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| Author(s): |
Marina Huete Fleury
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2009-06-10 |
| Examining board members: |
Mauro Galetti Rodrigues;
Hilton Thadeu Zarate do Couto;
Katia Maria Paschoaletto Michi de Barros Ferraz;
Marco Aurélio Pizo Ferreira;
Gislene Maria da Silva Ganade
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| Advisor: | Mauro Galetti Rodrigues; Ricardo Ribeiro Rodrigues |
| Abstract | |
Island ecosystems, either continental or oceanic, are considered the most sensible to anthropogenic influences. Most Brazilian coastal islands have their original fauna and flora composition altered. The Anchieta Island (southeast Brazil) is a Protected Area that suffered deforestation and introduction of alien species. It is known that the fauna plays a key role in composing and structuring the vegetal community, favoring some species and harming others. Thus, the loss or change of animal-plant interactions affects the framework and composition of species. We simultaneously analyzed the antagonistic animal-plant interactions as possible limiting factors in the natural regeneration on tree successional stages of the Anchieta Island: the old fields (OF), the early secondary forest (ESF) and old growth forest (OGF). Therefore, in each habitat we are evaluating post-dispersal seed predation processes: post-dispersal seed predation, soil seed bank, and the herbivory. We found spatial (OGF>ESF>OF) and temporal effects on seed predation, with highest rates on dry season. Quantitatively, soil seed bank did not represent a limiting factor; but qualitatively, it was composed by few woody species. Our data pointed to the absence of a viable soil seed bank in the OF, probably due to an intense runoff. The forested habitats presented similar soil bank. Moreover, the total mortality of saplings was 72.27%, being higher on the unfenced treatment for all species and in all habitats, showing a very strong negative effect of vertebrate herbivores on the vegetal community. Therefore, we are detecting distinct bottlenecks acting simultaneously in the natural regeneration process in all of the successional stages of the Anchieta Island. Our results showed that management actions are required, aiming to both minimize the abiotic effects on the old fields and in the early secondary forest and to favor the mutual interactions and inhibit the activity of antagonic animals in the old growth and early secondary forests, accelerating, this way, the natural regeneration process of the Anchieta Island. Considering simultaneously the obstacles in the regeneration process will help to define restoration and recuperation procedures of degraded areas more effective and affordable. (AU) | |