Tree species dominance in neotropical savanna aboveground biomass and productivity

Abstract

The relationship between biodiversity and ecosystem functioning is one of the most currently acclaimed ecological topics. One remarkable aspect of tree communities in tropical forests and savannas is the concentration of individuals into few species or simply the species stem dominance. In addition, species dominance in biomass and productivity are indicators of how much it can affect ecosystem processes. Here, we investigated if tree species dominance in abundance is followed by a dominance in biomass and productivity, and if there is consistence in the functional traits associated to dominance in biomass, productivity, and stem abundance in neotropical savannas of Central and Southeastern Brazil. Our findings showed slightly stronger functional (biomass and productivity) dominance compared to the abundance dominance, with 3.4 and 4.2% of the species accounting for 50% of the biomass and productivity, respectively, and 4.3% of the species accounting for 50% of the individuals. There were overlaps, but mostly mismatches, between dominant species lists for biomass, productivity, and abundance, especially in the top three species. We found that the same traits which make a species capable to deal with savanna environmental odds (i.e., adaptations) and achieve high abundance, also make it possible for this species to reach larger diameters and consequently dominance in biomass. Species relative contributions to productivity responded to bark thickness, wood density and maximum potential size. The fact that just a few species concentrate most savanna trees, biomass, and productivity show a high level of adaptation of this species to the environmental conditions found in this biome. Regardless, the conservation of the entire pool of species is crucial because climate change, land use and species invasion might cause shifts in the vegetation structure and function.