Functional Biogeography and Ecological Strategies of Trees Across the Amazon–Cerrado Transition

The large transition zone between the Amazon and Cerrado biogeographic domains. Methods: We field-collected and analyzed an extensive new database of 182 tree species from six vegetation types, resulting in 55,895 records of functional traits. We selected 15 traits that affect different aspects of ecosystem processes and ecological strategies of trees. Then we compared the distribution of functional traits among vegetation types and assessed their association with edaphic and macroclimatic variables. Results: We recorded a functional continuum between the extremes of Cerrado (Typical Cerrado) and the Amazon (Open Ombrophilous Forest), with most traits forming a gradient along the vegetation types. Our data also indicate that tree-dominated Cerrado formations (Cerradão) are functionally intermediate between savannas and forests, reinforcing the importance of accounting for the full floristic and structural variation of neighboring biogeographic domains. Our work revealed that CEC, soil pH, mean temperature, maximum temperature, total precipitation, and climatic water deficit are consistently related to key functional traits across the Amazon-Cerrado transition. Conclusions: Functional traits can be used to efficiently characterize and distinguish multiple communities where South America's two largest biogeographic domains meet. We were able to delimit morpho-physiological requirements that ensure tree species' maintenance in different vegetation types and to characterize the transition zone in terms of ecosystem functioning.