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

Abstract

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 Amapá, 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 × 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.

Soil flooding filters evolutionary lineages of tree communities in Amazonian riparian forests

“…Variations in precipitation patterns influence flooding, affecting plant ability to disperse seeds in water. Species adapted to different flooding conditions may gain competitive advantages (Da Silva et al., 2023 ), thereby shaping the phylogenetic composition of communities over time. River continuum concept (Vannote et al., 1980 ) emphasizes considering the ecological integrity of the entire rivers and their watersheds for effective management.…”

“…With its most distant headwaters in the Guiana Shield, this black‐water river carries a low sediment and nutrient load (Junk et al., 2015 ). Historically, the Araguari River discharged into the Atlantic Ocean; however, due to erosion of the Urucurituba channel, most of its water now diverts to the Amazon River (Da Silva et al., 2023 ; dos Santos et al., 2018 ).…”

Numerical Simulation of Oil Spills in the Lower Amazonas River

“…Therefore, this was considered the worst possible spreading scenario among all analyzed intervals in both seasonal hydrological periods. In the ebb phases during the rainy season, there is a greater fluvial influence and less influence from marine waters entering the estuary [33,39,40]. Therefore, the recorded flow in this flow direction is higher.…”

“…However, because it is still at the beginning of the ebb tide, the flood tide (previous interval) and ebb tide (just started interval) flows still oppose each other. This balance of forces [33] partially retains the contaminant in the stretch between the mainland and Ilha de Santana. Therefore, the plume tends to remain partially trapped in the Santana Channel and neighboring islands, affecting both banks of the channel and the mouth of the Vila Nova River.…”

“…Therefore, the recorded flow in this flow direction is higher. The opposite applies in the dry season because the low river level causes the flood tide level to have a greater influence on the amount of water entering the channel [33,40]. This contributes to the inversion of the flow in the Amazonas River [12] and its tributaries [41].…”