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1.
We describe experiments to better understand how CH4 oxidation rates by different methanotroph communities respond to changing CH4 concentrations. We used a novel system of automatically monitored chambers to investigate the response of CH4 oxidation rates in a New Zealand pasture and adjacent pine forest soil exposed to varying atmospheric CH4 concentrations.Type II methanotrophs that dominate CH4 oxidation in the forest soil became progressively saturated as CH4 concentrations rose from ambient (1.8 ppmv) to 570 ppmv, as shown by a decrease in uptake efficiency from 20% to 2% removal. By contrast, CH4 oxidation in the pasture soil where Type I methanotrophs dominate increased in proportion to the increase in CH4 inlet concentration, oxidising about 2% of the inlet CH4 flux throughout. Modelling based on Michaelis-Menten kinetics revealed that low-affinity (Type I) methanotrophs were solely responsible for CH4 oxidation in pasture soils, whereas high affinity (Type II) methanotrophs only contributed about 10% of the CH4 oxidation in the forest soil. Increased aeration status using a soil–perlite (1:1) mixture doubled CH4 oxidation rates at both ambient (1.8 ppmv) and 40 ppmv atmospheric CH4. A similar volcanic soil previously exposed for 8 y to high CH4 fluxes from a landfill had removal efficiencies consistently above 95% for atmospheric CH4 concentrations up to 7500 ppmv when the CH4 oxidation rate was7000 μg CH4 kg−1soil h−1.  相似文献   

2.
Afforestation of pastures in New Zealand reduces methane (CH4) production from soil, while also stimulating oxidation of atmospheric CH4 by soil methanotrophs. However, neither the mechanisms by which soil CH4 oxidation is enhanced by afforestation, nor how long after forest planting tree-dependent responses in CH4 oxidation become detectable are fully known. Here, we investigated the effects of different-aged stands (5-20 y) of the exotic pine (Pinus radiata (D. Don)) on CH4 oxidation and methanotrophic community structure in soils, compared with adjacent, long-established pastures. Two of the pastures were on volcanic soils and two were on non-volcanic soils. Although the CH4 fluxes in soils from these young stands were not significantly different from those in the associated pastures, the rate of oxidation of added 13CH4 was higher in the pine soils. Both fluxes and 13CH4 oxidation rates were higher in the volcanic than the non-volcanic soils. Combined phospholipid fatty acid (PLFA) and stable isotope probe (SIP) analyses suggested that type II methanotrophs (PLFA C18:1ω7) were most active in all soils followed by uncultivable bacteria (C17:0ai). Molecular analysis of the methanotrophic community structure using pmoA (particulate methane monooxygenase) genes suggested that a particular type II methanotroph (TRF 35) was dominant in all soils, but more so in the pine than in pasture soils. A type I methanotroph (TRF 245) was more prevalent in the pasture than in associated pine soils, whereas TRF 128 (a type II methanotroph) was slightly more dominant in soils under pine. Cloning and sequencing data suggest TRFs 35 and 128, which differ from one another, belong to distant relatives of Methylocapsa sp; TRF 245 is related to Methylococcus capsulatus. Land-use change resulted in changes in soil bulk density, porosity, moisture contents and in methanotrophic community structure. Methane oxidation rates were most closely related to soil moisture, as well as to the methanotrophic community structure, and nitrate-N, extractable C and total C concentrations. Stepwise multiple regression also suggested a weak effect (P = 0.06) of stand age on CH4 oxidation rate. By contrast, the responses of the methanotrophic community structure to this land-use change were more readily detected by the specific molecular analyses, and indicated a predominance of type II methanotrophs in pine soils.  相似文献   

3.
The soil microbial communities of a landfill cover substrate, which was treated with landfill gas (100 l CH4 m?2 d?1) and landfill leachate for 1.5 years, were investigated by phospholipid fatty acid (PLFA), ergosterol and respiratory quinone analyses. The natural 13C depletion of methane was used to assess the activity of methanotrophs and carbon turnover in the soil system. Under methane addition, the soil microbial community was dominated by PLFAs (14:0 and 16:1 isomers) and quinones (ubiquinone-8 and 18-methylene-ubiquinone-8) related to type I methanotrophs, and 18:1 PLFAs contained in type II methanotrophs. While type I methanotrophic PLFAs were 13C depleted, i.e. type I methanotrophs were actively oxidising and assimilating methane, 13C depletion of 18:1 PLFAs was low and inconsistent with their abundance. This, possibly reflects isotopic discrimination, assimilation of carbon derived from type I methanotrophs and a high contribution of non-methanotrophic bacteria to the 18:1 isomers. Landfill leachate irrigation caused the methanotrophic community to shift closer to the soil surface. It also decreased 18:1 PLFAs, while type I methanotrophs were probably stimulated. Gram positive bacteria, but not fungi, were also 13C depleted and consequently involved in the secondary turnover of carbon originating from methanotrophic bacteria. Cy17:0 PLFA was 13C depleted in deep soil layers, indicating anaerobic methane oxidation.  相似文献   

4.
Soil moisture strongly controls the uptake of atmospheric methane by limiting the diffusion of methane into the soil, resulting in a negative correlation between soil moisture and methane uptake rates under most non-drought conditions. However, little is known about the effect of water stress on methane uptake in temperate forests during severe droughts. We simulated extreme summer droughts by exclusion of 168 mm (2001) and 344 mm (2002) throughfall using three translucent roofs in a mixed deciduous forest at the Harvard Forest, Massachusetts, USA. The treatment significantly increased CH4 uptake during the first weeks of throughfall exclusion in 2001 and during most of the 2002 treatment period. Low summertime CH4 uptake rates were found only briefly in both control and exclusion plots during a natural late summer drought, when water contents below 0.15 g cm−3 may have caused water stress of methanotrophs in the A horizon. Because these soils are well drained, the exclusion treatment had little effect on A horizon water content between wetting events, and the effect of water stress was smaller and more brief than was the overall treatment effect on methane diffusion. Methane consumption rates were highest in the A horizon and showed a parabolic relationship between gravimetric water content and CH4 consumption, with maximum rate at 0.23 g H2O g−1 soil. On average, about 74% of atmospheric CH4 was consumed in the top 4-5 cm of the mineral soil. By contrast, little or no CH4 consumption occurred in the O horizon. Snow cover significantly reduced the uptake rate from December to March. Removal of snow enhanced CH4 uptake by about 700-1000%, resulting in uptake rates similar to those measured during the growing season. Soil temperatures had little effect on CH4 uptake as long as the mineral soil was not frozen, indicating strong substrate limitation of methanotrophs throughout the year. Our results suggest that the extension of snow periods may affect the annual rate of CH4 oxidation and that summer droughts may increase the soil CH4 sink of temperate forest soils.  相似文献   

5.
Afforestation and reforestation of pastures are key land-use changes in New Zealand that help sequester carbon (C) to offset its carbon dioxide (CO2) emissions under the Kyoto Protocol. However, relatively little attention has been given so far to associated changes in trace gas fluxes. Here, we measure methane (CH4) fluxes and CO2 production, as well as microbial C, nitrogen (N) and mineral-N, in intact, gradually dried (ca. 2 months at 20 °C) cores of a volcanic soil and a heavier textured, non-volcanic soil collected within plantations of Pinus radiata D. Don (pine) and adjacent permanent pastures. CH4 fluxes and CO2 production were also measured in cores of another volcanic soil under reverting shrubland (mainly Kunzea var. ericoides (A. Rich) J. Thompson) and an adjacent pasture. CH4 uptake in the pine and shrubland cores of the volcanic soils at field capacity averaged about 35 and 14 μg CH4-C m−2 h−1, respectively, and was significantly higher than in the pasture cores (about 21 and 6 μg CH4-C m−2 h−1, respectively). In the non-volcanic soil, however, CH4-C uptake was similar in most cores of the pine and pasture soils, averaging about 7-9 μg m−2 h−1, except in very wet samples. In contrast, rates of CO2 production and microbial C and N concentrations were significantly lower under pine than under pasture. In the air-dry cores, microbial C and N had declined in the volcanic soil, but not in the non-volcanic soil; ammonium-N, and especially nitrate-N, had increased significantly in all samples. CH4 uptake was, with few exceptions, not significantly influenced by initial concentrations of ammonium-N or nitrate-N, nor by their changes on air-drying. A combination of phospholipid fatty acid (PLFA) and stable isotope probing (SIP) analyses of only the pine and pasture soils showed that different methanotrophic communities were probably active in soils under the different vegetations. The C18 PLFAs (type II methanotrophs) predominated under pine and C16 PLFAs (type I methanotrophs) predominated under pasture. Overall, vegetation, soil texture, and water-filled pore space influenced CH4-C uptake more than did soil mineral-N concentrations.  相似文献   

6.
The abundance, activity, and temperature response of aerobic methane-oxidizing bacteria were studied in permafrost-affected tundra soils of northeast Siberia. The soils were characterized by both a high accumulation of organic matter at the surface and high methane concentrations in the water-saturated soils. The methane oxidation rates of up to 835 nmol CH4 h−1 g−1 in the surface soils were similar to the highest values reported so far for natural wetland soils worldwide. The temperature response of methane oxidation was measured during short incubations and revealed maximum rates between 22 °C and 28 °C. The active methanotrophic community was characterized by its phospholipid fatty acid (PLFA) concentrations and with stable isotope probing (SIP). Concentrations of 16:1ω8 and 18:1ω8 PLFAs, specific to methanotrophic bacteria, correlated significantly with the potential methane oxidation rates. In all soils, distinct 16:1 PLFAs were dominant, indicating a predominance of type I methanotrophs. However, long-term incubation of soil samples at 0 °C and 22 °C demonstrated a shift in the composition of the active community with rising temperatures. At 0 °C, only the concentrations of 16:1 PLFAs increased and those of 18:1 PLFAs decreased, whereas the opposite was true at 22 °C. Similarly, SIP with 13CH4 showed a temperature-dependent pattern. When the soils were incubated at 0 °C, most of the incorporated label (83%) was found in 16:1 PLFAs and only 2% in 18:1 PLFAs. In soils incubated at 22 °C, almost equal amounts of 13C label were incorporated into 16:1 PLFAs and 18:1 PLFAs (33% and 36%, respectively). We concluded that the highly active methane-oxidizing community in cold permafrost-affected soils was dominated by type I methanotrophs under in situ conditions. However, rising temperatures, as predicted for the future, seem to increase the importance of type II methanotrophs, which may affect methane cycling in northern wetlands.  相似文献   

7.
Methane oxidation in aerated soils is a significant sink for atmospheric methane (CH4). Salt-affected soils are extensively present and constitute about 7% of total land surface. However, our knowledge about CH4 turnover between the atmosphere and the saline soils is very limited. In order to evaluate the potential of CH4 consumption in saline soils, CH4 fluxes were measured in intact cores of the slightly (ECe = 3.2 mS cm−1), moderately (ECe = 7.1 mS cm−1) and extremely (ECe = 50.7 mS cm−1 and 112.6 mS cm−1) saline soils from the Yellow River Delta, China. CH4 uptake of cores from the slightly saline soil ranged from 14 to 24 μg CH4-C m−2 h−1, comparable to those in the non-saline forest soils with similar texture. CH4 uptake of cores from the moderately saline soil was only about 6% of that in the slightly saline soil. CH4 uptake was too low to be measurable in the extremely saline soil. Compared with the non-saline soil, CH4 uptake in the saline soils was much less sensitive to salt, suggesting the higher salt-tolerance of CH4 oxidizers in the saline soil. The result also indicated an underestimate in CH4 uptake for the naturally-occurring saline soils by adding salt to non-saline soils. These results should be useful to study the global CH4 budget and to explore the physiological and ecological characteristics of methanotrophic bacteria in the salt-affected soils.  相似文献   

8.
The influence of NH4+ on microbial CH4 oxidation is still poorly understood. Therefore, the influence of NH4Cl and (NH4)2SO4 on CH4 oxidation was studied in soils at the different stages of the induction of enhanced methanotrophic activity. After a brief peak in the methanotrophic activity, a steady state was observed in which NH4+ inhibited CH4 oxidation at low CH4 concentrations, and stimulated CH4 oxidation at high concentrations. Chloride did not strongly inhibit CH4 oxidation during this phase. During a second phase methanotrophic activity increased again. Ammonium no longer stimulated CH4 oxidation, and Cl− became an important source of uncompetitive inhibition. It was hypothesized that type I methanotrophs dominated during the first, soil-N-dependent phase while N2-fixing type II methanotrophs dominated the second, soil-N-independent phase.  相似文献   

9.
It has been known that nitrogenous fertilizers can either stimulate or inhibit methane oxidation in soils. The mechanism, however, remains unclear. Here we conducted laboratory incubation experiments to evaluate the effects of ammonium versus nitrate amendment on CH4 oxidation in a rice field soil. The results showed that both N forms stimulated CH4 oxidation. But nitrate stimulated CH4 oxidation to a greater extent than ammonium per unit N base. The 16S rRNA genes and the pmoA genes were analyzed to determine the dynamics of total bacterial and methanotrophic populations, respectively. The methanotrophic community consisted of type I and type II methanotrophs and was dominated by type I group after two weeks of incubation. Nitrate promoted both types of methanotrophs, but ammonium promoted only type I. DNA-based stable isotope probing confirmed that ammonium stimulated the incorporation of 13CH4 into type I methanotrophs but not type II, while nitrate caused almost homogenous distribution of 13CH4 in type I and type II methanotrophs. Our study suggests that nitrate can promote CH4 oxidation more significantly than ammonium and is probably a better N source for both types of methanotrophs in rice field soil. More investigations, e.g. using 15N labeling, are necessary to elucidate this possibility.  相似文献   

10.

Purpose

Methane-oxidizing bacteria (methanotrophs) biologically consume and consequently affect the concentration of atmospheric methane (CH4), the second most prominent greenhouse gas, and therefore play critical roles in the mitigation of global warming effect. Long-term fertilization often affects the methanotrophic community and CH4 oxidation in various soils. Here, the immediate effects of nitrogen (N), phosphorus (P), and potassium (K) amendments on the CH4 oxidation activity and methanotrophic community structure were evaluated.

Materials and methods

Paddy soil samples were collected from the Taoyuan Experimental Station of the Chinese Academy of Sciences in central Hunan Province of China. A laboratory-based incubation experiment was conducted to investigate the immediate effects of N, P, and K amendments on the methanotrophs in soil. The CH4 oxidation rates and methanotrophic activities were determined by measuring the dynamic changes of CH4 concentration in the incubation system. The methanotrophic abundance and community changes in all of the seven treatments with and without nutrients addition were studied using real-time PCR and denaturing gradient gel electrophoresis, respectively.

Results and discussion

All of the N, P, and K treatments significantly decreased the CH4 oxidation activities. Compared with the control, the P and K amendments significantly increased the methanotrophic population size, but the N treatments have no effect on the methanotrophic abundance. A negative correlation was found between methanotrophic activity and methanotrophic abundance. We suggested that methanotrophic activity may not be inferred through the pmoA gene copies, especially in the short-term simulation experiments. Investigation of the methanotrophic population size and diversity is not enough to evaluate the soil CH4 sink accurately.

Conclusions

We concluded that the additions of N, P, and K reduce the activity but enhance the abundance of methanotrophs in a Chinese paddy soil through a short-term incubation experiment. Additionally, we found that the CH4 oxidation activity could be completely inhibited by Cl? toxicity. Our results implied that caution should be exercised in the types and amounts of fertilizers, especially KCl in agricultural systems to control the instantaneous increase in CH4 emission from the field.  相似文献   

11.
Aerobic soils are important sinks for atmospheric methane. CH4 oxidation, mediated mainly by methanotrophic bacteria, is the responsible process, which is strongly inhibited by ammonium accessible for nitrification. An inhibitory effect immediately after fertilization as well as a long-term effect exists, which results from repeated ammonium applications and which is independent from the actual concentration of NH4+-N in soil. This long-term effect could be caused by a shift in the microbial population of the soil. Thus, with soil samples from long-term fertilization treatments of the field experiment ”︁Ewiger Roggenbau” at Halle (Germany) incubation studies were conducted to investigate the interference between CH4 oxidation and nitrification and to determine the cell numbers of methanotrophic bacteria. Including the treatments PK, NPK, and farmyard manure, which were established in 1878, a close negative correlation between CH4 oxidation and net nitrification was found (r = —0.92). The CH4 oxidation rates, determined with an initial concentration of 10 μl CH4 l—1, varied between 6.7 and 1.1 μg C kg—1 d—1 in the PK and NPK treatment, respectively. After application of NH4Cl a strong inhibition of CH4 oxidation occurred, which was 91%, 88%, 81%, and 63% in the treatments PK, NPK, FYM, and U (unfertilized), respectively. After a lag-phase of 2 to 3 weeks an incubation with high CH4 concentrations (20 Vol.% CH4) could induce CH4 oxidizing activity in the NPK treatments under continuous rye or maize cropping. An increase of up to 40 times in comparison to the control under atmospheric CH4 (2 μl CH4 l—1) was observed. A negative correlation (r = —0.74) existed between the CH4 oxidation rates of the soils without recently applied NH4+ and the numbers of methanotrophic bacteria, determined with the ”︁most probable number” method (MPN). Thus, the MPN technique is not suitable to characterize the physiologically active population of methanotrophic bacteria in soils, which oxidize CH4 in the atmospheric concentration range. The results of this study suggest that in aerobic arable soils methanotrophic bacteria and not nitrifiers are responsible for CH4 oxidation.  相似文献   

12.
Methane oxidising activity and community structure of 11, specifically targeted, methanotrophic species have been examined in an arable soil. Soils were sampled from three different field plots, receiving no fertilisation (C), compost (G) and mineral fertiliser (M), respectively. Incubation experiments were carried out with and without pre-incubation at elevated CH4 mixing ratios (100 ml CH4 l−1) and with and without ammonium (100 mg N kg−1) pre-incubation. Four months after fertilisation, plots C, G and M did not show significant differences in physicochemical properties and CH4 oxidising activity. The total number of methanotrophs (determined as the sum the 11 specifically targeted methanotrophs) in the fresh soils was 17.0×106, 13.7×106 and 15.5×106 cells g−1 for treatment C, G and M, respectively. This corresponded to 0.11 to 0.32% of the total bacterial number. The CH4 oxidising activity increased 105-fold (20–26 mg CH4 g−1 h−1), the total number of methanotrophs doubled (28–76×106 cells g−1) and the methanotrophic diversity markedly increased in treatments with a pre-incubation at elevated CH4 concentrations. In all soils and treatments, type II methanotrophs (62–91%) outnumbered type I methanotrophs (9–38%). Methylocystis and Methylosinus species were always most abundant. After pre-incubation with ammonium, CH4 oxidation was completely inhibited; however, no change in the methanotrophic community structure could be detected.  相似文献   

13.
Production of C2H4, but not of CH4, was observed in anoxically incubated soil samples (cambisol on loamy sand) from a deciduous forest. Ethylene production was prevented by autoclaving, indicating its microbial origin. Ethylene production gradually decreased from 4 to 12 cm soil depth and was not affected by moisture or addition of methionine, a possible precursor of C2H4. Oxidation of atmospheric CH4 in soil samples was inhibited by C2H4. Ethylene concentrations of 3, 6 and 10 μl l−1 decreased CH4 uptake by 21, 63 and 98%, respectively. Methionine and methanethiol, a possible product of methionine degradation, also inhibited CH4 oxidation. Under oxic conditions, C2H4 was consumed in the soil samples. Ethylene oxidation kinetics exhibited two apparent Km values of 40 μl l−1 and 12,600 μl l−1 suggesting the presence of two different types of C2H4-oxidizing microorganisms. Methanotrophic bacteria were most probably not responsible for C2H4 oxidation, since the maximum of C2H4 oxidation activity was localized in soil layers (2-8 cm depth) above those (8-10 cm depth) of CH4 oxidation activity. Our observations suggest that C2H4 production in the upper soil layers inhibits CH4 oxidation, thus being one reason for the localization of methanotrophic activity in deeper soil layers.  相似文献   

14.
Agricultural factors affecting methane oxidation in arable soil   总被引：9，自引：0，他引：9  
CH4 oxidation activity in a sandy soil (Ardoyen) and agricultural practices affecting this oxidation were studied under laboratory conditions. CH4 oxidation in the soil proved to be a biological process. The instantaneous rate of CH4 consumption was in the order of 800 mol CH4 kg–1 day–1 (13 mg CH4 kg–1 day–1) provided the soil was treated with ca. 4.0 mmol CH4 kg–1 soil. Upon repeated supplies of a higher dose of CH4, the oxidation was accelerated to a rate of at least 198 mg CH4 kg–1 day–1. Addition of the plant-growth promoting rhizopseudomonad strains Pseudomonas aeruginosa 7NSK2 and Pseudomonas fluorescens ANP15 significantly decreased the CH4 oxidation by 20 to 30% during a 5-day incubation. However, with further incubation this suppression was no longer detectable. Growing maize plants prevented the suppression of CH4 oxidation. The numbers of methanotrophic bacteria and fungi increased significantly after the addition of CH4, but there were no significant shifts in the population of total bacteria and fluorescent pseudomonads. Drying and rewetting of soil for at least 1 day significantly reduced the activity of the indigenous methanotrophs. Upon rewetting, their activity was regained after a lag phase of about 3 days. The herbicide dichlorophenoxy acetic acid (2,4-D) had a strong negative effect on CH4 oxidation. The application of 5 ppm increased the time for CH4 removal; at concentrations above 25 ppm 2,4-D CH4–oxidizing activity was completely hampered. After 3 days of delay, only the treatments with below 25 ppm 2,4-D showed recovery of CH4–oxidizing activity. This finding suggests that it can be important to include a CH4–removal bioassay in ecotoxicology studies of the side effects of pesticides. Changes in the native soil pH also affected the CH4–oxidizing capacity. Permanent inhibition occurred when the soil pH was altered by 2 pH units, and partial inhibition by 1 pH unit change. A rather narrow pH range (5.9–7.7) appeared to allow CH4 oxidation. Soils pre-incubated with NH 4 + had a lower CH4–removal capacity. Moreover, the nitrification inhibitor 2-chloro-6-trichloromethyl pyridine (nitrapyrin) strongly inhibited CH4 oxidation. Probably methanotrophs rather than nitrifying microorganisms are mainly responsible for CH4 removal in the soil studied. It appears that the causal methanotrophs are remarkably sensitive to soil environmental disturbances.  相似文献   

15.
《Soil biology & biochemistry》2001,33(12-13):1625-1631
Forest soils are an important sink for atmospheric CH4 but the contribution of CH4 oxidation, production and transport to the overall CH4 flux is difficult to quantify. It is important to understand the role these processes play in CH4 dynamics of forest soils, to enable prediction of how the size of this sink will respond to future environmental change. Methane oxidation, production and transport were investigated for a temperate forest soil, previously shown to be a net CH4 consumer, to determine the extent to which physical and biological processes contributed to the net flux. The sum of oxidation rates for soil layers were significantly greater (P<0.05) than for the intact soil cores from which the layers were taken. Combined with the immediate inhibition of CH4 uptake on waterlogging soils, the findings suggested that soil CH4 diffusion was an important regulator of CH4 uptake. In support of this, a subsurface maximum for CH4 oxidation was observed, but the exact depth of the maximum differed when rates were calculated on a mass or on an areal basis. Markedly varying potential CH4 uptake activities between soil cores were masked in intact core rates. Potential CH4 oxidation conformed well to Michaelis–Menten kinetics but Vmax, Kt and aA○ values varied with depth, suggesting different functional methanotrophic communities were active in the profile. The presence of monophasic kinetics in fresh soil could not be used to infer that the soil was exposed only to CH4 mixing ratios ≤ atmospheric, as challenging soils with 20% CH4 in air did not induce low-affinity oxidation kinetics. Atmospheric CH4 oxidation potentials exceeded production potentials by 10–220 times. The results show that the forest soil CH4 flux was dominated by CH4 oxidation and transport, methanogenesis played only a minor role.  相似文献   

16.
温室气体的大量人为排放导致了近百年来的全球气候变化。甲烷是重要的温室气体,随着全球气温升高,甲烷排放量会随之增加,进一步加剧了全球温室效应。土壤是甲烷重要的源和汇,土壤中的甲烷氧化细菌在平衡甲烷的释放过程中发挥着关键作用。探究温度变化对土壤甲烷氧化能力的影响成为近年来的研究热点。本文综述了温度对土壤甲烷氧化过程以及甲烷氧化细菌的影响,分析了在不同温度下,各生态系统中的土壤甲烷氧化及甲烷氧化细菌响应特点和规律,比较了不同生态系统中土壤发生甲烷氧化的温度范围以及甲烷氧化菌株的生长温度范围。综述结果表明,不同生态系统能够发生甲烷氧化的温度范围不同;在能发生甲烷氧化的温度范围内,甲烷氧化速率随温度升高而增加;培养温度与土壤原位温度越相近时,甲烷氧化响应较为灵敏。与温度对甲烷氧化过程的影响类似,甲烷氧化细菌的丰度也随着温度升高而增加,并与增温幅度、优势甲烷氧化细菌的原位生长温度密切相关。土壤中的II型甲烷氧化细菌对温度较敏感,随着温度升高,II型甲烷氧化细菌丰度增加,因此,温度会通过影响甲烷氧化细菌的丰度和群落结构,从而影响甲烷氧化过程。但温度是否仅通过调控优势菌种更替来改变土壤甲烷氧化能力目前还尚未定论,未来需要进一步探究。本文讨论了土壤甲烷氧化过程对温度的响应及其微生物机制,可为全面解析全球变暖下的土壤甲烷氧化过程的变化提供参考。  相似文献   

17.
Background, aim, and scope  As the second most important greenhouse gas, methane (CH4) is produced from many sources such as paddy fields. Methane-oxidizing bacteria (methanotrophs) consume CH4 in paddy soil and, therefore, reduce CH4 emission to the atmosphere. In order to estimate the contribution of paddy fields as a source of CH4, it is important to monitor the effects of fertilizer applications on the shifts of soil methanotrophs, which are targets in strategies to combat global climate change. In this study, real-time polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) based on 16S rRNA and pmoA genes, respectively, were used to analyze the soil methanotrophic abundance and community diversity under four fertilization treatments: urea (N), urea and potassium chloride (NK), urea, superphosphate, and potassium chloride (NPK), and urea, superphosphate, potassium chloride, and crop residues (NPK+C), compared to an untreated control (CON). The objective of this study was to examine whether soil methanotrophs responded to the long-term, different fertilizer regimes by using a combination of quantitative and qualitative molecular approaches. Materials and methods  Soil samples were collected from the Taoyuan Experimental Station of Agro-ecosystem Observation at Changde (28°55′ N, 111°26′ E), central Hunan Province of China, in July 2006. Soil DNAs were extracted from the samples, then the 16S rRNA genes were quantified by real-time PCR and the pmoA genes were amplified via general PCR followed by DGGE, cloning, sequencing, and phylogenetic analysis. The community diversity indices were assessed through the DGGE profile. Results  Except for NPK, other treatments of N, NK, and NPK+C showed significantly higher copy numbers of type I methanotrophs (7.0–9.6 × 107) than CON (5.1 × 107). The copy numbers of type II methanotrophs were significantly higher in NPK+C (2.8 × 108) and NK (2.5 × 108) treatments than in CON (1.4 × 108). Moreover, the ratio of type II to type I methanotrophic copy numbers ranged from 1.88 to 3.32, indicating that the type II methanotrophs dominated in all treatments. Cluster analyses based on the DGGE profile showed that the methanotrophic community in NPK+C might respond more sensitively to the environmental variation. Phylogenetic analysis showed that 81% of the obtained pmoA sequences were classified as type I methanotrophs. Furthermore, the type I-affiliated sequences were related to Methylobacter, Methylomicrobium, Methylomonas, and some uncultured methanotrophic clones, and those type II-like sequences were affiliated with Methylocystis and Methylosinus genera. Discussion  There was an inhibitory effect on the methanotrophic abundance in the N and a stimulating effect in the NK and NPK+C treatments, respectively. During the rice-growing season, the type II methanotrophs might be more profited from such a coexistence of low O2 and high CH4 concentration environment than the type I methanotrophs. However, type I methanotrophs seemed to be more frequently detected. The relatively complex diversity pattern in the NPK+C treatment might result from the strong CH4 production. Conclusions  Long-term fertilization regimes can both affect the abundance and the composition of the type I and type II methanotrophs. The inhibited effects on methanotrophic abundance were found in the N treatment, compared to the stimulated effects from the NK and NPK+C treatments. The fertilizers of nitrogen, potassium, and the crop residues could be important factors controlling the abundance and community composition of the methanotrophs in the paddy soil. Recommendations and perspectives  Methanotrophs are a fascinating group of microorganisms playing an important role in the biogeochemical carbon cycle and in the control of global climate change. However, it is still a challenge for the cultivation of the methanotrophs, although three isolates were obtained in the extreme environments very recently. Therefore, future studies will be undoubtedly conducted via molecular techniques just like the applications in this study.  相似文献   

18.
Methane emission by soils results from antagonistic but correlated microbial activities. Methane is produced in the anaerobic zones of submerged soils by methanogens and is oxidised into CO2 by methanotrophs in the aerobic zones of wetland soils and in upland soils. Methanogens and methanotrophs are ubiquitous in soils where they remain viable under unfavourable conditions. Methane transfer from the soil to the atmosphere occurs mostly through the aerenchyma of aquatic plants, but also by diffusion and as bubbles escaping from wetland soils. Methane sources are mainly wetlands. However 60 to more than 90 % of CH4 produced in the anaerobic zones of wetlands is reoxidised in their aerobic zones (rhizosphere and oxidised soil-water interface). Methane consumption occurs in most soils and exhibits a broad range of values. Highest consumption rates or potentials are observed in soils where methanogenesis is or has been effective and where CH4 concentration is or has been much higher than in the atmosphere (ricefields, swamps, landfills, etc.). Aerobic soils consume atmospheric CH4 but their activities are very low and the micro-organisms involved are largely unknown. Methane emissions by cultivated or natural wetlands are expressed in mg CH4·m–2·h–1 with a median lower than 10 mg CH4·m–2·h–1. Methanotrophy in wetlands is most often expressed with the same unit. Methane oxidation by aerobic upland soils is rarely higher than 0.1 mg CH4·m–2·h–1. Forest soils are the most active, followed by grasslands and cultivated soils. Factors that favour CH4 emission from cultivated wetlands are mostly submersion and organic matter addition. Intermittent drainage and utilisation of the sulphate forms of N-fertilisers reduce CH4 emission. Methane oxidation potential of upland soils is reduced by cultivation, especially by ammonium N-fertiliser application.  相似文献   

19.
Plant species exert strong effects on ecosystem functions and one of the emerging, and difficult to test hypotheses, is that plants alter soil functions through changing the community structure of soil microorganisms. We tested the hypothesis for atmospheric CH4 oxidation by using soil samples from a Siberian afforestation experiment and exposing them to 13C-CH4. We determined the activity of the soil methanotrophs under different tree species at three levels of initial CH4 concentration (30, 200 and 1000 ppm) thus distinguishing the activities of low- and high-affinity methanotrophs. Half of the samples were incubated with 13C-enriched CH4 (99.9%) and half with 12C-CH4. This allowed an estimation of the amount of 13C incorporated into individual PLFAs and determination of PLFAs of methanotrophs involved in CH4 oxidation at the different CH4 concentrations. Tree species strongly altered the activity of atmospheric CH4 oxidation without appearing to change the composition of high-affinity methanotrophs as evidenced by PLFA 13C labeling. The low diversity of atmospheric CH4 oxidizers, presumably belonging to the UCSα group, may explain the lack of tree species effects on the composition of soil methanotrophs. We submit that the observed tree species effects on atmospheric CH4 oxidation indicate an effect on biomass or cell-specific activities rather than by a community change and this may be related to the impact of the tree species on soil N cycling.  相似文献   

20.
Abstract

Methane (CH4) production in paddy soils and sediments as influenced by nitrate (NO3) addition was studied under a closely controlled soil pH and oxidation‐reduction (redox) potential (Eh) conditions. CH4 production was affected by soil pH and NO3 ‐. Added NO3 ‐ reduced the amount of CH4 produced of each pH level studied. Nitrate addition primary effect in reducing CH4 production was through the resultant increase in soil redox potential (Eh). Using Methyl Fluoride (MF), a CH4 oxidation inhibitor we found that added NO3 ‐ was not used in CH4 oxidation by methanotrophic bacteria.  相似文献   

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