Melt ponds cause the Artic sea ice to melt more rapidly

Alfred Wegener Institute: The Arctic sea ice has not only declined over the past decade but has also become distinctly thinner and younger. Researchers are now observing mainly thin, first-year ice floes which are extensively covered with melt ponds in the summer months where once metre-thick, multi-year ice used to float. Sea ice physicists at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), have now measured the light transmission through the Arctic sea ice for the first time on a large scale, enabling them to quantify consequences of this change. They come to the conclusion that in places where melt water collects on the ice, far more sunlight and therefore energy is able to penetrate the ice than is the case for white ice without ponds. The consequence is that the ice is absorbing more solar heat, is melting faster, and more light is available for the ecosystems in and below the ice. The researchers have now published these new findings in the scientific journal Geophysical Research Letters.

Melt ponds count among the favourite motifs for ice and landscape photographers in the Arctic. They are captured glistening in a seductive Caribbean sea blue or dark as a stormy sea on the ice floe. “Their colour depends entirely on how thick the remaining ice below the melt pond is and the extent to which the dark ocean beneath can be seen through this ice. Melt ponds on thicker ice tend to be turquoise and those on thin ice dark blue to black”, explains Dr. Marcel Nicolaus, sea ice physicist and melt pond expert at the Alfred Wegener Institute.

In recent years he and his team have observed a strikingly large number of melt ponds during summer expeditions to the central Arctic. Virtually half of the one-year ice was covered with melt ponds. Scientists attribute this observation to climate change. “The ice cover of the Arctic Ocean has been undergoing fundamental change for some years. Thick, multi-year ice is virtually nowhere to be found any more. Instead, more than 50 per cent of the ice cover now consists of thin one-year ice on which the melt water is particularly widespread. The decisive aspect here is the smoother surface of this young ice, permitting the melt water to spread over large areas and form a network of many individual melt ponds”, explains Marcel Nicolaus. By contrast, the older ice has a rougher surface which has been formed over the years by the constant motion of the floe and innumerable collisions. Far fewer and smaller ponds formed on this uneven surface which were, however, considerably deeper than the flat ponds on the younger ice.

...To find out the extent to which Arctic sea ice permits the penetration of the sun’s rays and how large the influence of the melt ponds is on this permeability, the AWI sea ice physicists equipped a remotely operated underwater vehicle (ROV “Alfred”) with radiation sensors and cameras. In the summer of 2011 during an Arctic expedition of the research ice breaker POLARSTERN, they sent this robot to several stations directly under the ice. During its underwater deployments, the device recorded how much solar energy penetrated the ice at a total of 6000 individual points all with different ice properties!...

Melt pond on Arctic sea ice, Photo: Stefan Hendricks, Alfred Wegener Institute

Pine beetle outbreak buffers watersheds from nitrate pollution

University of Colorado-Boulder News: A research team involving several scientists from the University of Colorado Boulder has found an unexpected silver lining in the devastating pine beetle outbreaks ravaging the West: Such events do not harm water quality in adjacent streams as scientists had previously believed.

According to CU-Boulder team member Professor William Lewis, the new study shows that smaller trees and other vegetation that survive pine beetle invasions along waterways increase their uptake of nitrate, a common disturbance-related pollutant. While logging or damaging storms can drive stream nitrate concentrations up by 400 percent for multiple years, the team found no significant increase in the nitrate concentrations following extensive pine beetle tree mortality in a number of Colorado study areas.

“We found that the beetles do not disturb watersheds in the same way as logging and severe storms,” said Lewis, interim director of CU’s Cooperative Institute for Research in Environmental Sciences. “They leave behind smaller trees and other understory vegetation, which compensate for the loss of larger pine trees by taking up additional nitrate from the system. Beetle-kill conditions are a good benchmark for the protection of sub-canopy vegetation to preserve water quality during forest management activities.”

....“The U.S. Forest Service and other agencies have established harvesting practices that greatly mitigate damage to forests caused by logging, and they deserve credit for that,” said Lewis. “But this study shows just how important the survival of smaller trees and understory vegetation can be to stream water quality.”

In waterways adjacent to healthy pine forests, concentrations of nitrate is generally far lower than in rivers on the plains in the West like the South Platte, said Lewis. Nitrate pollution is caused by agricultural runoff from populated areas and by permitted discharges of treated effluent from water treatment facilities....

Fog at the treeline in Rocky Mountain State Park, shot by Michael Gäbler, Wikimedia Commons, under the Creative Commons Attribution 3.0 Unported license

NASA chases climate change clues into the stratosphere

Science Daily: Starting this month, NASA will send a remotely piloted research aircraft as high as 65,000 feet over the tropical Pacific Ocean to probe unexplored regions of the upper atmosphere for answers to how a warming climate is changing Earth.

The first flights of the Airborne Tropical Tropopause Experiment (ATTREX), a multi-year airborne science campaign with a heavily instrumented Global Hawk aircraft, will take off from and be operated by NASA's Dryden Flight Research Center at Edwards Air Force Base in California. The Global Hawk is able to make 30-hour flights.

Water vapor and ozone in the stratosphere can have a large impact on Earth's climate. The processes that drive the rise and fall of these compounds, especially water vapor, are not well understood. This limits scientists' ability to predict how these changes will influence global climate in the future. ATTREX will study moisture and chemical composition in the upper regions of the troposphere, the lowest layer of Earth's atmosphere. The tropopause layer between the troposphere and stratosphere, 8 miles to 11 miles above Earth's surface, is the point where water vapor, ozone and other gases enter the stratosphere.

Studies have shown even small changes in stratospheric humidity may have significant climate impacts. Predictions of stratospheric humidity changes are uncertain because of gaps in the understanding of the physical processes occurring in the tropical tropopause layer. ATTREX will use the Global Hawk to carry instruments to sample this layer near the equator off the coast of Central America.

"The ATTREX payload will provide unprecedented measurements of the tropical tropopause," said Eric Jensen, ATTREX principal investigator at NASA's Ames Research Center in Moffett Field, Calif. "This is our first opportunity to sample the tropopause region during winter in the northern hemisphere when it is coldest and extremely dry air enters the stratosphere."...

NASA In its new white-and-blue NASA livery, an early development model of the Global Hawk unmanned aircraft rests on the ramp at the Dryden Flight Research Center, Edwards AFB, Calif. Photo Credit: NASA

Lower nitrogen losses with perennial biofuel crops

Debra Levey Larson in the University of Illinois College of Agricultural, Consumer and Environmental Sciences News: Perennial biofuel crops such as miscanthus, whose high yields have led them to be considered an eventual alternative to corn in producing ethanol, are now shown to have another beneficial characteristic–the ability to reduce the escape of nitrogen in the environment. In a 4-year University of Illinois study that compared miscanthus, switchgrass, and mixed prairie species to typical corn-corn-soybean rotations, each of the perennial crops were highly efficient at reducing nitrogen losses, with miscanthus having the greatest yield.

“Our results clearly demonstrate that environmental nitrogen fluxes from row-crop agriculture can be greatly reduced after the establishment of perennial biofuel crops,” said U of I postdoctoral research associate Candice Smith.  “Because of the establishment variability, we were able to compare annual row crops with perennial crops. Although in the first two years, nitrate leaching remained high in the non-established miscanthus crop, once a dense, productive crop was established in the second year of growth, nitrate leaching in tile drainage quickly decreased.”

Smith said that this ability to reduce the loss of nitrogen into the environment will prove to be greatly beneficial.

 “Intensive corn production with large fertilizer inputs leads to large losses of nitrogen into the environment, both through gas emissions of nitrous oxide and leaching of nitrate to surface waters through tile drainage systems,” added Mark David, U of I biogeochemist. “Nitrous oxide is a greenhouse gas, and nitrate can contaminate drinking water supplies and leads to coastal ocean problems. The hypoxic zone that forms each summer in the Gulf of Mexico is a result of nitrate leaching from the tile-drained Corn Belt of the midwestern United States – a likely location for biofuel production,” he said....

An aerial view of the bioenergy farm near South First Street in Champaign, Illinois, photo from the university's website

Fear of 'catastrophic' sea-level rise as ice sheets melt faster than predicted

Steve Connor in the Independent (UK): Glaciologists fear they may have seriously underestimated the potential for melting ice sheets to contribute to catastrophic sea-level rises in coming decades which could see increases of a metre or more by 2100.

The ice sheets of Greenland and Antarctica contain about 99.5 per cent of the Earth's glacier ice and could raise sea levels by 65 metres if they melted completely – although experts think this is highly unlikely in the foreseeable future. However, a survey of the world's top 26 glaciologists found most believe melting of the ice sheets could be more rapid and severe than previously estimated. They believe that melting of the ice sheets alone this century would be likely to raise the average global sea level by 29cm, the poll found, but there is a five per cent chance of it increasing even further by a catastrophic 84cm.

This would take the total sea-level increase to well over a metre if other factors such as the thermal expansion of oceans and runoff from mountain glaciers are taken into account. "Our analysis shows the biggest uncertainty when it comes to sea levels is the contribution from the ice sheets," said Professor Jonathan Bamber of Bristol University, lead author of the study published in the journal Nature Climate Change.

"It shows glaciologists believe there is a one-in-20 chance of sea levels rising by a metre or more by 2100, and a metre rise in sea level is really very serious. "The impacts of sea-level rise of this magnitude are potentially severe, implying a conceivable risk of the forced displacement of up to 187 million people within this century."...

The 1872 Baltic sea flood in southern Lolland, Denmark. Xylography from Illustreret Tidende

US study says El Nino, climate change link fuzzy

Space Daily via AFP: The frequency and volatility of El Nino, a weather pattern that hammers the tropical Pacific Ocean every five years or so, does not seem linked to climate change, said US research released Thursday. The study involved scientists measuring the monthly growth of ancient coral fossils found on two tropical Pacific islands to determine what, if any, impact the warming climate had on the weather phenomenon.

By reconstructing temperatures and precipitation over the millenniums, the study compared it to the frequency and intensity of El Nino and found that the latter had indeed become more intense and frequent in the 20th century.

But although the increase was statistically significant and could be linked to climate change, the long historic record provided by the coral fossils allowed the researchers to determine that the El Nino Southern Oscillation, or ENSO, has also had large natural variations in past centuries. Thus, it is not clear that changes seen in recent decades can be linked to climate change caused by rising levels of carbon dioxide, the researchers said.

"The level of ENSO variability we see in the 20th century is not unprecedented," said climatologist Professor Kim Cobb, from the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology. "But the 20th century does stand out, statistically, as being higher than the fossil coral baseline," she added....

Fossilized coral stones, shot by Irwan Holmes, Wikimedia Commons, under the Creative Commons Attribution 3.0 Unported license

New study documents the natural relationship between CO2 concentrations and sea level

AlphaGalileo via the National Oceanography Centre: By comparing reconstructions of atmospheric CO2 concentrations and sea level over the past 40 million years, researchers based at the National Oceanography Centre, Southampton have found that greenhouse gas concentrations similar to the present (almost 400 parts per million) were systematically associated with sea levels at least nine metres above current levels.

The study determined the ‘natural equilibrium’ sea level for CO2 concentrations ranging between ice-age values of 180 parts per million and ice-free values of more than 1,000 parts per million. It takes many centuries for such an equilibrium to be reached, therefore whilst the study does not predict any sea level value for the coming century, it does illustrate what sea level might be expected if climate were stabilized at a certain CO2 level for several centuries.

Lead author Dr Gavin Foster, from Ocean and Earth Science at the University of Southampton which is based at the centre, said, “A specific case of interest is one in which CO2 levels are kept at 400 to 450 parts per million, because that is the requirement for the often mentioned target of a maximum of two degrees global warming.”

The researchers compiled more than two thousand pairs of CO2 and sea level data points, spanning critical periods within the last 40 million years. Some of these had climates warmer than present, some similar, and some colder. They also included periods during which global temperatures were increasing, as well as periods during which temperatures were decreasing.

...The researchers found that the natural relationship displays a strong rise in sea level for CO2 increase from 180 to 400 parts per million, peaking at CO2 levels close to present-day values, with sea level at 24 +7/-15 metres above the present, at 68 per cent confidence limits.

“This strong relationship reflects the climatic sensitivity of the great ice sheets of the ice ages,” said Dr Foster. “It continues above the present level because of the apparently similar sensitivity of the Greenland and West Antarctic ice sheets, plus possibly some coastal parts of East Antarctica.”...

The Mertz Glacier in Antarctica, shot by Jacques.verron, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Why some grasses got better photosynthesis

Brown University News: Even on the evolutionary time scale of tens of millions of years there is such a thing as being in the right shape at the right time. An anatomical difference in the ability to seize the moment, according to a study led by Brown University biologists, explains why more species in one broad group, or clade, of grasses evolved a more efficient means of photosynthesis than species in another clade.

Biologists refer to the grasses that have evolved this better means of making their food in warm, sunny, and dry conditions with the designation “C4.” Grasses without that trait are labeled “C3.” What scientists had already known is that while all of the grasses in the BEP and PACMAD clades have the basic metabolic infrastructure to become C4 grasses, the species that have actually done so are entirely in the PACMAD clade. A four-nation group of scientists wondered why that disparity exists.

To find out, Brown postdoctoral researcher and lead author Pascal-Antoine Christin spent two years closely examining the cellular anatomy of 157 living species of BEP and PACMAD grasses. Using genetic data, the team also organized the species into their evolutionary tree, which they then used to infer the anatomical traits of ancestral grasses that no longer exist today, a common analytical technique known as ancestral state reconstruction. That allowed them to consider how anatomical differences likely evolved among species over time.

…Erika Edwards“Now that we have this increasingly detailed bird’s-eye view, we can start to become a more predictive science. ... In terms of genetic engineering we’re going to be able to provide some useful information to people who want to improve species, such as important crops.”

“Now that we have this increasingly detailed bird’s-eye view, we can start to become a more predictive science. ... In terms of genetic engineering we’re going to be able to provide some useful information to people who want to improve species, such as important crops.” Credit: Mike Cohea/Brown UniversityIn C4 plants, such an anatomical arrangement facilitates a more efficient transfer and processing of CO2 in the bundle sheath cells when CO2 is in relatively short supply. When temperatures get hot or plants become stressed, they stop taking in as much CO2, creating just such a shortage within the leaf…

A grassland in Canastra, Brazil, shot by BDG2007, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license

African scientists call for climate change evidence

Emeka Johnkingsley in SciDev.net: African scientists urgently need to build more evidence on the impact of climate change on the continent, a conference has heard. A joint statement issued at the eighth Annual Meeting of African Science Academies last month (12–14November) in Nigeria, notes that Africa lacks much home-grown data about the impacts of extreme weather events and sea level rise.

It says: "Actions required of science include contributions to the development of risk assessments and mapping for various anticipated climate-related extreme events. The refinement of modelling techniques, taking account also of natural systems and traditional knowledge, in developing early warning systems contributes to strengthen risk reduction.”

Nigeria's president, Goodluck Jonathan, launched the statement, entitled 'Climate change in Africa: using science to reduce climate risks', and stressed that climate change information is needed for planning. "We believe that strong evidence-based knowledge on climate change will help policymakers take decisions and actions required to reduce climate risks in Africa," he said.

Roseanne Diab, executive officer of the Academy of Science of South Africa, toldSciDev.Net that a study on the impact of climate change on Africa would take at least two years and should be coordinated by the Network of African Science Academies (NASAC)….

Touaregs in Mali, shot by Alfred Weidinger, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

Amazon deforestation brings loss of microbial communities

EurekAlert via the University of Massachusetts at Amherst: An international team of microbiologists led by Klaus Nüsslein of the University of Massachusetts Amherst has found that a troubling net loss in diversity among the microbial organisms responsible for a functioning ecosystem is accompanying deforestation in the Amazon rainforest.

Nüsslein, an expert in tropical rain forest microbial soil communities, says, "We found that after rainforest conversion to agricultural pastures, bacterial communities were significantly different from those of forest soils. Not only did the pasture soils show increased species numbers, these species were also less related to one another than in rainforest soil. This is important because the combination of lost forest species and the homogenization of pasture communities together signal that this ecosystem is now a lot less capable of dealing with additional outside stress."

He and colleagues studied a large farm site over the past four years at the frontier where farmers drive agriculture into pristine rainforest in Rondonia, Brazil, to convert rainforest to agricultural use. Findings in part validated previous research showing that bacteria in the soil became more diverse after conversion to pasture. However, in its fourth year, their study overcame limitations of earlier investigations to show that changes in microbial diversity occurred over larger geographic scales. Results appear in the current issue of Proceedings of the National Academy of Sciences.

In addition to Nüsslein at UMass Amherst, the research group includes first author Jorge Rodrigues at the University of Texas at Arlington with Brendan Bohannan at the University of Oregon, James Tiedje at Michigan State University, and others at the University of Sao Paulo. Lead investigators Nüsslein and Rodrigues emphasize that the study is an equal collaboration among the four research groups.

Findings do not support earlier study conclusions, instead they show that the loss of restricted ranges for different bacteria communities results in a biotic homogenization and net loss of diversity overall. Scientists worry that the loss of genetic variation in bacteria across a converted forest could reduce ecosystem resilience. The researchers hope their work will provide valuable data to those making decisions about the future of the Amazon rainforest....

From NASA: The 38-kilometer-long Lago do Erepecu (Lake Erepecu) in Brazil runs parallel to the lower Rio Trombetas (Trombetas River), which snakes along the upper half of this astronaut photograph. Water-bodies in the Amazon Rainforest are often so dark they can be difficult to distinguish. In this image, however, the lake and river stand out from the uniform green of the forest in great detail as a result of sun-glint on the water surface. Sun-glint is the mirror-like reflection of sunlight off of a surface directly back towards the viewer, in this case an astronaut on-board the International Space Station. Forest soil is red, as shown by airfield clearings near Porto Trombetas (image far upper left), a river port on the south side of the Trombetas River.

Severe drought has lasting effects on Amazon

Hannah Hoag in Nature: A study published today in the Proceedings of the National Academy of Sciences sheds light on the long-term effects of drought on the Amazon rainforest — giving clues about how the rainforest might be affected by global warming in the future. The researchers report that the severe drought that hit the rainforest in 2005 had lasting effects on the forest canopy, such that it remained damaged at least four years later.

The effects of the 2005 drought have been debated since 2007, when researchers reported in Science that photosynthesis within the canopy had increased, leading the Amazon basin to ‘green up’ during the dry period. But in 2010 another group reported that they were unable to reproduce the results using the same data3.

“The ‘green-up’ is a short-term response and a bit of a red herring,” says Oliver Phillips, a tropical ecologist at the University of Leeds, UK. But the latest study “transcends that debate”, he says. “The question of the underlying health of the forest is much deeper than the instantaneous response.”

A drawback of the method used in the earlier studies — which used satellite measurements to estimate forest greenness using reflected solar radiation — is that the data can be muddied by clouds and atmospheric aerosols. So for the latest study, Sassan Saatchi, a remote-sensing expert at the California Institute of Technology Jet Propulsion Laboratory in Pasadena, California, studied the forest’s microwave ‘silhouette’, showing its contours instead of its greenness. To look at canopy structure, he and his colleagues used microwave satellite data, which are unaffected by clouds, from a NASA probe. When it passed over lush canopy, the satellite sensor recorded a smooth signal. Bare branches, thinned leaves and missing trees showed more roughness.

The researchers found that more than 70 million hectares of rainforest in the western Amazon — an area nearly twice the size of California — were hit by the drought. And the canopy’s recovery dragged on long after the drought ended, with its biomass and fullness still below pre-drought levels in 2009 when the satellite suffered a mechanical failure. In 2010, an even stronger drought hit a larger swathe of the Amazon....

Aerial view of the Amazon, shot by lubasi, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license

Science key to reducing impacts of future natural hazards in developing countries

University of Cambridge Enterprise: The use of science to reduce the effects of future natural hazards such as floods, droughts and earthquakes must be stepped up and adopted more widely, according to a newly published Foresight report.

The report, 'Reducing Risks of Future Disasters: Priorities for Decision Makers' sets out how the threat of future disasters resulting from natural hazards can be stabilised if decision makers make better use of technological developments and existing risk assessment methods. This will save lives, livelihoods and resources in developing countries.

The report also urges that disaster risk reduction is routinely built in to developments as diverse as urban infrastructure, ecosystem protection and mobile telephone regulation. These measures would help reduce the cost of disasters, which has outstripped the total international aid investment over the past 20 years and has led to the loss of 1.3 million lives and $2 trillion of damage.

Professor Peter Guthrie, Thalia Konaris and former PhD student Faye Karababa, all from the Department of Engineering, have been involved in the report. The work was undertaken through Consultancy Services at Cambridge Enterprise.

“Death and destruction are not the inevitable consequences of natural hazards,” said Government Chief Scientific Adviser Sir John Beddington, who led the research. “We need to grasp this. Urbanisation over the next three decades, particularly in Africa and Asia, will continue. While this could lead to greater exposure and vulnerability, it also presents the greatest opportunity to protect large concentrations of people....

A fatal gap between science and policy?

David Dickson in SciDev.net: little more than 30 years ago, a major UN conference on science and technology for development held in Vienna, Austria, ended on an upbeat note with an agreement in principle to set up a US$250-million fund to finance capacity-building projects.

Sadly, the heady optimism among delegates, which I remember vividly, was short lived. No major donations were received and science slipped off the international aid agenda for the next two decades, during which time the gap in scientific capacity between rich and poor nations grew larger.

The latest negotiations, COP 18, ended in Doha, Qatar, earlier this month with a similar agreement to establish a mechanism to transfer money from rich to poor nations to compensate for the "loss and damage" caused by rich countries' addiction to carbon-based fuels. Judging from media reports, this decision was met with an enthusiasm similar to that at the 1979 Vienna conference.

But there is no binding commitment, and the possibility of significant money becoming available looks remote given that rich nations have so far failed to act on the 2010 promise to raise US$100 billion a year by 2020 to help developing nations cope with climate change.

The otherwise disappointing outcome of COP 18 reflects the growing gap between the science and the politics of climate change. While the scientific case for action hardens, the ability politicians to act appropriately — by replacing the soon-to-terminate Kyoto Protocol, for example — appears to be diminishing, creating a scenario for global disaster.

Science communicators in general — and science journalists in particular — have a key role in bridging this gap. We must present scientific evidence to politicians and the public in a way that means such evidence becomes the basis for sound decisions....

Reading a newspaper in Addis Ababa, shot by Terje Skjerdal, Wikimedia Commons via Flickr,  under the Creative Commons Attribution 2.0 Generic license

The Green Revolution is wilting

Seed Daily via SPX: The Green Revolution has stagnated for key food crops in many regions of the world, according to a study published in the Nature Communications by scientists with the University of Minnesota's Institute on the Environment and McGill University in Montreal, Canada. Led by IonE research fellow Deepak Ray, the study team developed geographically detailed maps of annual crop harvested areas and yields of maize (corn), rice, wheat and soybeans from 1961 to 2008.

It found that although virtually all regions showed a yield increase sometime during that period, in 24 to 39 percent of the harvested areas (depending on the crop) yield plateaued or outright declined in recent years.

Among the top crop-producing nations, vast areas of two of the most populous - China and India - are witnessing especially concerning stagnation or decline in yield. "This study clearly delineates areas where yields for important food crops are stagnating, declining, or never improved, as well areas where yields are still rapidly improving," Ray says.

"As a result, it both sounds the alert for where we must shift our course if we are to feed a growing population in the decades to come, and points to positive examples to emulate."

Interestingly, the researchers found that yields of wheat and rice - two crops that are largely used as food crops, and which supply roughly half of the world's dietary calories - are declining across a higher percentage of cropland than those of corn and soybean, which are used largely to produce meat or biofuels....

A rice field in Indonesia, shot by Mark Veeraart, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

Soil determines fate of phosphorus

Brown University News: Just 20 years ago, the soils of the Amazon basin were thought unsuitable for large-scale agriculture, but then industrial agriculture — and the ability to fertilize on a massive scale — came to the Amazon. What were once the poorest soils in the world now produce crops at a rate that rivals that of global breadbaskets. Soils no longer seem to be the driver — or the limiter — of agricultural productivity. But a new Brown University-led study of three soybean growing regions, including Brazil, finds that soils have taken on a new role: mediating the environmental consequences of modern farming.

The study focuses on the relationship between soils and phosphorus, a key agricultural nutrient. Typically in short supply, particularly in tropical soils, phosphorus is unique among fertilizer requirements. It is finite, irreplaceable and mined in just a few places around the world.

“If that suggests scarcity, which is a concern, the overuse of phosphorus can also pose another problem, causing harmful algal blooms in waterways,” said Stephen Porder, assistant professor of biology in the Department of Ecology and Evolutionary Biology and co-author of the study in the January 2013 edition of BioScience, posted early online. “It’s a bit of a Goldilocks problem — too much and our waterways are choked with algae, too little and we cannot produce enough food.”

...The new study compares the production of a single crop, soybeans, in the three places they are grown most — Iowa in the United States, Mato Grosso in Brazil, and Buenos Aires in Argentina. What the authors found was an example that illustrates how the combination of management and soil type frames the phosphorus-related concerns associated with these massive agricultural enterprises.

“Here are three regions where the crop that comes off the farm field is the same, but the fertilizer that goes in and the effects of this fertilizer on the environment are very different,” said lead author Shelby Riskin of Brown University and the Marine Biological Laboratory.

 “Having a one-size-fits-all approach to our understanding of interaction between people and their environment via agriculture is going to lead us to some erroneous concerns and conclusions if we don’t take the regional biophysical setting into account,” Porder said. “If you are concerned about the global phosphorus supply, Brazil is your problem — they are using a ton of it. If you are concerned about lakes and rivers being filled with algae, then Iowa is your problem, and learning how to mitigate even very small amounts of loss after decades of overfertilization is a real challenge.”...

Harvesting cotton in Brazil, shot by João Felipe C.S, public domain

Invasive plant species may harm native grasslands by changing soil composition

Newswise: The future landscape of the American Midwest could look a lot like the past—covered in native grasslands rather than agricultural crops. This is not a return to the past, however, but a future that could depend on grasslands for biofuels, grazing systems, carbon sequestration, and other ecosystem services. A major threat to this ecosystem is an old one—weeds and their influence on the soil.

According to a study in the journal Invasive Plant Science and Management, when invasive plants spread, they can leave behind a “legacy” of alteration in the native soil. Even after an invading species has been controlled, its effects can inhibit the regrowth of native plant species. The causes of this process are still being investigated and may involve changes in soil food webs, soil microbial communities, and mutualistic fungi.

In the study, researchers tested soil conditions for changes in composition after three growth cycles of invasive plant species. Researchers looked for changes in colonization rates, diversity, and composition of arbuscular-mycorrhizal fungi (AMF).

Three exotic plant species—crested wheatgrass, smooth brome, and leafy spurge—were tested in a glasshouse experiment. These plants, all characterized as strong invaders, were grown in native soil collected from North Dakota grasslands. Native species, including western wheatgrass, little bluestem, and blue gramma, were also grown, and after three growth cycles, soil composition was compared among these treatments....

Grasslands in Inner Mongolia, shot by Shizhao, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Tropical trees are largest emitter of methane in their ecosystem

The Open University News: Researchers at The Open University have found that trees in Bornean rainforests emit more methane than any other element of the ecosystem, which provides a new understanding about sources of this powerful greenhouse gas from tropical ecosystems.

In a paper titled Trees are major conduits for methane egress from tropical forested wetlands by Dr Vincent Gauci and Sunitha Pangala, published in New Phytologist on 18 December, the researchers announced new findings which show that trees in tropical peat forests of Southeast Asia release more methane through their stems than is emitted from the soil surface.

Sunitha Pangala, final year PhD student at The Open University’s Centre for Earth, Planetary Space and Astronomical Research, and lead author on the paper said: "This is the first study to measure methane release from tree stems in tropical peat swamps and evaluate its importance at an ecosystem level. Our research establishes that trees in tropical peat swamps are the largest emission pathway of methane in that ecosystem."

Previously it was thought that methane was only emitted via diffusion and bubbles at the wetland surface. The team measured methane emissions from healthy tree stems in a tropical forested peatland in the upper Sebangau River catchment in Borneo. They found significant quantities of methane being released from the stems of seven of the eight tree species studied. They estimated up to 87% of the methane are released from tree stems, highlighting that the previous methane emission inventories of this ecosystem may have been severely underestimated.

"This work challenges our previous understanding of how these ecosystems exchange methane with the atmosphere and adds another piece to the tropical methane emission puzzle,” said Dr Vincent Gauci, Senior Lecturer, Earth Systems, and the project’s leader. "It further shows that for wet tropical forested ecosystems, the like of which span south America, Africa and southeast Asia, researchers may have been missing most of the methane emitted from these ecosystems if they neglected to measure tree stem emissions.”...

A 1859 rendering of Borneo

Fertile soil doesn't fall from the sky: The contribution of bacterial remnants to soil fertility has been underestimated until now

Helmholtz Centre for Environmental Research: Remains of dead bacteria have far greater meaning for soils than previously assumed. Around 40 per cent of the microbial biomass is converted to organic soil components, write researchers from the Helmholtz Centre for Environmental Research (UFZ), the Technische Universität Dresden (Technical University of Dresden) , the University of Stockholm, the Max-Planck-Institut für Entwicklungsbiologie (Max Planck Institute for Developmental Biology) and the Leibniz-Universität Hannover (Leibniz University Hannover) in the professional journal Biogeochemistry.

Until now It was assumed that the organic components of the soil were comprised mostly of decomposed plant material which is directly converted to humic substances. In a laboratory experiment and in field testing the researchers have now refuted this thesis. Evidently the easily biologically degradable plant material is initially converted to microbial biomass which then provides the source material to soil organic matter.

Soil organic matter represent the largest fraction of terrestrially bound carbon in the biosphere. The compounds therefore play an important role not only for soil fertility and agricultural yields. They are also one of the key factors controlling the concentration of carbon dioxide in the atmosphere. Climatic change can therefore be slowed down or accelerated, according to the management of the soil resource.

In laboratory incubation experiment, the researchers initially labelled model bacteria with the stable isotope 13C and introduced the bacteria to soil deriving from the long-term cultivation experiment "Ewiger Roggenbau" in Halle/Saale. Following the incubation time of 224 days the fate of the carbon of bacterial origin was determined. "As a result we found fragments of bacterial cell walls in sizes of up to 500 x 500 nanometres throughout our soil samples. Such fragments have also been observed in other studies, but have never been identified or quantified", declares Professor Matthias Kästner of the UFZ.

...."This new approach explains many properties of organic soil components which were previously viewed as contradictory", says Matthias Kästner....

A canyon formed in the soft loess soil by a small stream that flows from the west into the Daxia He River, in the northeastern part of Linxia County (probably, Xihe Township), in western China. Shot by Vmenkov, Wikimedia Commons,  under the Creative Commons Attribution-Share Alike 3.0 Unported license

Agricultural research 'key to easing climate-change impacts'

Rasha Dewedar in SciDev.net:  Agricultural research should be a strategic priority of the UN's efforts to lessen the impacts of climate change, according to a report launched at a UN climate change conference in Doha, Qatar.

The report, released by a group of leading international experts in climate change and agriculture last month (30 November), is intended to inform policymakers and agricultural planners about the risks climate change poses to dry areas. It offers practical solutions to reduce these threats and boost the productivity of this type of land.

'Strategies for Combating Climate Change in Drylands Agriculture' was produced by the International Center for Agricultural Research in the Dry Areas (ICARDA) with two CGIAR research programmes — on Dryland Systems and on Climate Change, Agriculture and Food Security (CCAFS) — and the Qatar National Food Security Programme.

Drylands constitute more than 40 per cent of the world's land surface and are home to 2.5 billion people, says the report. Those lands have less than eight per cent of the world's renewable water sources and are vulnerable to temperature extremes, frequent drought, land degradation and desertification, it adds....

A dry field in Chandeni, India, shot by Nitin.i.azam, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Dead or alive? A new test to determine viability of soybean rust spores

Seed Daily via SPX: Spores from Asian soybean rust (Phakopsora pachyrhizi) pose a serious threat to soybean production in the United States because they can be blown great distances by the wind. University of Illinois researchers have developed a method to determine whether these spores are viable.

"Finding spores is different from finding spores that are living and able to infect plants," said USDA Agricultural Research Service (ARS) scientist and crop sciences professor Glen Hartman.

Soybean rust, which first appeared in Japan at the beginning of the 20th century, is a foliar infector that reduces plant photosynthetic activity and causes defoliation, premature death, and high yield loss. An obligate pathogen, it grows only on plants and dies when the plant dies or is harvested.

The fungus first appeared In the U.S. in 2004. It is concentrated in the southern states where it is able to overwinter on kudzu. Spraying with fungicides is the only way to control it because resistant soybean cultivars are not yet available to U.S. farmers....

A photo of soybean rust from the US Department of Agriculture