Setting out the best strategies for achieving this goal by studying examples of good practice globally, the Zero Carbon Homes Project was inspired by a progressive new policy introduced in 2007 by the UK government to ensure that all new homes built post 2016 would be zero carbon. It was this move that marked the most radical approach to residential carbon reduction to date.

Dr Jo Williams, principal investigator of the Zero Carbon Homes Project from the UCL Bartlett School of Planning said: “Since 2007 very little has happened in the UK, at least in part due to the economic crisis and subsequent housing slump. However there are other factors at play here not least a lack of political support and significant institutional inertia to change.” The findings of the project were recently published in the book Zero Carbon Homes — A Road Map.

Housing currently generates 7% of global CO₂ emissions, according to 2009 International Energy Agency Statistics. In Europe this figure rises to 10%, with CO₂ emissions in the US even higher at 20%. However, currently the largest regional increase in CO₂ emissions for residential buildings is in developing Asia (accounting for 42%) and the Middle East/North Africa (accounting for 42%), providing a real challenge to the mitigation of climate change.

Dr Williams said: “Zero carbon homes are technically feasible to build, and with the right legislative and fiscal framework they are also affordable as demonstrated in Europe and the USA. With rapid reduction in the price of low carbon technologies and rising energy costs, zero carbon homes will make increasing economic sense, even in the short-term.”

Yet while the technology exists, the research highlights that currently the biggest barrier to the development of zero carbon homes internationally are the construction and energy industries, particularly the energy industry. The project identified lots of examples of good practice globally, but few where low carbon prototypes had become widespread across cities or regions.

For wider deployment of low carbon development to occur it would require that the international regulatory framework forced the energy industry to diversify their current portfolios, to become suppliers of low carbon energy and of services to reduce energy consumption.

“In the absence of an international framework the onus rests on nation states or individual cities to have the political courage to support the delivery of this agenda,” said Dr Williams.

So far purely market-based approaches to the deployment of zero carbon homes haven’t worked, even when there are high concentrations of green consumers. As in the past, where wider deployment of prototypes had occurred within nation states and cities it had been driven by legislation, in conjunction with some form of subsidy in the early phases of deployment.

With the limited market demand for zero carbon homes, house purchase decisions aren’t based on the energy efficiency of a house, let alone its CO₂ emissions. The research demonstrated that cost, location and design are the most important factors influencing purchase decisions, even amongst green consumers. However, if in those three respects housing is comparable, the potential for energy savings does become a consideration for consumers.

“It is important to have a range of options when providing zero carbon homes, to offer a diversity of designs, price and location. However, our studies found that the simpler you make it for the consumer to have installed and operate low carbon technologies, the greater market interest,” said Dr Williams.

“Consumers want to be able to move from house to house without having to be taught how to use the technology provided in their new home. Most also don’t want to have to make the decision as to whether they want PV or a ground-source heat-pumps installed. Universal user-technology interfaces, companies offering management and maintenance services and house-builders who make the technological decisions on the part of the house-purchaser will all help to increase market demand.”

She added: “The bigger picture is that zero carbon homes are a win-win option. Of course they reduce CO₂ emissions thus slowing the process of global warming, but they also significantly reduce energy costs for the householder. They increase the potential for cities and nations states to be more energetically self-sufficient, an important consideration when we are entering a period of fuel scarcity.”

There are also potential economic and social benefits which accrue from the development of zero carbon homes. The research suggests that zero carbon developments can offer a potential investment opportunity. For example a 10% return on investment was reported for a community energy project in Germany, more lucrative than putting it in a savings account or investing in an ISA.

The new infrastructure required for zero carbon homes has also led to the creation of associated new industries and jobs with the obvious social and economic benefits. In some models where residents are more involved in the management and maintenance of the new infrastructure it has also helped to build stronger social networks within local communities.

Story Source: University College London

Article source: http://www.sciencedaily.com/releases/2011/12/111215095501.htm

The study, recently published in the peer-reviewed online journal PLoS ONE, finds that the birds aren’t migrating as rapidly as scientists previously anticipated based on recorded temperature increases.

The animals instead may be tracking changes in vegetation, which can only move slowly via seed dispersal.

“This is the first study to evaluate the effects of warming on the elevation ranges of tropical birds,” says Stuart Pimm, Doris Duke Professor of Conservation Ecology at Duke’s Nicholas School of the Environment and a co-author of the study. “It provides new evidence of their response to warming, but also shows there is a delay in their response.”

Evidence from temperate areas, such as North America and Europe, shows that many animal and plant species are adapting to climate change by migrating northward, breeding earlier or flowering earlier in response to rising temperatures.

“However, our understanding of the response of tropical birds to warming is still poor,” says German Forero-Medina, a PhD student at Duke’s Nicholas School who is lead author of the new study. “Moving to the north doesn’t help them, because tropical temperatures do not change very much with latitude. So moving “up” to higher elevations is the only way to go — but there are few historical data that can serve as baselines for comparison over time.”

What is going on with tropical species at higher altitudes is important, Forero-Medina explains, because about half of all birds species live at 3500 feet or more above sea level, and of these species, more than 80 percent may live within the tropics.

In 2010, the authors of the new study and a team of biologists participated in an expedition to the summit of the remote Cerros del Sira mountains in central Peru — a place visited by only a few ornithologists on prior occasions. The complex topography, geology, and climate of the mountains have produced isolated patches of habitat with unique avian communities and distinct taxa.

Forero-Medina and his colleagues used survey data collected on bird species in the region in the 1970s by John Terborgh, research professor emeritus at Duke, to compare past and present distributions.

“Using John Terborgh’s groundbreaking data — the first ever collected from this region -gave us a unique opportunity to understand the effects of 40 years of warming on tropical birds,” Forero-Medina says.

The biologists found that although the ranges of many bird species have shifted uphill since Terborgh’s time, the shifts fell short of what scientists had projected based on temperature increases over the four decades.

“This may be bad news,” Pimm says. “Species may be damned if they move to higher elevations to keep cool and then simply run out of habitat. But, by staying put, they may have more habitat but they may overheat.”

Story Source: Duke University

Anti-fungal and anti-bacterial additives in house paint are present in dangerous quantities in the Vauchère river basin in the city of Lausanne, says a study to be presented the 9th of December, at the American Geophysical Union (AGU) conference in San Francisco. Chemicals engineered to kill microorganisms, called biocides, are added to exterior paints in order to prevent molding and plant growth. Washed off of building facades during heavy rains, however, these chemicals can be wind up in soil, groundwater and river basins where they attack bacteria, fungi and algae at the bottom of the food chain. Researchers at EPFL’s Ecological Engineering Laboratory have now modeled the flow of biocides from building façades into river basins with surprising accuracy, which could lead to stricter regulations for Switzerland and abroad.

In Switzerland, biocides are present in exterior paint on some 60% of buildings and they are common worldwide. The global demand on all biocides for use in industrial and consumer goods was estimated at US$6.4 billion in 2008. Certain antifouling biocides have been phased out of use on boat hulls after being proven toxic to marine life.

The mathematical tool developed by Sylvain Coutu at EPFL accurately predicts peak concentration levels in a local river of three biocides commonly found in industrial paint: DCMU, Terbutryn and Carbendazim. Coutu predicted the concentration of these biocides after four rainstorms during the spring of 2011 and compared the numbers to actual measurements taken from the river. The model proved accurate up to a couple of nanograms per liter, an impressive feat considering the variety and complexity of variables. The model’s strength comes from its delicate balance between the simplification of urban surface hydraulic behaviors — how water is channeled down streets and gutters compared to lawns and gardens — and the necessity for extreme accuracy.

“A true toxicology report should include these peaks, and we have created the first model that takes them into account over a period of time,” says Coutu.

Establishing a working model has the advantage of reproducibility as well as reducing dependency on expensive testing. Once a reliable model has been created it can be used in other regions, although the model needs to be adapted to the specific geography, for example the surface area of contaminated façades as well as the quick water drainage of urban surfaces. Once the input is determined and the dynamics of the hazardous substances reacting to rainfall are worked out, it is possible to estimate the concentrations of these substances to see if they exceed acceptable levels.

The biocides that reached the river basin in Switzerland did so in extremely small concentrations — 30 nanograms per liter, or 30 parts per trillion, of the chemical DCMU were present after heavy rains. DCMU is a common herbicide and algicide developed in the 1950s in Germany and the threshold concentration after which this substance is considered a threat for the environment is 20 nanograms per liter. DCMU is considered harmful and can potentially kill algae and other plantlife by inhibiting photosynthesis and thus depriving the organisms of energy. Biocides in general do not degrade easily, thus increasing their risk of moving up the food chain and making their way, in higher and higher concentrations, throughout the environment.

“While it may seem like a very small concentration, 20 nanograms is all that is needed to have an impact on the ecosystem since these chemicals are engineered to kill at very low doses,” explains Coutu. Furthermore, the study also proves that water behavior in urban environments can be accurately modeled, opening the door to further toxicology studies for city ecosystems.

Story Source: Ecole Polytechnique Fédérale de Lausanne

Article source: http://www.sciencedaily.com/releases/2011/12/111209150150.htm

As part of ongoing research to understand how miniaturization affects brain size and behavior, researchers measured the central nervous systems of nine species of spiders, from rainforest giants to spiders smaller than the head of a pin. As the spiders get smaller, their brains get proportionally bigger, filling up more and more of their body cavities.

“The smaller the animal, the more it has to invest in its brain, which means even very tiny spiders are able to weave a web and perform other fairly complex behaviors,” said William Wcislo, staff scientist at the Smithsonian Tropical Research Institute in Panama. “We discovered that the central nervous systems of the smallest spiders fill up almost 80 percent of their total body cavity, including about 25 percent of their legs.”

Some of the tiniest, immature spiderlings even have deformed, bulging bodies. The bulge contains excess brain. Adults of the same species do not bulge. Brain cells can only be so small because most cells have a nucleus that contains all of the spider’s genes, and that takes up space. The diameter of the nerve fibers or axons also cannot be made smaller because if they are too thin, the flow of ions that carry nerve signals is disrupted, and the signals are not transferred properly. One option is to devote more space to the nervous system.

“We suspected that the spiderlings might be mostly brain because there is a general rule for all animals, called Haller’s rule, that says that as body size goes down, the proportion of the body taken up by the brain increases,” said Wcislo. “Human brains only represent about 2-3 percent of our body mass. Some of the tiniest ant brains that we’ve measured represent about 15 percent of their biomass, and some of these spiders are much smaller.”

Brain cells use a lot of energy, so these small spiders also probably convert much of the food they consume into brain power.

The enormous biodiversity of spiders in Panama and Costa Rica made it possible for researchers to measure brain extension in spiders with a huge range of body sizes. Nephila clavipes, a rainforest giant weighs 400,000 times more than the smallest spiders in the study, nymphs of spiders in the genus Mysmena.

Story Source: Smithsonian Tropical Research Institute.

Article source: http://www.sciencedaily.com/releases/2011/12/111212124707.htm

Furthermore, forest inventory statistics have been applied. These statistics are based on forest plot data that are aggregated over regions in the Nomenclature of Territorial Units for Statistics (NUTS).

In areas with available national forest inventory data, area proportions covered by the 20 species were obtained by compositional kriging. For the rest of Europe a multinomial logistic regression model was fitted to ICP-level-I plots using various abiotic factors as predictors (soil, biogeographical zones, and bioindicators derived from temperature and precipitation data). The regression results were iteratively scaled to fit NUTS-II forest inventory statistics and the European Forest Map.

The predictions for the twenty tree species were validated using 230 plot data separated from the calibration.

Story Source: European Forest Institute

The study, published in the journal Environmental Science Technology, reports on concentrations of two compounds measured in atmospheric samples collected in the Great Lakes region between 2008 and 2010. Authors are doctoral student Yuning Ma, Assistant Research Scientist Marta Venier and Distinguished Professor Ronald A. Hites, all of the IU School of Public and Environmental Affairs.

The chemicals — 2-ethylhexyl tetrabromobenzoate, also known as TBB; and bis(2-ethylhexyl) tetrabromophthalate, or TBPH — are used to reduce flammability in such products as electronic devices, textiles, plastics, coatings and polyurethane foams.

They are included in commercial mixtures that were introduced in recent years to replace polybrominated diphenylethers (PBDEs), widely used flame retardants that have been or are being removed from the market because of their tendency to leak from products into the environment.

“We find that the environmental concentrations of these compounds are increasing rather rapidly,” Hites said. “It’s rare to find that concentrations of any compound are doubling within a year or two, which is what we’re seeing with TBB and TBPH.”

The researchers measured concentrations of TBB and TBPH in 507 air samples collected at six locations on the shores of the Great Lakes. The samples were collected by the Integrated Atmospheric Deposition Network, a joint U.S.-Canada project, conducted by IU researchers, to monitor airborne toxic chemicals that are deposited in the Great Lakes.

The results constitute the first self-consistent data set that shows environmental concentrations of TBB and TBPH increasing relatively rapidly. Previous studies have found the compounds in sewage sludge in California, marine mammals in Hong Kong and household dust and furniture foam in the U.S.

As would be expected, the IU researchers found the largest concentrations of TBB and TBPH in atmospheric samples collected in urban areas: Chicago and, especially, Cleveland. But the compounds were also detected in about half the samples from remote sites at Sleeping Bear Dunes and Eagle Harbor in Michigan and Point Petre in Ontario, Canada. They also were detected at rural Sturgeon Point, N.Y.

TBPH was detected more frequently and in higher concentrations than TBB. The concentrations are similar to those reported previously by Hites and Venier for PBDEs at the Great Lakes sites, suggesting the newer-generation flame retardants may be replacing their predecessors in the environment.

Story Source: Indiana University

Article source: http://www.sciencedaily.com/releases/2011/12/111214094843.htm

Researchers from NASA’s Jet Propulsion Laboratory and the California Institute of Technology in Pasadena, Calif., investigated how Earth’s plant life is likely to react over the next three centuries as Earth’s climate changes in response to rising levels of human-produced greenhouse gases. Study results are published in the journal Climatic Change.

The model projections paint a portrait of increasing ecological change and stress in Earth’s biosphere, with many plant and animal species facing increasing competition for survival, as well as significant species turnover, as some species invade areas occupied by other species. Most of Earth’s land that is not covered by ice or desert is projected to undergo at least a 30 percent change in plant cover — changes that will require humans and animals to adapt and often relocate.

In addition to altering plant communities, the study predicts climate change will disrupt the ecological balance between interdependent and often endangered plant and animal species, reduce biodiversity and adversely affect Earth’s water, energy, carbon and other element cycles.

“For more than 25 years, scientists have warned of the dangers of human-induced climate change,” said Jon Bergengren, a scientist who led the study while a postdoctoral scholar at Caltech. “Our study introduces a new view of climate change, exploring the ecological implications of a few degrees of global warming. While warnings of melting glaciers, rising sea levels and other environmental changes are illustrative and important, ultimately, it’s the ecological consequences that matter most.”

When faced with climate change, plant species often must “migrate” over multiple generations, as they can only survive, compete and reproduce within the range of climates to which they are evolutionarily and physiologically adapted. While Earth’s plants and animals have evolved to migrate in response to seasonal environmental changes and to even larger transitions, such as the end of the last ice age, they often are not equipped to keep up with the rapidity of modern climate changes that are currently taking place. Human activities, such as agriculture and urbanization, are increasingly destroying Earth’s natural habitats, and frequently block plants and animals from successfully migrating.

To study the sensitivity of Earth’s ecological systems to climate change, the scientists used a computer model that predicts the type of plant community that is uniquely adapted to any climate on Earth. This model was used to simulate the future state of Earth’s natural vegetation in harmony with climate projections from 10 different global climate simulations. These simulations are based on the intermediate greenhouse gas scenario in the United Nations’ Intergovernmental Panel on Climate Change Fourth Assessment Report. That scenario assumes greenhouse gas levels will double by 2100 and then level off. The U.N. report’s climate simulations predict a warmer and wetter Earth, with global temperature increases of 3.6 to 7.2 degrees Fahrenheit (2 to 4 degrees Celsius) by 2100, about the same warming that occurred following the Last Glacial Maximum almost 20,000 years ago, except about 100 times faster. Under the scenario, some regions become wetter because of enhanced evaporation, while others become drier due to changes in atmospheric circulation.

The researchers found a shift of biomes, or major ecological community types, toward Earth’s poles — most dramatically in temperate grasslands and boreal forests — and toward higher elevations. Ecologically sensitive “hotspots” — areas projected to undergo the greatest degree of species turnover — that were identified by the study include regions in the Himalayas and the Tibetan Plateau, eastern equatorial Africa, Madagascar, the Mediterranean region, southern South America, and North America’s Great Lakes and Great Plains areas. The largest areas of ecological sensitivity and biome changes predicted for this century are, not surprisingly, found in areas with the most dramatic climate change: in the Northern Hemisphere high latitudes, particularly along the northern and southern boundaries of boreal forests.

“Our study developed a simple, consistent and quantitative way to characterize the impacts of climate change on ecosystems, while assessing and comparing the implications of climate model projections,” said JPL co-author Duane Waliser. “This new tool enables scientists to explore and understand interrelationships between Earth’s ecosystems and climate and to identify regions projected to have the greatest degree of ecological sensitivity.”

“In this study, we have developed and applied two new ecological sensitivity metrics — analogs of climate sensitivity — to investigate the potential degree of plant community changes over the next three centuries,” said Bergengren. “The surprising degree of ecological sensitivity of Earth’s ecosystems predicted by our research highlights the global imperative to accelerate progress toward preserving biodiversity by stabilizing Earth’s climate.”

JPL is managed for NASA by the California Institute of Technology in Pasadena.

Story Source: NASA/Jet Propulsion Laboratory.

Article source: http://www.sciencedaily.com/releases/2011/12/111218221321.htm

Our analysis of water samples from 23 sites along West Virginia’s Upper Mud River and its tributaries shows that salinity and trace element concentrations, including selenium, increased at a rate directly proportional to the cumulative amount of surface mining in the watershed,” said Duke researcher Ty Lindberg. “We found a strong linear correlation.”

Changes in water quality due to the increased salinity in the Upper Mud from mine runoff also were found to be “exceptionally persistent,” Lindberg said. “Mines reclaimed almost two decades ago are continuing to release effluents with salinity similar to active mines in the region.”

The Duke team’s study appears this week in the peer-reviewed online Early Edition of the Proceedings of the National Academy of Sciences.

In mountaintop mining, companies use explosives and heavy machinery to clear away surface rocks and extract shallow deposits of high-quality coal below. The companies typically dispose of the waste rock in adjacent valleys, where it buries existing headwater streams.

To assess the cumulative impact of the more than 100 permitted discharge outlets draining approximately 28 square kilometers of active and reclaimed mountaintop coal mines in the Upper Mud watershed, the Duke researchers collected 152 sets of samples from 23 sites — including two sites upstream of any active or reclaimed surface mines — between May and December 2010. They sampled for electrical conductivity, a measure of salinity and for concentrations of major ions and trace elements derived from coal or its matrix rock.

All conductivity measurements taken downstream of mine discharge outlets exceeded levels known to be harmful to aquatic life, said Richard Di Giulio, professor of environmental toxicology. At the two sampling sites upstream of any mines, conductivity levels were within an acceptable range. Concentrations of selenium, a known fish toxin, followed a similar trend, Di Giulio said. The researchers also observed deformities typical of selenium exposure in fish collected from downstream waters.

“As eight separate mining-impacted tributaries flowed into the Upper Mud, conductivity and concentrations of selenium, sulfate, magnesium and other inorganic solutes increased proportionately,” said Avner Vengosh, professor of geochemistry and water quality. “Nearly 90 percent of the variation in trace elements and salinity could be explained by the amount of upstream surface mining.”

The Upper Mud flows through sparsely populated sections of Boone and Lincoln counties in southern West Virginia as a headwater stream until reaching its impoundment in the Mud River reservoir 25 kilometers downstream. For about 10 kilometers, the river passes through the Hobet 21 surface mining complex, which has been active since the 1970s and is among the largest in the Appalachian coalfields region.

The Duke team selected the Upper Mud watershed for their field survey because water-quality impacts from other potential sources are largely absent. Historically, surface rather than underground mining has been the dominant form of coal extraction in the Upper Mud’s river basin, and there are very few people now living within the Hobet mine’s permitted boundary. This helped to minimize other factors that might account for changes in water quality.

“This is a remarkably clean dataset and that’s why it’s so powerful,” said Emily Bernhardt, associate professor of biogeochemistry. “We see these incredibly strong patterns, which previously have not been well established.” Past studies have shown that individual mines profoundly impact stream water quality, biological community structure and ecosystem function immediately downstream of valley fills, but empirical data on the cumulative impacts of multiple mining operations on larger downstream rivers has been lacking, she said.

“Individual permitting decisions are typically made without consideration of the extent of historic mining impacts already occurring within a watershed,” Bernhardt said. “Our survey helps fill that gap.”

Duke PhD students Raven Bier and Brittany Merola and postdoctoral researcher Ashley Helton co-authored the study.

Story Source: Duke University

Although the temperate climates of central Europe provide plentiful food in summer, finding enough to eat is much more problematic in winter. Many small mammals avoid the problem by hibernating but this survival strategy is generally not practised by larger animals. With the exception of some bears, large mammals remain fully awake throughout the year, yet they too must reduce their metabolism to cope with the comparative scarcity of food. Red deer, for example, are known to lower their heart rate and to allow their extremities to cool substantially during winter. These changes have been interpreted as a mechanism for conserving energy but could simply reflect the fact that the animals cannot find enough food to eat, as the act of digestion is known to have a direct influence on a ruminant’s metabolism.

It is clear that red deer must minimise their energy requirements to be able to survive on little but their own body fat over the long winter season. To understand how they do so, Christopher Turbill and colleagues at the University of Veterinary Medicine, Vienna inserted special transmitters into the reticulum (the foremost part of the stomach) of 15 female red deer and monitored the animals’ heart rate and stomach temperature for a period of 18 months, including two winters. The deer lived under near-natural conditions but their food intake was tightly controlled, with the amount and the protein richness determined by the scientists. The air temperature was also recorded and statistical modeling was used to untangle the effects of the various different factors — including swallowing snow, which naturally led to a rapid and dramatic decrease in stomach temperature — on the animals’ metabolism.

The slow season

The most striking result was that the deer lowered their heart rates in winter regardless of how much food they ate. A heart rate of 65-70 beats per minute in May declined gradually to about 40 beats per minute throughout the winter, even when the deer were supplied with plenty of protein-rich food. Heart rate is a good indicator of metabolic rate, so as Turbill says, “The decrease in metabolism occurred exactly when food is normally scarce — although our animals always had enough to eat — and this shows that the deer are somehow ‘programmed’ to conserve reserves during winter.” The enormous rise in heart rate in spring, at the start of the breeding season, was not associated with any change in food availability so also forms part of the animals’ internal programming. As expected, when the deer were offered less food, their heart rates dropped even further. Surprisingly, however, this effect could also be observed in summer and was not solely caused by the reduced amount of digestion, showing that red deer react both to the winter season and to food shortages by actively lowering their metabolism.

Turbill, Arnold and coworkers found that the lowered heart rate was associated with a reduction in stomach (core body) temperature, suggesting that the deer adjust energy expenditure by regulating their internal heat production. However, relatively small changes in stomach temperature had larger than expected effects on metabolic rate, implying that the animals have an additional mechanism for saving energy. The key to explaining the results came from previous studies in Arnold’s group, which had shown that red deer can greatly lower the temperature of their legs and other extremities, especially during cold winter nights. It thus seems likely that a small reduction in stomach temperature indicates a much greater reduction in the temperature of the deer’s entire body, which could explain the substantial reduction in heart rate and metabolism. “Perhaps larger animals are able to make use of their size to enable temperature gradients,” Arnold proposes. “This would enable them to reduce their metabolism dramatically without requiring a big decrease in core body temperature. It seems as though peripheral cooling might be an important mechanism for red deer — and maybe other large mammals — to conserve energy during winter and when food is scarce.”

Story Source:

The above story is reprinted from materials provided by Veterinärmedizinische Universität Wien.

Over the past four decades, sugar maple abundance has declined in some regions of the northeastern United States and southeastern Canada, due largely to acidification of calcium-poor granitic soils in response to acid rain.

Sugar maple forests in the Upper Great Lakes region, in contrast, grow in calcium-rich soils. Those soils provide a buffer against soil acidification. So sugar maple forests here have largely been spared the type of damage seen in mature sugar maples of the Northeast.

But now, a U-M-led team of ecologists has uncovered a different and previously unstudied mechanism by which acid rain harms sugar maple seedlings in Upper Great Lakes forests.

The scientists have concluded that excess nitrogen from acid rain slows the microbial decay of dead maple leaves on the forest floor, resulting in a build-up of leaf litter that creates a physical barrier for seedling roots seeking soil nutrients, as well as young leaves trying to poke up through the litter to reach sunlight.

“The thickening of the forest floor has become a physical barrier for seedlings to reach mineral soil or to emerge from the extra litter,” said ecologist Donald Zak, a professor at the U-M School of Natural Resources and Environment and co-author of an article published online Dec. 8 in the Journal of Applied Ecology. Zak is also a professor of ecology and evolutionary biology.

“What we’ve uncovered is a totally different and indirect mechanism by which atmospheric nitrogen deposition can negatively impact sugar maples,” Zak said.

The new findings are the latest results from a 17-year experiment at four sugar maple stands in Michigan’s lower and upper peninsulas.

By the end of this century, nitrogen deposition from acid rain is expected to more than double worldwide, due to increased burning of fossil fuels. For the last 17 years at the four Michigan sugar maple test sites, Zak and his colleagues have added sodium nitrate pellets (six times throughout the growing season, every year) to three 30-meter by 30-meter test plots at each of the four Michigan maple stands. Adding the pellets was done to simulate the amount of nitrogen deposition expected by the end of the century.

Seedling-establishment data from the nitrogen-spiked test plots were compared to the findings from a trio of nearby control plots that received no additional nitrogen. Most of the fieldwork and analysis was done by 2010 SNRE graduate Sierra Patterson, who conducted the study for her master’s thesis.

Patterson and her colleagues found that adding extra nitrogen increased the amount of leaf litter on the forest floor by up to 50 percent, causing a significant reduction in the successful establishment of sugar maple seedlings.

When the number of seedlings on nitrogen-supplemented treatment was compared to the number of seedlings on the no-nitrogen-added treatment, the mean abundance of second-year seedlings was 13.1 stems per square meter under ambient nitrogen deposition and 1.6 stems per square meter under simulated nitrogen deposition.

The mean abundance of seedlings between three and five years of age also significantly declined under simulated nitrogen deposition: 10.6 stems per square meter grew under ambient nitrogen deposition, compared to 0.6 stems per square meter under simulated nitrogen deposition.

“Increasing nitrogen deposition has the potential to lead to major changes in sugar maple-dominated northern hardwood forests in the Great Lakes region,” said Patterson, who now works as a botanist for the Huron-Manistee National Forests in Michigan.

“In terms of regeneration, it looks like it’ll be difficult for new seeds to replace the forest overstory in the future,” she said “So the populations of sugar maples in this region could potentially decline.”

Funding for the study has been provided by grants from the National Science Foundation and the U.S. Department of Energy’s Division of Environmental Biology.

“The surprising results reported in this study are an example of the value of long-term research,” said Saran Twombly, program director in the National Science Foundation’s Division of Environmental Biology, which funded the work.

“Uncovering the unexpected link between nitrogen deposition and sugar maple seedling success depended on the ability to simulate increased nitrogen deposition year after year,” Twombly said. “The manipulations used to reveal the details of this link could not have worked in other than a long-term study.”

Story Source:

The above story is reprinted from materials provided by University of Michigan.

Article source: http://www.sciencedaily.com/releases/2011/12/111215135933.htm