Beyond trees: Mapping total aboveground biomass density in the Brazilian savanna using high-density UAV-lidar data

• Published in: Forest ecology and management Vol. 491; p. 119155
• Main Authors: da Costa, Máira Beatriz Teixeira, Silva, Carlos Alberto, Broadbent, Eben North, Leite, Rodrigo Vieira, Mohan, Midhun, Liesenberg, Veraldo, Stoddart, Jaz, do Amaral, Cibele Hummel, de Almeida, Danilo Roberti Alves, da Silva, Anne Laura, Ré Y. Goya, Lucas Ruggeri, Cordeiro, Victor Almeida, Rex, Franciel, Hirsch, Andre, Marcatti, Gustavo Eduardo, Cardil, Adrian, de Mendonça, Bruno Araujo Furtado, Hamamura, Caio, Corte, Ana Paula Dalla, Matricardi, Eraldo Aparecido Trondoli, Hudak, Andrew T., Zambrano, Angelica Maria Almeyda, Valbuena, Ruben, de Faria, Bruno Lopes, Silva Junior, Celso H.L., Aragao, Luiz, Ferreira, Manuel Eduardo, Liang, Jingjing, e Carvalho, Samuel de Pádua Chaves, Klauberg, Carine
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-07-2021
• Subjects: Biomass; Cerrado; GatorEye; Mapping; Remote sensing; Tropical savanna; Vegetation; Vegetation; GatorEye; Tropical savanna; Mapping; Biomass; Cerrado; Remote sensing
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2021.119155

•UAV-lidar collects data sensitive to vegetation structure in tropical savanna.•First study to map total aboveground biomass density (AGBt) from UAV-lidar in Cerrado.•Besides tree biomass, AGBt includes surface and shrubs biomass.•AGBt uncertainty was lower in forest and savanna than in grassland formations.•The study is a step forward in using UAV-lidar for AGBt mapping in tropical savanna ecosystems.
Tropical savanna ecosystems play a major role in the seasonality of the global carbon cycle. However, their ability to store and sequester carbon is uncertain due to combined and intermingling effects of anthropogenic activities and climate change, which impact wildfire regimes and vegetation dynamics. Accurate measurements of tropical savanna vegetation aboveground biomass (AGB) over broad spatial scales are crucial to achieve effective carbon emission mitigation strategies. UAV-lidar is a new remote sensing technology that can enable rapid 3-D mapping of structure and related AGB in tropical savanna ecosystems. This study aimed to assess the capability of high-density UAV-lidar to estimate and map total (tree, shrubs, and surface layers) aboveground biomass density (AGBt) in the Brazilian Savanna (Cerrado). Five ordinary least square regression models estimating AGBt were adjusted using 50 field sample plots (30 m × 30 m). The best model was selected under Akaike Information Criterion, adjusted coefficient of determination (adj.R2), absolute and relative root mean square error (RMSE), and used to map AGBt from UAV-lidar data collected over 1,854 ha spanning the three major vegetation formations (forest, savanna, and grassland) in Cerrado. The model using vegetation height and cover was the most effective, with an overall model adj-R2 of 0.79 and a leave-one-out cross-validated RMSE of 19.11 Mg/ha (33.40%). The uncertainty and errors of our estimations were assessed for each vegetation formation separately, resulting in RMSEs of 27.08 Mg/ha (25.99%) for forests, 17.76 Mg/ha (43.96%) for savannas, and 7.72 Mg/ha (44.92%) for grasslands. These results prove the feasibility and potential of the UAV-lidar technology in Cerrado but also emphasize the need for further developing the estimation of biomass in grasslands, of high importance in the characterization of the global carbon balance and for supporting integrated fire management activities in tropical savanna ecosystems. Our results serve as a benchmark for future studies aiming to generate accurate biomass maps and provide baseline data for efficient management of fire and predicted climate change impacts on tropical savanna ecosystems.