Simultaneous measurements of vertical accretion from artificial soilmarker horizons and soil elevation change from sedimentation-erosion table(SET) plots were used to evaluate the processes related to soil building infringe, basin, and overwash mangrove forests located in a low-energy lagoonwhich receives minor inputs of terrigenous sediments. Vertical accretionmeasures reflect the contribution of surficial sedimentation (sedimentdeposition and surface root growth). Measures of elevation change reflectnot only the contributions of vertical accretion but also those ofsubsurface processes such as compaction, decomposition and shrink-swell. Thetwo measures were used to calculate amounts of shallow subsidence (accretionminus elevation change) in each mangrove forest. The three forest typesrepresent different accretionary environments. The basin forest was locatedbehind a natural berm. Hydroperiod here was controlled primarily by rainfallrather than tidal exchange, although the basin flooded during extreme tidalevents. Soil accretion here occurred primarily by autochthonous organicmatter inputs, and elevation was controlled by accretion and shrink-swell ofthe substrate apparently related to cycles of flooding-drying and/or rootgrowth-decomposition. This hydrologically-restricted forest did notexperience an accretion or elevation deficit relative to sea-level rise. Thetidally dominated fringe and overwash island forests accreted throughmineral sediment inputs bound in place by plant roots. Filamentous turfalgae played an important role in stabilizing loose muds in the fringeforest where erosion was prevalent. Elevation in these high-energyenvironments was controlled not only by accretion but also by erosion and/orshallow subsidence. The rate of shallow subsidence was consistently3–4 mm y^–1 in the fringe and overwash island forests butwas negligible in the basin forest. Hence, the vertical development ofmangrove soils was influenced by both surface and subsurface processes andthe processes controlling soil elevation differed among forest types.