Ng CH4 Research Articles

Carbon Dioxide Driven Methane Consumption in Soil Ecosystem

Soil is an important source and sink of greenhouse gas carbon dioxide (CO2) and methane (CH4). During CH4 consumption CO2 is produced as an end product. It is generally assumed that CO2 would inhibit CH4 consumption due to feedback inhibition. To test the effect of CO2 on methanotrophy, experiments were conducted in microcosms with different initial concentration of CO2 and CH4. Changes in CH4 consumption potential and abundance of pmoA gene copies in relation to CO2 concentration were estimated. In general, CH4 consumption ceased in the absence of CO2. In presence of CO2, rate of CH4 consumption (ng CH4 consumed g−1 soil d−1) varied from 0.283 to 0.481 at 1000 ppm of CH4 and 2.958 to 4.994 at 10,000 ppm of CH4. Abundance of methanotrophs (pmoA gene copies g−1 soil) ranged from 4.5 × 105 to 107 × 105 g−1 soil. A follow up experiment was carried out to evaluate CH4 consumption in the presence or absence of CO2, which proved that CO2 is essential for CH4 consumption. Study concludes that CO2 is a precursor molecule for CH4 consumption in soil ecosystem and methanotrophs are capable of mitigating both the greenhouse gases, CH4 and CO2.

Microbial Communities in Standing Dead Trees in Ghost Forests are Largely Aerobic, Saprophytic, and Methanotrophic

Standing dead trees (snags) are recognized for their influence on methane (CH4) cycling in coastal wetlands, yet the biogeochemical processes that control the magnitude and direction of fluxes across the snag-atmosphere interface are not fully elucidated. Herein, we analyzed microbial communities and fluxes at one height from ten snags in a ghost forest wetland. Snag-atmosphere CH4 fluxes were highly variable (− 0.11–0.51 mg CH4 m−2 h−1). CH4 production was measured in three out of ten snags; whereas, CH4 consumption was measured in two out of ten snags. Potential CH4 production and oxidation in one core from each snag was assayed in vitro. A single core produced CH4 under anoxic and oxic conditions, at measured rates of 0.7 and 0.6 ng CH4 g−1 h−1, respectively. Four cores oxidized CH4 under oxic conditions, with an average rate of − 1.13 ± 0.31 ng CH4 g−1 h−1. Illumina sequencing of the V3/V4 region of the 16S rRNA gene sequence revealed diverse microbial communities and indicated oxidative decomposition of deadwood. Methanogens were present in 20% of the snags, with a mean relative abundance of < 0.0001%. Methanotrophs were identified in all snags, with a mean relative abundance of 2% and represented the sole CH4-cycling communities in 80% of the snags. These data indicate potential for microbial attenuation of CH4 emissions across the snag-atmosphere interface in ghost forests. A better understanding of the environmental drivers of snag-associated microbial communities is necessary to forecast the response of CH4 cycling in coastal ghost forest wetlands to a shifting coastal landscape.

Differential influence of legume and cereal crop residue incorporation on methane production and consumption in a tropical vertisol

Crop residue incorporation to the soil is an essential strategy to improve soil quality and crop productivity in order to attain sustainable development goals. Experiments were conducted to evaluate the differential effect of crop residues on CH4 production and consumption in a tropical vertisol. Soils were incubated with residues of cereals (maize and wheat) and legumes (chickpea and soybean) at 1% w/w, under non-flooded and flooded conditions to estimate CH4 consumption and CH4 production rates, respectively. Rates of CH4 production (ng CH4 produced g/soil/day) varied from 0.068 to 0.107 with lowest in chickpea residue and highest in wheat straw amended soil. CH4 consumption rates (ng CH4 consumed g/soil/day) was highest (0.79) in wheat straw amended soil and lowest (0.53) in chickpea residue amended soil. Organic carbon (%) and available NO3− (mM) contents increased significantly (P &gt; 0.05) in residue amended soils over control under both flooded (methanogenic) and non-flooded (methane consuming) conditions. Abundance of methanogens and methanotrophs was estimated as mcr and pmoA gene copies g−1 soil, indicated that both the microbial groups were stimulated significantly due to the amendment of crop residues. Linear models exhibited significant correlation among CH4 production and consumption with organic carbon, available nitrate and microbial abundance. The study highlights that crop residues incorporation influences both CH4 consumption and production potential of soil and this effect is more pronounced with biomass of cereals than legumes.

Methanotrophs dominate methanogens and act as a methane sink in a subterranean karst cave

Karst caves are potential sinks of atmospheric methane due to microbial consumption. However, knowledge gaps on methanogens (methane producing microorganisms) and their interaction with methane-oxidizing bacteria (MOB) hinder our further understanding about methane dynamics in karst caves. Here we reported methanogenic community composition and their interaction with MOBs in the Heshang Cave to comprehensively understand methane cycling in subsurface biosphere. MOBs in karst cave were dominated by high-affinity MOB, upland soil cluster (USC), with USCγ pmoA gene abundance within the range of 1.34 × 104 to 1.8 × 107 copies·g−1 DW. In contrast, methanogens were dominated by Methanoregula and cluster ZC-I. The mcrA numbers were 7.21 × 103 to 8.31 × 104 copies·g−1 DW, 1–3 orders of magnitude lower than those of MOB. The inter-domain network analysis indicated that MOBs and methanogens cooperated more in the interior of the cave. Despite of the higher number of methanogenic nodes in the network, MOB dominated the keystone taxa, suggesting a leading functional role of MOB. MOB in caves showed a comparable with or higher potential methane oxidizing rate (PMOR, 0.63 ng CH4·g−1 DW·h−1 in sediment versus 11.02 ng CH4·g−1 DW·h−1 in weathered rock) than those in soils, whereas methane produced by methanogens was undetected. Collectively, high absolute abundances of MOB, high PMORs, the dominance of methanotrophic keystone taxa in the inter-domain network confirmed the superiority of MOBs over methanogens in the oligotrophic karst cave, mounting new evidence on caves as an important methane sink in terms of the interaction between methanogens and MOBs.

Photovoltaics literature survey (no. 182)

Photovoltaics literature survey (no. 182)

Niche differentiation of atmospheric methane-oxidizing bacteria and their community assembly in subsurface karst caves.

Karst caves are recently proposed as atmospheric methane sinks in terrestrial ecosystems. Despite of the detection of atmospheric methane-oxidizing bacteria (atmMOB) in caves, we still know little about their ecology and potential ability of methane oxidation in this ecosystem. To understand atmMOB ecology and their potential in methane consumption, we collected weathered rocks and sediments from three different caves in southwestern China. We determined the potential methane oxidization rates in the range of 1.25 ± 0.08 to 1.87 ± 0.41 ng CH4 g-1 DW h-1 , which are comparable to those reported in forest and grassland soils. Results showed that alkaline oligotrophic caves harbour high numbers of atmMOB, particularly upland soil cluster (USC), which significantly correlated with temperature, CH4 and CO2 concentrations. The absolute abundance of USCγ was higher than that of USCα. USCγ-OPS (open patch soil) and USCγ-SS (subsurface soil) dominated in most samples, whereas USCα-BFS (boreal forest soil) only predominated in the sediments near cave entrances, indicating niche differentiation of atmMOB in caves. Overwhelming dominance of homogenous selection in community assembly resulted in convergence of atmMOB communities. Collectively, our results demonstrated the niche differentiation of USC in subsurface alkaline caves and their non-negligible methane-oxidizing potential, providing brand-new knowledge about atmMOB ecology in subsurface biosphere.

Impact of land use change on soil methane fluxes and diffusivity in Pampean plains, Argentina

Upland soils are the main methane (CH4) biological sink, and may be affected by land-use change. Changes in land uses and soil management affect soil properties that control diffusion of gases, which in combination with microbial activity, determine CH4 flux (fCH4) through the soil. Net CH4 fluxes and diffusivity -estimated by the CH4 diffusion coefficient- were measured in three common land uses typical from Pampean plains, South America (natural grassland NG; Eucalyptus globulus Labill. afforestation E; and agricultural land AL: oat, soybean and red clover in successive cultivation) during two years (March 2017–March 2019). Methane fluxes in the soil-atmosphere interface were measured using the static chamber technique, and a diffusion model was applied to estimate soil CH4 diffusivity from soil porosity. We aimed to quantify the effect of land use change (both E and AL vs. NG, the reference system) on fCH4 and gas diffusivity due to changes in the soil parameters. Soils were net sinks in the three land uses, with mean CH4 flux higher in the afforestation, intermediate in the natural grassland and lower in the agricultural land (− 10.99 ± 5.85, − 8.9 ± 5.32 and − 4.58 ± 4.19 ng CH4 m−2 s−1, respectively). CH4 fluxes varied significantly through seasons and space coinciding with variations in water-filled pore space and air-filled pore space variables (ρ > 0.7 and <−0.7 respectively; p < 0.05). Land-use change metric for methane flux ΔfCH4 was − 2.1 ± 3.7 and 4.4 ± 2.5 for NG-E and NG-AL, respectively, indicating a significant increment in net CH4 uptake when the natural grassland is afforested and a decrease when it was converted to agricultural use. This change was mainly explained by changes in soil physical properties (bulk density, soil water content, WFPS and air filled porosity). In relation to this, soil CH4 diffusion coefficient followed the same pattern as fCH4 (0.024 ± 0.011; 0.015 ± 0.007 and 0.008 ± 0.007 cm2 s−1 for E, NG and AL respectively); and allowed us to recalculate mean CH4 fluxes. Theoretical and in situ measured CH4 fluxes were similar and followed the same patterns across land uses, suggesting the possibility to determine CH4 fluxes by means of simple measures of soil properties (bulk density and soil water content) and soil CH4 gradient concentration.

Atmospheric Methane Consumption and Methanotroph Communities in West Siberian Boreal Upland Forest Ecosystems

Upland forest ecosystems are recognized as net sinks for atmospheric methane (CH4), one of the most impactful greenhouse gases. Biological methane uptake in these ecosystems occurs due to the activity of aerobic methanotrophic bacteria. Russia hosts one-fifth of the global forest area, with the most extensive forest landscapes located in West Siberia. Here, we report seasonal CH4 flux measurements conducted in 2018 in three types of stands in West Siberian middle taiga–Siberian pine, Aspen, and mixed forests. High rates of methane uptake of up to −0.184 mg CH4 m−2 h−1 were measured by a static chamber method, with an estimated total growing season consumption of 4.5 ± 0.5 kg CH4 ha−1. Forest type had little to no effect on methane fluxes within each season. Soil methane oxidation rate ranged from 0 to 8.1 ng CH4 gDW−1 h−1 and was negatively related to water-filled pore space. The microbial soil communities were dominated by the Alpha- and Gammaproteobacteria, Acidobacteriota and Actinobacteriota. The major group of 16S rRNA gene reads from methanotrophs belonged to uncultivated Beijerinckiaceae bacteria. Molecular identification of methanotrophs based on retrieval of the pmoA gene confirmed that Upland Soil Cluster Alpha was the major bacterial group responsible for CH4 oxidation.

English

‘ No thi ng Ch an ge s i f No t hi ng Ch an ge s’ Treating a case of full mouth rehabilitation has remained a challenge till date. Dentistry has witnessed many advancements in terms of material science, technology and treatment procedures. What has not evolved is the thought process of application of these newer methods and technology. Any treatment procedure performed on a patient is not a straightforward mathematical calculation which can be implemented in a specified manner. Clinical processes, especially a case of full mouth rehabilitation requires comprehensive knowledge and understanding of the stomatognathic system. The word rehabilitation in itself conveys responsibility. A lot is involved at both the ends - the receiver (patient) and the donor (the rehabilitation specialist). The oxford dictionary defines rehabilitation as ‘The action of restoring someone to health or normal life through training and therapy after imprisonment, addiction, or illness.’ 1 It is a great responsibility on restoring dentist to bring the abnormal and compromised oral functions back on track. The multidisciplinary dimension of the treatment cannot be ignored. Although the culmination of an elaborate treatment is by a restoring specialist which happens to be prosthodontist most of the time, other specialists such as endodontist, periodontist, oral surgeon, orthodontist and an oral radiologist play a significant role throughout the planning and execution. It is advisable to seek expert opinion and include specialty procedures whenever deemed necessary.

Changes in &lt;i&gt;pmoA&lt;/i&gt; Gene Containing Methanotrophic Population and Methane Oxidation Potential of Dry Deciduous Tropical Forest Soils

In natural ecosystems such as forests topographical gradients, species composition variability and seasonality, are the potential drivers of methane (CH 4 ) metabolism, and thus, of the population size and activities of methane oxidizing bacteria (MOB). To test the hypothesis that topography, tree species and seasonal variability influence MOB population and soil methane oxidation potential (MOP), we conducted two consecutive years of study selecting three sites in a dry deciduous tropical forest in Chandauli district of eastern Uttar Pradesh, India. The qPCR results showed a large variation in MOB population size (copies g −1 dws), ranging from 1.0 × 10 6 to 2.1 × 10 7 and 9.0 × 10 5 to 2.2 × 10 7 during 2016 and 2017 respectively. The distribution of MOB population revealed the trend: hilltop > middle > hillbase with its maxima in the winter and minima in the rainy season. Laboratory incubation study revealed a similar trend in soil MOP (ng CH 4 g −1 h −1 dws), it varied from 10.6 to 20.6 and 10.5 to 20.7 during 2016 and 2017 respectively. The outer canopy soils showed lower MOB population and MOP compared to under canopy soils of tree species Butea monosperma, Madhuca indica and Tectona grandis during both years of study. The topography, season and tree species significantly influenced the MOB population size and MOP. Soil MOP showed a highly significant correlation (r = 0.89; p < 0.01) with MOB population, and a negative correlation was found with soil moisture (r = 0.76; p < 0.01). The results indicate that the dry deciduous tropical forest soils are potential sinks of atmospheric CH 4 wherein, the MOB population characteristically responds to topographical changes, tree species and seasonal shifts driving collectively the overall MOP of forest soils.

Temporal shift in methanotrophic community and methane oxidation potential in forest soils of dry tropics: high-throughput metagenomic approach

Forest soil contributes to global methane (CH4) cycle as the natural sink for atmospheric CH4 by methane-oxidizing bacteria (MOB). In this study, high-throughput sequencing of pmoA gene amplicons based approach was used to investigate temporal variations in molecular diversity of MOB in soil of tropical dry forest. Quantitative PCR (qPCR) analysis revealed pmoA and 16S rRNA gene copy numbers (copies g−1 dws) ranging from 2.23 × 106 to 14.62 × 106 and from 0.92 × 109 to 14.99 × 109, respectively, in the year 2016. In 2017, the respective values varied from 1.96 × 106 to 13.62 × 106 and from 2.55 × 109 to 20.15 × 109, respectively. The sequence analysis revealed the existence of both type I and type II methanotrophs in soils. The average observed OTUs were about 800/sample, and Shannon diversity index ranged between 4.24 and 6.22 being highest in winter season. The rice paddy clusters (RPCs), Methylocystis, Methlylocystis-Methylosinus and JR2 and JR3, dominated the methanotrophic community with relative abundance of 32.7–50.2, 15.4–34.2, 0.45–15.8, 0.0–17.8 and 1.6–19.2%, respectively. Relatively, higher CH4 oxidation potential (MOP) (ng CH4 g−1 h−1 dws) was observed in winter (14.12) compared with rainy (2.10) and summer (3.72) coinciding with high methanotrophic diversity and abundance. Overall, the study suggests that tropical dry deciduous forest soils favour considerable range of methanotrophic diversity and abundance that positively correlates with MOP of soils across season.

Sea animal activity controls CO2, CH4 and N2O emission hotspots on South Georgia, sub-Antarctica

Colonies of mammals and sea birds are known hotspots for biogeochemical cycles with potentially large element stocks and fast turnover in the soil. Although penguin and seal colonies are sites with potentially extremely fast biogeochemical turnover, these sites as potential sources of GHG have largely been neglected. This study aims to quantify magnitudes and environmental drivers of GHG fluxes effected by the activity of Antarctic fur seal (Arctocephalus gazella) and King penguin (Aptenodytes patagonicus) in South Georgia, sub-Antarctica. In-situ CO2 and CH4 gas flux measurements were combined with laboratory incubations of intact soil cores collected from sites along two transects away from a seal and a penguin colony. Variations in laboratory incubations were consistent with the in-situ fluxes measured in February 2017, and showed high ecosystem respiration rates at colonies (mean 44.3 μg CO2 cm−3 h−1 for seal colony, and 52.9–159 μg CO2 cm−3 h−1 for penguin colony) and a marked decrease away from these hotspots. Moderate methane production rates were found within the colonies (mean 0.1 ng CH4 cm−3 h−1 for seal colony, 44–145.5 ng CH4 cm−3 h−1 for penguin colony), while relatively high consumption rates (mean −1.8 ng CH4 cm−3 h−1) occurred outside the colonies. Incubations also included N2O production rates, which were highly variable within the colonies (1.1–293 ng N2O cm−3 h−1 for seal colony, 0.8–594.7 ng N2O cm−3 h−1 for penguin colony) and decreased markedly to near zero away from the colonies. Bacterial and pmoA communities and drivers of GHG turnover and microbe community along both transects varied according to the sea animal activity intensity gradient. This is the first study at these latitudes to quantify the overall capacity of in-situ soil methane uptake at hot spots linked to sea animal colonies versus ambient conditions. All colony sites in this study were net sources of N2O, while sites beyond colonies, which dominate the ice-free areas in South Georgia, were sinks of methane.

Methanogenic potential of lignites in Poland

Microbial coal gasification is of great interest due to the necessity to develop more environmentally friendly methods of energy production. The two main lignite deposits in Poland (Bełchatów and Turów) have been studied for their natural methanogenic potential. The biological origin of gases occurring in the investigated strata was confirmed by carbon stable isotope fractionation. Methanogenesis was examined via long-term anaerobic microcosm incubations which were performed using coal extracted from upper- and lower- most parts of the deposits at 10 to 40 °C. Present-day methane formation was distinguished from physical desorption by application of 2-bromoethane sulphonate (BES), an inhibitor of terminal methane formation steps. Furthermore, glycerol dialkyl glycerol tetraethers (GDGTs), were used to reconstruct the palaeoenvironmental conditions and explain how the lignite environment affects the methanogenic consortia.The data obtained reveal that microbial degradation of lignite occurs in the uppermost layers of the coal seam at the Bełchatów lignite mine. Methane release was up to 0.064 ng CH4 g−1 day−1 at 30 °C. Biomarker analysis shows high abundance of GDGT-0 confirming the presence of methanogenic Archaea and implies that pH was an important factor regulating the development and activity of organic matter-degrading microbiota under neutral conditions as the most favourable for the methanogens.Inactivation of methanogenic pathways by BES led to stimulation of bacterial respiration, which suggests the presence of an active bacterial community, putatively involved in the decomposition of lignin. The biomarker analysis, depicting metabolic capabilities of the microbiota (especially GDGT-0 and GDGT-0/crenarchaeol ratio) and recognition of palaeoenvironmental conditions, is a useful tool to determine the methanogenic potential of coals.

Interactive effect of climate factors, biochar and insecticide chlorpyrifos on methane consumption and microbial abundance in a tropical Vertisol

Climate change may increase the pest infestation leading to intensive use of insecticides. However, the effect of insecticide and climate factors on soil methane (CH4) consumption is less understood. A laboratory experiment was carried out to evaluate the effect of temperature (15 °C, 35 °C, and 45 °C), moisture holding capacity (MHC) (60%, 100%), biochar (0%, 1%) and chlorpyrifos (0 ppm, 10 ppm) on CH4 consumption and microbial abundance in a tropical Vertisol of central India. Methane consumption rate k (ng CH4 consumed g−1 soil d−1) varied from 0.065 ± 0.005 to 0.608 ± 0.018. Lowest k was in 15 °C-60% moisture holding capacity (MHC)-no biochar and with 10 ppm chlorpyrifos. Highest k was in 35 °C-100% MHC-1% biochar and without (0 ppm) chlorpyrifos. Cumulative CO2 production (ng CO2 produced g−1 soil d−1) varied from 446 ± 15 to 1989 ± 116. Both CH4 consumption and CO2 production peaked in the treatment of 35 °C-100% MHC-1% biochar. Chlorpyrifos inhibited CH4 consumption irrespective of treatments. Abundance of 16S rRNA of eubacteria (× 106 g−1 soil) varied from 2.33 ± 0.58 to 85.67 ± 7.00. Abundance of 16S rRNA genes representing Actinomycetes (× 104 g−1 soil) varied from 7.67 ± 1.53 and pmoA gene (Methanotrophs) (× 105 g−1 soil) varied from 1.23 ± 0.59 to 34.33 ± 6.51. Chlorpyrifos inhibited abundance of heterotrophic bacteria and methanotrophs but stimulated actinomycetes. Biochar stimulated the CH4 consumption, CO2 production and microbial abundance. Study highlighted that use of chlorpyrifos under climate change factors may inhibit CH4 consumption but the use of biochar may alleviate the negative effect of the chlorpyrifos.

Temperature response of ex-situ greenhouse gas emissions from tropical peatlands: Interactions between forest type and peat moisture conditions

Climate warming is likely to increase carbon dioxide (CO2) and methane (CH4) emissions from tropical wetlands by stimulating microbial activity, but the magnitude of temperature response of these CO2 and CH4 emissions, as well as variation in temperature response among forest types, is poorly understood. This limits the accuracy of predictions of future ecosystem feedbacks on the climate system, which is a serious knowledge gap as these tropical wetland ecosystems represent a very large source of greenhouse gas emissions (e.g. two-thirds of CH4 emissions from natural wetlands are estimated to be from tropical systems). In this study, we experimentally manipulated temperatures and moisture conditions in peat collected from different forest types in lowland neotropical peatlands in Panama and measured how this impacted ex-situ CO2 and CH4 emissions. The greatest temperature response was found for anaerobic CH4 production (Q10 = 6.8), and CH4 consumption (mesic conditions, Q10 = 2.7), while CO2 production showed a weaker temperature response (Q10 < 2) across the three moisture treatments. The greatest temperature response of CO2 production was found under flooded oxic conditions. Net emissions of CO2 and CH4 were greatest from palm forest under all moisture treatments. Furthermore, the temperature response of CH4 emissions differed among dominant vegetation types with the strongest response at palm forest sites where fluxes increased from 42 ± 25 to 2166 ± 842 ng CH4 g−1 h−1 as temperatures were raised from 20 to 35 °C. We conclude that CH4 fluxes are likely to be more strongly impacted by higher temperatures than CO2 fluxes but that responses may differ substantially among forest types. Such differences in temperature response among forest types (e.g. palm vs evergreen broad leaved forest types) need to be considered when predicting ecosystem greenhouse gas responses under future climate change scenarios.

Afforested sites in a temperate grassland region: influence on soil properties and methane uptake

Methane (CH4) flux at the soil-atmosphere interface (SAI) results from the balance between CH4 production (methanogenesis) and CH4 consumption (methanotrophy). The latter predominates in well-aerated mineral soils; is affected by a combination of abiotic and biotic factors, especially soil diffusivity, which depends on soil properties, and methanotroph activity. This work reports results of CH4 fluxes from afforested sites located in a temperate region of formerly native grassland in Buenos Aires Province (Argentina, Southern Hemisphere), taking a naturalized pasture as a reference. Methane concentration [CH4] and soil parameters along the soil profile were also measured to understand intersite differences in CH4 fluxes at the SAI, that could be related to vegetation cover and its influence on soil properties and therefore, on CH4 soil diffusivity. At all sites soils were CH4 sinks in the range of −3.55 to −14.39 ng CH4 m−2 s−1; the naturalized pasture presented the weakest one. Intersite differences in CH4 fluxes may result from differences observed in [CH4] profiles and CH4 diffusion coefficients. [CH4] variation could be explained mainly by differences in silt and clay content and bulk density that affect CH4 soil diffusivity. These could be the result of afforestation that seems to improve the physical and biological soil attributes linked to CH4 consumption as it meliorates its diffusivity.

Stimulation of methane oxidation by CH4-emitting rose chafer larvae in well-aerated grassland soil

In this study, the impact of rose chafer (Cetonia aurata L.) larvae on net and gross methane (CH4) fluxes in soil from an old permanent grassland site (Giessen, Germany) was investigated. Previous studies at this site suggested the existence of Scarabaeidae larvae-induced “CH4-emitting hot spots” within the soil profile which may subsequently lead to increased CH4 oxidation. The net (soil + larvae) and gross (soil and larvae separated) CH4 fluxes were studied in a 3-month laboratory incubation. Addition of larvae changed the soil from a net sink (−330 ± 11 ng CH4 kg−1 h−1) to a net source (637 ± 205 ng CH4 kg−1 h−1). Supply of plant litter to the soil + larvae incubation jars tended to increase CH4 emissions which was not significant due to large variability. After 11–13 weeks of incubation, the net soil CH4 oxidation was significantly stimulated by 13–21% in the treatments containing larvae when these were taken out. Analysis of archaeal 16S rRNA genes revealed that the majority of the obtained clones were closely related to uncultured methanogens from guts of insects and other animals. Other sequences were relative to cultivated species of Methanobrevibacter, Methanoculleus, and Methanosarcina. Hence, Scarabaeidae larvae in soils (i) may represent an underestimated source of CH4 emissions in aerobic upland soils, (ii) may stimulate gross CH4 consumption in their direct soil environment, and, thus, (iii) contribute to the spatial heterogeneity often observed in the field with closed-chamber measurements. Long-term CH4-flux balances may be wrongly assessed when “exceptional” net CH4 flux rates (due to larvae hot spots) are excluded from data sets.

Emission of methane, carbon monoxide, carbon dioxide and short-chain hydrocarbons from vegetation foliage under ultraviolet irradiation.

The original report that plants emit methane (CH 4) under aerobic conditions caused much debate and controversy. Critics questioned experimental techniques, possible mechanisms for CH 4 production and the nature of estimating global emissions. Several studies have now confirmed that aerobic CH 4 emissions can be detected from plant foliage but the extent of the phenomenon in plants and the precise mechanisms and precursors involved remain uncertain. In this study, we investigated the role of environmentally realistic levels of ultraviolet (UV) radiation in causing the emission of CH 4 and other gases from foliage obtained from a wide variety of plant types. We related our measured emissions to the foliar content of methyl esters and lignin and to the epidermal UV absorbance of the species investigated. Our data demonstrate that the terrestrial vegetation foliage sampled did emit CH 4, with a range in emissions of 0.6–31.8 ng CH 4 g−1 leaf DW h−1, which compares favourably with the original reports of experimental work. In addition to CH 4 emissions, our data show that carbon monoxide, ethene and propane are also emitted under UV stress but we detected no significant emissions of carbon dioxide or ethane.

Endogeic earthworms lower net methane production in saturated riparian soils

Methane (CH4) emissions from soils are erratic, the typical pattern being long periods of imperceptible emissions punctuated by short periods of high CH4 release. These short peaks are a result of higher gross CH4 production rates (methanogenesis) relative to gross rates of CH4 consumption (methanotrophy), and can be induced by rising water table level and periodic flooding in riparian soils. Soil fauna, specifically earthworms, affected soil CH4 cycling in some studies. We studied the effect of the endogeic earthworm Aporrectodea turgida (Eisen) on CH4 production and consumption activities in saturated and field-moist soils collected from a riparian area in southern Quebec, Canada. Saturated (100 % water-filled pore space, WFPS) and field-moist soils (31.5 % WFPS) were incubated at 20 °C, with difluoromethane added to quantify gross CH4 production (i.e., methanogenesis activity) and consumption rates (i.e., methanogenic activity). The pattern of gross CH4 consumption followed that of gross CH4 production, and net CH4 production was an order of magnitude lower than the gross rate. Gross rates of CH4 production were 41 to 65 ng CH4 g−1 h−1, gross CH4 consumption rates were estimated to be 37 to 63 ng CH4 g−1 h−1, and the net CH4 production ranged from 2 to 4 ng CH4 g−1 h−1. Saturated soils with earthworms had consistently lower net CH4 production, relative to field-moist and saturated soils without earthworms. This means that earthworms could potentially reduce the impact of periodic flooding on CH4 emissions from riparian soils.

2013年生态学术年会论文——遮荫对米槠和杉木原位排放甲烷的影响

Although there were controversies on whether terrestrial plants emit methane( CH4) under aerobic conditions, more and more researches confirmed that plants themselves did emit CH4.,and sunlight was one of the important factors which effected the CH4emissions from plants. In this study,we used stable carbon isotope-labelling technique combining with potted experiments to discussed the source of methane emitted in situ from Castanopsis carlesii and Cunninghamia lanceolata and their responses to sunlight and shadowing. The results showed that there were significant differences in the stable carbon isotopic value of labeled and unlabeled leaves between Castanopsis carlesii and Cunninghamia lanceolata,the stable carbon isotopic value( δ13C) of the labeled Castanopsis carlesii and Cunninghamia lanceolata leaves was 128.9.and 71.1 times higher than that of the unlabeled ones. Similarly,there were significant differences in the stable carbon isotopic value of methane from the labeled branch leaves of Castanopsis carlesii and Cunninghamia lanceolata and that from the unlabeled ones. Been sealed 2 hours,the stable carbon isotopic value of methane( δ13CH4) isotopic signatures of methane, which emitted from Castanopsis carlesii and Cunninghamia lanceolata were 21. 1 and 28. 2 times higher than that of the unlabeled ones. These results indicated that the most detected CH4emission during our experiments were from plants themselves. Shadowing and natural lighting experiments showed that the CH4emission rate of Cunninghamia lanceolata was29% higher than Castanopsis carlesii under sunlight,the mean CH4emission rates of them were 6.3 and 4.88 ng CH4·g-1DW ·h-1,respectively. The fluctuation rule of CH4emission rates are similar between the two species under sunlight,both of them were reduced at first,and then increased,finally,they were reduced again. However,the rule was different under shadowing,the mean CH4emission rate of Cunninghamia lanceolata was 23% lower than under sunlight,especially after 15 days,the CH4emission rate reduced significantly,until June 30th,it was only 15.1% of that detected under sunlight. The mean CH4emission rate of Castanopsis carlesii were not significantly different under sunlight and shadowing,they were 6.3 and 5.67ng CH4·g-1DW·h-1,respectively; but after 5 days,the CH4emission rate was 71% higher than under sunlight,it reached up to 10.45 ng CH4·g-1DW·h-1,then it dropped sharply,and obviously lower than under sunlight,until June 30th, it was only 43.1% of that detected under sunlight. These results suggested that sunlight promoted methane emission rate from plants.