Variabilidade intra e interespecífica da densidade da madeira em função da variação ambiental ocupada por espécies de árvores dominantes na Amazônia Central

Abstract

The Amazon is dominated by relatively few tree species that can occupy relatively homogeneous habitats or a high environmental variation. It is still not well known how the characteristics of individuals of dominant species vary in relation to the environmental variation occupied by these species. Knowing this relationship will help us understand the success of the dominant species. Wood density (WD) is considered a key characteristic of plant properties; therefore, we used branch wood density values (WDB) from 290 individuals and stem wood density values (WDS) from 219 individuals of 17 dominant species, along 500 km of extension in the central Amazon to answer the question: How does the variation in WDB and WDS within and between dominant species respond to the environmental variability occupied by the species and the environmental gradients of central Amazonia? For this, we tested three hypotheses: (H1) The intraspecific variation of WD in dominant species changes as a function of the environmental variability occupied by the species, (H2) the mean value of WD changes according to the degree of environmental variability occupied by the species, and finally, (H3) the WD among individuals varies depending on local characteristics (e.g., water, soil texture, and nutrients and forest dynamics). We test these hypotheses using multiple phylogenetic linear regression models (H1 and H2) and mixed linear models (H3). We used the coefficient of variation (CV) of WD as a measure of intraspecific variation and estimated the environmental variation occupied by the species based on an index of environmental variability occupied by the species. Our results showed that as the environmental variability occupied by the species increases, the greater the intraspecific variation in the values of WDB, but not of WDS. Furthermore, as the environmental variability increases, the lower the average WDB and WDS of species. We did not find a particular model that explained the variation in WD among individuals according to the environment, the variation in WD was shown to be species-dependent. Such results suggest that the success of the dominant species may be in the ability of individuals to vary the WDB, and in the acquisition strategies adopted in the construction of the wood of the branch and stem of the species to colonize heterogeneous environments, or around more conservative strategies when they occur on more homogeneous environments. In a scenario of environmental changes, habitat modifications can favor the establishment of species that occupy more variable environments, and consequently, with lower WD, decreasing carbon stocks and altering the functioning of the forest.