It's fun when you can combine your two favorite research interests into one project, then place it in an island paradise! Working with Tim Warner (Department of Geology and Geography), Rick Landenberger (now of West Virginia View) and I initiated this project, which has further developed remote sensing censusing of a rare, endangered species - Argyroxiphium sandwicense) on the barren volcano of Haleakala, Maui. Our work showed that for plants larger than ca. 5 - 10 cm, we can reliably census plants from a helicopter. The advantage of this approach is that no one has to trample the delicate cinders of the crater to census the populations, the census is spatially explicit, and one can census >90% of the area containing ca. 30,000 silverswords in a few dozen images. We have shown that we can distinguish silverswords from most other objects seen from above with automated image processing. Further, by using the IR band, we can distinguish dead from live swords. Detecting population change in these plants is the next step. This is likely to be extremely timely as two forces appear to be potentially impacting N in a detrimental way: First, Argentine ants are invading the crater and there is strong concern that they will devastate the native pollinator population that are, required by silversword for successful seed production. Second, recent consecutive drought years appear to be taking their toll in reduced flowering and increased mortality, with significant declines in numbers of plants in monitored plots. Finally, we believe remote sensing may provide important data for evaluating hybridization of silverswords with close relatives (e.g., Dubautia). At the present time, we do not have funding to continue this work, but it remains of interest and seems to be one of the most promising avenues of research to connect remote sensing and demography.
| Haleakala silversword (Argyroxiphium sandwicense) image from oblique angle |  |
Below is one of the helicopter platform images taken in October, 2000.
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This is a much-reduced image of a silversword population taken from a helicopter. The white specks are silversword individuals, which often stand out spectrally from the lava flow background. The blue flagging marks the corner of National Park Service Monitoring plots. We have compared (a) 'ground truth' data, (b) photointerpreter output, and (c) output from automated image processing algorithms. Ultimately, we are testing the limits of current remote sensing tools for monitoring rare plants such as silversword. |
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