Canopy Crane Access System

Canopy Access and Canopy Cranes

Canopy access - Background

The study of forest canopy is strongly associated with problems of accessing the upper canopy, often 20-60m above the forest floor. This represents a major impediment in canopy science. Many of the earlier studies of forest canopy relied upon ground-based methods, such as observation with binoculars, and there were few opportunities to study canopy organisms directly. Life-histories and population dynamics could only be inferred from such data. During the past two decades, several methods of canopy access have broadened the ability of scientists to access the canopy and have allowed the observation and collection of canopy organisms in situ.

Most of the means for gaining access to the canopy were developed in the tropics. A pioneering attempt to study the canopy in situ was by means of ladders and pulley systems, utilized during the Oxford University’s expedition of 1929 in British Guiana (now Guyana) (Hingston, 1932). The few studies performed before the late 1970’s used fixed systems including towers, platforms, walkways and ladders. In 1978, Perry reported the inexpensive adaptation of a single-rope technique (used by cavers to ascend vertical shafts) to the safe climbing of tall forest trees. Further, in the late 1970’s, entomologists developed ground-based techniques, such as insecticide knockdown and light-trapping, to obtain mass collections of arthropods from the tropical canopy. This led to an expansion of canopy studies, augmented in the following decade with newer methods permitting access to the upper canopy, including the canopy raft and peripherals, and canopy cranes. Landscape ecologists also study the canopy with satellite remote-sensing. Canopy access is reviewed historically in Mitchell (1982), Moffett (1993), Moffett and Lowman (1995), and Sutton (2001), among others.

Canopy access: canopy fogging, single rope techniques and canopy sledge. For the latter, more info here.

Canopy cranes

Alan P. Smith and the Smithsonian Tropical Research Institute pioneered the installation and use of a construction tower crane to gain access to the canopy in a tropical forest in Panama (Wright & Colley, 1994, 1996). This was realised in 1990 in collaboration with the United Nations Environment Programme (UNEP), with funding provided by the governments of Belgium, Denmark, Finland, Germany and Norway through UNEP’s Clearing House Mechanism and by the Smithsonian National Board of Associates for the purchase and installation of the construction crane. The construction crane as a research tool was so successful that a permanent crane was installed in 1992 in Panama, followed by a second in 1997. Since then, other cranes have been established in a variety of temperate and tropical forests (Parker et al., 1992; Wright, 1995; Wright & Colley, 1996; Stork et al., 1997; Basset et al., 2003).

The International Canopy Crane Network (ICCN) was founded in 1997 to capitalize fully on the growing number of canopy cranes installed in forests worldwide. By replicating experiments in different forest types, the network provides the opportunity to evaluate the generality of hypotheses in a variety of situations. The main objectives of the network are to promote collaborative research on the forest canopy and to exchange students and scientists among sites. The network is composed of eleven crane facilities (one is not in operation anymore), located in eight countries. Six cranes are erected in temperate forests (Basel in Switzerland, Kranzberg, Leipzig and Solling, all in Germany, Tomakomai in Japan and Wind River in the USA) and five cranes are installed in tropical forests (Cape Tribulation in Australia, Lambir Hills in Malaysia, Surumoni in Venezuela, and Parque Natural Metropolitano and San Lorenzo in Panama). These sites are located in forests from different biomes and biogeographical regions, including northern coniferous forest, mixed temperate forest, deciduous broad leaf forest, tropical dry lowland forest, and tropical wet lowland forest.

Diagram of a canopy crane

A metal basket called the gondola, in which observers stand, is hoisted above the forest by the crane and lowered to research locations within the canopy. Since gondolas and cranes are standard equipment in the construction industry, no modifications are necessary to adapt this equipment for scientific purposes. Different sizes of gondola exist, able to carry from 1 to 6 persons. Canopy cranes enable easy and safe three-dimensional access to the canopy. The gondola may be lowered into gaps, all the way to the ground, or into the crown of large open trees. The crane facilitates access to the whole forest column within reach of the crane. Heavy equipment can be carried onboard the gondola, and some cranes have power outlets in the gondola for electrical equipment. Movement of the crane and gondola is controlled through radio communication with the crane operator.

One-person gondola, used here to study epiphyte communities

The main advantages of canopy cranes are the safety and excellent access within much of the canopy (less so in the lower part), the possibility of obtaining many temporal replicates, and the ability to lift heavy equipment into the canopy rapidly. Easy and non-destructive access to the upper canopy are particularly useful for measuring photosynthesis in situ, which can be measured on a single leaf or with the help of dataloggers that can be installed to record measurements continuously. Behavioural observations of animals foraging in the upper canopy may be made routinely. In particular, studies of canopy insects, observations on their feeding behaviour and life cycles are easily performed in the upper canopy with canopy cranes. However, problems related to pseudoreplication at the meso-scale are patent within the relatively small and fixed crane perimeter (seldom exceeding 1ha in area), and the costs of purchasing, erecting and maintaining a crane are high, particularly in remote tropical locations. Crane use may also be restricted during stormy or windy weather.

Lift of heavy equipment in the canopy to make leaf-level measurements of photosynthesis and reactive nitrogen uptake

View short video of the view up the canopy from the San Lorenzo crane
Click Here (Courtesy of G. Castaño-Meneses, 3MB)

View short video of going down with the San Lorenzo crane
Click Here (Courtesy of G. Castaño-Meneses, real time, 13MB)

References cited

Basset, Y., Horlyck, V. & Wright, S.J. (2003)
Studying Forest Canopies from Above: The International Canopy Crane Network. Smithsonian Tropical Research Institute and UNEP, Panama City.

Hingston, R. W. G. (1932). A Naturalist in the Guiana Forest. London, Edward Arnold & Company.

Mitchell, A. W. (1982). Reaching the Rain Forest Roof. Leeds, Leeds Philosophical and Literary Society.

Moffett, M. W. (1993). The High Frontier. Exploring the Tropical Rainforest Canopy. Cambridge, Massachusetts, Harvard University Press.

Moffett, M. W. & Lowman, M. D. (1995). Canopy access techniques. Forest Canopies. M. D. Lowman and N. M. Nadkarni. San Diego, Academic Press: 3-26.

Parker, G. G., Smith, A. P. & Hogan, K. P. (1992) Access to the upper forest canopy with a large tower crane. BioScience, 42, 664-670.

Perry, D. R. (1978) A method of access into crowns of emergent and canopy trees. Biotropica, 10, 155-157.

Stork, N. E., Wright, S. J. & Mulkey, S. S. (1997) Craning for a better view: the Canopy Crane Network. Trends in Ecology and Evolution, 12, 415-420.

Sutton, S. L. (2001) Alice grows up: canopy science in transition from Wonderland to reality. Plant Ecology, 153, 13-21.

Wright, S. J. (1995). The canopy crane. Forest Canopies. M. D. Lowman and N. M. Nadkarni. San Diego, Academic Press: 15.

Wright, S. J. & Colley, M. (1994). Accessing the Canopy. Assessment of Biological Diversity and Microclimate of the Tropical Forest Canopy: Phase I. Nairobi, Kenya, United Nations Environment Programme.

Wright, S. J. & Colley, M. (1996). Tropical Forest Canopy Programme. Nairobi, Kenya, United Nations Environment Programme / Smithsonian Tropical Research Institute.

Other textbooks/compilations of interest

Basset, Y., Horlyck, V. & Wright, S.J. (2003)
Studying Forest Canopies from Above: The International Canopy Crane Network. Smithsonian Tropical Research Institute and UNEP, Panama City.

Basset, Y., Novotny, V., Miller, S. E. & Kitching, R. L., Eds. (2003).
Arthropods of Tropical Forests. Spatio-temporal Dynamics and Resource Use in the Canopy. Cambridge, Cambridge University Press.

Linsenmair, K. E., Davis, A. J., Fiala, B. & Speight, M. R. (2001).
Tropical Forest Canopies: Ecology and Management. Dordrecht, The Netherlands, Kluwer Academic Publishers.

Lowman, M.D. & Rinker, H.B. (2004) Forest Canopies. 2nd edition. San Diego, Academic Press.

Stork, N. E., Adis, J. & Didham, R. K., Eds. (1997b). Canopy Arthropods. London, Chapman & Hall.

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