Estimating Eucalyptus Stand Volume in Northeast Brazil Using UAV Images and Field Measurements
Abstract
Abstract Eucalyptus plays a key role in Brazil’s forest sector, yet studies in northeastern Brazil remain scarce, particularly on stand volume estimation. This study evaluated different integration levels between unmanned aerial vehicle (UAV) data and traditional forest inventory (TFI) in a 10-year-old Eucalyptus spp. stand in Palmeira do Piauí, Brazil. Twelve plots were sampled, and UAV-RGB imagery was used to generate an orthomosaic and canopy height model. Diameter-height models were fitted using ordinary least squares and linear mixed-effects (LME). UAV-derived tree heights matched TFI measurements, with a difference of 0.9 m. Automated tree detection underestimated tree density, indicating that improvements in detection algorithms are required under the evaluated canopy conditions. Combining LME-based diameter model with visually interpreted tree counts, UAV-derived stand volume estimates (63.5-75.6 m³ ha⁻¹) were statistically equivalent to TFI (79.3 m³ ha⁻¹). These findings support use of low-cost UAV-RGB data with LME modeling for reliable stand volume estimation.