Institutional background and description of crane sites
The late Alan P. Smith, a research scientist at the Smithsonian Tropical Research Institute (STRI), and STRI engineer Fernando Pascal were the first to develop the idea of using construction cranes to access the forest canopy (Parker et al., 1992; Anonymous, 1993; Illueca & Smith, 1993; Smith et al., 1993; Allen, 1996). In 1990, Smith rented a construction tower crane for two years, and two years later, a larger crane was permanently installed in the Parque Natural Metropolitano, near Panama City, on the Pacific coast of the Isthmus. A second crane was installed in 1997 in the San Lorenzo Protected (SLP) Area on the Caribbean coast. These two canopy access facilities were funded by the Smithsonian Institution and its National Board of Associates and by the governments of Belgium, Denmark, Finland, Germany and Norway through the clearinghouse mechanism of the United Nations Environment Program.
STRI manages the canopy cranes, which represent the core of the Tropical Canopy Biology Program. Visiting researchers are welcome to use the cranes; fees for longer research projects are negotiable, students are usually exempted from crane use fees. In addition, STRI provides a wide range of fellowships that may facilitate canopy research in Panama. These are open to all nationalities and all investigators, from predoctoral students to full professors.
The two canopy cranes are 80 km apart from each other; one is located in a semi-deciduous Pacific coastal forest (at the Parque Natural Metropolitano) and the other in a wet evergreen Caribbean coastal forest (at Parque Nacional San Lorenzo). Since there is a steep rainfall gradient from the Pacific to Caribbean coast in Panama, this provides an ideal opportunity to compare the influence of rainfall on different forest processes. Annual rainfall averages 3,300 mm at Parque Nacional San Lorenzo and just 1,740 mm at the Parque Natural Metropolitano. Consequently, there is a nearly complete change in plant species composition between the two sites.
Canopy Crane at Parque Natural Metropolitano (PNM)
Parque Natural Metropolitano Crane
In 1990, STRI pioneered the use of construction cranes to access the forest canopy in Panama 's Parque Natural Metropolitano. A fifteen-minute drive from downtown Panama City, the PNM crane provides a spectacular view of the forest canopy, the city skyline and the Pacific entrance of the canal. The forest edge site was selected to minimize the costs of installation at a time when canopy cranes were unproven. For more than fifteen years, the canopy crane has facilitated studies of arthropod diversity, pollination biology, trophic interactions, physiology of canopy trees and lianas. Plant phenology, gas exchange, water transport and light limitation data for understory, sub-canopy and canopy level plants are easily measured as the gondola lifts and lowers biologists. Recent research also includes ground-truthing of remote sensing data for measurement of landscape scale phenology.
The crane in Parque Natural Metropolitano accesses 0.85 hectares of forest, characterized as a tropical semi-deciduous dry forest. Annual rainfall averages 1740 mm with a distinct dry season from December through April, when rainfall is usually less than 100mm per month. The crane stands in the center of a 1-hectare plot where all 316 trees with a bole size of 10cm in dbh or greater have been measured, mapped and identified (click here to download raw data of the PNM botanical plot). Trees in this plot are 30-40 meters tall, and the summed basal area of all stems larger than 10 cm in dbh is 26 m2 per hectare. The dominant tree species in the forest is Anacardium excelsum (Anacardiaceae). Others include Luehea seemannii, Cordia alliodora, Ficus insipida and Castilla elastica. Thirty-six species of trees belonging to 20 families are present in the botanical plot and more than 60 species of trees and lianas can be reached within the crane perimeter.
Parque Natural Metropolitano protects 265 ha of semideciduous Pacific dry forest near Panama City and is contiguous with Camino de Cruces National Park, which in turn is contiguous with the Soberania National Park. This forests represents one of the few remaining dry coastal Pacific forests in Central and South America. It has been protected since the construction of the Panama Canal, beginning in 1903. A total of 284 species of trees, 45 species of mammals and 254 species of nesting birds have been recorded in the Park. BirdLife International and the Panama Audubon Society have declared this forest to be an area of global importance for birds, because of its value for migratory raptors. It also protects several nationally threatened birds, including the Sepia-capped Flycatcher (Leptopogon amaurocephalus). In addition, several species listed on the Cites Appendix I are also present, including Geoffroy’s tamarin (Saguinus geoffroyi), jaguarundi (Herpailurus yaguarondi), margay (Leopardus wiedii) and peregrine falcon (Falco peregrinus).
Ascending to the canopy
Parque Nacional San Lorenzo Canopy Crane (PNSL)
STRI's second canopy crane, installed in 1997 on the Caribbean coast of Panama offers an amazing look into the rainforest in the Parque Nacional San Lorenzo. This evergreen humid rainforest receives annual rainfall of 3300mm. February and March, the driest months of the year, receive an average of 45mm of rain each month. At the wet end of the rainfall gradient across the Isthmus, the site is often included in comparative studies with the less humid forest on Barro Colorado and the drier Parque Natural Metropolitano.
The forest is perhaps 300 years old and forms part of the Mesoamerican Biological Corridor and the forested area of the Panama Canal basin. From 1953 until 1999, the area was an important jungle warfare training site for U.S. soldiers. In June 1999, the 12,000 ha of forest was declared the San Lorenzo Protected Area, then the Parque Nacional San Lorenzo.
The San Lorenzo crane provides access to 0.92 hectares of tropical wet evergreen forest, which includes more than 240 species of trees and lianas. The crane stands in a 6-hectare plot (click here for additional data) where all 22,400 trees with a bole size of 1 cm in dbh or greater have been identified, measured and mapped. Structurally, the forest can be characterized as including 3,338 stems per hectare (greater than 1 cm dbh) and a total basal area of almost 32 m2 per hectare with the tallest trees being 45 m tall. The canopy is dominated by the trees Brosimum utile and Manilkara bidentata. Geoffroy’s tamarin and the Howler monkey (Alouatta palliata), both listed in the CITES Appendix I, are readily observed. Jaguar (Panthera onca), ocelot (Leopardus pardalis), southern river otter (Lontra longicaudis) and jaguarondi (Herpailurus yagouarundi) are also present.
The San Lorenzo crane has supported a wide range of research topics, including studies of pollination systems, epiphyte communities, arthropod biodiversity, trophic interactions, plant uptake of nitrous oxides, isoprene emission by trees, phenology and water transport.
San Lorenzo canopy crane
Condit R, Watts K, Bohlman SA, Pérez R, Foster RB, Hubbell SP (2000)
Quantifying the deciduousness of tropical forest canopies under varying climates. J. Veg. Sci. 11: 649-658
Condit R, Aguílar S, Hernández A, Pérez R, Lao S, Angehr G, Hubbell SP, Foster RB (2004)
Tropical forest dynamics across a rainfall gradient and the impact of an El Niño dry season. J. Trop. Ecol. 20: 51-72
Wright, S.J., Horlyck, V., Basset, Y., et al. (2003)
Tropical Canopy Biology Program, Republic of Panama. In: Y. Basset, Y. Horlyck, V. & S.J. Wright (eds) Studying Forest Canopies from Above: The International Canopy Crane Network, pp. 138-158. Smithsonian Tropical Research Institute and UNEP, Panama City.