Dry Biomass Estimation of Hedge Banks: Allometric Equation vs. Structure from Motion via Unmanned Aerial Vehicle

Abstract

The wood yield of hedge banks is very heterogeneous and hard to estimate in advance. The aim of the present study was to estimate the dry biomass of hedge banks shortly before harvesting using two different non-destructive approaches: (i) allometric equation based on DBH, (ii) volume calculations based on Structure from Motion; and to compare these estimations to the results of the (invasive) reference method: weighing after harvesting. Study objects were three different 100 m hedge banks in Schleswig-Holstein, Germany that were divided into 10 m segments (n = 30). These segments were harvested and weighed separately to calculate dry biomass. The allometric equation yielded a relative root mean square error (rRMSE) of 32.4%. The Structure from Motion (SfM) volume models yielded an rRMSE of 30.0%. These results indicate that SfM approaches are comparably precise to allometric equations for dry mass estimations of hedge banks. SfM approaches are less time consuming but have higher technical requirements.

Keywords

• drone
• dry mass
• point cloud
• trees outside forests