Estrutura funcional de uma comunidade de palmeiras (Arecaceae) ao longo de gradientes ambientais em uma floresta da Amazônia Central

Abstract

The functional approach allows us to understand how the environment selects the characteristics of the species that form the communities, and therefore how communities can be modified according to new conditions, such as those induced by climate change. Two forces can functionally structure a community: convergence, which promotes similarity of functional characteristics, and divergence, which promotes variability. Theoretically, it is expected that the environmental filters cause convergence, since they select characteristics suitable for the occupation of each environment. Contrarily, it is expected that biotic interactions and disturbances promote functional divergence by increasing environmental heterogeneity, selecting species with multiple functional strategies. Using palm trees (Arecaceae), an abundant and diverse way of life in the Amazon, as model group we analyze which environmental factors are responsible for generating convergence and functional divergence in local communities. This study was developed in the Adolpho Ducke Forest Reserve, where seven functional characteristics were observed that affect photosynthetic performance, balance and hydraulic safety and leaf economy (stomatal density, stomata size, venation density, dry matter content, leaf thickness, area specific leaf and estimated leaf area) of the 14 most abundant species of the reserve. We tested models including hydrological conditions and soil fertility as resource gradients and the mortality rate of trees as a proxy for the intensity of disturbance. Our results show that: 1) there is a functional differentiation between the hydrological environments, and in the plateaus conservative strategies are selected while in the bottomlands acquisitive strategies are favoured, 2) hydrological environments are the main filter of the functional composition 3) in the bottomlands there is a greater functional divergence of all the characteristics, while in the lowlands functional convergence and 4) the intensity of disturbance can generate both convergence and functional divergence. This means that the functional characteristics are selected mainly by the hydrological conditions of the soil, the disturbances can lead to convergence when its intensity is low and the divergence, when it increases the spatial and temporal heterogeneity of resources. Also, the variability of all the characteristics is greater in the lowlands, since the environmental heterogeneity existing in these places and the plateaus tend to have greater internal convergence due to the low dynamism and the spatial and temporal availability of resources. Thus, convergence is associated with responses to abiotic filters as the ecological theory of communities addresses, but contrary to what is predicted for processes that generate divergence, abiotic disturbances can also generate functional divergence.