Merging technology with biology

Lasers are useful as pointers in public meetings, for aiming weapons, for directing energy and for many other purposes—but they also can play an important role in biology.

Increasingly, biologists are employing the most complex technologies available, and merging multiple technologies to accomplish things that were never before possible in the natural sciences.

In a recent example on the Big Island, scientists from the U.S. Forest Service and Carnegie Institution combined high-accuracy GPS, plus advanced spectral imaging, with distance-measuring lasers to measure large-area changes in the natural landscape.

The equipment was mounted in aircraft, and permitted a three-dimensional detailed look at the forest cover.

A report on the project was published this month in the journal Ecosystems, under the title, "Environmental and Biotic Controls Over Above Ground Biomass Throughout a Tropical Rain Forest.” The combined airborne technology is called the Carnegie Airborne Observatory. More on that here.

The satellite-based positioning inherent in GPS tells researchers precisely where on the ground they're looking. The laser, which can measure distances with six-inch accuracy, tells them the relative heights of various parts of the canopy, creating a three-dimensional image. The spectrometer can be used to distinguish individual plant species from each other—a koa tree has a distinctly different light signature from an 'olapa, for example.

By assessing the forest while flying over it, vast regions can be cataloged quickly. And preliminary results—comparing the aerial imagery with information gathered by foresters trudging through the woods on the ground—show that it works.

"These findings showed airborne data correlated with data derived from study plots on the ground," said Forest Service ecologist and paper co-author Flint Hughes, of the service's Institute of Pacific Islands Forestry.

The researchers did more than just mapping. Their work was able to show that areas dominated by alien plant invaders had different amounts of biomass than those that were primarily native—and that a native forest is better at sucking up and storing carbon dioxide than an alien-dominated one.

"Our results clearly show the interactive role that climate and invasive species play on carbon stocks in tropical forests, and this may prove useful in projecting future changes in carbon sequestration in Hawaii and beyond," said co-author Gregory Asner, of the Carnegie Institution's Department of Global Ecology.

For the research leading to the paper, the researchers flew their aerial observatory over Mauna Kea's northeast flank, covering the Hawai'i Experimental Tropical Forest, a site that is a candidate of the National Science Foundation for designation as a part of the National Ecological Observatory Network.

The work observed the diameter of trees, the height of the canopy and allowed calculations of the biomass present in the forest. In a press release, the authors said that “study results suggest fast-growing invaders decrease biomass levels, while slower-growing species increase biomass stocks.”

The Nature Conservancy is using similar technology on Kaua'i, working with Dana Slaymaker of Resource Mapping Hawai'i to collect detailed imagery from aircraft of the Alaka'i region. One key difference between the two systems is the kind of spectral data collected, and its level of detail.

©2009 Jan TenBruggencate