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Livestock slurry is a major source of atmospheric methane (CH4), but surface crusts harboring methane-oxidizing bacteria (MOB) could mediate against CH4 emissions. This study examined conditions for CH4 oxidation by in situ measurements of oxygen (O2) and nitrous oxide (N2O), as a proxy for inorganic N transformations, in intact crusts using microsensors. This was combined with laboratory incubations of crust material to investigate the effects of O2, CH4, and inorganic N on CH4 oxidation, using 13CH4 to trace C incorporation into lipids of MOB. Oxygen penetration into the crust was 2 to 14 mm, confining the potential for aerobic CH4 oxidation to a shallow layer. Nitrous oxide accumulated within or below the zone of O2 depletion. With 102 ppmv CH4 there was no O2 limitation on CH4 oxidation at O2 concentrations as low as 2%, whereas CH4 oxidation at 104 ppmv CH4 was reduced at ≤5% O2. As hypothesized, CH4 oxidation was in general inhibited by inorganic N, especially NO-2, and there was an interaction between N inhibition and O2 limitation at 102 ppmv CH4, as indicated by consistently stronger inhibition of CH4 oxidation by NH+4 and NO-3 at 3% compared with 20% O2. Recovery of 13C in phospholipid fatty acids suggested that both Type I and Type II MOB were active, with Type I dominating high-concentration CH4 oxidation. Given the structural heterogeneity of crusts, CH4 oxidation activity likely varies spatially as constrained by the combined effects of CH4, O2, and inorganic N availability in microsites. [ABSTRACT FROM AUTHOR]

The terrestrial vegetation is a source of UV radiation-induced aerobic methane ( CH4) release to the atmosphere. Hitherto pectin, a plant structural component, has been considered as the most likely precursor for this CH4 release. However, most of the leaf pectin is situated below the surface wax layer, and UV transmittance of the cuticle differs among plant species. In some species, the cuticle effectively absorbs and/or reflects UV radiation. Thus, pectin may not necessarily contribute substantially to the UV radiation-induced CH4 emission measured at surface level in all species. Here, we investigated the potential of the leaf surface wax itself as a source of UV radiation-induced leaf aerobic CH4 formation. Isolated leaf surface wax emitted CH4 at substantial rates in response to UV radiation. This discovery has implications for how the phenomenon should be scaled to global levels. In relation to this, we demonstrated that the UV radiation-induced CH4 emission is independent of leaf area index above unity. Further, we observed that the presence of O2 in the atmosphere was necessary for achieving the highest rates of CH4 emission. Methane formation from leaf surface wax is supposedly a two-step process initiated by a photolytic rearrangement reaction of the major component followed by an α-cleavage of the generated ketone. [ABSTRACT FROM AUTHOR]

Soil applications of recalcitrant biochar offer the possibility of mitigating climate change effects through long-term carbon sequestration and potentially also by reducing emissions of the potent greenhouse gas nitrous oxide (N2O). This laboratory study examined the effect of combining a fast-pyrolysis biochar at small (1% by mass) and large (3%) concentrations with anaerobically digested slurry on soil N2O and carbon dioxide (CO2) emissions over a period of 55 days. The results showed that fast-pyrolysis biochar applied on its own increased N2O emissions from soil. However, when biochar was applied together with slurry, the larger biochar concentration decreased N2O emissions by 47%, relative to those from the slurry treatment with the smaller biochar concentration. Reduced N2O emissions coincided with enhanced soil microbial activity and immobilization of nitrogen. A combined application of biochar and anaerobic digested slurry could therefore be beneficial for cropping systems in terms of soil nitrogen retention while concurrently mitigating N2O fluxes and sequestering carbon in soil. [ABSTRACT FROM AUTHOR]

As soil-atmosphere fluxes of greenhouse gases are characterized by high temporal fluctuations, frequent measurements in the range of hours to days need to be deployed, resulting in high analytical costs. We have therefore developed a new low-cost system that combines high-frequency automated sampling with low-frequency chemical analysis. The System for Inert Gas Monitoring by Accumulation (SIGMA) is suited particularly for stand-alone observations in remote locations. The SIGMA is connected to an automated chamber with headspace sampling several times per day. Air samples are aggregated in sampling bags, which reduces the number of subsequent laboratory analyses and allows calculation of average flux rates over extended sampling periods. The SIGMA was tested under field conditions and compared with a conventional autochamber system, where flux rates were measured several times per day. Sample air fillings of the SIGMA sampling bags varied less than 5% between bags and diverged <1 to 6% of the pre-set values, justifying the assumption about proportional mixing of chamber headspace samples. When the SIGMA and conventional autochambers were compared simultaneously over the same patch of grassland in Denmark, the estimates agreed within ±12% in the assessment of average N2O fluxes. When deployed to discrete autochambers situated a few metres apart and under various environmental conditions in Denmark and the UK, we found no consistent difference between the two measuring systems. For a N-fertilized cropland in Denmark the SIGMA N2O and CO2 fluxes were 28 and 23% less, respectively than those recorded with the conventional autochamber, while for a N-fertilized grassland in the UK the SIGMA N2O flux was 47% more than that recorded with the conventional autochamber and 6% less than that recorded with a manual chamber system. Such differences are within the range of natural spatial variability in trace gas fluxes for these ecosystems and indicate the potential for further application of the SIGMA approach as a cost-effective technique to estimate long-term trace gas fluxes. [ABSTRACT FROM AUTHOR]

This study examines the effects of different irradiance types on aerobic methane (CH4) efflux rates from terrestrial plant material. Furthermore, the role of the enzyme pectin methyl esterase (PME) on CH4 efflux potential was also examined. Different types of plant tissue and purified pectin were incubated in glass vials with different combinations of irradiation and/or temperature. Purified dry pectin was incubated in solution, and with or without PME. Before and after incubation, the concentration of CH4 was measured with a gas chromatograph. Rates of CH4 emission were found to depend exponentially on temperature and linearly on UV-B irradiance. UV-B had a greater stimulating effect than UV-A, while visible light had no effect on emission rates. PME was found to substantially reduce the potential for aerobic CH4 emissions upon demethylation of pectin. [ABSTRACT FROM AUTHOR]

1. Recent findings indicate that the interactions among CO2, temperature and water can be substantial, and that the combined effects on the biological systems of several factors may not be predicted from experiments with one or a few factors. Therefore realistic multifactorial experiments involving a larger set of main factors are needed. 2. We describe a new Danish climate change-related field scale experiment, CLIMAITE, in a heath/grassland ecosystem. CLIMAITE is a full factorial combination of elevated CO2, elevated temperature and prolonged summer drought. The manipulations are intended to mimic anticipated major environmental changes at the site by year 2075 as closely as possible. The impacts on ecosystem processes and functioning (at ecophysiological levels, through responses by individuals and communities to ecosystem-level responses) are investigated simultaneously. 3. The increase of [CO2] closely corresponds with the scenarios for year 2075, while the warming treatment is at the lower end of the predictions and seems to be the most difficult treatment to increase without unwanted side effects on the other variables. The drought treatment follows predictions of increased frequency of drought periods in summer. The combination of the treatments does not create new unwanted side effects on the treatments relative to the treatments alone. [ABSTRACT FROM AUTHOR]

Examines the effects of injection method, soil conditions, and slurry properties on the infiltration of several slurry components. Application of slurry by direct injection; Protection of natural ecosystems against excessive nitrogen loads; Dependence of the redistribution of slurry liquids on the physical properties of the injection slit.

Widespread application of sewage sludge to agricultural soils in Denmark has led to concern about the possible accumulation and effects of linear alkylbenzene sulfonate (LAS) in the soil ecosystem. Therefore, we have studied the uptake and degradation of LAS in greenhouse pot experiments. Sewage sludge was incorporated into a sandy soil to give a range from very low to very high applications (0.4 to 90 Mg dry wt. ha−1). In addition, LAS was added as water solutions. The soil was transferred to pots and sown with barley (Hordeum vulgare L. cv. Apex), rape (Brassica napus L. cv. Hyola 401), or carrot (Daucus carota L.). Also, plant‐free controls were established. For all additions there was no plant uptake above the detection limit at 0.5 mg LAS kg−1 d.w, but plant growth stimulated the degradation. With a growth period of 30 d, LAS concentrations in soil from pots with rape had dropped from 27 to 1.4 mg kg−1 dry wt., but in plant‐free pots the concentration decreased only to 2.4 mg kg−1 dry wt. When LAS was added as a spike, the final concentration in soil from planted pots was 0.7 mg kg−1 dry wt., but in pots without plants the final concentration was much higher (2.5 mg kg−1 dry wt.). During degradation, the relative fraction of homologues C10, C11, and C12 decreased, while C13 increased. [ABSTRACT FROM AUTHOR]

Examines the production of nitrous oxide from dentrification and nitrification in temperate forest, grassland and agricultural soils in Europe. Contribution of the nitrification in the nitrous oxide production in the riparian grassland; Emphasis on the need to separate nitrification and denitrification at the process level; Recognition of topography at the field scale.

Presents a description and tests results of an automated system for near-continuous measurement of carbon dioxide (CO2) and nitrous oxide (NO2) fluxes from soil chambers. Materials and methods used; Techniques used to provide means of obtaining data on global fluxes; Results and discussion.

In this work we investigate how lime and crushed concrete waste (CCW) affect carbon cycling in the vadose zone and explore whether these amendments could be employed to mitigate climate change by increasing the transport of CO2 from the atmosphere to the groundwater. We use a combination of experimental and modeling tools to determine ongoing biogeochemical processes. Our results demonstrate that lime and CCW amendments to acid soil contribute to the climate forcing by largely increasing the soil CO2 efflux to the atmosphere. In a series of mesocosm experiments, with barley (Hordeum vulgare L.) grown on podzolic soil material, we have investigated inorganic carbon cycling through the gaseous and liquid phases and how it is affected by different soil amendments. The mesocosm amendments comprised the addition of 0, 9.6, or 21.2 kg m-2 of crushed concrete waste (CCW) or 1 kg lime m-2. The CCW and lime treatments increased the dissolved inorganic carbon (DIC) percolation flux by about 150 and 100%, respectively, compared to the controls. However, concurrent increases in the CO2 efflux to the atmosphere (ER) were more than one order of magnitude higher than increases in the DIC percolation flux. Analysis of soil solutions, coupled reactive-transport modeling studies, and a decrease in soil carbonate contents over the experiment altogether suggested that the increased ER from amended mesocosms was derived from the carbonate contained in the amendments, which, hence, mostly escaped to the atmosphere. Our results are important in the context of climate change due to the widespread application of lime to acidic soils. The CCW amendment had no adverse effects on plant growth and groundwater quality. [ABSTRACT FROM AUTHOR]