New Online Course Explores Social and Ecological Diversity of Himalayan Region

The conversion of forests into cropland worldwide has triggered an atmospheric change that, while seldom considered in climate models, has had a net cooling effect on global temperatures, according to a new Yale study.

Writing in the journal Nature Climate Change, Professor Nadine Unger of the Yale School of Forestry & Environmental Studies (F&ES) reports that large-scale forest losses during the last 150 years have reduced global emissions of biogenic volatile organic compounds (BVOCs), which control the atmospheric distribution of many short-lived climate pollutants, such as tropospheric ozone, methane, and aerosol particles.

Using sophisticated climate modeling, Unger calculated that a 30-percent decline in BVOC emissions between 1850 and 2000, largely through the conversion of forests to cropland, produced a net global cooling of about 0.1 degrees Celsius. During the same period, the global climate warmed by about 0.6 degrees Celsius, mostly due to increases in fossil fuel carbon dioxide emissions.

According to her findings, the climate impact of declining BVOC emissions is on the same magnitude as two other consequences of deforestation long known to affect global temperatures, although in opposing ways: carbon storage and the albedo effect. The lost carbon storage capacity caused by forest conversion has exacerbated global warming. 
Meanwhile, the disappearance of dark-colored forests has also helped offset temperature increases through the so-called albedo effect. (The albedo effect refers to the amount of radiation reflected by the surface of the planet. Light-colored fields, for instance, reflect more light and heat back into space than darker forests.)

“Without doing an earth-system model simulation that includes these factors, we can’t really know the net effect on the global climate.”— Nadine Unger

Unger says the combined effects of reduced BVOC emissions and increased albedo may have entirely offset the warming caused by the loss of forest-based carbon storage capacity.

“Land cover changes caused by humans since the industrial and agricultural revolutions have removed natural forests and grasslands and replaced them with croplands,” said Unger, an assistant professor of atmospheric chemistry at F&ES. “And croplands are not strong emitters of these BVOCs — often they don’t emit any BVOCs.”

“Without doing an earth-system model simulation that includes these factors, we can’t really know the net effect on the global climate. Because changes in these emissions affect both warming and cooling pollutants,” she noted.

Unger said the findings do not suggest that increased forest loss provides climate change benefits, but rather underscore the complexity of climate change and the importance of better assessing which parts of the world would benefit from greater forest conservation.

Since the mid-19th century, the percentage of the planet covered by cropland has more than doubled, from 14 percent to 37 percent. Since forests are far greater contributors of BVOC emissions than crops and grasslands, this shift in land use has removed about 30 percent of Earth’s BVOC sources, Unger said.

Not all of these compounds affect atmospheric chemistry in the same way. Aerosols, for instance, contribute to global “cooling” since they generally reflect solar radiation back into space. Therefore, a 50 percent reduction in forest aerosols has actually spurred greater warming since the pre-industrial era.

“[These emissions] don’t get as much attention as human-generated emissions... but if we change how much forest cover exists, then there is a human influence on these emissions.”— Nadine Unger

However, reductions in the potent greenhouse gases methane and ozone — which contribute to global warming — have helped deliver a net cooling effect.

These emissions are often ignored in climate modeling because they are perceived as a “natural” part of the earth system, explained Unger. “So they don’t get as much attention as human-generated emissions, such as fossil fuel VOCs,” she said. “But if we change how much forest cover exists, then there is a human influence on these emissions.”

These impacts have also been ignored in previous climate modeling, she said, because scientists believed that BVOC emissions had barely changed between the pre-industrial era and today. But a study published last year by Unger  showed that emissions of these volatile compounds have indeed decreased. Studies by European scientists have produced similar results.

The impact of changes to ozone and organic aerosols are particularly strong in temperate zones, she said, while methane impacts are more globally distributed.

The sensitivity of the global climate system to BVOC emissions suggests the importance of establishing a global-scale long-term monitoring program for BVOC emissions, Unger noted.

– Kevin Dennehy    kevin.dennehy@yale.edu    203 436-4842

Source: Yale University

Earth-like soils on Mars? Ancient fossilized soils potentially found deep inside impact crater suggest microbial life

Rover image from Gale Crater reveals soil features similar to paleosols on Earth. Credit: NASA

Soil deep in a crater dating to some 3.7 billion years ago contains evidence that Mars was once much warmer and wetter, saysUniversity of Oregon geologist Gregory Retallack, based on images and data captured by the rover Curiosity.

NASA rovers have shown Martian landscapes littered with loose rocks from impacts or layered by catastrophic floods, rather than the smooth contours of soils that soften landscapes on Earth. However, recent images from Curiosity from the impact Gale Crater, Retallack said, reveal Earth-like soil profiles with cracked surfaces lined with sulfate, ellipsoidal hollows and concentrations of sulfate comparable with soils in Antarctic Dry Valleys and Chile's Atacama Desert.

His analyses appear in a paper placed online this week by the journal Geology in advance of print in the September issue of the world's top-ranked journal in the field. Retallack, the paper's lone author, studied mineral and chemical data published by researchers closely tied with the Curiosity mission. Retallack, professor of geological sciences and co-director of paleontology research at the UO Museum of Natural and Cultural History, is an internationally known expert on the recognition of paleosols -- ancient fossilized soils contained in rocks.

"The pictures were the first clue, but then all the data really nailed it," Retallack said. "The key to this discovery has been the superb chemical and mineral analytical capability of the Curiosity Rover, which is an order of magnitude improvement over earlier generations of rovers. The new data show clear chemical weathering trends, and clay accumulation at the expense of the mineral olivine, as expected in soils on Earth. Phosphorus depletion within the profiles is especially tantalizing, because it attributed to microbial activity on Earth."

The ancient soils, he said, do not prove that Mars once contained life, but they do add to growing evidence that an early wetter and warmer Mars was more habitable than the planet has been in the past 3 billion years.

Curiosity rover is now exploring topographically higher and geologically younger layers within the crater, where the soils appear less conducive to life. For a record of older life and soils on Mars, Retallack said, new missions will be needed to explore older and more clayey terrains.

Surface cracks in the deeply buried soils suggest typical soil clods. Vesicular hollows, or rounded holes, and sulfate concentrations, he said, are both features of desert soils on Earth.

"None of these features is seen in younger surface soils of Mars," Retallack said. "The exploration of Mars, like that of other planetary bodies, commonly turns up unexpected discoveries, but it is equally unexpected to discover such familiar ground."

The newly discovered soils provide more benign and habitable soil conditions than known before on Mars. Their dating to 3.7 billion years ago, he noted, puts them into a time of transition from "an early benign water cycle on Mars to the acidic and arid Mars of today." 

Life on Earth is believed to have emerged and began diversifying about 3.5 billion years ago, but some scientists have theorized that potential evidence that might take life on Earth farther back was destroyed by plate tectonics, which did not occur on Mars.

In an email, Malcolm Walter of the Australian Centre for Astrobiology, who was not involved in the research, said the potential discovery of these fossilized soils in the Gale Crater dramatically increases the possibility that Mars has microbes. "There is a real possibility that there is or was life on Mars," he wrote.

Retallack noted that Steven Benner of the Westheimer Institute of Science and Technology in Florida has speculated that life is more likely to have originated on a soil planet like Mars than a water planet like Earth. In an email, Benner wrote that Retallack's paper "shows not only soils that might be direct products of an early Martian life, but also the wet-dry cycles that many models require for the emergence of life."

Source: University of Oregon

Native fungus suggested as another tool for restoring ghostly whitebark pine forests

Siberian slippery jack is a native fungus that may help in the effort to restore whitebark pine forests.
Credit: Cathy Cripps

Cathy Cripps doesn't seem to worry about the grizzly bears and black bears that watch her work, but she is concerned about the ghosts and skeletons she encounters.

The ghosts are whitebark pine forests that have been devastated by mountain pine beetles and white pine blister rust, said the Montana State University scientist who studies fungi that grow in extreme environments. The skeletons are dead trees that no longer shade snow or produce pine cones. The round purple pine cones hold the seeds that feed bears, red squirrels and Clark's nutcracker birds. Shade at the top of watersheds keeps snow from melting too fast in the spring, preventing trout streams from drying up too early in the summer.

Fortunately, she has found hope in a native fungus called Siberian slippery jack, or Suillus sibiricus, said Cripps, a mycologist in MSU's Department of Plant Sciences and Plant Pathology.

Cripps conducted a three-year study in collaboration with Waterton Lakes National Park in Canada that showed a 10 to 15 percent increase in the survival rate of whitebark pine seedlings when Siberian slippery jack spores are injected into the soil around them. The injection takes place in nurseries before the seedlings are transplanted in the mountains.

That increase is significant and good news for those trying to reinstate whitebark pine trees to the north-central Rocky Mountains and Pacific Northwest, Cripps said. The whitebark pine is a keystone species that grows at high elevations where other trees cannot, but it has been declared an endangered species in Canada and awaits the designation in the United States.

"That (jump in survival rates) might not sound like a big difference, but a small amount is a big deal considering the labor-intensive process," Cripps said.

Cyndi Smith, scientist emeritus at Waterton, said "The positive results have encouraged Waterton Lakes National Park to continue inoculating both whitebark and limber pine seedlings, to give them the best opportunity we can to establish and survive to maturity."

Participants in the research project, in addition to Cripps' and Smith's teams, were the U.S. Forest Service, National Park Service and volunteers from the United States and Canada.

Explaining how the collaboration began, Smith said, "Cathy gave a presentation on some of her Yellowstone work at the annual science meeting of the Whitebark Pine Ecosystem Foundation in Hailey, Idaho, in 2006. I was really taken with the idea that the ecosystem may have lost the beneficial fungi because our forests have been dead and dying for so long and that perhaps there was a way to reverse that trend so I approached Cathy with the idea.

"I'm a big believer in collaboration, whether locally or internationally, but certainly working with someone of Cathy's academic stature has been very helpful when I have applied for funding for whitebark and limber pine projects," Smith said, adding that, "Cathy's enthusiasm is very infectious, and it is a delight to work with her."

To carry out the research project, the participants placed cages around whitebark pine trees to collect pine cones without interference from wildlife. Then they tested the cones to see if they were resistant to white pine blister rust, removed seeds by hand from the resistant cones, grew the seeds into seedlings and shipped them to the nursery in Glacier National Park.

Cripps and former graduate student Erin Lonergan drove to Waterton Lakes 

National Park and throughout the Greater Yellowstone area, hiked to the tops of mountains and collected the Siberian slippery jack and other fungi from whitebark pine forests. Then they returned to MSU where they used a coffee grinder to process the spongy outer layer of the fungi. They added water to create a spore slurry, stored the mixture at MSU and later injected about 3 million spores into the soil around each seedling temporarily housed at the Glacier National Park nursery.

A few months later, volunteers planted more than 1,000 seedlings into MSU's test plots. Most of those test plots were located in Waterton, while others were in the neighboring Glacier National Park. The two parks together comprise Waterton-Glacier International Peace Park.

Two years into the study, Lonergan, Cripps and Smith reported success in the journal, American Forests. One year later, they announced their final results in the spring/summer 2014 issue of Nutcracker Notes, a small journal hosted by the Whitebark Pine Ecosystem Foundation.

"We wanted to get the word out that results after three years showed that inoculation with these native fungi significantly improved the survival of rust resistant seedlings, especially when inoculated seedlings were planted in burned areas near shelter objects such as stumps and logs," Cripps said.

High nitrogen fertilizations and fungicides prevent the inoculations from working, Cripps said. The age of the seedlings is important because they need to grow plenty of side roots before being inoculated.

When successful, the injected fungi slip like tiny socks over the ends of every root of the whitebark pine seedling and form a relationship that benefits both the tree and the fungi, Cripps said. The fungi help the seedling take in more nutrients and water from the soil. The tree produces the sugars that feed the fungi.

"Instead of being bad guys, these fungi are beneficial," Cripps said of the Siberian slippery jack. "They help plants take up nitrogen and phosphorus from the soil. That's a big deal."

Her study is one of many research projects involving whitebark pine forests, but it's unique because it focuses on beneficial native fungi, Cripps said. She added that land managers might want to incorporate MSU's findings into their overall strategy for restoring whitebark pine forests. She noted that large-scale inoculations are already planned for nurseries in Canada. She said inoculating beneficial fungi into nursery stock is common in Europe.

"As we work to save the vital whitebark pine from disappearing from the landscape, it is essential to use all available tools," Cripps said. "Ectomycorrhizal fungi are an integral part of forest integrity, ecology and health. Showing respect for these mighty microbes might just mean the difference between the restoration and death of a forest."

"Ectomycorrhizal fungi" refers to beneficial fungi that form a symbiotic relationship with the roots of trees. Siberian slippery jack is one of those fungi, and it only associates with five-needle pines. White pine blister rust is another type of fungus, one of the "bad guys."

Source: Montana State University

Soil mineral surfaces linked to key atmospheric processes

Pictured are, from left, are David Bish, Melissa Donaldson and Jonathan Raff. Credit: Indiana University

Research by Indiana University scientists finds that soil may be a significant and underappreciated source of nitrous acid, a chemical that plays a pivotal role in atmospheric processes such as the formation of smog and determining the lifetime of greenhouse gases.

The study shows for the first time that the surface acidity of common minerals found in soil determines whether the gas nitrous acid will be released into the atmosphere. The finding could contribute to improved models for understanding and controlling air pollution, a significant public health concern.

"We find that the surfaces of minerals in the soil can be much more acidic than the overall pH of the soil would suggest," said Jonathan Raff, assistant professor in the School of Public and Environmental Affairs and Department of Chemistry. "It's the acidity of the soil minerals that acts as a knob or a control lever, and that determines whether nitrous acid outgasses from soil or remains as nitrite."

The article, "Soil surface acidity plays a determining role in the atmospheric-terrestrial exchange of nitrous acid," will be published this week in the journal Proceedings of the National Academy of Sciences. Melissa A. Donaldson, a Ph.D. student in the School of Public and Environmental Affairs, is the lead author. Co-authors are Raff and David L. Bish, the Haydn Murray Chair of Applied Clay Mineralogy in the Department of Geological Sciences.

Nitrous acid, or HONO, plays a key role in regulating atmospheric processes. Sunlight causes it to break down into nitric oxide and the hydroxyl radical, OH. The latter controls the atmospheric lifetime of gases important to air quality and climate change and initiates the chemistry leading to the formation of ground-level ozone, a primary component of smog.
Scientists have known about the nitrous acid's role in air pollution for 40 years, but they haven't fully understood how it is produced and destroyed or how it interacts with other substances, because HONO is unstable and difficult to measure.

"Only in the last 10 years have we had the technology to study nitrous acid under environmentally relevant conditions," Raff said.

Recent studies have shown nitrous acid to be emitted from soil in many locations. But this was unexpected because, according to basic chemistry, the reactions that release nitrous acid should take place only in extremely acidic soils, typically found in rain forests or the taiga of North America and Eurasia.

The standard method to determine the acidity of soil is to mix bulk soil with water and measure the overall pH. But the IU researchers show that the crucial factor is not overall pH but the acidity at the surface of soil minerals, especially iron oxides and aluminum oxides. At the molecular level, the water adsorbed directly to these minerals is unusually acidic and facilitates the conversion of nitrite in the soil to nitrous acid, which then volatilizes.

"With the traditional approach of calculating soil pH, we were severely underestimating nitrous acid emissions from soil," Raff said. "I think the source is going to turn out to be more important than was previously imagined."

The research was carried out using soil from a farm field near Columbus, Ind. But aluminum and iron oxides are ubiquitous in soil, and the researchers say the results suggest that about 70 percent of Earth's soils could be sources of nitrous acid.

Ultimately, the research will contribute to a better understanding of how nitrous acid is produced and how it affects atmospheric processes. That in turn will improve the computer models used by the U.S. Environmental Protection Agency and other regulatory agencies to control air pollution, which the World Health Organization estimates contributes to 7 million premature deaths annually.

"With improved models, policymakers can make better judgments about the costs and benefits of regulations," Raff said. "If we don't get the chemistry right, we're not going to get the right answers to our policy questions regarding air pollution."

Source: Indiana University

Earthworms, ants, termites: The real engineers of the ecosystem

The contribution of home gardens in the preservation of biodiversity, economics and human health prompted a multidisciplinary group at the South Border College (Ecosur) in Mexico to work on a project in Tabasco, a south state of the country, with the aim to improve the production and environmental management of these plantations. Credit: Image courtesy of Investigación y Desarrollo

The contribution of home gardens in the preservation of biodiversity, economics and human health prompted a multidisciplinary group at the South Border College (Ecosur) in Mexico to work on a project in Tabasco, a south state of the country, with the aim to improve the production and environmental management of these plantations.

Although the research was conducted from different perspectives, head of research Esperanza Huerta Lwanga focused on the study of soil invertebrates because they are indicators of its quality.

"These organisms fulfill various functions,like allowing the soil to absorb processed organic matter such as leaves, wood, trunks and branches and with this nourishing crops; they also maintain an ecological balance capable of preventing the invasion of pests and provide greater fertility without using chemicals. This happens when growing different types of plants, allowing the existence of a wide variety of soil invertebrates" the researcher explains.

The project, which began in 2009 and was funded by the Ministry of Energy, Natural Resources and Environmental Protection (SERNAPAM), arises because home gardens are places where there is a wealth of soil. In total, the research team worked in 50 home gardens located in different physiographic regions of the state: mountains, coast, floodplain and hillocks.

"During the fieldwork I realized that the orchards whose owners had family harmony, were characterized by a rich vegetation and greater diversity of soil invertebrates was found. However, in other orchards we observed garbage instead vegetation and organisms, revealing a gap between people and nature, " relates Huerta Lwanga.

An important finding of this project was when the researcher found a anecic earthworm, initially thought to be a new species, however, it was only a new entry in the state of Tabasco. "Such organism is characterized by its vertical movements, thereby creating tunnels, helping to integrate the organic matter in the soil, aerating it and forming its structure," the researcher says.

Other species were also identified, like earthworms, ants, termites, centipedes, beetles, grasshoppers, cockroaches and woodlice, which may also be called "ecosystem engineers" (specifically earthworms, termites and some ants) because their activities modify the soil, enriching its productivity.

According to the researcher, it is important to note that the presence of such organisms does not mean that the garden is infested with pests. "If you let me live there, they fulfill their tasks and at the same time control their population because the variety of invertebrates generates food chains."

The pest problem, she says, appears when the land is handled as a monoculture. In these cases only one type of organisms thrives and rapidly increases in number and , because nobody eats them, they become a threat to the plantations.

The research results revealed that the coastal region was the one with more garbage, followed by the hillocks. "In the mountains we found healthy vegetation and a great variety of crops, high diversity of invertebrates and greater earthworm biomass, which was estimated at more than 33 grams per square meter," highlights Huerta Lwanga.

That amount is important because according to previous studies it was established that if biomass is equal or greater than 30 grams per square meter germination induction and plant growth are achieved.

Additionally, this project included environmental education, which was given by mini-workshops and training in the production of vermi-compost.

"At Ecosur, we designed a box for composting, which is equiped with a small mill and worms, where we place the fresh waste to be processed. A device like this was given to all farmers, but was only accepted by 47 percent of them," she sadly concludes.

Source: Investigación y Desarrollo

Live fast, die young: Soil microbes in a warmer world

Aerial view of the Northern Minnesota landscape including numerous conifer peatlands, deciduous uplands and lakes. Credit: USDA Forest Service Northern Research Station

Warmer temperatures shorten the lifespan of soil microbes and this may affect soil carbon storage, according to a new NSF-funded study published in Nature Climate Change this week.

A research team led by Shannon Hagerty and Paul Dijkstra from Northern Arizona University measured two key characteristics of soil microbes that determine their role in the soil carbon cycle: how efficiently they use carbon to grow and how long they live. "Higher temperatures make microbes grow faster, but they also die faster," said Hagerty, who conducted the research as part of her master's degree and was lead author on the study.

Soil microbes consume organic carbon compounds in soil, use some of it to make more microbes and release the rest to the atmosphere as carbon dioxide. The efficiency with which microbes use their food to make new microbes affects how much carbon remains in soil, and how much is released back to the atmosphere. The accepted idea before this study was that microbes would become less efficient at warmer temperatures.

The scientists incubated soil from a peatland and a forest in Minnesota at different temperatures and measured the efficiency with which microbes grew. They used a new method to measure microbial efficiency: they added small amounts of sugar and tracked how individual atoms in this sugar were turned into carbon dioxide.

"Microbes process sugars in similar ways as we do," says Paul Dijkstra. "We know very well how these processes work in laboratory studies, and can predict which carbon atoms in sugar molecules end up as carbon dioxide, and which are used to build new microbes. We applied this knowledge to the microbes living in soil."

The researchers found, contrary to expectation, that temperature had no effect on how microbes utilized their food, but instead boosted microbial death. "We don't yet know why microbes are dying faster at higher temperatures. Maybe they are eaten by nematodes or mites, or they die because of viruses," said Hagerty. "We need to know more about how temperature affects microbial death."

To explore what these new findings could mean for soil carbon storage in a warming world, the team compared output from a soil model that includes the effect of temperature on microbial lifespan to models unaffected by temperature change. "Models are used to predict how soil processes change, for example, in response to climate change," said Steve Allison, coauthor from the University of California, Irvine. "If we want to predict the future correctly, we'd better use models that accurately describe these microbial processes."

Including a temperature-dependent lifespan to the model increased the amount of carbon retained in soils at warmer temperatures compared to estimates from traditional models. The study concludes that incorporating this new insight into soil models will improve our understanding of how soils influence atmospheric carbon dioxide levels and global climate.

Does this mean that with climate change, more carbon will stay in the soil? "Too early to tell," said Bruce Hungate, Director of the Center for Ecosystem Science and Society at NAU. 

"The results suggest that the biochemistry of the microbes remains the same with warmer temperature, but that predation and death become more important. This laboratory study is just the first step, identifying a potential mechanism. Now we need to study how, in the real world, and in the long-term, the processes of biochemical efficiency and lifespan will change. And nobody has done that yet."

Source: Northern Arizona University

Sunlight, not microbes, key to carbon dioxide in Arctic

Terrestrial organic matter is shown spilling into a lake. Credit: Image courtesy of Oregon State University

The vast reservoir of carbon stored in Arctic permafrost is gradually being converted to carbon dioxide (CO2) after entering the freshwater system in a process thought to be controlled largely by microbial activity.

However, a new study -- funded by the National Science Foundation and published this week in the journal Science -- concludes that sunlight and not bacteria is the key to triggering the production of CO2 from material released by Arctic soils.

The finding is particularly important, scientists say, because climate change could affect when and how permafrost is thawed, which begins the process of converting the organic carbon into CO2.

"Arctic permafrost contains about half of all the organic carbon trapped in soil on the entire Earth -- and equals an amount twice of that in the atmosphere," said Byron Crump, an Oregon State University microbial ecologist and co-author on the Science study. "This represents a major change in thinking about how the carbon cycle works in the Arctic."

Converting soil carbon to carbon dioxide is a two-step process, notes Rose Cory, an assistant professor of earth and environmental sciences at the University of Michigan, and lead author on the study. First, the permafrost soil has to thaw and then bacteria must turn the carbon into greenhouse gases -- carbon dioxide or methane. While much of this conversion process takes place in the soil, a large amount of carbon is washed out of the soils and into rivers and lakes, she said.

"It turns out, that in Arctic rivers and lakes, sunlight is faster than bacteria at turning organic carbon into CO2," Cory said. "This new understanding is really critical because if we want to get the right answer about how the warming Arctic may feedback to influence the rest of the world, we have to understand the controls on carbon cycling.

"In other words, if we only consider what the bacteria are doing, we'll get the wrong answer about how much CO2 may eventually be released from Arctic soils," Cory added.

The research team measured the speed at which both bacteria and sunlight converted dissolved organic carbon into carbon dioxide in all types of rivers and lakes in the Alaskan Arctic, from glacial-fed rivers draining the Brooks Range to tannin-stained lakes on the coastal plain. Measuring these processes is important, the scientists noted, because bacteria types and activities are variable and the amount of sunlight that reaches the carbon sources can differ by body of water.

In virtually all of the freshwater systems they measured, however, sunlight was always faster than bacteria at converting the organic carbon into CO2.

"This is because most of the fresh water in the Arctic is shallow, meaning sunlight can reach the bottom of any river -- and most lakes -- so that no dissolved organic carbon is kept in the dark," said Crump, an associate professor in Oregon State's College of Earth, Ocean, and Atmospheric Sciences. "Also, there is little shading of rivers and lakes in the Arctic because there are no trees."

Another factor limiting the microbial contribution is that bacteria grow more slowly in these cold, nutrient-rich waters.

"Light, therefore, can have a tremendous effect on organic matter," University of Michigan's Cory pointed out.

The source of all of this organic carbon is primarily tundra plants -- and it has been building up for hundreds of thousands of years, but doesn't completely break down immediately because of the Arctic's cold temperatures. Once the plant material gets deep enough into the soil, the degradation stops and it becomes preserved, much like peat.

"The level of thawing only gets to be a foot deep or so, even in the summer," Crump said. "Right now, the thaw begins not long before the summer solstice. If the seasons begin to shift with climate change -- and the thaw begins earlier, exposing the organic carbon from permafrost to more sunlight -- it could potentially trigger the release of more CO2."

The science community has not yet been able to accurately calculate how much organic carbon from the permafrost is being converted into CO2, and thus it will be difficult to monitor potential changes because of climate change, they acknowledge.

"We have to assume that as more material thaws and enters Arctic lakes and rivers, more will be converted to CO2," Crump said. "The challenge is how to quantify that."

Some of the data for the study was made available through the National Science Foundation's Arctic Long-Term Ecological Research project, which has operated in the Arctic for nearly 30 years.

Source:  Oregon State University

Kudzu can release soil carbon, accelerate global warming

This layer of decomposing knotweed will eventually form soil organic matter in invaded ecosystems.
 Credit: Image courtesy of Clemson University

Clemson University scientists are shedding new light on how invasion by exotic plant species affects the ability of soil to store greenhouse gases. The research could have far-reaching implications for how we manage agricultural land and native ecosystems.

In a paper published in the scientific journal New Phytologist, plant ecologist Nishanth Tharayil and graduate student Mioko Tamura show that invasive plants can accelerate the greenhouse effect by releasing carbon stored in soil into the atmosphere.
Since soil stores more carbon than both the atmosphere and terrestrial vegetation combined, the repercussions for how we manage agricultural land and ecosystems to facilitate the storage of carbon could be dramatic.

In their study, Tamura and Tharayil examined the impact of encroachment of Japanese knotweed and kudzu, two of North America's most widespread invasive plants, on the soil carbon storage in native ecosystems.

They found that kudzu invasion released carbon that was stored in native soils, while the carbon amassed in soils invaded by knotweed is more prone to oxidation and is subsequently lost to the atmosphere.

The key seems to be how plant litter chemistry regulates the soil biological activity that facilitates the buildup, composition and stability of carbon-trapping organic matter in soil.

"Our findings highlight the capacity of invasive plants to effect climate change by destabilizing the carbon pool in soil and shows that invasive plants can have profound influence on our understanding to manage land in a way that mitigates carbon emissions," Tharayil said.

Tharayil estimates that kudzu invasion results in the release of 4.8 metric tons of carbon annually, equal to the amount of carbon stored in 11.8 million acres of U.S. forest.
This is the same amount of carbon emitted annually by consuming 540 million gallons of gasoline or burning 5.1 billion pounds of coal.

"Climate change is causing massive range expansion of many exotic and invasive plant species. As the climate warms, kudzu will continue to invade northern ecosystems, and its impact on carbon emissions will grow," Tharayil said.

The findings provide particular insight into agricultural land-management strategies and suggest that it is the chemistry of plant biomass added to soil rather than the total amount of biomass that has the greatest influence on the ability of soil to harbor stable carbon.

"Our study indicates that incorporating legumes such as beans, peas, soybeans, peanuts and lentils that have a higher proportion of nitrogen in its biomass can accelerate the storage of carbon in soils," Tharayil said.

Thrarayil's lab is following up this research to gain a deeper understanding of soil carbon storage and invasion.

Tharayil leads a laboratory and research team at Clemson that studies how the chemical and biological interactions that take place in the plant-soil interface shape plant communities. He is also the director of Clemson's Multi-User Analytical Laboratory, which provides researchers with access to highly specialized laboratory instruments.

Source: Clemson University

Nitrogen fingerprint in biomolecules could be from early sun

Ultraviolet light splits more readily splits molecules of nitrogen gas if one or both are the heavier isotope, nitrogen-15. Free nitrogen atoms combine with hydrogen to form ammonia molecules enriched in nitrogen-15. Credit: Image courtesy of University of California - San Diego

Chemical fingerprints of the element nitrogen vary by extremes in materials from the molecules of life to the solar wind to interstellar dust. Ideas for how this great variety came about have included alien molecules shuttled in by icy comets from beyond our solar system and complex chemical scenarios.

New experiments using a powerful source of ultraviolet light have shown that no extra-solar explanation is needed and the chemistry is straight forward, scientists from the University of California, San Diego, Hebrew University and UCLA report in the early online edition of the Proceedings of the National Academy of Sciences the week of September 29.

Nitrogen occurs in two stable forms. Nitrogen-14, with an equal number of protons and neutrons in its nucleus, is most abundant. Nitrogen-15, with an extra neutron, is far more rare, but biological molecules like proteins have larger proportions; they're enriched in nitrogen-15 relative to the nitrogen gas in Earth's atmosphere. And Earth's atmosphere itself has relatively more nitrogen-15 than other sources, such as the solar wind and Jupiter's atmosphere.

Samples from the icy comet Wild 2, retrieved by NASA's Stardust mission, and several kinds of meteorites also have relatively more nitrogen-15, and within the inhomogenous mix that makes up stony meteorites are inclusions, individual crystals that can have extremely high proportions of nitrogen-15. These observations led to the idea that the building blocks of life could have been 'seeded' on Earth, delivered perhaps by comet.

The new experiments render that hypothesis unnecessary. "We can generate this nitrogen enrichment inside the solar system. You can form all these building blocks of life inside our solar system. You don't have to bring the pieces in from outside," said Subrata Chakraborty, a project scientist in chemistry at UC San Diego and lead author of the report.

By shining a bright beam of very short wave ultraviolet light through nitrogen and hydrogen gas, Chakraborty and colleagues generated ammonia with drastically skewed ratios of nitrogen-15 relative to that found in the initial gas, which matched that of Earth's atmosphere. Pairs of nitrogen atoms -- the molecules of the gas -- were more likely to be split by UV photons if one or both atoms are the heavier version. Those freed nitrogen atoms recombined with hydrogen to form ammonia.

Ammonia molecules, a nitrogen atom bound to three hydrogen atoms, makes up a fundamental chemical group, the 'amines' the characterize amino acids, which link up in long chains to form proteins. They also join aromatic rings of carbon to form nitrogenous bases, the information carrying components of DNA and RNA. And RNA is how many think life got its start.

Light like this, with wavelengths this short, doesn't make it to Earth anymore. It's deflected by Earth's atmosphere. In fact, the experiments took place in a custom-engineered vacuum chamber aligned with the Lawrence Berkeley National Laboratory's Advanced Light Source synchrotron and were a challenge to pull off.

The chemical events that produced amines with extra nitrogen-15 would have happened long ago, probably in the icy outer reaches of the early solar nebula said Mark Thiemens, professor of chemistry at UC San Diego who directed the work. "It's the right time for this to have happened: before planets, before life."

Additional authors include Harel Muskatel of Hebrew University in Jerusalem, Teresa Jackson of UC San Diego, Musahid Ahmed of Lawrence Berkeley National Laboratory and R.D. Levine of Hebrew University and UCLA. NASA's Cosmochemistry and Origins of Solar System programs funded this work. The U.S. Department of Energy supports the operation of the Advanced Light Source.

Source:  University of California - San Diego

Logging destabilizes forest soil carbon over time

Chelsea Petrenko, a doctoral candidate at Dartmouth College, is lead author of a study showing that logging triggers the gradual release of the carbon stored in a forest's mineral soils. Credit: Dartmouth College

Logging doesn't immediately jettison carbon stored in a forest's mineral soils into the atmosphere but triggers a gradual release that may contribute to climate change over decades, a Dartmouth College study finds.

The results are the first evidence of a regional trend of lower carbon pools in soils of harvested hardwood forests compared to mature or pristine hardwood forests. The findings appear in the journal Global Change Biology Bioenergy. A PDF of the study is available on request.

Despite scientists' growing appreciation for soil's role in the global carbon cycle, mineral soil carbon pools are largely understudied and previous studies have produced differing results about logging's impact. For example, the U.S. Forest Service assumes that all soil carbon pools do not change after timber harvesting.

The Dartmouth researchers looked at how timber harvesting affects mineral soil carbon over 100 years following harvest in the northeastern United States, where soils account for at least 50 percent of total ecosystem carbon storage. Mineral soils, which underlie the carbon-rich organic layer of the soil, make up the majority of that storage, but are sometimes not included in carbon studies due to the difficulty in collecting samples from the rocky, difficult terrain. The researchers hypothesized that the mineral soil carbon would be lower in forests that had been harvested in the last century than in forests that were more than 100 years old. They collected mineral soil cores from 20 forests in seven areas across the northeastern United States and compared the relative amounts of carbon in the soil from forests that were logged five years ago, 25 years ago, 50 years ago, 75 years ago and 100 years ago.

The results showed no significant differences between mineral soil carbon in the older versus harvested forests. But there was a significant relationship between the time since forest harvest and the size of the carbon pools, which suggested a gradual decline in carbon across the region that may last for decades after harvesting and result in increased atmospheric carbon dioxide.

"Our study suggests that forest harvest does cause biogeochemical changes in mineral soil, but that a small change in a carbon pool may be difficult to detect when comparing large, variable carbon pools," says lead author Chelsea Petrenko) (formerly Vario), a doctoral candidate in the Graduate Program in Ecology and Evolutionary Biology and a trainee in Dartmouth's IGERT program for Polar Environmental Change. "Our results are consistent with previous studies that found that soil carbon pools have a gradual and slow response to \disturbance, which may last for several decades following harvest."

A previous Dartmouth study found that clear-cutting releases detectible amounts of carbon stored in deep forest soils, challenging the notion that burning woody biomass for energy is more carbon-neutral than fossil fuels. "Mineral soil, which is the most significant ecosystem carbon pool in temperate forests, should be studied more closely before the carbon neutrality of bioenergy from local wood in temperate forests is asserted," says Petrenko, whose research focuses on the biogeochemistry of warming ecosystems and the impact on climate change.

Source:  Dartmouth College

Impact of climate change on the soil ecosystem

The Basque Institute for Agricultural Research and Development NEIKER-Tecnalia has had a Microbial Observatory in the Ordesa and Monte Perdido National Nature Reserve (Huesca Pyrenees) since 2011. Its purpose is to evaluate the impact of climate change on the ecosystems of the soil by monitoring its microbial properties over time. Credit: Image courtesy of Basque Research

The Basque Institute for Agricultural Research and Development NEIKER-Tecnalia has had a Microbial Observatory in the Ordesa and Monte Perdido National Nature Reserve (Huesca Pyrenees) since 2011. Its purpose is to evaluate the impact of climate change on the ecosystems of the soil by monitoring its microbial properties over time. The research areas are located at altitudes of between 1,500 and 2,600 metres, which provides a broad range of different climate conditions and makes it possible to observe how the altitude affects the properties of the soil and the micro-organisms living in it. Preliminary results indicate that microbial properties are highly dependent on the physical and chemical properties of the soil on a small scale and on the environmental conditions existing at the moment when the samples are gathered.

To conduct this research, NEIKER-Tecnalia is using the most advanced techniques in the matter of molecular biology, which have revolutionised microbial ecology. Specifically, massive sequencing analyses are being carried out right now; they allow a large number of genes to be sequenced and identified within a short space of time. The genetic sequencing of the subterranean biosphere is seeking to gain a better understanding of the structure and function of the microbial communities across the altitude gradient.

NEIKER-Tecnalia's Microbial Observatory will contribute towards improving the current understanding of the effects of climate change on soil microbial communities and associated ecological processes. The alpine area where it is located is particularly suitable for a climate change observatory. Firstly, it is a remote spot relatively isolated from direct anthropogenic impacts, which means that global effects like climate change can be clearly perceived without the interference of more local environmental factors. Secondly, the altitude gradients that exist in the mountains in turn create clearly marked climate gradients within short distances; in other words, different climate conditions can be found at different altitudes.

Micro-organisms adapt more quickly than plants and macro-organisms

Micro-organisms adapt more quickly to changes than plants or other macro-organisms, which means they are ideal bioindicators of the impact of sources of environmental stress on the functioning of ecosystems. It is very important to have a record of the alterations gradually occurring in the soil ecosystem as a result of climate change to be able to more accurately predict what future scenarios are going to be in store. It is important to stress that the soil is our most important resource; it is the basis of the terrestrial ecosystem and 95% of our food comes directly or indirectly from it.

The role of micro-organisms in relation to the functioning of the soil ecosystem is fundamental. The soil, which has been traditionally regarded as an inanimate item made up of minerals and chemical substances, contains a myriad of micro-organisms that are responsible for many of its vital functions and, consequently, its health. These functions include the decomposition and recycling of nutrients from dead plant and animal tissue, nitrogen fixing, the maintaining of soil structure and the elimination of contaminants.
It can be predicted that, in the long term, climate change will cause the biota of mountain soil to migrate towards higher altitudes in the quest for the optimum bioclimatic environment. The problem is that this migration has a limit, which is the summit of the mountain, beyond which no migration or escape is possible.

Source:  Basque Research

Groundwater patches play important role in forest health, water quality

This is Kevin McGuire, associate director of the Virginia Water Resources Research Center. Credit: Virginia Tech

Even during summer dry spells, some isolated patches of soil in forested watersheds remain waterlogged.

These patches act as hot spots of microbial activity that remove nitrogen from groundwater and return it to the atmosphere, researchers from several institutions, including Virginia Tech, report in a leading scientific journal.

The discovery provides insight into the health of a forest. Nitrogen is an important nutrient for plant growth and productivity, but in streams, it can be a pollutant.

"The importance of these fragmented patches of saturated soil and their role in the fate of nitrogen in forested watersheds has been underappreciated until recently," said Kevin McGuire, an associate director of the Virginia Water Resources Research Center based in Virginia Tech's College of Natural Resources and Environment, co-author of the article to be published in the Proceedings of the National Academy of Sciences.

"We were able to determine the importance of denitrification in patches of shallow groundwater, which have largely been overlooked control points for nitrogen loss from temperate forested watersheds," McGuire said.

Most nitrogen is deposited by rain. Temperate forests receive much larger inputs of nitrogen from the atmosphere than they export to streams. Once nitrogen leaves the forest in streams, it can become a water pollutant.

"In some ecosystems, there have been long-term declines in stream water export of nitrogen when inputs have remained elevated," said co-author Christine Goodale, an associate professor of ecology and evolutionary biology at Cornell University.

"Understanding the fate of this nitrogen has been a challenge because denitrification -- a gaseous loss of nitrogen to the atmosphere -- is notoriously difficult to measure," said co-author Peter Groffman, an expert on denitrification at the Cary Institute of Ecosystem Studies.

Denitrification removes nitrogen from water and can therefore improve water quality in downstream lakes and estuaries.

However, nitrogen is also an important nutrient for plant growth in the forest so removals of nitrogen by natural processes can reduce the productivity of the forest.
The research, led by Sarah Wexler while she was a postdoctoral associate in hydrology and stable isotope geochemistry at Cornell University, took place in the Hubbard Brook Experimental Forest in the White Mountains of New Hampshire, where the atmosphere annually deposits five to seven pounds of nitrogen per acre.

The Hubbard Brook Experimental Forest is part of the National Science Foundation's Long Term Ecological Research Network.

McGuire, also an associate professor of hydrology in the Department of Forest Resources and Environmental Conservation, led another National Science Foundation-funded project at the site, which developed an organizing framework to describe and map variations of soil in the watershed that explain shallow groundwater occurrence and frequency.
Groundwater wells from this earlier study were used in the new research to monitor soils that may have had the right conditions to function as hot spots for denitrification.

At sites throughout the forest, the research team measured the presence of nitrate, a form of nitrogen that is highly mobile and reactive in the environment, determined whether the nitrate is a result of atmospheric deposition or microbial conversion, and discovered the nitrogen loss to the atmosphere.

"We were able to differentiate sources of nitrate and show that some of the nitrate was lost to the atmosphere by looking at nitrate at the atomic level, that is, at the isotopic composition of the nitrogen and oxygen in nitrate," said Wexler, who is now at the School of Environmental Sciences at the University of East Anglia in the United Kingdom. "The isotopic composition of nitrate provides a natural way to directly track the details of nitrogen cycling."

McGurie said, "Some work remains to be done, but the aim is to be able to develop a better sense of where and how nitrogen is processed in the environment and be in a position to predict how changes in climate, for example warmer and wetter conditions, affect nitrogen cycling and water quality in forested ecosystems."

Source: Virginia Tech

NASA Goddard instrument makes first detection of organic matter on Mars

MSL Curiosity rover at "John Klein" drill site. This self-portrait of NASA's Mars rover Curiosity combines dozens of exposures taken by the rover's Mars Hand Lens Imager on Feb. 3, 2013 plus three exposures taken May 10, 2013 to show two holes (in lower left quadrant) where Curiosity used its drill on the rock target "John Klein". Credit: NASA/JPL-Caltech/MSSS

The team responsible for the Sample Analysis at Mars (SAM) instrument suite on NASA's Curiosity rover has made the first definitive detection of organic molecules at Mars. Organic molecules are the building blocks of all known forms of terrestrial life, and consist of a wide variety of molecules made primarily of carbon, hydrogen, and oxygen atoms. However, organic molecules can also be made by chemical reactions that don't involve life, and there is not enough evidence to tell if the matter found by the team came from ancient Martian life or from a non-biological process. Examples of non-biological sources include chemical reactions in water at ancient Martian hot springs or delivery of organic material to Mars by interplanetary dust or fragments of asteroids and comets.

The surface of Mars is currently inhospitable to life as we know it, but there is evidence that the Red Planet once had a climate that could have supported life billions of years ago. For example, features resembling dry riverbeds and minerals that only form in the presence of liquid water have been discovered on the Martian surface. The Curiosity rover with its suite of instruments including SAM was sent to Mars in 2011 to discover more about the ancient habitable Martian environment by examining clues in the chemistry of rocks and the atmosphere.

The organic molecules found by the team were in a drilled sample of the Sheepbed mudstone in Gale crater, the landing site for the Curiosity rover. Scientists think the crater was once the site of a lake billions of years ago, and rocks like mudstone formed from sediment in the lake. Moreover, this mudstone was found to contain 20 percent smectite clays. On Earth, such clays are known to provide high surface area and optimal interlayer sites for the concentration and preservation of organic compounds when rapidly deposited under reducing chemical conditions.

While the team can't conclude that there was life at Gale crater, the discovery shows that the ancient environment offered a supply of reduced organic molecules for use as building blocks for life and an energy source for life. Curiosity's earlier analysis of this same mudstone revealed that the environment offered water and chemical elements essential for life and a different chemical energy source.

"We think life began on Earth around 3.8 billion years ago, and our result shows that places on Mars had the same conditions at that time -- liquid water, a warm environment, and organic matter," said Caroline Freissinet of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "So if life emerged on Earth in these conditions, why not on Mars as well?" Freissinet is lead author of a paper on this research submitted to the Journal of Geophysical Research-Planets.

The organic molecules found by the team also have chlorine atoms, and include chlorobenzene and several dichloroalkanes, such as dichloroethane, dichloropropane and dichlorobutane. Chlorobenzene is the most abundant with concentrations between 150 and 300 parts-per-billion. Chlorobenzene is not a naturally occurring compound on Earth. It is used in the manufacturing process for pesticides (insecticide DDT), herbicides, adhesives, paints and rubber. Dichloropropane is used as an industrial solvent to make paint strippers, varnishes and furniture finish removers, and is classified as a carcinogen.
It's possible that these chlorine-containing organic molecules were present as such in the mudstone. However, according to the team, it's more likely that a different suite of precursor organic molecules was in the mudstone, and that the chlorinated organics formed from reactions inside the SAM instrument as the sample was heated for analysis. Perchlorates (a chlorine atom bound to four oxygen atoms) are abundant on the surface of Mars. It's possible that as the sample was heated, chlorine from perchlorate combined with fragments from precursor organic molecules in the mudstone to produce the chlorinated organic molecules detected by SAM.

In 1976, the Gas Chromatograph Mass Spectrometer instrument on NASA's Viking landers detected two simple chlorinated hydrocarbons after heating Martian soils for analysis (chloromethane and dichloromethane). However they were not able to rule out that the compounds were derived from the instrument itself, according to the team. While sources within the SAM instrument also produce chlorinated hydrocarbons, they don't make more than 22 parts-per-billion of chlorobenzene, far below the amounts detected in the mudstone sample, giving the team confidence that organic molecules really are present on Mars.

The SAM instrument suite was built at NASA Goddard with significant elements provided by industry, university, and national and international NASA partners.

For this analysis, the Curiosity rover sample acquisition system drilled into a mudstone and filtered fine particles of it through a sieve, then delivered a portion of the sample to the SAM laboratory. SAM detected the compounds using its Evolved Gas Analysis (EGA) mode by heating the sample up to about 875 degrees Celsius (around 1,600 degrees Fahrenheit) and then monitoring the volatiles released from the sample using a quadrupole mass spectrometer, which identifies molecules by their mass using electric fields. SAM also detected and identified the compounds using its Gas Chromatograph Mass Spectrometer (GCMS) mode. In this mode, volatiles are separated by the amount of time they take to travel through a narrow tube (gas chromatography -- certain molecules interact with the sides of the tube more readily and thus travel more slowly) and then identified by their signature mass fragments in the mass spectrometer.

The first evidence for elevated levels of chlorobenzene and dichloroalkanes released from the mudstone was obtained on Curiosity Sol 290 (May 30, 2013) with the third analysis of the Cumberland sample at Sheepbed. The team spent over a year carefully analyzing the result, including conducting laboratory experiments with instruments and methods similar to SAM, to be sure that SAM could not be producing the amount of organic material detected.

"The search for organics on Mars has been extremely challenging for the team," said Daniel Glavin of NASA Goddard, a co-author on the paper. "First, we need to identify environments in Gale crater that would have enabled the concentration of organics in sediments. Then they need to survive the conversion of sediment to rock, where pore fluids and dissolved substances may oxidize and destroy organics. Organics can then be destroyed during exposure of rocks at the surface of Mars to intense ionizing radiation and oxidants. Finally, to identify any organic compounds that have survived, we have to deal with oxychlorine compounds and possibly other strong oxidants in the sample which will react with and combust organic compounds to carbon dioxide and chlorinated hydrocarbons when the samples are heated by SAM."

As part of Curiosity's plan for exploration, an important strategic goal was to sample rocks that represent different combinations of the variables thought to control organic preservation. "The SAM and Mars Science Laboratory teams have worked very hard to achieve this result," said John Grotzinger of Caltech, Mars Science Laboratory's Project Scientist. "Only by drilling additional rock samples in different locations, and representing different geologic histories were we able to tease out this result. At the time we first saw evidence of these organic molecules in the Cumberland sample it was uncertain if they were derived from Mars, however, additional drilling has not produced the same compounds as might be predicted for contamination, indicating that the carbon in the detected organic molecules is very likely of Martian origin."

Source: NASA/Goddard Space Flight Center