CrownPrint: A crown-profile approach to quantifying canopy structure

Stand development processes are characterized by variation in vertical foliage distribution. Early differences in growth, or mortality/disturbance induced gaps, can result in a layering, or stratification, pattern of leaf area. Despite widespread acceptance that these processes occur, numerous methods exist to define, conceptualize, and quantify the forest canopy, suggesting standardized approaches are needed, especially given increased emphasis on managing forest structural attributes. The objective of this work was to test a simple framework for quantifying vertical foliage distribution through integrating allometric models and common stand inventory measurements. Canopy space is defined as the vertical foliage between the tallest tree and lowest live crown at the plot level. Individual tree crowns are tallied across profile space and summed by species, and corresponding frequency distributions are estimated with a beta distribution. Application of the method to managed conifer forests of Maine and Washington, USA, as case studies demonstrate that the approach can be used to quantify differences in vertical canopy distribution and occupancy by species. These trends further vary with common silvicultural practices, soil nutrients, and topography, yet rely on locally fit allometric equations. More work is needed to test sensitivity of the approach to variations in base equations and forest types.