The recent research shows thatairborne laser scanning with Light Detecting And Ranging (LiDAR) can beespecially valuable in ensuring that forests and other lands continueto be diverse, healthy, and productive, while still meeting the needsof society and the environment. The study, funded by theNASA/University of Maryland Vegetation Canopy LiDAR (VCL) mission and aNASA Interdisciplinary Science (IDS) Program grant, was published inthe June 2005 issue of the journal Remote Sensing of the Environment.
"Whenwe compared the data gathered from the LiDAR, including information oncanopy height and cover, to measurements taken on the ground, we foundthat LiDAR was very accurate, even in extremely rugged mountainousterrain," said Peter Hyde of the Department of Geography, University ofMaryland-College Park, and lead author of the study. "The use of suchtechnology is advantageous compared with field-based measurements offorest structure that are very time consuming and often limited byaccessibility, resulting in relatively small field studies."
Theresearch flights, using NASA's C-130 aircraft, took place in the SierraNevada mountains in northern California in 1999. A unique LiDAR, calledthe Laser Vegetation Imaging Sensor (LVIS), was used. It was built atNASA's Goddard Space Flight Center (GSFC) in Greenbelt, Md., andcontains five lasers that send pulses of energy to the Earth's surface.Photons from the lasers bounce off leaves, branches, and the ground andreflect back to the instrument.
By analyzing returned LiDARsignals, scientists receive measurements on a forest's canopy, thelayer formed by the leaves and branches of the forest's tallest trees.They also get information on tree height and biomass, the amount ofliving material in a given area. All of this provides athree-dimensional look at forests and represents a significantimprovement over earlier radar and other technology that were not ableto penetrate thick forest cover very well.
"LiDAR can alsoeffectively distinguish and map old-growth forests, a feat that isdifficult with other technology, said Principal Investigator RalphDubayah, also of the Department of Geography, University ofMaryland-College Park.
A similar study looked at the role offorest structure on a specific animal habitat, and was led by RossNelson, a physical scientist at GSFC. By using data from NASA'sairborne LiDAR, called the Portable Airborne System (PALS), theresearchers examined about 800 miles of forest in Delaware in thesummer of 2000. They also found LiDAR to be successful, especially inlocating tall, dense forests that might support endangered Delmarva foxsquirrel (DFS) populations. The study was also published in the June2005 issue of the journal Remote Sensing of the Environment.
"Perhapsthe most surprising finding was that about 80 percent of the foreststhat we identified as tall and dense could serve as a suitable habitatfor the DFS," said Nelson. "But, ground visits would be needed todetermine if each site is suitable for DFS reintroduction."
DFS,which plays an important role in its ecosystem by distributing tree andother plant seeds, live in mature pine and hardwood forests, especiallynear farmland. Large trees provide an abundant supply of acorns andseeds for food and provide suitable nests. The conversion of forestsinto agricultural land, development, timber harvesting, sea level riseand over-hunting have all contributed to the decline in DFS populations.
Inorder to protect the DFS habitat, biologists rely on up-to-dateinformation to identify habitats where food and potential nestlocations are plentiful. "In the future, say every 5 years, we canfollow the same flight paths used in this study to determine if habitathas been lost or gained," said Nelson.
Airborne LiDAR and similartechniques are also being used to help monitor and reintroduce otherendangered species around the world, like the northern spotted owl thattypically resides in old forests in Oregon and California, where treesare more than 100 years old.
The above story is based on materials provided by NASA/Goddard Space Flight Center--EOS Project Science Office. Note: Materials may be edited for content and length.
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