Invader’s Chemical Fingerprint

These overlayed images of the rain forest near the Kilauea Volcano in the Hawaii Volcanoes National Park show the battle between native and invasive species. 

The bottom image is a traditional picture from a high-altitude airplane, whereas the top and middle are maps of spectroscopic data that show levels of nitrogen and water content, respectively.

"We found chemical fingerprints from the plant leaves and used them to tell which species dominated specific areas," said Gregory Asner of the Carnegie Institution.

Asner and his colleagues used measurements from NASA's Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) to detect the chemical signatures of certain plant varieties.

The native dominant tree "ohia" (Metrosideros polymorpha) typically has a low concentration of nitrogen in its leaves - a fact that distinguishes it from the invading Canary Islands tree (Myrica faya), which acquires nitrogen from the atmosphere. 

The researchers were also surprised to find a signal for another invader, the Kahili ginger plant (Hedychium gardnerianum). Because the ginger grows under the forest canopy, it cannot be seen using traditional remote sensing from aircraft or satellite, but the new spectroscopic methods are sensitive to the invasive weed's high water content.

The study was published in last week's early online edition of the Proceedings of the National Academy of Sciences.

-- LiveScience Staff

Credit: Gregory Asner