METHODS FOR HORIZONTAL MOVEMENT THROUGH FOREST CANOPIES

摘要

Canopy access includes primarily vertical techniques for reaching the canopy from the ground, and canopy movement includes primarily horizontal techniques for moving through the canopy. Both directions of motion are necessary to fully explore and sample the forest canopy. Walkways, cranes, and rafts offer extensive canopy movement but involve substantial material, labor, forest impact, and freedom-to-research costs. In reviewing rope-based methods for canopy movement within forest canopies, the authors conclude that the advantages are (1) substantially lower costs, (2) lighter weight, (3) freedom for individual research teams to carry out replicated manipulative studies, and (4) greater availability of sample sites. Techniques developed by arboristsprovide within-crown movement, enabling transfers between trees less than 7 m apart. Special tools, such as the "mini-grapnel," extend traverse distances to 13 m. The authors describe a new technique based on a retrieval bolt (crossbow arrow) that allows crossing of gaps up to 40 m between trees without descending to the ground. They illustrate the application of these rope techniques in canopy research with a 200-m traverse through a 75-m-tall lowland rain forest, in which they establish a rope-basedsystem to sample forest structure, microclimate, and arthropod distribution and abundance.