Experimentation, modelling, and simulation of hydrochory in an Amazonian river

Seed transport by hydrochory is a key mechanism of long-distance dispersal constrained by attributes of the seed and hydrodynamics of the river, influenced by seasonal precipitation and hydrological pulses. However, the extent to which a hydrodynamic model can predict seed dispersal influenced by a tributary is unknown. The study was conducted along a 10-km stretch of the Falsino River in Amapa, Brazil. Hydrodynamic parameters from the 2021 rainy season were used to calibrate a three-dimensional numerical model (SisBaHia) and simulate hydrochory of Macrolobium bifolium, a widely distributed species in the Amazon floodplains. This model was coupled with a Lagrangian dispersal model to estimate the average transport distance of the fruit plume. The simulated results were compared statistically with those of dispersal quantified in the field. The field experiment coincided with the maximum hydrological pulse, providing with a maximum potential distance of longitudinal dispersal fruit of c. 10 km in 2 hr. The orders of magnitude of the mean plume transport (observed and numerically simulated centre of mass) were compatible with each other over six longitudinal tracking sections (4.0% <= estimated x observed error <= 16.5%). Different channel stretches had distinct hydraulic characteristics that influenced spatial dispersal dynamics and are likely to be factors influencing the distribution of M. bifolium in these environments. The present research is a contribution to understanding fluvial hydrodynamics and hydrochory by M. bifolium, whose seed dispersal syndrome is an adaptive characteristic that might explain its abundance and richness in these Amazonian riparian zones. We used M. bifolium as a model species to understand the role of seasonal flood pulse and fluvial hydrodynamics related to hydrochory favouring.