Impact of allometric reference selection on management scale aboveground biomass estimation via Sentinel-2 and...

Accurate estimation of aboveground biomass (AGB) is essential for sustainable forest management, carbon accounting, and climate change mitigation. In remote sensing-based biomass mapping, field-derived AGB values are commonly used as reference data; however, these values are strongly influenced by the selected allometric equation. This study evaluates how alternative allometric reference datasets affect Sentinel-2-based AGB estimation at the forest management scale in Pinus brutia stands. Reference AGB values were derived from 112 field plots using three allometric approaches: the diameter-based equations of Sun et al. (1980) and Yılmaz (2015), and the volume-based conversion framework of Durkaya et al. (Bartın Orman Fakültesi Dergisi 22(3):1053-1060, 2020). CART was used as the primary modeling framework to isolate the effect of allometric reference selection, while Random Forest was retained as a secondary robustness check. The results showed that the choice of allometric reference substantially altered both the magnitude and spatial distribution of predicted AGB. At the management-unit scale, the Sun et al. (1980) reference produced the closest agreement with forest management plan data, whereas the Yılmaz (2015) and Durkaya et al. (2020) references resulted in considerably higher total AGB estimates. Across the 13,687 ha evaluation area, total AGB estimates differed by more than 700,000 Mg depending on the selected allometric reference. These findings demonstrate that allometric reference selection is a dominant source of uncertainty in operational AGB mapping and should be explicitly evaluated before scaling plot-level biomass estimates to forest management units.