Quantifying Ecosystem Structural Components with Highly Portable Lidar

Abstract:

Terrestrial laser scanners (TLS), which utilize light detection and ranging (lidar) have demonstrated the ability to produce accurate reconstructions of ecosystems, including spatially complex systems such as forests. Reconstructions at the object or plot scale can be used to interpret or simulate satellite observations, particularly for lidar instruments such as those involved in the forthcoming GEDI and ICESat 2 missions.

The Compact Biomass Lidar (CBL) is a TLS optimized for portability and scanning speed, developed and operated by University of Massachusetts Boston. This 905nm wavelength scanner achieves an angular resolution of 0.25 degrees at a rate of 33 seconds per scan. The rapid scanning of the CBL and similar highly portable TLS improve acquisition of 3D surfaces such as canopy height models and digital elevation models derived from point clouds. This is due to the ability to capture additional scanning points within the window of temporal stability for the ecosystem, mitigating the rapid loss of information density associated with distance and occlusion. Utilizing terrestrial lidar in tandem with airborne lidar profiles vertically distributed structural components of ecosystems, such as the canopy of forests.

We will present 3D surfaces documenting the growth of vegetation species including the invasive Phragmites australis over the 2015 growing season at Plum Island Long Term Ecological Research sites, derived from CBL. Additionally we will show vertical structure profiles from voxelization analyses in tropical forest (La Selva, Costa Rica) and temperate forest (Harvard Forest, MA, USA). We will discuss and present results from emerging point cloud reconstruction methods, including the Quantitative Structure Model (QSM) for tree modeling, and their implications particularly for GEDI-related calibration and validation studies.