 AVIRIS Spectrum Image
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July 23, 2003 — Researchers from the University of California, Davis, are taking on invasive iceplants and jubata grasses along the California coast by using airborne NASA technology to seek out and map the invaders by the their unique colors.
"There would never be enough time or people to map invasive species on the ground," said botanical geographer Deanne DiPietro, who worked on the study with colleagues Susan Ustin and Emma Underwood.
They reported their findings in the July 30 issue of the journal Remote Sensing of Environment.
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"There would never be enough time or people to map invasive species on the ground," said botanical geographer Deanne DiPietro, who worked on the study with colleagues Susan Ustin and Emma Underwood.
They reported their findings in the July 30 issue of the journal Remote Sensing of Environment.
The technology that they put on the trail of the invaders is called the Airborne Visible/Infrared Imaging Spectrometer, or AVIRIS.
Flown over areas where invading plants are found, the system records digital images of the land and breaks them down into 8,000 separate spectrum — little rainbows — per second. Each spectrum represents, for instance, a square meter of land seen from 5,000 feet above the ground.
Each in turn can be analyzed for 224 different light bands that go far beyond the visible light we can see with our eyes, said AVIRIS researcher Robert Green of NASA's Jet Propulsion Laboratory in Pasadena, Calif.
The molecules that make up different substances absorb and reflect different bands of light in very specific ways, Green said, giving substances spectral signatures that can be seen by AVIRIS.
Normally AVIRIS is used to find substances that point to non-living things, like minerals on the surface of the Earth or even asbestos that was spread by the World Trade Center's collapse, Green said.
Applied to plants, AVIRIS can not only identify specific kinds of plants by their signature spectrums, but because water has an easy-to-detect spectral signature, repeated fly-overs can show how plants are drying out and increasing wildfire dangers, he said.
Water's spectral signature also happens to make the invasive iceplant easy to map, DiPietro said. The succulent, watery leafs of iceplant make it stand out in the dry hills of coastal California. On the other hand, the spectral signatures of jubata grasses were a bit subtler, she said, because they are similar in color to native scruffy vegetation.
Besides just showing where the invaders are, the new approach to mapping will help land managers decide where they need to focus their efforts and funds in fighting the non-native plants, DiPietro said.
At stake, she said, is the survival of many native plants and animals that can't live side-by-side with the iceplant and jubata grasses.
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