Context-dependent plant–soil regulation of tree water transport in tropical forests

Abstract. Plant water transport is a key process linking vegetation physiology with soil and atmospheric conditions and regulating ecosystem water and carbon fluxes. Yet, how intraspecific hydraulic strategies vary across heterogeneous tropical environments remains poorly constrained. We investigated hydraulic architecture of Mangifera sylvatica, a canopy tree species of South Asian moist tropical forests, across two climatically and edaphically contrasting sites in Bangladesh. Stem and branch xylem anatomical traits were quantified to estimate theoretical hydraulic conductivity and percent loss of conductivity, alongside measurements of tree structural attributes and soil physical and chemical properties. Despite pronounced differences in elevation, soil texture, moisture availability, and stand structure between sites, hydraulic strategies—including conductivity, vessel traits, and safety–efficiency trade-offs—were conserved across forests. In contrast, the mechanisms regulating hydraulic function differed strongly between sites, with crown architecture and soil sand content dominating in the drier site, and sapwood allocation, tree height, and soil bulk density governing hydraulic behavior in the wetter site. These results indicate that similar hydraulic outcomes can emerge from distinct plant–soil–atmosphere interactions across space. Such context-dependent regulation of plant water transport has implications for predicting tropical forest transpiration, drought sensitivity, and land–atmosphere feedbacks under increasing vapor pressure deficit and climate change.