It is the boundary between forest and atmosphere, the edge between tree and sky where many of the atmospheric processes that affect global climate take place. The forest canopy, like the deep sea or outer space, is difficult for human beings to access, much less study in a meaningful way. Until recently, this crucial ecosystem remained almost completely unexamined, except for the pioneering efforts of a few adventurous souls who used mountain climbing gear and towers to conduct their research in the tree tops.
A new era of forest canopy research began in the fall of 1994, when UW researchers started construction of a 260-foot crane in the Gifford Pinchot National Forest in southwestern Washington State. The crane carries a gondola that can be lowered in almost any location in a 550-ft circle, enabling scientists to study almost six acres of forest canopy in three dimensions. The facility is managed by the UW, the Pacific Northwest Research Station of the Forest Service, and the Wind River Ranger District of the Gifford Pinchot National Forest.
The Gifford Pinchot crane, the largest of three such cranes operating in the world as of early 1996, is the first such apparatus in the world used to study a temperate, old-growth forest. The other two cranes--one operating in Panama since the early 1990s, and the other erected in April 1995 in Venezuela--operate in tropical zones. The crane in Panama, erected by the Smithsonian Tropical Research Institute, has already yielded important new information about tropical rain forests.
"We're going to discover some really exciting things—things we can't even imagine now," says Jerry Franklin, UW professor of forest resources management, and one of the prime movers behind the forest canopy crane project. "This crane is going to make us look at canopies in ways we've never thought about, because before, we simply didn't have a good way to get out there."
One of the researchers' first tasks will be to map the canopy's structure--the live and dead wood, the distribution of foliage, snags, and canopy gaps. With this three-dimensional map in hand, scientists will be able to return to specific spots for long-term observations.
The crane will permit scientists to analyze processes such as photosynthesis and transpiration at the branch tips where they actually take place. Previously, researchers were limited to studying cuttings or seedlings. And they'll gain a greater understanding of canopy conditions, which are much harsher than those on the forest floor. The uppermost levels of the canopy experience greater daily and seasonal variations in temperature and humidity, and they are exposed to more wind and sunlight. Plant tissues and fauna found in the forest canopy are exposed to more pollutants, ionizing radiation, and desiccation than on the forest floor, where conditions are moderated by the canopy above.
"One area where we expect some dramatic breakthroughs is in understanding canopy/atmosphere interactions, including the way in which the canopy influences hydrologic cycles," says Franklin. "Another key area of study is the use of the canopy by wildlife." Information gained in the course of the project ultimately may be used to better manage forest canopies.