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- Nitrous oxide emissions from soils: how well do we understand the processes and their controls?
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- Editorial: The Impact of Microorganisms on Consumption of Atmospheric Trace Gases
Several of these trace gases originate from biological processes in marine and terrestrial ecosystems and are of relevance for the climate as they contribute to global warming, to the troposphere's chemical reactive system that builds the ozone layer, or they impact on the stability of aerosols, greenhouse, and pollutant gases Conrad, ; Arneth et al.
These gases include methane CH 4 , a multitude of volatile organic compounds of biogenic origin bVOCs and inorganic gases such as nitrogen oxides or ozone Conrad, ; Hewitt et al. The important role of microorganisms for trace gas cycling has been intensively studied for the greenhouse gases nitrous oxide N 2 O and methane CH 4 , but is less well-understood for organisms that metabolize H 2 , carbon monoxide CO , or bVOCs.
The studies compiled in this Research Topic reflect this very well. The Research Topic is complemented by three review articles about the consumption of CH 4 and monoterpenes, as well as the role of the phyllosphere as a particular habitat for trace gas-consuming microorganisms, and points out future research directions in the field Marmulla and Harder ; Bringel and Couee ; Knief. Articles in this research topic on N 2 O cycling are related to terrestrial environments and denitrification.
Soil N 2 O emissions result from different biological processes with nitrification and denitrification being the most important ones. Denitrifiers are facultative aerobic microorganisms that reduce nitrate NO 3 - or nitrite NO 2 - to the gaseous products nitric oxide NO , nitrous oxide N 2 O , or dinitrogen N 2 under oxygen-limited conditions.
Various environmental factors have been identified that affect the composition, abundance, and activity of these microbial groups reviewed in Braker and Conrad, The study of Brenzinger et al. Their observation of changes in gene expression of specific taxa demonstrates that functional redundancy of the soil microbiome is important to maintain denitrification upon acidification. Functional redundancy and process partitioning among NO 3 - - and N 2 O-reducing denitrifiers can also explain the findings that in situ N 2 O fluxes were largely unaffected upon manipulations of the water table in a wetland, although an increase in N 2 O reduction activity was observed upon flooding Palmer et al.
In contrast, land-use change of an agroforest system to an open area converted a cork oak wood from a N 2 O source to a sink Shvaleva et al. This change was not reflected in the abundance of the denitrifier gene nosZ.
All of these studies demonstrate that the underlying microbial processes that control N 2 O fluxes are complex and require a comprehensive analysis of all the different microbial groups that may be involved. Moreover, information about microbiome composition needs to be complemented by data on taxon abundance, activity, and ecophysiology of isolates in order to obtain an understanding of the mechanisms underpinning the observable net ecosystem N 2 O fluxes.
To better assess the biotic mechanisms driving N 2 O fluxes, in vitro analyses of pure cultures are helpful, as exemplified by two studies in this Research topic. Remarkably, it appears that this strain is not able to grow via NO 3 - respiration, although it can express all genes encoding a complete set of denitrification enzymes. More work is needed to elucidate this peculiarity.
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Although methanotrophs are considered to be the major biological sink for CH 4 in soil, some of them also form N 2 O through denitrification under hypoxic conditions. The authors prove in their study that M. The microbial ecology of methanotrophs has been studied for decades, due to the importance of CH 4 as greenhouse gas. This has substantially increased knowledge on their ecophysiology and environmental distribution, as summarized in the review by Knief. Methanotrophic communities are often analyzed based on the marker gene pmoA , encoding a subunit of the membrane-bound methane monooxygenase.
The extensive sequencing of pmoA has led to the identification of a number of new taxa. Based on this information, the occurrence of the different taxa in diverse ecosystems was analyzed within a meta-analysis, thus providing new knowledge about habitat preferences of specific methanotroph taxa. Some methanotroph taxa were identified as specialists, occurring only in specific ecosystems, while other genera appear to be generalists Knief.
The conversion of an Amazonian forest into a manioc cassava plantation resulted in drastically decreased abundance of this group of methanotrophs concomitant with the CH 4 sink activity Lima et al. Green Social Work Lena Dominelli. The Worst of Times Paul B. Reaching for the Sun John King. Climate Change in Practice Robert L. Fire in the Night Stephen McGinty.
Responsive Environments Sue McGlynn. Marine Pollution Judith S. Other books in this series. Climate in Asia and the Pacific Michael Manton. Swarming Landscapes Rob Roggema.
Comparative Environmental Politics Jonathan Rosenberg. Remote Sensing and Climate Modeling: Synergies and Limitations Michel M. Remote Sensing of Atmosphere and Ocean from Space: Models, Instruments and Techniques Guido Visconti. Published by the American Meteorological Society. Q Where can I find information on the use of liquefied carbon dioxide in the extraction of alkaloids from plant materials? National Institute of Standards and Technology's website. Earliest quantitative measurements indicate that decomposition can be entirely attributed to biological processes.
Nitrous oxide emissions from soils: how well do we understand the processes and their controls?
First-year breakdown of leaf litter in southern Appalachian forests. Energy storage and the balance of producers and decomposers in ecological systems. There may be some photo-oxidation but it is likely to be minor. For a more modern treatment but largely based on the model develobet over 30 years ago by Olson see:. Theoretical analysis of decomposition of heterogeneous substrates. Soil Biology and Biochemistry The power and reactive continuum models as particular cases of the q-theory of organic matter dynamics.
Geochemica et Cosmochimica Acta The variations within each year are the result of the annual cycles of photosynthesis and respiration. Photosynthesis, in which plants take up carbon dioxide from the atmosphere and release oxygen, dominates during the warmer part of the year.
- Emissions of Atmospheric Trace Compounds.
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Respiration, by which plants and animals take up oxygen and release carbon dioxide, occurs all the time but dominates during the colder part of the year. Overall, then, atmospheric carbon dioxide decreases during the growing season and increases during the rest of the year. Because the seasons in the northern and southern hemispheres are opposite, carbon dioxide in the atmosphere is decreasing in the northern hemisphere summer while increasing at the same time in the southern hemisphere winter, and vice versa.
The magnitude of this cycle is strongest nearer the poles and approaches zero towards the Equator, where it reverses sign. The cycle is more pronounced in the northern hemisphere which has relatively more land mass and terrestrial vegetation than in the southern hemisphere which is more dominated by oceans. This program, CO2SYS , performs calculations relating parameters of the carbon dioxide system in seawater and freshwater by using two of the four measurable parameters of the CO 2 system [total alkalinity TA , total inorganic CO 2 TCO 2 , pH, and either fugacity fCO 2 or partial pressure of CO 2 pCO 2 ] to calculate the other two parameters at a set of input conditions temperature and pressure and a set of output conditions chosen by the user.
All of the reports, graphics, data, and other information on the CDIAC website are freely and publicly available without copyright restrictions. However as a professional courtesy, we ask that the original data source be acknowledged. Suggested citations appear at the bottom of the Web page for each data set. Please identify the URL of the Web page in which the information or graphic appears. These educational links on global climate change were chosen because we have found them useful in responding to those with inquiring minds.
We are not responsible for the content or intent of these outside links. Key resources related to carbon cycle and climate change research. Global Change Research Program U. Questions Should we grow trees to remove carbon in the atmosphere? Where can I find information on the naming of halocarbons? Can you quantify the sources and sinks of the global carbon cycle? How much carbon is stored in the different ecosystems? In terms of mass, how much carbon does 1 part per million by volume of atmospheric CO 2 represent? What percentage of the CO 2 in the atmosphere has been produced by human beings through the burning of fossil fuels?
How much carbon dioxide is produced from the combustion of cubic feet of natural gas? Why is the sum of all national and regional CO 2 emission estimates less than the global totals?
Why do some smaller nations have larger per capita emission estimates than industrialized nations like the US? What is the greenhouse effect?
Is it the same as the ozone hole issue? Should we be concerned with human breathing as a source of CO 2? How does the oxygen cycle relate to the greenhouse effect and global warming? Is it possible to reduce CO 2 emissions without cutting back on the burning of fossil fuels?
In other words, can higher efficiency or better technology reduce the impact of the consumption of fossil fuels? How long does it take for the oceans and terrestrial biosphere to take up carbon after it is burned? How much CO 2 is emitted as a result of my using specific electrical appliances? What are the conditions happening in certain countries that could upset or disturb the oxygen cycle? Why do certain compounds, such as carbon dioxide, absorb and emit infrared energy?
What kinds of radiation pass through the atmosphere, and what kinds are absorbed? Why do clear winter nights tend to be colder than cloudy ones; and why is the daily temperature variation in the desert greater than that found in a moist environment? Is it possible to separate the carbon and oxygen from CO 2 as is possible with other molecules? I am curious about the global warming potential of water vapor.
Do you know if estimates are done of this in the same way as global warming potentials are calculated for other greenhouse gases? I am also interested in why no mention is ever made of the enhanced greenhouse effect caused by anthropogenic emissions of water vapor. Are the anthropogenic emissions not significant? If so, are there current or impending regulation specific to their use? Could you tell me, please, if I have 1 gallon of fuel in my car, how many units? Is there any difference if the car 4 or 6 or 8 cylinders or in respect of horse power in percentage?
How much CO 2 do you get from combustion of fossil fuels? How can the mass of the CO 2 be greater than the mass of the fuel burned? Is there any ONE person who discovered global warming? If not, what year was global warming discovered? Where can I find information on the use of liquefied carbon dioxide in the extraction of alkaloids from plant materials?
Where can I obtain information on the properties of CO 2? In other words, can I consider that entire CO 2 emitted from soil is derived from biological processes? I understand that atmospheric concentrations of CO 2 are increasing, but when I look at a graph for example, Keeling's Mauna Loa data , the curve is squiggly. For half of each year, the concentrations increases, and for the other half it decreases.
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What is the reason for this? How can I perform CO 2 calculations of the carbon dioxide system in seawater? Are organizations elsewhere in the world studying technologies that could help us address the problem of global climate change? How can I obtain permission? Are there copyright restrictions? Can you suggest some education resources on global climate change? Global Carbon Project And, click here to see figures summarizing the global cycles of biologically active elements. According to the Ideal Gas Law: Solving again at this higher relative to STP temperature, we get: Bunker fuels are fuels used by ships and aircraft in international transportation, global totals include estimates for the oxidation of non-fuel hydrocarbon products e.
Editorial: The Impact of Microorganisms on Consumption of Atmospheric Trace Gases
For further reading, we suggest: Global Biogeochemical Cycles 7: The lifetime of excess atmospheric carbon dioxide. Global Biogeochemical Cycles 8: Seasonal and interannual variations in atmospheric oxygen and implications for the global carbon cycle. For an animation of the vibrational modes of the CO 2 molecule, see http: