Access to the Upper Forest Canopy with a Large Tower Crane Sampling the treetops in three dimensions

Figure 1. Sketch of the canopy crane operating in a forest showing the tower (a), jib (b), counterjib and counterweight (c), the operator's cab (d), and the gondola (e) attached to the hook. The radius and height of the jib are 82 and 52 m, respectively. T he uppermost forest canopy is a frontier ofscientific research (Erwin 1983). It is the primary interface between the atmosphere and the forest and is a reservoir of biological diversity. But understanding of this important portion of the forest is far from adequate because of the difficulties in gaining access to the tops of trees. Most techniques currently available to study canopies provide limited flexibility and maneuverability, little safety, and almost no access to the important outermost canopy zone. The inability to study the functioning of the upper forest canopy in situ has stalled progress on a variety of critical research pursuits. For example, the examination of forest/atmosphere interactions (crucial to understanding global climate) and rigorous analyses of canopy biodiversity (an essential basis for conservation decisions) are both severely limited by the lack of controlled canopy access. A tower crane with a long horizontal jib brings the previously unreachable portions of forests within the range of scientific scrutiny. It allows repeatable observations and experimental manipulations on individual