<jats:p>Abstract. In mangrove forests, soil salinity is one of the most significant environmental factors determining forest distribution and productivity as it
limits plant water uptake and carbon gain. However, salinity control on mangrove productivity through plant hydraulics has not been investigated by
existing mangrove models. Here we present a new individual-based model linked with plant hydraulics to incorporate physiological characterization of
mangrove growth under salt stress. Plant hydraulics was associated with mangroves' nutrient uptake and biomass allocation apart from water flux and
carbon gain. The developed model was performed for two coexisting species – Rhizophora stylosa and Bruguiera gymnorrhiza – in a
subtropical mangrove forest in Japan. The model predicted that the productivity of both species was affected by soil salinity through downregulation
of stomatal conductance. Under low-soil-salinity conditions (< 28 ‰), B. gymnorrhiza trees grew faster and suppressed the
growth of R. stylosa trees by shading that resulted in a B. gymnorrhiza-dominated forest. As soil salinity increased, the
productivity of B. gymnorrhiza was significantly reduced compared to R. stylosa, which led to an increase in biomass of
R. stylosa despite the enhanced salt stress (> 30 ‰). These predicted patterns in forest structures across the soil salinity
gradient remarkably agreed with field data, highlighting the control of salinity on productivity and tree competition as factors that shape the
mangrove forest structures. The model reproducibility of forest structures was also supported by the predicted self-thinning processes, which
likewise agreed with field data. Aside from soil salinity, seasonal dynamics in atmospheric variables (solar radiation and temperature) were
highlighted as factors that influence mangrove productivity in a subtropical region. This physiological principle-based improved model has the
potential to be extended to other mangrove forests in various environmental settings, thus contributing to a better understanding of mangrove
dynamics under future global climate change.
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