Assessing the effects of disturbance severity and spatial patterning on forest canopy structure and complexity outcomes

Abstract Disturbances modify the three‐dimensional (3D) physical structure of forest canopies, which cascades to influence numerous ecosystem functions. The capacity to model the structural outcomes of disturbance may aid in predicting ecosystem functional responses, especially for novel disturbance types and regimes. Disturbance characteristics, such as severity and spatial patterning, influence 3D canopy structure, but our understanding of structure–disturbance relationships is limited to a small number of empirical studies and experiments that investigate a narrow range of disturbance variables with limited or no replication. We conducted a novel coupled field‐modeling experiment using 3D forest canopy models derived from terrestrial laser scanning to evaluate how three different disturbance characteristics interact to affect canopy structure: disturbance severity (proportion basal area removed) and the horizontal and vertical distribution of canopy removal. Our analysis suggested that initial stand structure and the vertical and horizontal distribution of disturbance have an equivalent or greater influence on canopy structure relative to severity. Disturbances affecting smaller stems and with more uniform spatial patterns of stem removal had the most consistently positive effects on structural complexity. The simulation framework developed here is broadly applicable to other forest or vegetation types and could be used to further evaluate the structural effects of a range of disturbances, including novel disturbance types and interactions, across a variety of sites and ecosystem types in a manner that is infeasible through field manipulations alone. In addition, this approach could facilitate opportunities to improve disturbance detection, predictive ecosystem modeling, and assessment and design of forest management approaches in an era of uncertainty and rapid environmental change.