Impact of Salinisation on the Neighbour-based Spatial Diversity of Tree Species in the Sundarbans Mangrove of Bangladesh

Climatic stressors, notably increased salinity, influence the vegetation dynamics of the Sundarbans, the largest single block of tidal halophytic mangrove forest in the world. However, their role in the spatial stand structure of trees remains poorly understood. The overall objective of the study was to assess the role of salinity on the spatial diversity of tree species by using some neighbourhood-based variables. Thirty permanent sample plots were classified as low, medium, and high saline areas based on water salinity level for collecting primary data. With the increase of salinisation, the trees started clumping from the random aggregation and dispersion by suffering the loss of species richness and natural regeneration. The highest species was found in the low saline area adjacent to human settlements despite the presence of merciless anthropogenic disturbances like illegal logging. This area also consisted of a handful of size (dbh and height) classes, which in turn described a decent mixture of young, adult, and old-growth trees. Contrarily, the high saline area was inhabited by only adult dwarf trees. Neighbourhood-based variables and methods were proven to be simple, easy, less technical, time-saving, and non-expensive, which can articulate the spatial dimensions of a complex ecosystem. Immediate mitigation actions are warranted to maintain the status quo and to protect from further degradation. The species-centric spatial dimensions should be examined further to measure the impact of stressors on the spatial pattern of each species.