The Drivers of Coexistence and Dominance of Plant Functional Types Across the Neotropics: An Integrated Approach Using Model and Regional-Scale Trait Data
Marcos Longo1* (firstname.lastname@example.org), Lara Kueppers1, Rosie Fisher2, Gregory Lemieux1, Ryan Knox1, Charles Koven1, Chonggang Xu3, Jeffrey Chambers1, Antonio Antonino4, Damien Bonal5, Paulo Brando6, Benoit Burban7, Géraldine Derroire8, Leandro Maracahipes9, José Silva10, Eduardo Souza10, Maria del Rosario Uribe-Diosa6
1Lawrence Berkeley National Laboratory, Berkeley CA; 2CICERO Center for International Climate Research, Oslo, Norway; 3Los Alamos National Laboratory, Los Alamos NM; 4Universidade Federal de Pernambuco, Recife, Brazil; 5Unités Mixtes de Recherche Silva, Nancy, France; 6Yale School of the Environment, Yale University, Yale, CT; 7National Research Institute for Agriculture, Food, and Environment, Joint Research Unit Ecology of Guianan Forests, Campus Agronomique, Kourou, French Guiana; 8Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Joint Research Unit Ecology of Guianan Forests, Campus Agronomique, Kourou, French Guiana; 9Instituto de Pesquisa Ambiental da Amazônia, Brasília DF, Brazil; 10Universidade Federal Rural de Pernambuco, Serra Talhada PE, Brazil
Climate change is expected to increase the frequency of hot drought events across the wet and dry tropics. To understand how recurrent droughts impact tropical ecosystems, terrestrial biosphere models must represent the observed trait trade-offs between drought resistance and productivity. To investigate the mechanisms that determine the distribution of deciduousness (a drought avoidance strategy) and evergreenness across the neotropics, researchers implemented a drought-deciduous representation into FATES. To define regional-scale plant functional types (PFTs), researchers used over 20 traits from >4,000 tree species in the neotropics. An unsupervised cluster algorithm was used to define PFTs based on these traits, resulting in PFTs that differed by either deciduousness or successional stage. The team selected multiple sites across a mean annual precipitation gradient in tropical South America (500 to 3,000 mm/yr) to test whether the model could represent different levels of coexistence. The model successfully predicted the biomass distribution across sites, the higher abundance of tall trees in wet sites, and the higher abundance of drought deciduous trees at dry forest sites. FATES correctly represented the seasonality of evapotranspiration and gross primary productivity, except for the early dry season in dry forest sites. In contrast, the model overestimated the abundance of pioneer evergreen trees and could not represent successional coexistence at moist tropical forests, suggesting that current parameterized trade-offs in moist forests are insufficient for representing coexistence. The study shows that incorporating existing trait observations can improve understanding of deciduous–evergreen coexistence across the tropics. However, more data and model processes are likely needed to better understand coexistence of multiple PFTs across successional gradients in moist tropical forests.