By applying novel measurement techniques from a high-altitude aircraft, scientists detected two species of invading plants that are changing the ecology of rain forest near the Kilauea Volcano in the Hawaii Volcanoes National Park. Lead author, Dr. Gregory Asner of the Carnegie Institutions Department of Global Ecology, explained: "We found chemical fingerprints from the plant leaves and used them to tell which species dominated specific areas. We employed the recently upgraded NASA Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) to measure leaf nitrogen and water content from the aircraft, and corroborated the data on the ground. The fingerprints showed where the native dominant tree ohia (Metrosideros polymorpha) has been taken over by the invading Canary Islands tree, Myrica faya, and more importantly identified areas where Myrica invasion is in its early stages. The aircraft imagery also showed us how the forest canopy chemistry is changing as a result of the invader." The study is published in the March 7-11, 2005, early online edition of the Proceedings of the National Academy of Sciences.
Traditional remote sensing of the forest canopy is shown at on the bottom. The middle and top images are the outputs from the new analytical techniques used in the study. They show canopy water content and leaf nitrogen concentration from high-altitude airborne imaging spectroscopy. (Image courtesy Gregory Asner.)
The new methods are exciting because they detect effects of biological invasions on ecosystems, not just the presence of an invader. Islands like Hawaii are vulnerable to biological invasion; new species can wreak havoc very quickly. The fact that the new techniques allowed the scientists to detect an invader before it dominated the landscape is important to future management strategies. As a result of the findings, the group has expanded to include collaborators from federal, state, and private organizations. Scientists and resource managers from Carnegie, Stanford University, the U.S. National Park Service, NASA, and The Nature Conservancy have teamed up with an unprecedented plan to map the chemical and structural composition of Hawaiian ecosystems and to find invasive species and track their ecological impacts. This month, Carnegie global ecologists and engineers from the NASA Jet Propulsion Laboratory are flying an upgraded version of the AVIRIS airborne spectrometer on a more nimble Twin Otter turboprop aircraft, not only to find invasive species, but to develop the next generation of ecosystem monitoring capabilities.
On Kilauea Volcano, the native Metrosideros tree typically has a low concentration of nitrogen in its leaves ( .6% to .8%), while the invading Canary Islands tree has relatively high nitrogen concentration (1.5% to 1.8%), because it can acquire nitrogen from the atmosphere.
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