NEW ANALYSIS LINKS TREE HEIGHT TO CLIMATE
From the FMS Global News Desk of Jeanne Hambleton Released: 14-Aug-2014 Citations Ecology Source Newsroom: University of Wisconsin-Madison
Newswise — MADISON, Wis. — What limits the height of trees? Is it the fraction of their photosynthetic energy they devote to productive new leaves? Or is it their ability to hoist water hundreds of feet into the air, supplying the green, solar-powered sugar factories in those leaves?
Both factors — resource allocation and hydraulic limitation — might play a role, and a scientific debate has arisen as to which factor (or what combination) actually sets maximum tree height, and how their relative importance varies in different parts of the world.
In research to be published in the journal Ecology — and currently posted online as a preprint — Thomas Givnish, a professor of botany at the University of Wisconsin-Madison, attempts to resolve this debate by studying how tree height, resource allocation and physiology vary with climate in Victoria state, located in southeastern Australia. There, Eucalyptus species exhibit almost the entire global range in height among flowering trees, from 4 feet to more than 300 feet.
“Since Galileo’s time,” Givnish says, “people have wondered what determines maximum tree height: ‘Where are the tallest trees, and why are they so tall?’ Our study talks about the kind of constraints that could limit maximum tree height, and how those constraints and maximum height vary with climate.”
One of the species under study, Eucalyptus regnans — called mountain ash in Australia, but distinct from the smaller and unrelated mountain ash found in the U.S. — is the tallest flowering tree in the world. In Tasmania, an especially rainy part of southern Australia, the tallest living E. regnans is 330 feet tall. (The tallest tree in the world is a coastal redwood in northern California that soars 380 feet above the ground.)
Southern Victoria, Tasmania and northern California all share high rainfall, high humidity and low evaporation rates, underlining the importance of moisture supply to ultra-tall trees. But the new study by Givnish, Graham Farquhar of the Australian National University and others shows that rainfall alone cannot explain maximum tree height.
A second factor, evaporative demand, helps determine how far a given amount of rainfall will go toward meeting a tree’s demands. Warm, dry and sunny conditions cause faster evaporation from leaves, and Givnish and his colleagues found a tight relationship between maximum tree height in old stands in Australia and the ratio of annual rainfall to evaporation. As that ratio increased, so did maximum tree height.
Other factors — like soil fertility, the frequency of wildfires and length of the growing season — also affect tree height. Tall, fast-growing trees access more sunlight and can capture more energy through photosynthesis. They are more obvious to pollinators, and have potential to outcompete other species.
“Infrastructure” — things like wood and roots that are essential to growth but do not contribute to the production of energy through photosynthesis — affect resource allocation, and can explain the importance of the ratio of moisture supply to evaporative demand.
“In moist areas, trees can allocate less to building roots,” Givnish says. “Other things being equal, having lower overhead should allow them to achieve greater height.
“And plants in moist areas can achieve higher rates of photosynthesis, because they can open the stomata on their leaves that exchange gases with the atmosphere. When these trees intake more carbon dioxide, they can achieve greater height before their overhead exceeds their photosynthetic income.”
The constraints on tree height imposed by resource allocation and hydraulics should both increase in drier areas. But Givnish and his team wanted to know the importance of each constraint.
The scientists examined the issue by measuring the isotopic composition of carbon in the wood along the intense rainfall gradient in their study zone. If hydraulic limitation alone were to set maximum tree height, the carbon isotope composition should not vary because all trees should grow up to the point at which hydraulics retards photosynthesis. The isotopic composition should also remain stable if resource allocation alone sets maximum height, because resource allocation does not directly affect the stomata.
But if both factors limit tree height, the heavier carbon isotopes should accumulate in moister areas where faster photosynthesis (enhanced by wide-open stomata) can balance the costs of building more wood in taller trees. Givnish, Farquhar and their colleagues found exactly that, implying that hydraulic limitation more strongly constrains maximum tree height under drier conditions, while resource allocation more strongly constrains height under moist conditions.
Most studies of tree height have focused on finding the tallest trees and explaining why they live where they do, Givnish says.
“This study was the first to ask, ‘How does the maximum tree height vary with the environment, and why?’”
WIRELESS SENSORS AND FLYING ROBOTS: A WAY TO MONITOR DETERIORATING BRIDGES
From the FMS Global News Desk of Jeanne Hambleton Released: 15-Aug-2014
Source Newsroom: Tufts University
Newswise — MEDFORD/SOMERVILLE, Mass. – As a recent report from the Obama administration warns that one in four bridges in the United States needs significant repair or cannot handle automobile traffic, Tufts University engineers are employing wireless sensors and flying robots that could have the potential to help authorities monitor the condition of bridges in real time.
Today, bridges are inspected visually by teams of engineers who dangle beneath the bridge on cables or look up at the bridge from an elevated work platform. It is a slow, dangerous, expensive process and even the most experienced engineers can overlook cracks in the structure or other critical deficiencies.
A New Monitoring System for Bridges
In the detection system being developed by Babak Moaveni, an assistant professor of civil and environmental engineering at Tufts School of Engineering, smart sensors are attached permanently to bridge beams and joints. Each sensor can continuously record vibrations and process the recorded signal. Changes in the vibration response can signify damage, he says.
Moaveni, who received a grant from the National Science Foundation (NSF) for his research, is collaborating with Tufts Assistant Professor of Electrical and Computer Engineering Usman Khan to develop a wireless system that would use autonomous flying robots (quad-copters) to hover near the sensors and collect data while taking visual images of bridge conditions. The drone-like robots would transmit data to a central collection point for analysis. Khan received a $400,000 Early Career Award from the NSF earlier this year to explore this technology, which requires addressing significant navigational and communications challenges before it could be a reliable inspection tool.
The recent Obama administration report that analyzed the condition of the transportation infrastructure, points across the country out that 25 percent of the approximately 600,000 bridges are in such a poor state that they are incapable of handling daily automobile traffic. In Massachusetts, more than 50 percent of the 5,136 bridges in use are deficient, the report says.
Moaveni and Khan’s work could help monitor bridges and identify those that are at risk more accurately than current methods. Once installed, the sensors would provide information about the condition of bridges that cannot be obtained by visual inspection alone and would allow authorities to identify and focus on bridges that need immediate attention.
Moaveni installed a network of 10 wired sensors in 2009 on a 145-foot long footbridge on Tufts’ Medford/Somerville campus. In 2011, Moaveni added nearly 5,000 pounds of concrete weights on the bridge deck to simulate the effects of damage on the bridge—a load well within the bridge’s limits. Connected by cables, the sensors recorded readings on vibration levels as pedestrians walked across the span before and after installation of the concrete blocks. From the changes in vibration measurements, Moaveni and his research team could successfully identify the simulated damage on the bridge, validating his vibration-based monitoring framework.
A major goal of his research, Moaveni says, is to develop computer algorithms that can automatically detect damage in a bridge from the changes in its vibration measurements. His work is ongoing.
“Right now, if a bridge has severe damage, we are pretty confident we can detect that accurately. The challenge is building the system so it picks up small, less obvious anomalies.”
Tufts University School of Engineering Located on Tufts’ Medford/Somerville campus, the School of Engineering offers a rigorous engineering education in a unique environment that blends the intellectual and technological resources of a world-class research university with the strengths of a top-ranked liberal arts college.
Close partnerships with Tufts’ excellent undergraduate, graduate and professional schools, coupled with a long tradition of collaboration, provide a strong platform for interdisciplinary education and scholarship.
The School of Engineering’s mission is to educate engineers committed to the innovative and ethical application of science and technology in addressing the most pressing societal needs, to develop and nurture twenty-first century leadership qualities in its students, faculty, and alumni, and to create and disseminate transformational new knowledge and technologies that further the well-being and sustainability of society in such cross-cutting areas as human health, environmental sustainability, alternative energy, and the human-technology interface.
SALT CONTRIBUTES TO 1,650,000 DEATHS GLOBALLY EACH YEAR
From the FMS Global News Desk of Jeanne Hambleton Posted on August 13, 2014 By Stone Hearth News Eureka Alert
BOSTON — More than 1.6 million cardiovascular-related deaths per year can be attributed to sodium consumption above the World Health Organization’s recommendation of 2.0g (2,000mg) per day, researchers have found in a new analysis evaluating populations across 187 countries. The findings were published in the August 14 issue of The New England Journal of Medicine.
“High sodium intake is known to increase blood pressure, a major risk factor for cardiovascular diseases including heart disease and stroke,” said first and corresponding author Dariush Mozaffarian, M.D.,
Dr.P.H., dean of the Friedman School of Nutrition Science and Policy at Tufts University, who led the research while at the Harvard School of Public Health. “However, the effects of excess sodium intake on cardiovascular diseases globally by age, sex, and nation had not been well established.”
The researchers collected and analyzed existing data from 205 surveys of sodium intake in countries representing nearly three-quarters of the world’s adult population, in combination with other global nutrition data, to calculate sodium intakes worldwide by country, age, and sex. Effects of sodium on blood pressure and of blood pressure on cardiovascular diseases were determined separately in new pooled meta-analyses, including differences by age and race. These findings were combined with current rates of cardiovascular diseases around the world to estimate the numbers of cardiovascular deaths attributable to sodium consumption above 2.0g per day.
The researchers found the average level of global sodium consumption in 2010 to be 3.95g per day, nearly double the 2.0g recommended by the World Health Organization. All regions of the world were above recommended levels, with regional averages ranging from 2.18g per day in sub-Saharan Africa to 5.51g per day in Central Asia. In their meta-analysis of controlled intervention studies, the researchers found that reduced sodium intake lowered blood pressure in all adults, with the largest effects identified among older individuals, blacks, and those with pre-existing high blood pressure.
“These 1.65 million deaths represent nearly one in 10 of all deaths from cardiovascular causes worldwide. No world region and few countries were spared,” added Mozaffarian, who chairs the Global Burden of Diseases, Nutrition, and Chronic Disease Expert Group, an international team of more than 100 scientists studying the effects of nutrition on health and who contributed to this effort.
“These new findings inform the need for strong policies to reduce dietary sodium in the United States and across the world.”
In the United States, average daily sodium intake was 3.6g, 80 percent higher than the amount recommended by the World Health Organization. [The federal government’s Dietary Guidelines for Americans recommend limiting intake of sodium to no more than 2,300mg (2.3g) per day.] The researchers found that nearly 58,000 cardiovascular deaths each year in the United States could be attributed to daily sodium consumption greater than 2.0g. Sodium intake and corresponding health burdens were even higher in many developing countries.
“We found that four out of five global deaths attributable to higher than recommended sodium intakes occurred in middle- and low-income countries,” added John Powles, M.B., B.S., last author and honorary senior visiting fellow in the department of public health and primary care at the University of Cambridge.
“Programs to reduce sodium intake could provide a practical and cost effective means for reducing premature deaths in adults around the world.”
The authors acknowledge that their results utilize estimates based on urine samples, which may underestimate true sodium intakes. Additionally, some countries lacked data on sodium consumption, which was estimated based on other nutritional information; and, because the study focuses on cardiovascular deaths, the findings may not reflect the full health impact of sodium intake, which is also linked to higher risk of nonfatal cardiovascular diseases, kidney disease and stomach cancer, the second most-deadly cancer worldwide.
This research was supported by a grant from the Bill and Melinda Gates Foundation.
Mozaffarian, D; Fahimi, S; Singh, G; Micha, R; Khatibzadeh, S; Engell, R; Lim, S; Goodarz, D; Ezzati, M; and Powles, J. “Global sodium consumption and death from cardiovascular causes.” N Engl J Med 2014. 371:7, 624-634. DOI: 10.1056/NEJMoa130412
About the Friedman School of Nutrition Science and Policy
The Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy at Tufts University is the only independent school of nutrition in the United States. The school’s eight degree programs – which focus on questions relating to nutrition and chronic diseases, molecular nutrition, agriculture and sustainability, food security, humanitarian assistance, public health nutrition, and food policy and economics – are renowned for the application of scientific research to national and international policy.
Back tomorrow – Jeanne