Tree-mediated methane emissions from tropical and temperate peatlands

Methane production and transport processes in peatlands are fairly well understood, but growing evidence for emission of methane through trees has highlighted the need to revisit methane transport processes. In wetland trees, morphological adaptations such as development of hypertrophied lenticels, aerenchyma and adventitious roots in response to soil anoxia mediates gas transport, transporting both oxygen from the atmosphere to oxygen-deprived roots and soil-produced methane from the root-zone to the atmosphere. Although, tree-mediated methane emissions from temperate tree species have been confirmed, methane emissions from tropical tree species and processes that control tree-mediated methane emissions remain unclear. This study explains the role of trees in transporting soil-produced methane to the atmosphere and uncovers the principal mechanisms of tree-mediated methane emissions. Methane emissions from eight tropical tree species and two temperate tree species were studied in situ. The mechanisms and controls on tree-mediated methane emissions were investigated using three year old common alder (Alnus glutinosa; 50 trees) grown under two artificially controlled water-table positions. Methane fluxes from whole mesocosms, the soil surface and tree stems were measured using static closed chambers. Both temperate and tropical tree species released significant quantities of methane, with tropical trees dominating ecosystem level methane fluxes. In temperate peatlands, both the methane gas transport mechanism and quantity of methane emitted from stems is tree-species dependent. In Alnus glutinosa, no correlations were observed between stomatal behaviour and tree-mediated methane emissions, however, stem methane emissions were positively correlated with both stem lenticel density and dissolved soil methane concentration. In Alnus glutinosa, no emissions were observed from leaf surfaces. The results demonstrate that exclusion of tree-mediated methane emissions from flux measurement campaigns in forested peatlands will lead to an underestimation of ecosystem-wide methane emissions

Which substitution pharmacotherapy is most effective in treating opioid dependence?

The document attached has been archived with permission from the editor of the Medical Journal of Australia. An external link to the publisher’s copy is included.Design: Randomised controlled trial, double-blind. Setting: Outpatient clinic in Baltimore, United States. Participants: 220 people categorised as opioid dependent by DSM-IV;1 groups similar on demographics and drug use history. Exclusion criteria were medical and psychiatric illness requiring long-term medication, and pregnancy. Interventions: (i) Levo acetyl methadol (LAAM) at 75–115 mg, (ii) buprenorphine at 16–32 mg, (iii) methadone at 60–100 mg ("high dose"), or (iv) methadone at 20 mg ("low dose"). LAAM and buprenorphine were given three times a week, methadone daily. LAAM and methadone were given orally, buprenorphine sublingually. Participants attended the clinic daily for two weeks of dose induction, then thrice weekly with take-home doses. The scheduled duration of the trial was 17 weeks. Main outcome measures: Retention in treatment; illicit drug use; participants' global ratings of their drug problem. Main results: Days retained in the study (mean ± SE) — LAAM (i), 89 ± 6; buprenorphine (ii), 96 ± 4; "high dose" methadone (iii), 105 ± 4; "low dose" methadone (iv) 70 ± 4. Significantly more days retained for groups (i), (ii) and (iii) compared with group (iv) (P < 0.001), and group (iii) compared with group (i) (P = 0.02). Trial was completed by 53% of group (i), 58% of group (ii), 73% of group (iii), and 20% of group (iv), with 4, 3, 6 and 26 of groups (i), (ii), (iii) and (iv), respectively, transferred to rescue treatment (standard methadone maintenance). Twelve or more consecutive opioid-negative urine specimens were obtained in 36% of group (i), 26% of group (ii), 28% of group (iii) and 8% of group (iv) (P < 0.005). Conclusion: Compared with low-dose methadone, LAAM, buprenorphine and high-dose methadone substantially reduce the use of illicit opioids.Linda R. Gowing, Robert L. Ali and Jason M. Whit

Integrated washland management for flood defence and biodiversity

A combination of reform of agricultural policy, changing priorities in the countryside, growing commitment to protect and enhance biodiversity, and concerns about increased flood risk in lowlands have drawn attention to the potential contribution that managed washlands can make to deliver benefits to biodiversity and flood management. In this context, and with funding from Defra and English Nature, the study reported here1 set out to determine the scope for simultaneously achieving flood management and biodiversity objectives, and how this might be achieved in practice. The broad purpose is to inform policy on washland creation and management, including mechanisms for implementation if deemed appropriate

Pharmacotherapies for cannabis withdrawal

ProtocolThis is the protocol for a review and there is no abstract. The objectives are as follows: To assess the effectiveness and safety of pharmacotherapies as compared with each other, placebo or no pharmacotherapy (supportive care) for reducing cannabis withdrawal and promoting cessation.Kushani S Marshall, Linda Gowing, Robert Al

Modelling the hydrological impacts of climate change on UK lowland wet grassland

Hydrological impacts of climate change upon the Elmley Marshes, southeast England, are simulated using a coupled hydrological/hydraulic model developed using MIKE SHE/MIKE 11 and calibrated to contemporary conditions. Predicted changes in precipitation, temperature, radiation and wind speed from the UK Climate Impacts Programme associated with four emissions scenarios for the 2050s are used to modify precipitation and potential evapotranspiration data. For each emissions scenario two sets of potential evapotranspiration data are derived, one using changes in temperature (PETtemp), the other incorporating changes in temperature, radiation and wind speed (PETtrws). Results indicate drier conditions through the progressively higher emissions scenarios when compared to contemporary conditions. Changes are particularly pronounced when using PETtrws. Summer water tables are lower (PETtemp 0.01�0.08 m; PETtrws 0.07�0.27 m) and the duration of high winter water tables is reduced. Although water tables still intercept the surface in winter when using PETtemp, this ceases when PETtrws is employed. Summer ditch water levels for the PETtemp scenarios are lower (0.01�0.21 m) and in dry winters they do not reach mean field level. Under the PETtrws scenarios summer and winter ditch water levels are lower by on average 0.21 and 0.30 m, respectively. Levels never reach the elevation of the marsh surface. Lower groundwater and ditch water levels result in declines in the magnitude and duration of surface inundation which is virtually eliminated with the PETtrws scenarios. The changes in hydrological conditions simulated by the model are of sufficiently fine resolution to infer ecological impacts which are likely to include the loss of some grassland species adapted to high water tables. Reductions in the extent of surface water in spring, especially for the PETtrws scenarios, are likely to reduce suitability for wading birds including lapwing (Vanellus vanellus) and redshank (Tringa totanus) for which the marshes are internationally renowned

Quantifying soil hydrology to explain the development of vegetation at an ex-arable wetland restoration site

Wetland restoration frequently sets well-defined vegetation targets, but where restoration occurs on highly degraded land such targets are not practical and setting looser targets may be more appropriate. Where this more ‘open-ended’ approach to restoration is adopted, surveillance methods that can track developing wetland habitats need to be established. Water regime and soil structure are known to influence the distribution and composition of developing wetland vegetation, and may be quantified using Sum Exceedence Values (SEV), calculated using the position of the water table and knowledge of soil stress thresholds. Use of SEV to explain patterns in naturally colonizing vegetation on restored, ex-arable land was tested at Wicken Fen (UK). Analysis of values from ten locations showed that soil structure was highly heterogeneous. Five locations had shallow aeration stress thresholds and so had the potential to support diverse wetland assemblages. Deep aeration stress thresholds at other locations precluded the establishment of a diverse wetland flora, but identified areas where species-poor wetland assemblages may develop. SEV was found to be a useful tool for the surveillance of sites where restoration targets are not specified in detail at the outset and may help predict likely habitat outcomes at sites using an open-ended restoration approach

Viruses in extreme environments

The original publication is available at www.springerlink.comInternational audienceThe tolerance limits of extremophiles in term of temperature, pH, salinity, desiccation, hydrostatic pressure, radiation, anaerobiosis far exceed what can support non-extremophilic organisms. Like all other organisms, extremophiles serve as hosts for viral replication. Many lines of evidence suggest that viruses could no more be regarded as simple infectious ‘‘fragments of life'' but on the contrary as one of the major components of the biosphere. The exploration of niches with seemingly harsh life conditions as hypersaline and soda lakes, Sahara desert, polar environments or hot acid springs and deep sea hydrothermal vents, permitted to track successfully the presence of viruses. Substantial populations of double-stranded DNA virus that can reach 109 particles per milliliter were recorded. All these viral communities, with genome size ranging from 14 kb to 80 kb, seem to be genetically distinct, suggesting specific niche adaptation. Nevertheless, at this stage of the knowledge, very little is known of their origin, activity, or importance to the in situ microbial dynamics. The continuous attempts to isolate and to study viruses that thrive in extreme environments will be needed to address such questions. However, this topic appears to open a new window on an unexplored part of the viral world