Taxonomic identity, but not evolutionary relatedness, determines the carbon stock and uptake of tropical forests trees

Abstract

Carbon stock and uptake are among the main ecosystem services provided by tropical forests. Understanding the role of different drivers in current patterns of carbon stock and uptake is critical to predicting tropical forest responses to environmental changes. That said, taxonomic identity and evolutionary relatedness among taxa may synthesize intrinsic functional characteristics and provide insight into these patterns. Here we investigated the main ecological drivers (taxonomic vs. environmental effects) and the evolutionary legacy on the expression of two important variables: carbon stock and carbon uptake. The dataset used are composed by tropical forests sites located in the southeast of Brazil along a climatic gradient including evergreen forests, semideciduous forests and deciduous forests. Relying on forest inventory data from 30 tropical forest sites (33.86 ha), we calculated individual tree carbon stocks and obtained two variables at the population level (species per site): average carbon stock (ton/ha) and average carbon uptake (ton/ha/year). These variables were used joint to phylogenetic trees and analysis to evaluate the main factors explained the variables variation and the evolutionary fingerprint on them. Variations in carbon stock and uptake by individual trees were mostly determined by taxonomic identity (28.7% and 26.7%, respectively) rather than environmental factors (7.1% and 8.9%, respectively), but evolutionary relatedness did not predict similarity among species. Our results indicate that the ability of species to store and absorb carbon depend on their intrinsic characteristics, although these are not shared among closely related taxa. Climate projections predict the loss of species unable to adapt to novel conditions, which, in light of our results, could impact tropical carbon dynamics. Although evolutionary relatedness does not predict similarity in terms of function at the scale of our study (suggesting lability of traits related to carbon storage), species losses indicate that environmental changes are beyond species’ ability to adapt to changes.