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The document attached has been archived with permission from the editor of the Medical Journal of Australia.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

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

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

Woody stem methane emission in mature wetland alder trees

Methane (CH4) is an important greenhouse gas that is predominantly emitted to the atmosphere from anoxic wetland ecosystems. Understanding the sources and emissions of CH4 is crucially important for climate change predictions; however, there are significant discrepancies between CH4 source estimates derived via so-called bottom-up and top-down methods. Here we report CH4 emission from the stems of mature wetland alder (Alnus glutinosa) trees in the UK, a common tree of northern hemisphere floodplains and wetlands. The alder stems most likely behave as conduits for soil-produced CH4 either in the gaseous or aqueous phase, and may, therefore, help to reconcile methodological differences in the way the wetland CH4 source is estimated. Alder tree stems emitted average peak CH4 fluxes of 101 μg CH4 m−2 h−1 (on a stem area basis) in early October, a rate that is similar to that obtained from mature Japanese ash (Fraxinus mandshurica var. japonica) in Japan and amounting to approximately 20% of the measured CH4 flux from the soil surface. The finding suggests that trees, which occupy 60% of Earth's wetlands and are normally excluded from the measurement programmes that form the basis for bottom-up estimates of the global wetland source, could be important contributors to overall terrestrial ecosystem CH4 flux

Acid-dissolution of antigorite, chrysotile and lizardite for ex situ carbon capture and storage by mineralisation

Serpentine minerals serve as a Mg donor in carbon capture and storage by mineralisation (CCSM). The acid-treatment of nine comprehensively-examined serpentine polymorphs and polytypes, and the subsequent microanalysis of their post-test residues highlighted several aspects of great importance to the choice of the optimal feed material for CCSM. Compelling evidence for the non-uniformity of serpentine mineral performance was revealed, and the following order of increasing Mg extraction efficiency after three hours of acid-leaching was established: Al-bearing polygonal serpentine (<5%) ≤ Al-bearing lizardite 1T (≈5%) < antigorite (24-29%) < well-ordered lizardite 2H1 (≈65%) ≤ Al-poor lizardite 1T (≈68%) < chrysotile (≈70%) < poorly-ordered lizardite 2H1 (≈80%) < nanotubular chrysotile (≈85%). It was recognised that the Mg extraction efficiency of the minerals depended greatly on the intrinsic properties of crystal structure, chemistry and rock microtexture. On this basis, antigorite and Al-bearing well-ordered lizardite were rejected as potential feedstock material whereas any chrysotile, non-aluminous, widely spaced lizardite and/or disordered serpentine were recommended. The formation of peripheral siliceous layers, tens of microns thick, was not universal and depended greatly upon the intrinsic microtexture of the leached particles. This study provides the first comprehensive investigation of nine, carefully-selected serpentine minerals, covering most varieties and polytypes, under the same experimental conditions. We focused on material characterisation and the identification of the intrinsic properties of the minerals that affect particle’s reactivity. It can therefore serve as a generic basis for any acid-based CCSM pre-treatment

Birds, resources and time in a tablelands forest

In forests on the Southern Tablelands of New South Wales seasonal events within the avian community were tied to the annual cycle of cold winters and warm summers. Insect, carbohydrate and seed abundance changed with the seasons and were tracked by the avifauna. Superimposed were events determined on a larger regional scale. Irruptions of birds from the arid interior and drought caused significant, if transitory, changes in the forest avifauna. This has implications for the conservation and management of forest ecosystems