Giants of the Amazon: How does environmental variation drive the diversity patterns of large trees?
Authors: de Lima Robson Borges , Görgens Eric Bastos , da Silva Diego Armando S. , de Oliveira Cinthia Pereira , Batista Anderson Pedro B. , Caraciolo Ferreira Rinaldo L. , Costa Flavia R. C. , Ferreira de Lima Renato A. , da Silva Aparício Perseu , de Abreu Jadson Coelho , da Silva José Antônio Aleixo , Guimaraes Aretha Franklin , Fearnside Philip M. , Sousa Thaiane R. , Perdiz Ricardo , Higuchi Niro , Berenguer Erika , Resende Angélica F. , Elias Fernando , de Castilho Carolina Volkmer , de Medeiros Marcelo Brilhante , de Matos Filho João Ramos , Sardinha Maurício Alves , Freitas Márcio André Furtado , da Silva José Jussian , da Cunha Aldemir Pereira , Santos Renan Mendes , Muelbert Adriane Esquivel , Guedes Marcelino Carneiro , Imbrózio Reinaldo , de Sousa Carla Samara Campelo , da Silva Aparício Wegliane Campelo , da Silva e Silva Breno Marques , Silva Celice Alexandre , Marimon Beatriz Schwantes , Junior Ben Hur Marimon , Morandi Paulo S. , Storck‐Tonon Danielle , Vieira Ima Célia Guimarães , Schietti Juliana , Coelho Fernanda , Alves de Almeida Danilo R. , Castro Wendeson , Carvalho Samuel P. C. , da Silva Robson dos Santos A. , Silveira Juliana , Camargo José Luís , Melgaço Karina , de Freitas Lucas Jose Mazzei , Vedovato Laura , Benchimol Maíra , de Oliveira de Almeida Gabriel , Prance Ghillean , da Silveira Alan Bernardes , Simon Marcelo Fragomeni , Garcia Marcos Leandro , Silveira Marcos , Vital Marcos , Andrade Maryane B. T. , Silva Natalino , de Araújo Raimunda Oliveira , Cavalheiro Larissa , Carpanedo Rainiellen , Fernandes Letícia , Manzatto Angelo Gilberto , de Andrade Ricardo T. G. , Magnusson William E. , Laurance Bill , Nelson Bruce Walker , Peres Carlos , Daly Douglas C. , Rodrigues Domingos , Zopeletto Ana Paula , de Oliveira Edmar Almeida , Dugachard Estelle , Barbosa Flávia Rodrigues , Santana Flavia , do Amaral Iêda Leão , Ferreira Leandro V. , Charão Leandro S. , Ferreira Joice , Barlow Jos , Blanc Lilian , Aragão Luiz , Sist Plinio , de Paiva Salomão Rafael , da Silva Antônio Sérgio Lima , Laurance Susan , Feldpausch Ted R. , Gardner Toby , Santiago Wagner , Balee William , Laurance William F. , Malhi Yadvinder , Phillips Oliver L. , da Silva Zanzini Antônio Carlos , Rosa Clarissa , Tadeu Oliveira Wagner , Pereira Zanzini Lucas , José Silva Ricardo , Mangabeira Albernaz Ana Luisa 
Published: June 2023

For more than three decades, major efforts in sampling and analyzing tree diversity in South America have focused almost exclusively on trees with stems of at least 10 and 2.5 cm diameter, showing highest species diversity in the wetter western and northern Amazon forests. By contrast, little attention has been paid to patterns and drivers of diversity in the largest canopy and emergent trees, which is surprising given these have dominant ecological functions. Here, we use a machine learning approach to quantify the importance of environmental factors and apply it to generate spatial predictions of the species diversity of all trees (dbh ≥ 10 cm) and for very large trees (dbh ≥ 70 cm) using data from 243 forest plots (108,450 trees and 2832 species) distributed across different forest types and biogeographic regions of the Brazilian Amazon. The diversity of large trees and of all trees was significantly associated with three environmental factors, but in contrasting ways across regions and forest types. Environmental variables associated with disturbances, for example, the lightning flash rate and wind speed, as well as the fraction of photosynthetically active radiation, tend to govern the diversity of large trees. Upland rainforests in the Guiana Shield and Roraima regions had a high diversity of large trees. By contrast, variables associated with resources tend to govern tree diversity in general. Places such as the province of Imeri and the northern portion of the province of Madeira stand out for their high diversity of species in general. Climatic and topographic stability and functional adaptation mechanisms promote ideal conditions for species diversity. Finally, we mapped general patterns of tree species diversity in the Brazilian Amazon, which differ substantially depending on size class.