Fine-scale effects of bamboo dominance on seed rain in a rainforest

Abstract

Bamboo dominance in tropical forests drives changes in floristic composition and vegetation structure. However, the role of bamboo dominance over ecosystem functions - including those related to forest regeneration - has received less attention. This study evaluated the fine-scale effects of the dominance of native bamboo Guadua weberbaueri Pilg. (Poaceae) on seed rain in a terra-firme forest in the southwest of the Brazilian Amazon to understand how bamboos remain a dominant element where they occur. We tested the hypothesis that bamboo dominance (i) reduces seed diversity and biomass and (ii) changes floristic composition and frequencies of seed dispersal mechanisms. For one year, we sampled seeds from seed rain in adjacent bamboo-dominated (BD) and bamboo-free (BF) environments in a forest without major anthropogenic disturbances. We found lower seed species richness in the BD environment and similar seed biomass between BD and BF. In addition, the seed species composition differed between BD and BF, with higher frequency of abiotic mechanisms to seeds dispersal in BD. We conclude that the dominance of bamboos acts as a filter for species that arrive via seed rain, modifying the floristic composition and dispersal mechanisms and, consequently, the dynamics of natural regeneration processes of terra-firme forests in the Amazon. This process can promote the permanence and expansion of the distribution area of bamboos in tropical forests.