Padrões de riqueza e utilização de plantas em florestas tropicais

Abstract

This thesis presents an approach on the relationship between the biological and utilitarian richness of plant species in tropical forests, applying ecological models and lines of thought that seek to understand the product resulting from this interaction. In terms of the environment, we carried out two studies with tropical forests: in the first approach, we used two areas of tropical forest, one in a rainforest environment with vegetation characteristic of a semideciduous forest and the other a caatinga environment with a seasonally dry forest ; already in the second study, we used a dry forest area with considerable relief elevations, where pluviometric regimes change considerably along a precipitation gradient. In order to study the patterns of species richness and utilization in tropical forests, we have used the hypothesis of versatility and the Utilitarian Redundancy Model as a support to understand the resource selection strategies in these environments. We performed phytosociological surveys in all selected areas, as well as collecting botanical material for herbarium identification. This collection process was necessary to compose the checklist interview, a visual stimuli method widely used in ethnobiological studies. All species identified in herbarium were presented together with photos of the living plant to all residents of the communities. In the first study, to test the first hypothesis, we used the chi-square test to verify the proportion of species and useful species richness, to analyze the second hypothesis on the versatility of the environments, a T test was used, and in the third hypothesis the Kruskal-Wallis test to verify the utilitarian redundancy of the environments. For the second study, we used the same hypotheses from the previous study, using the chi-square test for the first one, Kruskal-Wallis for the second and the third hypothesis, using an ANOVA from an intracategory perspective and a test of Kruskal- Wallis in the perspective of intercategory. The results of the first study demonstrated that the two areas are relatively similar in the proportion of species and species richness used, leading us to suggest that other studies that aim to verify patterns of richness and useful species, carry out their approaches in more physiognomically distinct environments , most probably because the fragment of rainforest, which should have a greater wealth than the dry forest, suffered considerable disturbance and loss of species over time due to the monoculture of sugarcane, which may have had a direct influence on its growth. wealth. The remarkable similarity etween the proportion of total richness and richness of useful species of the areas may also have influenced the results of the Utilitarian Redundancy Model, where we can not observe significant differences with respect to the quantity of species that perform the same use within a system , which makes us believe how the availability of species in the environment directly influences the choices of plant resources by local populations. As for the versatility, we have been able to corroborate our hypothesis by demonstrating that the species of the environment with low richness suffer a relatively higher use pressure than the environment represented by a greater species richness. In the second approach at the rainfall gradient level, we find a significant relation with the environmental richness and richness of useful species, demonstrating that in environments with a greater species richness, they present a greater amount of useful species. ANOVA proved to be significant for testing the versatility of species, but we found that the most versatile environment was the one with the highest rainfall indexes, which can be explained by the greater availability of plant resources throughout the year, since in the absence of water, many structures such as folas and fruits disappear. Decreasing the intensity of the deciduous phenomenon has enabled people to experiment and test a greater amount of resources, which may have given this environment a greater versatility of uses for plants. For the third hypothesis, we did not find significant relation with any of the categories of use verified, with respect to the Utility Redundancy. Bringing our findings to a conservationist approach, we recommend a greater attention and investment of management and conservation strategies for environments that have a low species richness, considering that the extinction of species can happen more sharply in these places.