subject: The Tradition Of Canopy Access [print this page] Geoffrey GGeoffrey G. Parker, Alan P. Smith, Kevin P. Hogan, BioScience Vol. 42
Ascending into the forest canopy is an old and elevated soul venture; exploration of the treetops in support of scientific reasoning is relatively topical. Mitchell (1982) described its history, particularly the methods used in the sphere of tropical forests. The various techniques range from regular to dense, with a thick distinction in regards to safety and flexibility.
Although tree trunks are often climbed without delay (e.g., Denison et al. 1972), climbing ropes attached to limbs in the tree is the new general access method (e.g., Nadkarni 1988, Perry 1977). This technique uses the vertical rope system similar to that of mountain climbing, caving, and elite rescue work (Padgett and Smith 1987). It is easily learned, and the amount of danger and hard work can be decreased with practice. However, the availability of secure anchor points limits movement to the vicinity of tree stems or limbs. Rope systems can be designed to provide selected lateral freedom. For example, the tangled web rope system of Perry and Williams (1981) permitted a person access to a hefty volume of canopy space, but it was elaborate to install and difficult to use. Climbing is typically not safe to perform in the upper heights of the forest; some limbs are too weak to safely support a person's burden.
Only a slight portion of the outer canopy may possibly be reached with fixed towers, masts, or via scaffolding. Aerial walkways (Mull and Liat 1970), cable tramways (Perry 1986), and horizontally supported spars (Denison et al. 1972, Mitchell 1982) provide other lateral movement, although habitually by the side of the lower levels of the outer canopy. Ultimately, fixed structures are incomplete in regards to flexibility. Besides, their installation may possibly cause selected modification of forest edifice: for example, the tower will always create a gap in the forest canopy.
A hefty, semi-rigid platform constructed of inflated tubes in a hexagonal array underneath a strapping mesh net was placed on the top of over-story trees in French Guiana (Halle 1990). With this canopy raft, researchers moved and worked without delay within 600 square meters of upper canopy access, animal and plant samples were readily made. The raft was deployed with a hefty hot-air dirigible, and it was easily transported from a single location to another.
The raft must be installed in the sphere of congested canopies of uniform height. For the reason that the presence of the raft alters the exchange between the atmosphere and the canopy, it is not right in support of measurements of natural world conditions or else of plant physiological responses. Furthermore, the raft tends to depress the crowns of the support trees, settling little by little downward. In conclusion, several pilots and a hefty ground crew are crucial to support the raft operation while in position.
Cranes and rafts present unique and complementary potentials. But the crane is employed in support of long-term measurements of many parameters by the side of a set location; the raft is effective in support of selected short-term sampling by the side of numerous sites.
