Morton Arboretum tree researchers and NASA aeronautical engineers recently held a week-long series of experiments and tests aimed at uncovering the mystery of tree biomechanics, or what makes trees stand, and what makes them fall.
Phase one: paint polka dots on trees.
Phase two: rig up an elaborate digital imaging camera system spanning the top of the tree trunks on trees in the Arboretum’s West Side research plot.
Phase three: employ an extensive cable system to bend, twist and knock down trees, capturing the action on 3-D cameras.
This is serious scientific research as the team of scientists from the Arboretum and colleagues from France, England and Germany teamed up with NASA aeromechanical engineers for a week in the Arboretum’s research plot to test if the technology used in Space Shuttle exploration safety testing is a potentially useful research tool when applied to the biomechanics of trees.
“We’re taking this vital technology used for the Shuttle program into the field of trees,” said Matt Melis, a longtime NASA engineer who leads NASA’s Glenn Research Center Ballistics Impact Lab, in Cleveland, Ohio where engineers tested Shuttle parts for their ability to withstand hits from debris. Melis’ team launched this testing in Feb. 2003 after Columbia broke apart while re-entering Earth’s atmosphere.
Some of the first work with this technology, based on stereo image correlation, occurred in the 1950’s with U. S. reconnaissance photos to measure changing conditions on the ground. With the advent of digital imagery, the technology rapidly matured and, would prove a critical tool in supporting the Space Shuttle Columbia Accident Investigation and flying the Shuttle more safely post Columbia. Since then, it has spun off for many purposes including: crime scene detection and by Playtex for the durability of women’s lingerie. Now, through a grant for tree risk assessment testing, Arboretum scientists are studying whether this three-dimensional digital camera system (called ARAMIS stereophotogrammetry technology) can help gain precise mathematical knowledge into trees’ strength, stability and resilience in wind and weather conditions. If so, it can become a central component in its tree risk assessment toolkit to help arborists and scientists identify zones of weakness and potential failure in trees.
The week’s research has an important outcome as tree scientists and arborists are hoping to identify tree risk management specifically in urban or landscape settings where damaged trees pose a public safety and property damage, said Gary Watson, Ph.D., senior research scientist at The Morton Arboretum. His research into tree biomechanics is funded The Tree Research and Education Endowment Fund (TREE Fund), which provides research grants, scholarships and educational programs to advance knowledge in the field of arboriculture and urban forestry. That funding supports the NASA involvement through a contractual arrangement known as a Space Act Agreement.
“On the simplest level it will help arborists determine whether a tree is safe and can be left standing,” said Dr. Watson.”It can also provide another tool and insight into tree’s resilience when they get wounded and its ability to compensate so we don’t have to take down trees.”
Here’s how it works: In a much more sophisticated way, the technology performs like a pair of human eyes, detecting movement and depth in three dimensions. The technique consists of configuring and installing pairs of calibrated cameras on custom rigid bars to look at the same area of interest on the trees. The cameras record a series of image pairs and send them to a computer with software that correlates the image pairs taken from each camera to compute the minutest movements of trees.
“As the fast-firing pixel images from the camera detect ‘hot spots’ on the tree where damage has been caused, they capture the injured areas in motion-picture imagery, allowing scientists to zero in on tree deformation,” said Melis.
The dots, which are painted on the trees, serve as the reference points to enable accurate software recognition for the computations. Now a highly matured technology, digital image correlation has replaced the need for employing the use of expensive, time-consuming, and more limiting strain gauge instrumentation typically used for recording such measurements. , In addition to this research, on September 24 and 25, 2012, the Arboretum and the International Society of Arboriculture will join forces to bring leading international experts for a two-day symposium: “Tree Risk Assessment: The Biomechanics of Stability, Strength and Structure.”