Contribution of vegetation (trees and ground vegetation) on the methane budget of a temperate forest

Methane (CH4) is one the most important greenhouse gas and is responsible for approximatively 20% of the global warming (IPCC, 2013). Soils and mainly upland forest soils where aerobic environment prevails, are one of the main global sink of methane (IPCC 2013). At the soil-atmosphere interface, the net methane efflux consists in a net balance between the production of CH4 by methanogenic bacteria mainly in deep anaerobic soil layers and the consumption by methanotrophic bacteria in the aerobic soil horizons of the methane produced in the soil or diffusing from the atmosphere into the soil. In upland forest, some episodic temporary waterlogging may exist, especially in managed forest where trafficked work on silty or clayey soils compacts the soil and then, enhanced the waterlogging (Startsev and McNabb, 2000). But the methane budget of ecosystem may be improved when considering not only soil but also plant compartments. Plants can impact the CH4 production and consumption by different pathways (enhance production, consumption, and/or gases transport). When the soil is submitted to compaction and then, to an increase of waterlogging, the ground vegetation is modified in favor of vegetation with aerenchymous tissues (Goutal-Pousse et al, 2012) and the soil can shift from a methane sink to an episodic methane source (Epron et al 2016). In the present study, our objectives were to determine (i) if vegetation emits CH4, (ii) if abiotic factors drive the seasonal CH4 flux pattern by plants (ground vegetation and trees) and (iii) to quantify the impact of the emissions by vegetation (tree and ground vegetation) on the methane budget of a forest submitted to compaction. We hypothesized that in an upland forest, vegetation (ground vegetation and tree stems) by enhancing the CH4 emission or by producing CH4 may reduce the methane sink of the forest ecosystem. This study was carried out in a 6-ha experimental site set up in 2007 in the state-owned forest of "les Hauts Bois" (north-eastern France) to assess the long-term impact of a loaded forwarder. To study this effect, the soil was compacted before afforestation. We recorded CH4 fluxes during 7 months at a 3-hour frequency using automated chambers on stem tree, bare soil and soil with vegetation, connected to a laser-based gas analyser in a forest site where the ground-vegetation consists mainly in two aerenchymous plants (glyceria striata and juncus sp) and trees in planted Quercus petraea. In contradiction with our hypothesis and previous studies, in this studied site, the presence of ground vegetation increases the methane forest ecosystem uptake compared to the bare soil but with an impact varying during the season. In addition, the increase in the methane uptake depended on the species, from 80 % to 120%. Methane emission by tree stem were low compared to methane uptake by soil (-3.6 ± 0.4 kg ha-1 and 0.90 ± 0.31 g ha-1 respectively) but methane emission by stem was enhanced when methane was produced into the soil

Prevalence and Predictors of Liver Fibrosis in People Living with Hepatitis B in Senegal.

Hepatitis B virus (HBV) infection is the first cause of liver cirrhosis and cancer in West Africa. Although the exposure to additional environmental and infectious risk factors may lead to the faster progression of liver disease, few large-scale studies have evaluated the determinants of HBV-related liver fibrosis in the region. We used transient elastography to evaluate the prevalence of liver fibrosis and assessed the association between HBV markers and significant liver fibrosis in a cohort of people living with HBV in Dakar, Senegal. The prevalence of significant liver fibrosis was 12.5% (95% confidence interval [CI] 9.6%-15.9%) among 471 people with HBV mono-infection (pwHBV) and 6.4% (95% CI 2.6%-12.7%) in 110 people with HIV/HBV co-infection (pwHIV/HBV) on tenofovir-containing antiretroviral therapy (p = 0.07). An HBV viral load > 2000 IU/mL was found in 133 (28.3%) pwHBV and 5 (4.7%) pwHIV/HBV, and was associated with significant liver fibrosis (adjusted odds ratio (aOR) 1.95, 95% CI 1.04-3.66). Male participants (aOR 4.32, 95% CI 2.01-8.96) and those with elevated ALT (aOR 4.32, 95% CI 2.01-8.96) were especially at risk of having significant liver fibrosis. Our study shows that people with an HBV viral load above 2000 IU/mL have a two-fold increase in the risk of liver fibrosis and may have to be considered for antiviral therapy, independent of other disease parameters

Contribution of vegetation (trees and ground vegetation) on the methane budget of a temperate forest

Methane (CH4) is one the most important greenhouse gas and is responsible for approximatively 20% of the global warming (IPCC, 2013). Soils and mainly upland forest soils where aerobic environment prevails, are one of the main global sink of methane (IPCC 2013). At the soil-atmosphere interface, the net methane efflux consists in a net balance between the production of CH4 by methanogenic bacteria mainly in deep anaerobic soil layers and the consumption by methanotrophic bacteria in the aerobic soil horizons of the methane produced in the soil or diffusing from the atmosphere into the soil. In upland forest, some episodic temporary waterlogging may exist, especially in managed forest where trafficked work on silty or clayey soils compacts the soil and then, enhanced the waterlogging (Startsev and McNabb, 2000). But the methane budget of ecosystem may be improved when considering not only soil but also plant compartments. Plants can impact the CH4 production and consumption by different pathways (enhance production, consumption, and/or gases transport). When the soil is submitted to compaction and then, to an increase of waterlogging, the ground vegetation is modified in favor of vegetation with aerenchymous tissues (Goutal-Pousse et al, 2012) and the soil can shift from a methane sink to an episodic methane source (Epron et al 2016). In the present study, our objectives were to determine (i) if vegetation emits CH4, (ii) if abiotic factors drive the seasonal CH4 flux pattern by plants (ground vegetation and trees) and (iii) to quantify the impact of the emissions by vegetation (tree and ground vegetation) on the methane budget of a forest submitted to compaction. We hypothesized that in an upland forest, vegetation (ground vegetation and tree stems) by enhancing the CH4 emission or by producing CH4 may reduce the methane sink of the forest ecosystem. This study was carried out in a 6-ha experimental site set up in 2007 in the state-owned forest of "les Hauts Bois" (north-eastern France) to assess the long-term impact of a loaded forwarder. To study this effect, the soil was compacted before afforestation. We recorded CH4 fluxes during 7 months at a 3-hour frequency using automated chambers on stem tree, bare soil and soil with vegetation, connected to a laser-based gas analyser in a forest site where the ground-vegetation consists mainly in two aerenchymous plants (glyceria striata and juncus sp) and trees in planted Quercus petraea. In contradiction with our hypothesis and previous studies, in this studied site, the presence of ground vegetation increases the methane forest ecosystem uptake compared to the bare soil but with an impact varying during the season. In addition, the increase in the methane uptake depended on the species, from 80 % to 120%. Methane emission by tree stem were low compared to methane uptake by soil (-3.6 ± 0.4 kg ha-1 and 0.90 ± 0.31 g ha-1 respectively) but methane emission by stem was enhanced when methane was produced into the soil

Surveillance of transmitted HIV-1 antiretroviral drug resistance in the context of decentralized HIV care in Senegal and the Ebola outbreak in Guinea

Abstract Objectives Disruption in HIV care provision may enhance the development and spread of drug resistance due to inadequate antiretroviral therapy. This study thus determined the prevalence of HIV-1 transmitted drug resistance (TDR) in settings of decentralized therapy and care in Senegal and, the Ebola outbreak in Guinea. Antiretroviral-naïve patients were enrolled following a modified WHO TDR Threshold Survey method, implemented in Senegal (January–March 2015) and Guinea (August–September 2015). Plasma and dried blood spots specimens, respectively from Senegalese (n = 69) and Guinean (n = 50) patients, were collected for direct sequencing of HIV-1 pol genes. The Stanford Calibrated Population Resistance program v6.0 was used for Surveillance Drug Resistance Mutations (SDRMs). Results Genotyping was successful from 54/69 (78.2%) and 31/50 (62.0%) isolates. In Senegal, TDR prevalence was 0% (mean duration since HIV diagnosis 4.08 ± 3.53 years). In Guinea, two patients exhibited SDRMs M184V (NRTI), T215F (TAM) and, G190A (NNRTI), respectively. TDR prevalence at this second site, however, could not be ascertained because of low sample size. Phylogenetic inference confirmed CRF02_AG predominance in Senegal (62.96%) and Guinea (77.42%). TDR prevalence in Senegal remains extremely low suggesting improved control measures. Continuous surveillance in both settings is mandatory and, should be done closest to diagnosis/transmission time and with larger sample size