The short-term and long-term effects of honeysuckle removal on canopy structure and implications for urban forest management

Abstract

Riparian forests across the continental United States are heavily invaded by Amur honeysuckle (Lonicera maackii (Rupr.)), an invasive shrub which suppresses native plants, homogenizes community structure and composition, and alters ecosystem processes. However, no studies have quantified the impacts of honeysuckle removal on forest canopy structure across the first decade of restoration. In this study we used a portable canopy LiDAR (PCL) to characterize the immediate (<1 year), short-term (1–2 years) and long-term (>10 years) impacts of honeysuckle removal on the horizontal and vertical complexity of canopy structure in 5 heavily invaded riparian forests in Ohio. Within two years of removal, forest canopies had a 40% reduction in canopy leaf volume, a greater average height of maximum canopy density, and increased aggregation of the remaining leaf area around trees than pre-removal conditions. Honeysuckle removal also prompted long-term (>10 years) increases in canopy structural complexity, but only in areas with initially high honeysuckle abundance and low native tree density. Honeysuckle cover had a much stronger influence on canopy structure than either its basal area or stem density. Our results suggest that removing honeysuckle from heavily-invaded stands can promote complex canopy structure over the long-term that is beyond the short-term accrual immediately following disturbance, but might depend on initial stand conditions.