Surface area to volume scaling of alpha shapes and convex hulls fit to lidar derived mangrove island point clouds

The importance of mangroves in marine community stability has become increasingly clear. Understanding the factors structuring mangrove communities, how they respond to disturbance, and how much biomass they contain has become a research priority. The study of mangroves using approaches adapted from terrestrial systems is common yet challenging, highlighting the need for novel approaches. In recent years, remote sensing techniques (lidar and photogrammetry) have provided insight into mangrove composition, extent, and size variability. Here, we build upon this previous work by examining the structure of mangrove islands using convex hulls and alpha shapes fit to airborne lidar data obtained from the United States Geological Survey (USGS). We find that across 527 different islands occurring in eight locations around coastal Florida, the scaling properties of these shapes are tightly constrained. Of particular interest is the scaling of surface area to volume, which differs from null models, and is close to the 3/4 scaling predicted by prominent theoretical models. Our results suggest that convex hulls and alpha shapes may be useful models to capture aspects of mangrove island vegetation structure and indicate the need to better understand how plant abundance, size, and biomass contribute to the structure and variability of lidar data.