February 6, 2008, 9:05 PM CT

Nitrogen pollution boosts plant growth

A study by UC Irvine ecologists finds that excess nitrogen in tropical forests boosts plant growth by an average of 20 percent, countering the belief that such forests would not respond to nitrogen pollution.

Faster plant growth means the tropics will take in more carbon dioxide than previously thought, though long-term climate effects are unclear. Over the next century, nitrogen pollution is expected to steadily rise, with the most dramatic increases in rapidly developing tropical regions such as India, South America, Africa and Southeast Asia.

Nitrogen fertilizer, applied to farmland to improve crop yield, also affects ecosystems downwind by seeping into runoff water and evaporating into the atmosphere. Industrial burning and forest clearing also pumps nitrogen into the air.

"We hope our results will improve global change forecasts," said David LeBauer, graduate student researcher of Earth system science at UCI and lead author of the study.

The research results appear in the recent issue of the journal Ecology.

Using data from more than 100 previously published studies, LeBauer and Kathleen Treseder, associate professor of ecology and evolutionary biology at UCI, analyzed global trends in nitrogen's effect on growth rates in ecosystems ranging from tropical forests and grasslands to wetlands and tundra. Nitrogen, they found, increased plant growth in all ecosystems except for deserts......... Posted by: Erica      Read more         Source

February 6, 2008, 8:39 PM CT

Barnacles go to great lengths to mate

Compelled to mate, yet firmly attached to the rock, barnacles have evolved the longest penis of any animal for their size - up to 8 times their body length - so they can find and fertilize distant neighbours.

Graduate student Christopher Neufeld and Dr. Richard Palmer from the Department of Biological Sciences at the University of Alberta have shown that barnacles appear to have acquired the capacity to change the size and shape of their penises to closely match local wave conditions. When wave action is light, a longer (thinner) penis can reach more mates, but at times of higher wave action, a shorter (stouter) penis is more manoeuvrable in flow and therefore can reach more mates.

The research, published in Proceedings of the Royal Society B, suggests that sexual selection - competition with other males, female choice, sexual conflict between males and females - is not mandatory to explain variation in genital form. In barnacles, this variation appears to be driven largely by the hydrodynamic conditions experienced under breaking waves......... Posted by: Kelly      Read more         Source

February 6, 2008, 5:30 AM CT

Wind as the Force Behind Fish Booms and Busts

The mid-20th century crash of the sardine fishery off California for decades has vexed marine ecologists searching for the root causes of large fluctuations in the sardine population. Before its collapse, the fishery was one of the world's most productive and formed the setting of John Steinbeck's "Cannery Row" in Monterey, Calif.

Researchers at Scripps Institution of Oceanography at UC San Diego have now shed light on the puzzle by proposing a plausible mechanism behind the mystery: wind.

Writing in the online early edition of the Proceedings of the National Academy of Sciences, Scripps scientists Ryan Rykaczewski and David Checkley propose that atmospheric wind forces can determine the availability of microscopic organisms that sardine and anchovy feed upon. When wind causes nutrient-rich waters to rise to the surface, plankton levels increase and sardine populations flourish. On the other hand, sardine numbers crash when plankton become scarce as wind conditions change.

The researchers say their findings may explain the sardine and anchovy booms and busts off California's coast and could explain similar population cycles elsewhere around the world.

"This paper is the first to show a mechanistic relationship between climate variability and the sardine fishery," said Rykaczewski, a Scripps graduate student researcher. "There have been a lot of hypotheses about climate change and sardine and anchovy fisheries, but there has been little scientific support for a mechanism connecting changes in climate to changes in these fish populations"......... Posted by: Kelly      Read more         Source

February 4, 2008, 9:32 PM CT

Gotta have heart!

According tohaps confirmed by their ubiquity on nature cable channels, crocodiles are among natures most fearsome predators. When the opportunity arises, crocodilians will gorge, voluntarily consuming meals weighing 23% of their own body weight. This is analogous to a 130 -pound woman eating, at one sitting, a hamburger weighing 30 pounds. But what to do with all of that food" If they do not digest their meal quickly, crocodilians risk death from within, or if they are young, by predators.

While it has long been known that reptiles have the ability to shunt blood past their lungs, the physiological function of this ability is poorly understood. In a breakthrough article for the March/April 2008 issue of Physiological and Biochemical Zoology, The Right-to-Left Shunt of Crocodilians Serves Digestion, Professor C.G. Farmer and her colleagues at the University of Utah, along with the Utah Artificial Heart Institute, were able to demonstrate through their experiments with American alligators that the bypass function is central in their digestion process, and ultimately, their survival.

After feasting, crocodilians like to find a warm place to lie down while they digest their meal. Eventhough on the outside this behavior seems ordinary, inside their bodies an extraordinary event takes place. During this period of digestion crocodilians divert blood through a special vessel that bypasses the lung, named the left aorta. Humans, other mammals, and birds lack this special vessel, and so all blood pumped by the right side of the heart flows through the pulmonary artery into the lungs, where carbon dioxide (CO2) moves from the blood into the gases of the lungs. Crocodilians can chose not to use the left aorta, in which case their cardiovascular system is very much like the mammalian system. However, when crocodilians are digesting a meal, they chose to shunt and direct CO2-rich blood straight to the stomach where glands make use of the CO2 to form gastric acid and bicarbonate. Consequently this shunt enables crocodilians to secrete gastric acid at a rate that is approximately 10 times the highest rates measured in mammals. If crocodilians are deprived of this ability to sidestep their lungs, their rates of acid secretion drop significantly and their ability to dissolve bone, a regular part of their normal diet, is impaired......... Posted by: Kelly      Read more         Source

February 4, 2008, 8:37 PM CT

Birds and bats hold secrets for aerospace engineers

Natural flyers like birds, bats and insects outperform man-made aircraft in aerobatics and efficiency. University of Michigan engineers are studying these animals as a step toward designing flapping-wing planes with wingspans smaller than a deck of playing cards.

A Blackbird jet flying nearly 2,000 miles per hour covers 32 body lengths per second. But a common pigeon flying at 50 miles per hour covers 75.

The roll rate of the aerobatic A-4 Skyhawk plane is about 720 degrees per second. The roll rate of a barn swallow exceeds 5,000 degrees per second.

Select military aircraft can withstand gravitational forces of 8-10 G. A number of birds routinely experience positive G-forces greater than 10 G and up to 14 G.

"Natural flyers obviously have some highly varied mechanical properties that we really have not incorporated in engineering," said Wei Shyy, chair of the Aerospace Engineering department and an author of the new book "The Aerodynamics of Low Reynolds Number Flyers".

"They're not only lighter, but also have much more adaptive structures as well as capabilities of integrating aerodynamics with wing and body shapes, which change all the time," Shyy said. "Natural flyers have outstanding capabilities to remain airborne through wind gusts, rain, and snow." Shyy photographs birds to help him understand their aerodynamics......... Posted by: Kelly      Read more         Source

January 30, 2008, 9:18 PM CT

African fruits could help alleviate hunger

Africa's own fruits are a largely untapped resource that could combat malnutrition and boost environmental stability and rural development in Africa, says a new report from the National Research Council. African science institutes, policymakers, nongovernmental organizations, and individuals could all use modern horticultural knowledge and scientific research to bring these "lost crops" -- such as baobab, marula, and butterfruit -- to their full potential, said the panel that issued the report.

Today, tropical fruit production in Africa is dominated by species introduced from Asia and the Americas, such as bananas, pineapples, and papayas. Because these and other crops arrived on the continent centuries ago already improved through horticultural selection and breeding, they increasingly displaced the traditional species that had fed Africans for thousands of years. The imported species also received the support of colonial powers who wanted familiar crops that were profitable to grow, and indigenous fruits continued their downward spiral of dwindling cultivation and knowledge.

With renewed scientific and institutional support, however, Africa's native fruits could make a much greater contribution to nutrition and economic development, the new report says. Fruit trees and shrubs also offer long-term benefits by improving the stability of the environment......... Posted by: Erica      Read more         Source

January 29, 2008, 10:04 PM CT

Genes That May Level Engineering Hurdle

Denizens of oceans, lakes and even wet soil, diatoms are unicellular algae that encase themselves in intricately patterned, glass-like shells. Curiously, these tiny phytoplankton could be harboring the next big breakthrough in computer chips.

Diatoms build their hard cell walls by laying down submicron-sized lines of silica, a compound correlation to the key material of the semiconductor industry - silicon. "If we can genetically control that process, we would have a whole new way of performing the nanofabrication used to make computer chips," says Michael Sussman, a University of Wisconsin-Madison biochemistry professor and director of the UW-Madison's Biotechnology Center.

To that end, a team led by Sussman and diatom expert Virginia Armbrust of the University of Washington has reported finding a set of 75 genes specifically involved in silica bioprocessing in the diatom Thalassiosira pseudonana, as published recently in the online Early Edition of the Proceedings of the National Academy of Sciences. Armbrust, an oceanography professor who studies the ecological role of diatoms, headed up the effort to sequence the genome of T. pseudonana, which was completed in 2004.

The new data will enable Sussman to start manipulating the genes responsible for silica production and potentially harness them to produce lines on computer chips. This could vastly increase chip speed, Sussman says, because diatoms are capable of producing lines much smaller than current technology allows......... Posted by: Janet      Read more         Source

January 29, 2008, 9:52 PM CT

Insects on coffee plants

Ever since a forward-thinking trio of physicists identified the phenomenon known as self-organized criticality-a mechanism by which complexity arises in nature-researchers have been applying its concepts to everything from economics to avalanches.

Now, scientists at the University of Michigan and the University of Toledo have shown that clusters of ant nests on a coffee farm in Mexico also adhere to the model. Their work, which has implications for controlling coffee pests, appears in the Jan. 24 issue of the journal Nature.

The basic idea of self-organized criticality often is illustrated with a sand pile. As you trickle sand onto the cone-shaped pile, the cone grows and grows until it reaches a "state of criticality" where it stops growing. Add more sand, and the grains just slide down the sides in mini-avalanches.

"What physicists have done-both mathematically and physically-is look at how a number of grains of sand actually fall with each avalanche," said John Vandermeer, the Margaret Davis Collegiate Professor of Ecology and Evolutionary Biology and one of the Nature paper's authors. "What they find is that most avalanches involve one or two sand grains, and relatively few avalanches involve hundreds of sand grains." Such a pattern-with small versions of a phenomenon being more common than big ones-characterizes what's known as a power law, a sort of fingerprint of systems that exhibit self-organized criticality......... Posted by: Kelly      Read more         Source

January 29, 2008, 9:37 PM CT

The Pitter Patter of Little Feet

Building upon several years of research into the gecko's uncanny ability to climb sheer walls, scientists at the University of California, Berkeley, have developed an adhesive that is the first to master the easy attach and easy release of the reptile's padded feet. The material could prove useful for a range of products, from climbing equipment to medical devices.

Unlike duct tape or glue, the new material is crafted from millions of tiny, hard, plastic fibers that establish grip; a mere square two centimeters on a side can support 400 grams (close to a pound). While tape sticks when it presses onto a surface, the new adhesive sticks as it slides on a surface and releases as it lifts -- this is the trick behind a gecko's speedy vertical escapes.

The new study appeared online Jan. 23, 2008, in the Journal of the Royal Society Interface.

There are other synthetic adhesives inspired by gecko feet and they adhere much like conventional tape. In contrast, the new adhesive brushes along a surface to develop traction. While ideal for hanging posters, the characteristic is even more important for any application that requires movement, such as climbing.

"The gecko has a very sophisticated hierarchical structure of compliant toes, microfibers, nanofibers and nanoattachment plates that allows the foot to attach and release with very little effort," said co-author and Berkeley professor Ron Fearing, "The gecko makes it look simple, but the animal needs to control the directions it is moving its toes--correct movement equates to little effort," he said......... Posted by: Kelly      Read more         Source

January 29, 2008, 9:33 PM CT

River plants may play major role in health of ocean

Recent research at MIT's Department of Civil and Environmental Engineering suggests how aquatic plants in rivers and streams may play a major role in the health of large areas of ocean coastal waters.

This work, which appeared in the Dec. 25 issue of the Journal of Fluid Mechanics (JFM), describes the physics of water flow around aquatic plants and demonstrates the importance of basic research to environmental engineering. This new understanding can be used to guide restoration work in rivers, wetlands and coastal zones by helping ecologists determine the vegetation patch length and planting density necessary to damp storm surge, lower nutrient levels, or promote sediment accumulation and make the new patch stable against erosion.

Professor Heidi Nepf is principle investigator on the research. Brian White, a former graduate student at MIT who is now an assistant professor at the University of North Carolina, is co-author with Nepf of the JFM paper. Marco Ghisalberti, a postdoctoral associate at the University of Western Australia, worked with Nepf on some aspects of this research when he was an MIT graduate student. This work was supported by grants from the National Science Foundation.

Traditionally people have removed vegetation growing along rivers to speed the passage of waters and prevent flooding. But in recent years that practice has changed. Ecologists now advocate replanting, because vegetation provides important habitat. In addition, aquatic plants and the microbial populations they support remove excess nutrients from the water. The removal of too a number of plants contributes to nutrient overload in rivers, which can subsequently lead to coastal dead zones-oxygen-deprived areas of coastal water where nothing can survive. One well-documented dead zone in the Gulf of Mexico, fed by nutrient pollution from the Mississippi River, grows to be as large as the state of New Jersey every summer......... Posted by: Erica      Read more         Source