Research
My research focuses on the structure and dynamics of tropical forests, integrating forest inventory and remote sensing data.
By integrating two decades of forest inventory data and drone images from a plot in ZF-2, 50 km north of Manaus, I was able to differentiate trees that have crowns in the light (canopy trees), from trees that have crowns in shade (understory trees). I found that 40% of trees with a trunk diameter greater than 10 cm are canopy trees, that they grow twice as large as trees in shade, and that they contribute 70% of aboveground carbon stocks.
Orthomosaic produced from photogrammetric analysis of photographs collected with drone showing trees that have their crowns in the light. The numbers in red represent tree tags and the black lines indicate the boundaries of field plots. The measurement of the actual size of tree crowns can be done using the orthomosaic.
Araujo et al., 2020. https://doi.org/10.1371/journal.pone.0243079
I worked on the dynamics of the forest gap formation in the Barro Colorado Island in Panama and its relationships with rainfall and wind data. I used drone images collected monthly over 5 years. I found that 66% of the total gap area was caused by treefalls, 24% by branchfalls, and 10% by the decomposition of standing dead trees. Gap formation varied significantly over time, with high rates during the rainy seasons, and was strongly related to heavy rainfall events.
Image showing a forest gap visualized in surface elevation models and orthomosaics calculated from photogrammetric analyzis of drone-collected photographs. (a, b) Elevation models of two successive dates, August 28 (a) and September 23, 2019 (b). (c) Elevation difference between the two dates, with the black region indicating a canopy height loss. (d, e) RGB orthomosaics of the same dates.
Araujo et al., 2021.https://doi.org/10.5194/bg-18-6517-2021
My research also focuses on mapping natural forest disturbances caused by wind blowdowns in the Amazon. I mapped the blowdowns that occurred in the year 2005 across the Amazon region using Landsat satellite images and field validation. I found that the blowdowns that were caused by a storm that occurred over 3 days in the Amazon accounted for 60 - 72% of all wind damage that year and were concentrated in the Central Amazon region.
Araujo et al., 2017,https://doi.org/10.1002/2017GL073564
Field and drone photos of a blowdown that occurred near the Tarumã Mirim River in 2016.
Publications
Lee, C. K. F., Song, G., Muller-Landau, H. C., Wu, S., Wright, S. J., Cushman, K. C., Araujo, R. F., Bohlman, S., Zhao, Y., Lin, Z., Sun, Z., Cheng, P. C. Y., Ng, M. K., Wu, J. (2023) Cost-effective and accurate monitoring of flowering across multiple tropical tree species over two years with a time series of high-resolution drone imagery and deep learning. ISPRS Journal of Photogrammetry and Remote Sensing, 201, 92-103, https://doi.org/10.1016/j.isprsjprs.2023.05.022.
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Araujo, R. F., Grubinger, S., Celes, C. H. S., Negrón-Juárez, R. I., Garcia, M., Dandois, J. P., Muller-Landau, H. C. (2021) Strong temporal variation in treefall and branchfall rates in a tropical forest is related to extreme rainfall: results from 5 years of monthly drone data for a 50 ha plot. Biogeosciences, 18, 6517-6531, https://doi.org/10.5194/bg-18-6517-2021.
Araujo R.F., Chambers J.Q., Celes C.H.S., Muller-Landau H.C., Santos A.P.F., Emmert F., Ribeiro G.H.P.M., Gimenez B.O., Lima A.J.N., Campos M.A.A., Higuchi N. Integrating high resolution drone imagery and forest inventory to distinguish canopy and understory trees and quantify their contributions to forest structure and dynamics. PLoS ONE 15(12): e0243079. https://doi.org/10.1371/journal. pone.0243079
Celes CHS, Araujo RF, Emmert F, Lima AJN, Campos MA. (2019) Digital approach for measuring tree diameters in the Amazon forest. FLORAM, 26(1): e20160384, doi: 10.1590/2179-8087.038416.
Araujo R.F., B.W. Nelson, C.H.S. Celes, and J. Q. Chambers (2017) Regional distribution of large blowdown patches across Amazonia in 2005 caused by a single convective squall line, Geophys. Res. Lett., 44, doi:10.1002/2017GL073564.
Condé TM, Tonini H, Silva F, Barni PE, Celes CHS, Araujo RF, Campos MA, Miranda DLC. (2016) Padrão espacial de espécies madeireiras da Amazônia pelo método de coordenadas cartesianas e espaciais. Pesquisa Florestal Brasileira, v. 36, p. 115-125.
Celes, C.H.S., Araujo, R.F., Campos, M.A.A. (2014) Influence of vegetation cover on the collection of geographic coordinates with GPS. In: Adriano José Nogueira Lima; Flavia Machado Durgante; Moacir Alberto Assis Campos; Joaquim dos Santos; Moriyoshi Ishizuka; Niro Higuchi. (Org.). Dinâmica do carbono das florestas da Amazônia: Resultados do projeto CADAF. 1ed. Manaus: Editora INPA, 2014, p. 1-92.
Araujo, R.F. de, Matricardi, E. A. T., Nappo, M. E. Zoneamento Ecológico de Pequena Escala para Espécies Florestais Tradicionais no Distrito Federal. Floresta, Curitiba, v. 12, p. 421-430, 2012.
Fank-De-Carvalho, S. M., Teles, A. M., Campos, M. B. S., Silva, P. I. T., Andrade, L. A. A., Santos, M. R. R., Araujo, R. F., Pereira, T. A., Proença, C. Levantamento Florístico do Parque Olhos d'Água, Brasília, DF, Brasil. Heringeriana, v. 2, p. 23-38, 2008.