Detalhes bibliográficos
| Ano de defesa: |
2009 |
| Autor(a) principal: |
SILVA, Kleber Andrade da
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| Orientador(a): |
ARAÚJO, Elcida de Lima |
| Banca de defesa: |
RODRIGUES, Ricardo Ribeiro,
SAMPAIO, Everardo Valadares de Sá Barretto,
CHAVES, Lúcia de Fátima de Carvalho,
MARAGON, Luis Carlos,
SALES, Margareth Ferreira de |
| Tipo de documento: |
Tese
|
| Tipo de acesso: |
Acesso aberto |
| Idioma: |
por |
| Instituição de defesa: |
Universidade Federal Rural de Pernambuco
|
| Programa de Pós-Graduação: |
Programa de Pós-Graduação em Botânica
|
| Departamento: |
Departamento de Biologia
|
| País: |
Brasil
|
| Palavras-chave em Português: |
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| Palavras-chave em Inglês: |
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| Área do conhecimento CNPq: |
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| Link de acesso: |
http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/4844
|
Resumo: |
The influence of seasonal and annual variations in precipitation on the dynamics of seed banks of four herbaceous species (Delilia biflora, Commelina obliqua, Phaseolus peduncularis e Poinsettia heterophylla) were evaluated in an area of caatinga, in the experimental station of Empresa Pernambucana de Pesquisa Agropecuária – IPA (8o14'18"S e 35o55'20"W, 535 m de altitude),in Caruaru, Pernambuco, Brazil. 105 samples of litter and soil (0-5 cm of depth) were collected from 20 x 20 cm plots, at three rainy seasons and three dry seasons. Richness and density were determined by the seedling emergence method. The dynamics of herbaceous populations was evaluated in 35 1 m x 1m plots, in plan, rocky and riparian microhabitats. At the plot interior, all individuals from the four species were counted and marked and, monthly, the plots were monitored for the counting of births and deaths. 79 species emerged from the seed bank and most of them were herbs. In the three years, richness and density were higher for the soil samples. There was a significant seasonal variation in richness only in the first year and there was no difference between years. Similarity among stations and years was lower than 50%. Only seven species were present in both rainy and dry seasons for the three years. The bank presented an estimated average density of 591 seeds. m-2. There was a significant seasonal variation in density in the second and third years. Density differed among years and most species occurred with few individuals. The four species formed more numerous populations in the first year and they drastically reduced in size in the second year, which was drier. Commelina obliqua was less sensible to variations in the pluviometric totals among years. In each year, population size was higher at the rainy season and it strongly decreased at the dry season. Although seasonal and annual reductions in density, the of the four species were present during the three years, but C. obliqua disappeared in the riparian microhabitat. Delilia biflora, Commelina obliqua and Phaseolus peduncularis occured in the three microhaitats, but with low density in the riparian micohabitat. There was no record for Poinsettia heterophylla in the riparian microhabitat. Population size and birth and death peaks vary in time for each microhabitat. Annual and seasonal variations in the pluviometric totals influences seed bank richness and density and the dynamics of herbaceous plants. Caatinga seed bank density may be higher at the rainy season, higher at the dry season or it may not present seasonal variation. Microhabitat can mitigate the impact of dry season water stress on mortality of herbaceous populations, since the higher mortality peaks of the four species were in the plan. The predictive role of rains of present times or ecologically recent does not explain seed density variations in the soil bank, but the predictive power of pluviometric totals from past years may have increased the explanation power on the dynamics of caatinga soil seed bank and it has a great implication for conservation for this kind of vegetation. |
