Features of the forest canopy include metrics such as canopy area index (CAI, similar to leaf area index), the vertical profile of canopy foliage, the shape and texture of the uppermost the canopy and the aggregation of foliage horizontally and vertically (Figure 1). These features both emerge from and directly affect numerous dynamics of a forest’s species composition, developmental history and environmental context (Kelty 1989, Bassow and Bazzaz 1997, Catovsky et al. 2002, Lai et al. 2005, Song et al. 2009). Ground-based LiDAR can effectively, objectively and economically measure these canopy features with simple transect censuses (Parker et al. 2004). All data collected will be cleaned and placed in a common database format.
Comparing measurements from younger and older forests offers an example of how these measurements can lead to insights about canopy development (Figure 1). Young forests tend to have many leaves in the upper canopy, have a smooth outer canopy surface and remain fairly uniform across horizontal transects (Figure 1a, b). Older forests show bi-modal or uniform vertical leaf profiles, more heterogeneity in leaf aggregation and a bumpy outer canopy surface (Figure 1c,d). Other forest metrics differ depending on species composition, environment or disturbance regime. The presence of conifers can change the outer canopy profile, drier forest can become more open and contain more canopy gaps, and endogenous disturbances, such as fire cycles, can greatly influence the pattern of canopy structure over time, independent of stand age or composition.