Abstract: The distribution of soil particle size is a fundamental parameter of soil physical properties and plays a crucial role in influencing material cycling and energy flow in mangrove ecosystems. We analyzed soil particle size composition, vertical distribution characteristics, and influencing factors across different vegetation types of Sonneratia apetala, Aegiceras corniculatum, Cyperus malaccensis, and bare flats in the Maoling River estuary of Beibu Gulf. Soil types in the study area included sandy chalk and silt. The average particle size (Φ) of the soils of Sonneratia apetala and bare flats decreased with increasing soil depth, while that of the soils of Aegiceras corniculatum and Cyperus malaccensis decreased first and then increased. Sand content decreased from upstream to downstream of the Sonneratia apetala sampling sites, and silt and clay contents increased. Sand content increased in the seaward and landward direction of secondary tidal channels, and silt and clay contents decreased. Our findings indicated that the particle size composition of estuarine mangrove soils was influenced by coastal zone type, runoff input, sand transport, and benthic fauna. Our results provide an important basis for the study of mangrove soil carbon sinks and coastal zone management.

Key words: mangrove wetland, soil particle size, spatial distribution, Maoling River estuary of Beibu Gulf