Ecologia populacional da palmeira Geonoma Schottiana Mart. em mata de Galeria no Brasil central

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The objective of this study was to describe aspects of the population ecology of Geonoma schottiana, an understory clonal palm, in gallery forest of Central Brazil. Specifically, three questions were raised: (i) how do climatic variations during the year and the stages in the life cycle affect growth and reproduction? (ii) how does regeneration occur and which factors influence seedling recruitment and survival? (iii) which factors influence population dynamics? To answer these questions, we evaluated: (a) reproductive activity and leaf production of plants for at least one year; (b) seedling recruitment through field experiments of seed germination, seed longevity in the soil, and viable seed density in the soil; (c) seedling survival for three years, which was correlated to microhabitat conditions; and (d) population demographic parameters for four years. These results were used to estimate the population growth rate (λ) and the extinction probability, through matrix analysis. This way, we verified that the leaf emergence begins at the start of the wet season, and the emergence of inflorescences occurred in the drought, but ripe fruits were available all year. As an individual grows, its rate of leaf production increases, but the production of reproductive structures does not depend on the individuals size. Plant senility seems to have little effect on the production of vegetative and reproductive structures than has been detected in congeneric species with greater clonal growth. The soil seed bank was abundant and did not vary between seasons and years. Seeds remained viable for 43 months on the soil next to reproductive plants. Just 3.3% of the seeds germinated, mainly in the wet season, because of high seed predation by Coccotrypes circumdatus (Coleoptera: Scolytinae). Despite this, the seedling recruitment occurred in abundance, mainly in microhabitats with higher seed density. The size of seedlings was directly related to the survival probability, even for seedlings in the third year of life. Nevertheless, the early stages in the life cycle contributed little to λ, which was influenced mainly by the survival of reproductive plants. The λ did not differ significantly during the years of study, but the mortality of juveniles was higher one of the four years, probably caused by vertebrate herbivory. If events of high mortality like this do not occur more frequently than every other year, the population will be able to maintain long-term stability in this gallery forest.

ASSUNTO(S)

crescimento populacional análise matricial reprodução ecologia germinação geonoma schottiana mart. crescimento

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