The Panama Canopy Crane

at the

Smithsonian Tropical Research Institute

Panama City, Panama

The world's first canopy crane stands 42 meters high and has a horizontal jib of 51 meters. The forest canopy under the crane provides researchers with access to 8,000 square meters of upper canopy surface, and 28,000 cubic meters of forest volume, including some 140 individual canopy trees. Researchers access the top of the canopy by being lifted above in a steel cage, or gondola, attached to the crane hook. The operator sits at the top of the main tower and communicates with researchers in the gondola via a two-way radio.

The canopy crane has two main advantages over other methods of canopy access. First, there is minimal impact on the canopy vegetation. With different gondolas of appropriate sizes and shapes, it is possible to penetrate the canopy from above and access virtually all canopy microsites. Secondly, the crane for the first time permits researchers to bring heavy analytical equipment into the forest canopy where living materials can be studied in situ. Thus the crane permits repeatable, nondestructive analytical studies to be done in the canopy.

The crane shown here was the brainchild of the late Dr. Alan P. Smith, who realized the utility of this device after exploring many other means of canopy access. The first permanent canopy crane was provided to the Smithsonian by the United Nations Environmental Program (UNEP), with logistic and support services provided by the Smithsonian Instititution. To date, three crane studies have been funded by the US National Science Foundation.

A new crane has just arrived in Panama (4/96), and will be erected on the Atlantic side in old-growth wet forest. This crane and research funds were donated (through UNEP) by the government of Denmark. This new crane will permit extensive, long-term studies of wet and dry tropical forest canopies. Future work will include landscape-level studies of carbon exchange with the atmosphere.

Selected research in the tropical canopy - 1995

Seed and Flower Predation in the Canopy

: Predoctoral student Cecilia Sanchez from the National Autonomous University of Mexico studies the consumers and reproductive structures of canopy trees, lianas and epiphytes. Reproductive structures both with and without evidence of predation are systematically collected and returned to the laboratory where they are held in controlled environmental chambers that maintain conditions similar to those in the field until eggs and larvae have hatched and grown into adult insects. 89% of the flowers of Anacardium excelsum have been found to be effectively sterile because of pre-dispersal predation by insects.

Photosynthesis and Photoinhibition in the Canopy

: The canopy of tropic forest receives stronger irradiance than forests in other parts of the world because of the steep solar angle near the equator. Accordingly, leaves frequently receive more energy than can constructively be used in photosynthesis, especially during the sunny dry season. This excess irradiance can be damaging to plant pigments and tissues. Dr. Klaus Winter, a Smithsonian staff scientist, and his colleagues study the photosynthetic capacities and energy management strategies of leaves at the top of the canopy. Recently, he discovered that Ficus insipida, a common species of Fig tree, has the highest recorded photosynthetic rate for any tree yet measured. This species dissipates excess irradiance through biochemical mechanisms that appear to common among many plants that receive strong irradiance.

Functional Syndromes in the Canopy

We know little about how plants distribute resources required for carbon gain in response to the complex mosaic of water, light, and temperature in the canopy. Spatial and seasonal variation in light and functional leaf characters were studied by Drs. Stephen S. Mulkey and Kaoru Kitajima (University of Florida - Dept. of Botany) and Dr. S. Joseph Wright (Smithsonian Tropical Research Institute) in the canopies of seven species of trees over two years in a dry tropical forest near Panama City, Panama. Light gradients in the canopies of the tallest trees were very steep, with up to two orders of magnitude decrease in irradiance from the outside to 1 meter inside the canopy. Generally, irradiance decreased with decreasing height above the ground. Diffuse light was higher than in the canopy and subcanopy immediately beneath the canopies of emergent trees. Irradiance was lowest beneath vines occupying gap openings. Across all species, leaf nitrogen concentration, construction cost, mass per area, and assimilation capacity scaled linearly with leaf longevity. When early successional species were excluded, the relationship among functional characters was more closely related to season of leaf production and light availability than to leaf longevity. Variation in functional characters across seasons and light environments was more continuous than discrete for each species. This project has been funded by NSF grants to S. Mulkey and S. J. Wright. Additional funding is being sought to expand this work with the new canopy crane in wet forest on the Atlantic side of the Isthmus of Panama.

Liana Physiology in the Canopy

: Lianas, or woody vines, can contribute up to 70% of the biomass in the canopy of some tropical forests. PhD student Gerardo Avalos (University of Missouri-St. Louis) studies the distribution and physiology of canopy vines from the crane. These unique life forms are rooted in the soil, but are parasitic on canopy trees for their access to sunlight and support. Lianas compete for light with their host trees and displace the foliage of the host tree. Despite their importance, lianas have received little study in tropical forests due to their inaccessibility in the uppermost canopy. Outstanding among the many questions that remain unexamined for lianas is their mechanism of water transport. Central to Avalos' dissertation are experiments to assess the degree of physiological flexibility shown by these remarkable plants, which traverse the entire range of light availability on their way to the top of the canopy.

Additional Information on Canopy Research: International Canopy Network (ICAN)

Call for Research Proposals for Canopy Cranes in Panama

Updated 7/97; mulkey@botany.ufl.edu