously exposed to a median of five NRTIs, one NNRTI and three PIs. Seventy-one percent harboured HIV-1 subtype B and the most frequent non-B subtype was CRF02_AG (13.3%). The most frequent mutations observed were N155H/S (19.1%), Q148G/H/K/R (15.4%) and Y143C/G/H/R/S (6.7%). At failure, viruses were considered as fully susceptible to all INSTIs in 61.0% of cases, whilst 38.6% were considered as resistant to raltegravir, 34.9% to elvitegravir and 13.9% to dolutegravir. In the case of resistance to raltegravir, viruses were considered as susceptible to elvitegravir in 11% and to dolutegravir in 64% of cases. High HIV-1 viral load at failure (P < 0.001) and low genotypic sensitivity score of the associated treatment with raltegravir (P < 0.001) were associated with the presence of raltegravir-associated mutations at failure. Q148 mutations were selected more frequently in B subtypes versus non-B subtypes (P = 0.004). CONCLUSIONS: This study shows that a high proportion of viruses remain susceptible to dolutegravir in the case of failure on a raltegravir-containing regimen

The Effects of Ash and Black Carbon (Biochar) on Germination of Different Tree Species

Forest fires generate large amounts of ash and biochar, or black carbon (BC), that cover the soil surface, interacting with the soil’s constituents and its seedbank. This study concerns reproductive ecology assessments supported by molecular characterisation to improve our understanding of the effects of fire and fire residues on the germination behaviour of 12 arboreal species with a wide geographic distribution. For this purpose, we analysed the effects of three ash and one BC concentration on the germination of Acacia dealbata Link, A. longifolia (Andrews) Willd., A. mearnsii De Wild., A. melanoxylon R. Br., Pinus nigra Arnold, P. pinaster Aiton, P. radiata D. Don, P. sylvestris L., Quercus ilex L., Q. pyrenaica Willd., Q. robur L., and Q. rubra L. Each tree species was exposed to ash and BC created from its foliage or twigs (except for Q. rubra, which was exposed to ash and BC of Ulex europaeus L.). We monitored germination percentage, the T50 parameter, and tracked the development of germination over time (up to 1 yr). The BC of A. dealbata, P. pinaster, and Q. robur was analysed by pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS) to assess the molecular composition. In six species, ash inhibited the germination, while in another five species, germination was not affected by ash or by BC. In Q. rubra, ash and BC stimulated its germination. This stimulating effect of the BC on Q. rubra is likely to be related to the chemical composition of the ash and BC obtained from Ulex feedstock. The BC of U. europaeus has a very different molecular composition than the other BC samples analysed, which, together with other factors, probably allowed for its germination stimulating effects.This study was carried out within the Project 10MDS200007PR, financed by the Xunta de Galicia; the Project AGL2013-48189-C2-2-R, financed by the Ministerio de Economía y Competitividad, Spain; and FEDERS

Antiretroviral-naive and -treated HIV-1 patients can harbour more resistant viruses in CSF than in plasma

Objectives The neurological disorders in HIV-1-infected patients remain prevalent. The HIV-1 resistance in plasma and CSF was compared in patients with neurological disorders in a multicentre study. Methods Blood and CSF samples were collected at time of neurological disorders for 244 patients. The viral loads were >50 copies/mL in both compartments and bulk genotypic tests were realized. Results On 244 patients, 89 and 155 were antiretroviral (ARV) naive and ARV treated, respectively. In ARV-naive patients, detection of mutations in CSF and not in plasma were reported for the reverse transcriptase (RT) gene in 2/89 patients (2.2%) and for the protease gene in 1/89 patients (1.1%). In ARV-treated patients, 19/152 (12.5%) patients had HIV-1 mutations only in the CSF for the RT gene and 30/151 (19.8%) for the protease gene. Two mutations appeared statistically more prevalent in the CSF than in plasma: M41L (P = 0.0455) and T215Y (P = 0.0455). Conclusions In most cases, resistance mutations were present and similar in both studied compartments. However, in 3.4% of ARV-naive and 8.8% of ARV-treated patients, the virus was more resistant in CSF than in plasma. These results support the need for genotypic resistance testing when lumbar puncture is performe