The International Canopy Crane Network
Many of the important scientific questions in understanding tropical and temperate forests and practical problems in managing these ecosystems require an understanding of the least known layers, the forest canopy. Inevitably, over the last 30 years a number of biologists have had to become canopy specialists in order to address widespread and far reaching issues such as forest fragmentation, extinction, water use, climate change and the distribution of global biodiversity. One recurrent problem these canopy scientists all face is the difficulty in obtaining enough spatially independent replicates to allow robust statistical analyses because of problems in gaining canopy access. Often, it leads to ‘pseudoreplication’ (Hurlbert, 1984) within the sampling universe and to disturbance and possible interference with the object being studied (Barker & Pinard, 2001). In statistical terms, when two or more supposed replicates are too close to each other they are considered not to be fully independent of each other and are therefore pseudoreplicates. Comparing data sets from different biogeographical regions may improve replication and may help to explore whether community patterns hold at different spatial scales and in different forest biomes.
The International Canopy Crane Network represents an answer to these problems. By replicating experiments in different forest types, data held collectively by the network have more statistical power and the generality of hypotheses can be tested in a variety of situations. The network represents a collaboration between eleven canopy crane sites. The main objective is to promote collaborative research on the forest canopy and to exchange students and scientists among the sites. The end product of the network is envisioned as a standardized, long-term monitoring of forest canopies, which should supply a wealth of data on the structure, biodiversity and function of forest canopies.
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A second goal is to increase the dissemination of data and results resulting from canopy studies to policymakers, governments and organisations involved in multilateral negotiations, via the International Canopy Network. Collaboration and comparative studies among the crane sites will be facilitated by implementing hierarchical research protocols for collecting baseline data such as on forest structure, arthropod diversity, and general plant physiology. Certain fields for future collaborative research have already been identified.
The first canopy crane was erected in a dry tropical forest in Panama in 1990 under the auspices of the Smithsonian Tropical Research Institute (STRI), the United Nations Environment Programme (UNEP), and the Parque Natural Metropolitano, Panama. This first crane attracted considerable interest from scientists and was instrumental in generating an array of studies published in leading scientific journals. In 1992, the University of Göttingen established a crane in a temperate forest at the Solling research station in Germany. In April 1995 a crane was erected in a temperate forest of Washington State, USA, by the University of Washington. In November of the same year the Austrian Academy of Science established a crane in the Amazonian lowland forest of southern Venezuela. STRI installed a second crane, funded by the Government of Denmark, in a wet forest in Panama in May 1997. Another crane was erected in November 1997 in the Tomakomai Experimental Forest on Hokkaido, with funds from the Japanese Government. One year later, the Australian Canopy crane was established in Queensland, followed by the Swiss Canopy crane (Basel) in 1999. In April 2000, a crane was further installed in Sarawak, Malaysia, with funding from the Japanese Government. Eventually, in 2001, two new cranes were erected in temperate forests of Germany, in Leipzig and Freising, respectively.
The network now consists of six cranes erected in temperate forests and five in tropical forests. They will be shortly joined by the Canopy Operation Permanent Access System (COPAS) in French Guiana, a fixed device with a different conception. These sites are located in forests from different types, biomes and biogeographical regions, such as northern coniferous forest, mixed temperate forest, decidous broad leaf forest, tropical dry lowland forest, and tropical wet lowland forest. To date, no crane site has been established in Africa.
The International Canopy Crane Network was founded in 1997 (Stork et al., 1997), during the organisation of a Tropical Forest Canopy Symposium held in Panama in March 1997, and in response to an earlier call to promote the long-term studies of forest canopies (Parker et al., 1993). Sixty-one participants representing 23 nations attended the meeting in Panama, including delegates from UNEP, UNESCO, CIFOR, and IUCN. This meeting complemented a series of International Canopy Conferences held in Sarasota, USA, in 1994 and 1998; in Cairns, Australia, in 2002; and in Leipzig, Germany, in 2005.
Each crane site has unique peculiarities and its associates are involved in different research topics. Yet some baseline investigations are common to all sites: identifications of plant and animals present, mapping and measurement of trees, microclimatic studies, etc. The 'Global Canopy Handbook', edited by the Global Canopy Programme (Mitchell et al., 2002), presented the different crane sites of the network, particularly in terms of technical characteristics and costs of installations. A compilation of the research performed so far (2003) at the crane sites is available below.
Studying Forest Canopies from Above: The International Canopy Crane Network
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Barker, M. G. & Pinard , M. A. (2001) Forest canopy research: sampling problems, and some solutions. Plant Ecology, 153, 23-38.
Hurlbert , S. (1984) Pseudoreplication and the design of ecological field experiments. Ecological Monographs, 54, 187-211.
Mitchell, A. W., Secoy , K. & Jackson, T., Eds. (2002). The Global Canopy Handbook. Techniques of Access and Study in the Forest Roof. Oxford, The Global Canopy Programme .
Parker, G. G., Shaw, D. C. & Smith, A. P. (1993) Announcement of long-term studies of canopies. Selbyana , 14, 36.
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.