Stemflow Dynamics in the Jamari National Forest (Brazilian Amazon): I. The Role of Tree Structure

A portion of rainfall that contacts tree canopies is drained down tree stems as stemflow. Stemflow is an underexamined component of rainfall partitioning in tropical forests. To investigate how tree canopy structural attributes influence stemflow in the Brazilian Amazon, we measured stemflow, rainfall, and dendrometric parameters of 56 trees in the Jamari National Forest. We categorized trees by crown area (CA), diameter at breast height (D), height-to-width ratio (H:W), and bark texture, and analyzed stemflow variability through correlation analysis, multiple linear regression, interaction modeling, and polynomial approaches. Results showed that H:W emerged as the strongest single predictor (p < 0.01), with slender trees directing significantly more water down their trunks than broader forms. Smooth-barked species exhibited higher stemflow yields than rough- and fissured-barked species, underscoring the importance of bark properties. Although crown area and diameter both influenced stemflow, they did so in complex, sometimes subtle ways: smaller-crowned and smaller-diameter trees generally exhibited higher stemflow fractions. Interaction effects further improved model performance (R2 up to 0.60), indicating that structural traits operate collectively rather than in isolation. This nuanced interplay among canopy geometry, trunk dimensions, and bark texture suggests that effective forest hydrological models must move beyond single-trait simplifications. Overall, our findings highlight the ecohydrological importance of structural diversity in tropical forests—particularly as deforestation, selective logging, and climate change may alter species composition and trait distributions.