Interações da vegetação herbácea e arbórea: implicações para restauração ecológica de uma floresta tropical sazonalmente seca
The Caatinga is one of the largest seasonally dry tropical forests in the world and home to a high diversity of species. Despite this, the Caatinga is susceptible to anthropogenic disturbances and invasion of exotic species, which leads to the loss of native species. Nonwoody life forms also contr...
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| Formato: | doctoralThesis |
| Idioma: | pt_BR |
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Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/50125 |
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| Resumo: | The Caatinga is one of the largest seasonally dry tropical forests in the world and home to
a high diversity of species. Despite this, the Caatinga is susceptible to anthropogenic
disturbances and invasion of exotic species, which leads to the loss of native species. Nonwoody life forms also contribute to the richness and functioning of the ecosystem, but little
is known about the interactions between herbaceous and tree communities. The objective
of the first chapter was to evaluate the influence of herbaceous vegetation on the
colonization of two native species, named Anadenanthera colubrina and Astronium
urundeuva, and one exotic species named Leucaena leucocephala in a degraded area of
Caatinga. We found that the herbaceous vegetation impaired the growth of the native tree
species and had a neutral effect on germination, establishment, and growth of the exotic
species. These results raise important questions about appropriate methods of restoration
with native species and management of exotic species. The objective of the second chapter
was to evaluate how the percent cover, height, and presence of vines of herbaceous and
shrub vegetation, including interactions with tree species richness and tree composition,
affect the growth attributes in height and diameter at ground height, and survival of native
tree species during ecological restoration. Herbaceous and shrub vegetation interacted
positively or negatively depending on tree species composition. The greater height,
diameter at ground height, and survival of the tree species were associated with the
presence of vines in the herbaceous and shrub layer. It was found that tree richness and
composition alone did not explain tree growth and survival variables. The best models
selected were those that included tree richness and composition acting simultaneously with
the herbaceous and shrub vegetation. The objective of the third chapter was to evaluate
how tree species richness (0, 1, 2, 4, 8, and 16 species) and their compositions affect the
richness, percent cover, height, and species composition of the herbaceous-shrub
vegetation. Tree richness did not affect the richness and percent total cover of the
herbaceous-shrub vegetation, however, percent cover by species varied between levels of
tree richness and there was limited effect of tree richness on species composition and
height of the herbaceous shrub vegetation. Tree species composition interfered with height,
percent cover, richness, and composition of herbaceous-shrub vegetation, indicating that
species composition during the early growth phase of tree species was important for
herbaceous vegetation. The functional attributes of the tree species, such as leaf biomass,
leaf area, number of leaves, height, diameter and number of leaves showed overall negative effects, indicating competition between herbaceous and tree species. According to these
results, it becomes important to consider herbaceous species diversity and tree
compositions, and their interactions, for effective ecological restoration in the semi-arid region. |
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