Effect of plant richness on the dynamics of coarse particulate organic matter in a Brazilian Savannah stream

- The plant diversity is important for the quality and quantity (productivity) of CPOM in riparian vegetation.
- Vegetation representing Atlantic Forest, Brazilian Savannah and Dry Forest biomes were found in this study.
- The CPOM were influenced by rainfall and seasonal characteristics, such as strong winds at the end of dry season.
- We observed a high productivity riparian zone, but low organic matter accumulation in this riparian zone.
- The low number of indicator species was identified for months in association with their phenological responses.
- A high number of indicator species was identified for HI because water washes organic matter from adjacent terrestrial areas.

The high plant richness in riparian zones of tropical forest streams and the relationship with an input of organic matter in these streams are not well understood. In this study, we assessed (i) the annual dynamics of inputs of coarse particulate organic matter (CPOM) in a tropical stream; and (ii) the relationship of species richness on riparian vegetation biomass. The fluxes and stock of CPOM inputs (vertical-VI = 512, horizontal-HI = 1912, and terrestrial-TI = 383 g/m2/year) and the benthic stock (BS = 67 g/m2/month) were separated into reproductive parts, vegetative parts and unidentified material. Leaves that entered the stream were identified and found to constitute 64 morphospecies. A positive relationship between species richness and litterfall was detected. The dynamics of CPOM were strongly influenced by rainfall and seasonal events, such as strong winds at the end of the dry season. Leaves contributed most to CPOM dynamics; leaf input was more intense at the end of the dry season (hydric stress) and the start of the rainy season (mechanical removal). Our study show an increase of litter input of CPOM by plant diversity throughout the year. Each riparian plant species contributes uniquely to the availability of energy resources, thus highlighting the importance of plant conservation for maintaining tropical streams functioning.