Scaling relations and substrate conditions controlling the complexity of Rhizophora prop root system

Abstract The complex structures of the prop root system mangrove genus Rhizophora attenuate storm surges and tsunamis promote sedimentation. While quantification mangrove's drag force is essential for assessing mangroves' ability to reduce risk disaster vulnerability rising sea-level, projected area having multiple orders roots (e.g., first-, second-, third-order roots, where order indicates level branching from stem) are still unexplored. To contribute quantitative evaluation force, we investigated vertical profile whole-tree number 156 trees sampled Indonesia, Philippines, Japan. Our results showed that above first-order up 80% area, highlighting importance presence third-, even higher-order on exerted by mangroves. Based field data, an empirical model system, described a scaling factor (S), maximum minimum heights (HRmax, HRmin), was developed assuming size distribution follows constant S. S HRmax significant correlations with stem diameter at breast height suggesting relations in system. model, which employs site- species-specific regression models HRmax, reproduced – good predictor reasonable accuracy. However, highly variable depending environment, morphological plasticity grow shallow sediment layer (around 0.1 m thickness) tend produce more compared those thicker response increase below-ground biomass development physically constrained. Multivariate analysis indicated hard substrate also possibly contributes higher complexity prediction these environmental variables needs be improved. Further research needed explain mechanisms systems gradients establish generalized predicting various environments.