Wetting stimulates atmospheric CH4 oxidation by alpine soil

Global warming, as a result of an increase in the mean temperature of the planet, might lead to catastrophic events for humanity. This temperature increase is mainly the result of an increase in the atmospheric greenhouse gases (GHG) concentration. Water vapor, carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N 2 O) are the most important GHG, and human activities, such as industry, livestock and agriculture, contribute to the production of these gases. Methane, at an atmospheric concentration of 1.7 µmol mol −1 currently, is responsible for 16% of the global warming due to its relatively high global warming potential. Soils play an important role in the CH 4 cycle as methanotrophy (oxidation of CH 4) and methanogenesis (production of CH 4) take place in them. Understanding methanogenesis and methanotrophy is essential to establish new agriculture techniques and industrial processes that contribute to a better balance of GHG. The current knowledge of methanogenesis and methanotrophy in soils, anaerobic CH 4 oxidation and methanotrophy in extreme environments is also discussed.

Microorganisms, 2021

Rising temperatures in the Arctic affect soil microorganisms, herbivores, and peatland vegetation, thus directly and indirectly influencing microbial CH4 production. It is not currently known how methanotrophs in Arctic peat respond to combined changes in temperature, CH4 concentration, and vegetation. We studied methanotroph responses to temperature and CH4 concentration in peat exposed to herbivory and protected by exclosures. The methanotroph activity was assessed by CH4 oxidation rate measurements using peat soil microcosms and a pure culture of Methylobacter tundripaludum SV96, qPCR, and sequencing of pmoA transcripts. Elevated CH4 concentrations led to higher CH4 oxidation rates both in grazed and exclosed peat soils, but the strongest response was observed in grazed peat soils. Furthermore, the relative transcriptional activities of different methanotroph community members were affected by the CH4 concentrations. While transcriptional responses to low CH4 concentrations were ...

Soil Biology and Biochemistry, 1997

The short-and long-term effects of NH:-fertilization on soil CH4 oxidation were examined in two upland taiga forests in interior Alaska. Both sites were fertilized for five consecutive snow-free seasons. A paper birch (Bern/a pupyrifera) stand exhibited a delayed inhibition response that became severe (60-70%) by the third season. CH4 flux was not affected in a white spruce (Picea gluucn) stand. In laboratory incubations, (NH&SO4 additions had no effect on extant CH4 oxidation rates in either soil, indicating that neither direct enzymatic inhibition nor acute toxicity were responsible for inhibition in the field. In both sites, maximal CH4 oxidation rates occurred within the upper 20 cm of the mineral soil profile. After the deeper birch soil (20-40 cm) was exposed to ambient atmospheric CH4 (1.8 ~1 I-') for 10 d; however, oxidation increased to rates similar to shallower soils, suggesting that methanotrophs in this soil experienced a physiological upshift in response to enhanced CH4 supply. When (NHd)$Od was added, however, methanotrophic activity did not increase. A similar upshift did not occur in the spruce soil. The CH4 oxidizers in the two soils differed with respect to NH:-sensitivity, salt-sensitivity, response to atmospheric CH4 and maximum CH4 oxidation capacities. Thus, the two different responses of CH4 consumption in the field to NH:-fertilization may have resulted from physiologically distinct CH4 oxidizer communities in the two study sites. 0 1997 Elsevier Science Ltd INTRODUmION Biological CH4 consumption directly from the atmosphere in well-drained soils is estimated to comprise 3-9% of the global atmospheric CH4 sink . Although this figure may seem small, the magnitude of the terrestrial CH4 sink is similar to the estimated annual increase in the atmospheric CH4 pool, making soil CH4 consumption a key determinant of the rate of change in atmospheric CH4 concentration . NHf-fertilization inhibits CH4 consumption in a variety of ecosystems and represents a means by which human activity could reduce the atmospheric CI& sink (Keller et al.

We investigated CH 4 oxidation in afforested soils over a 200-year chronosequence in Denmark including different tree species (Norway spruce, oak and larch) and ages. Samples of the top mineral soil (0-5 cm and 5-15 cm depth) were incubated and analyzed for the abundance of the soil methane-oxidizing bacteria (MOB) and ammonia-oxidizing bacteria (AOB) and archaea (AOA) based on quantitative PCR (qPCR) on pmoA and amoA genes. Our study showed that CH 4 oxidation rates and the abundance of MOB increased simultaneously with time since afforestation, suggesting that the methanotrophic activity is reflected in the abundance of this functional group.

Applied and environmental microbiology, 1998

NH4+ inhibition kinetics for CH4 oxidation were examined at near-atmospheric CH4 concentrations in three upland forest soils. Whether NH4+-independent salt effects could be neutralized by adding nonammoniacal salts to control samples in lieu of deionized water was also investigated. Because the levels of exchangeable endogenous NH4+ were very low in the three soils, desorption of endogenous NH4+ was not a significant factor in this study. The Km(app) values for water-treated controls were 9.8, 22, and 57 nM for temperate pine, temperate hardwood, and birch taiga soils, respectively. At CH4 concentrations of </=15 &mgr;l liter-1, oxidation followed first-order kinetics in the fine-textured taiga soil, whereas the coarse-textured temperate soils exhibited Michaelis-Menten kinetics. Compared to water controls, the Km(app) values in the temperate soils increased in the presence of NH4+ salts, whereas the Vmax(app) values decreased substantially, indicating that there was a mixture of...

Environmental Science & Technology, 2008

The amounts and δ 13 C values of CH 4 at subambient concentrations in soil gas were determined along depth profiles in a U.K. grassland (Bronydd Mawr) and woodland (Leigh Woods). The data were used to determine in situ kinetic isotope effects (KIEs) associated with uptake of atmospheric CH 4 by highaffinity methanotrophic bacteria that inhabit soil. Three independent calculation approaches yielded similar mean KIEs of 1.0211 (0.0020 (n) 18) for Bronydd Mawr and 1.0219 (0.0010 (n) 24) for Leigh Woods. Soil methanotrophy KIEs were largely invariant among oak, beech, and pine forest soils of different ages at Leigh Woods but exhibited a statistically significant relationship with methanotroph biomass in individual plots at Bronydd Mawr and Leigh Woods quantified previously by 13 C stable isotope probing. This finding, albeit based upon a small data set, suggests that 13 C and 12 C partitioning associated with the global soil sink for atmospheric CH 4 may occur in part as a result of biological as well as physical processes. An accurate assessment of the relative importance of each process to the total KIE requires confirmation that significant partitioning of 13 CH 4 and 12 CH 4 occurs in pore spaces as a result of differences in diffusion rates.

Soil Biology and Biochemistry, 1998

The soil organisms that consume atmospheric CH4 in upland ecosystems have not been identified. Whether these organisms benefit from oxidizing atmospheric CH4 or whether CH4 i& cooxidized fortuitously is uncertain. We investigated the general nutritional physiology of atmospheric CH4 oxidizers occurring in three forest soils by starving them of CH4 for 1-2 months and monitoring their abilities to consume atmospheric CH4 over time. In two Alaskan taiga forest soils, CH4 starvation caused the atmospheric CH4 oxidizers to lose their ability to consume CH4, indicating that they benefitted from oxidizing atmospheric CH4, possibly requiring it for maintenance and growth. In contrast, the organisms in a temperate hardwood forest soil from Massachusetts maintained their ability to consume atmospheric CH4 despite prolonged CH4 deprivation, suggesting that they either cooxidized CH4 fortuitously, or that they used alternative substrates for maintenance and growth. These results may point to diverse nutritional physiologies among atmospheric CH4 oxidizers. «;)

Global Change Biology, 2013

In humid ecosystems, the rate of methane (CH 4) oxidation by soil-dwelling methane-oxidizing bacteria (MOB) is controlled by soil texture and soil water holding capacity, both of which limit the diffusion of atmospheric CH 4 into the soil. However, it remains unclear whether these same mechanisms control CH 4 oxidation in more arid soils. This study was designed to measure the proximate controls of potential CH 4 oxidation in semiarid soils during different seasons. Using a unique and well-constrained 3-million-year-old semiarid substrate age gradient, we were able to hold state factors constant while exploring the relationship between seasonal potential CH 4 oxidation rates and soil texture, soil water holding capacity, and dissolved organic carbon (DOC). We measured unexpectedly higher rates of potential CH 4 oxidation in the wet season than the dry season. Although other studies have attributed low CH 4 oxidation rates in dry soils to desiccation of MOB, we present several lines of evidence that this may be inaccurate. We found that soil DOC concentration explained CH 4 oxidation rates better than soil physical factors that regulate the diffusion of CH 4 from the atmosphere into the soil. We show evidence that MOB facultatively incorporated isotopically labeled glucose into their cells, and MOB utilized glucose in a pattern among our study sites that was similar to wet-season CH 4 oxidation rates. This evidence suggests that DOC, which is utilized by MOB in other environments with varying effects on CH 4 oxidation rates, may be an important regulator of CH 4 oxidation rates in semiarid soils. Our collective understanding of the facultative use of DOC by MOB is still in its infancy, but our results suggest it may be an important factor controlling CH 4 oxidation in soils from dry ecosystems.

Biogeosciences, 2008

Frontiers in microbiology, 2013

Methanogens typically occur in reduced anoxic environments. However, in recent studies it has been shown that many aerated upland soils, including desert soils also host active methanogens. Here we show that soil samples from high-altitude cold deserts in the western Himalayas (Ladakh, India) produce CH4 after incubation as slurry under anoxic conditions at rates comparable to those of hot desert soils. Samples of matured soil from three different vegetation belts (arid, steppe, and subnival) were compared with younger soils originating from frontal and lateral moraines of receding glaciers. While methanogenic rates were higher in the samples from matured soils, CH4 was also produced in the samples from the recently deglaciated moraines. In both young and matured soils, those covered by a biological soil crust (biocrust) were more active than their bare counterparts. Isotopic analysis showed that in both cases CH4 was initially produced from H2/CO2 but later mostly from acetate. Ana...