Phenology, growth, and root biomass in a tidal floodplain forest in the Amazon estuary

Abstract

ABSTRACT – (Phenology, litterfall, growth, and root biomass in a tidal floodplain forest in the Amazon estuary). The dynamics of forests subject to inundation appears to be strongly influenced by the frequency and intensity of natural disturbances such as flooding. In a late successional tidal floodplain forest near the Amazon port of Belém, Brazil, we tested this prediction by measuring seasonal patterns of phenology and litterfall in relation to two key variables: rainfall and tide levels. In addition, we estimated the root biomass and the annual growth of the forest community by measuring stem increments over time. Our results showed high correlations between phenological events (flowering and fruiting) and rainfall and tide levels, while correlations between litterfall and these variations were generally weaker. Contrary to our prediction, root biomass to 1 m depth showed no significant differences along the topographic gradient, and the root biomass at all topographic levels was low to intermediate compared with other neotropical forests. Both litterfall and total stem increment were high compared to other tropical forest, indicating the high productivity of this ecosystem. Key words- Amazon, floodplain forest, litterfall, Phenology, productivity RESUMO – (Fenologia, queda de serrapilheira, biomassa de raízes e crescimento em uma floresta de várzea no estuário Amazônico). A dinâmica de floresta sujeita à inundação parece ser fortemente influenciada pela freqüência e intensidade de distúrbios naturais como a inundação. Em uma antiga floresta sucessional de várzea próxima ao porto de Belém, Brasil, testou-se esta hipótese pela medição sazonal dos padrões de fenologia, incluindo queda de serrapilheira, em relação a duas variáveis chaves: chuva e nível da maré. Em adição, nós estimamos o crescimento anual da comunidade florestal pela medição do incremento do diâmetro de troncos ao longo do tempo e desenvolvimento radicular. Encontrou-se alta correlação entre