Padrões de coocorrência de espécies vegetais de cerrado em diferentes regimes de fogo

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

Fire plays an important role in determining the structure of cerrado. Annual and biennial fires favor herbaceous species and constrain woody species. As a consequence, frequent burnings are expected to change the pattern of cooccurrence of plant species. We tested (1) whether high fire frequencies increase the number of occurrences of herbaceous and shrubby species pairs, (2) whether, at fine spatial scale, high fire frequencies assemble functionally similar and closely related woody species, and (3) whether, at regional spatial scale, high fire frequencies assemble closely related woody species. In 2006, we sampled the plant species in three nearby cerrado sites in Emas National Park, central Brazil, under different fire frequencies: two firebreaks, one burned annually since 1994, another burned around every two years since 1994, and a site without fires since 1994. To test the first postulate, we compared the observed frequency of species pairs in each site to a distribution of random frequencies generated by Monte Carlo method. To test the second postulate, we examined the relationship between co-occurrence indices and both phylogenetic distances and functional differences, calculated for all pairs of species, with quantile regressions. And to test the third postulate, we compared mean phylogenetic distances of sites with high and low fire frequencies to a null model, using also data from literature. We found that the fire exclusion decreases the number of occurrences herbaceous species pairs. However, frequent fires changed this pattern, generating stochastic occurrences of species pairs. We found that, at fine spatial scale, frequent burnings assembled functionally similar species. Nonetheless, we did not observe any pattern relative to phylogenetic distances. At regional scale, high fire frequencies did not modify the phylogenetic structure of cerrado sites. Thus, fire is an important environmental filter for cerrado plants at fine spatial scale, driving phenotypic clustering of species. When fire frequencies are reduced, competition may promote phenotypic overdispersion. However, no phylogenetic pattern emerged at studied spatial scales. We postulate that the absence of phylogenetic clustering in cerrado is due to the persistence of long-lived resprouting species and to the presence of species from phylogenetically distant lineages.

ASSUNTO(S)

ecologia do cerrado similaridade funcional diversidade taxonômica savanas exclusão competitiva traços regenerativos facilitação ecologia regras de montagem

ACESSO AO ARTIGO

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