A cost-effective method to passively sample communities at the forest canopy–aerosphere interface

Abstract

The ecology of the canopy–aerosphere interface within forested ecosystems remains underexplored largely due to the challenges of physically accessing this zone. Sky bridges, towers and other permanent structures are most commonly used to sample the forest canopy–aerosphere interface, but these methods are costly, challenging to replicate, and often alter and degrade the local environment during construction. Thus, there is a clear need for cost-effective and replicable methods for accessing and passively sampling above the forest canopy. We designed and deployed an inexpensive and lightweight telescopic hanger composed of common materials to sample aerial invertebrates above the forest canopy. Deployment involved climbing into tree crowns and securing our hanger design to vertical branches. We sampled the invertebrate community above forest fragments on the campus of the University of Massachusetts Amherst, USA by suspending blue vane traps from hangers, which were extended to approximately 1 m above the highest terminal bud of the tree, continuously from April through August 2021. We also recorded the microclimate conditions above the canopy at each hanger, including temperature and light intensity. All hangers and traps remained in place and active throughout the study period. In May, we made minor repairs at two locations where the hangers were attached to the trees and, following an intense weather event in July, observed damage to one hanger that did not affect sampling effort. We include cost breakdowns of design components as well as detailed building instructions. This tool offers a durable and inexpensive solution for researchers to access and sample the forest canopy–aerosphere interface that has minimal impacts on the environment and is more easily replicated compared to previous methods. Assembly pitfalls and design alterations are discussed based on our experience with the installation and implementation of the tested design, as well as included prototypes.