Characterisation of Acid Sulfate Soils Along a Temperate Coastal Vegetation Gradient

Abstract

Acid sulfate soils (ASS) pose a significant environmental risk, yet their systematic characterisation is often overlooked in conservation areas, leaving an important gap in understanding their distribution and management. This study characterises ASS in three temperate coastal wetland vegetation communities—mangroves, saltmarshes and paperbark forests—located in southern Australia. Soil samples were collected from two sites, Rhyll and Corner Inlet, representing typical low-energy embayment environments. The study aimed to assess the acidification risk by analysing key soil properties, including pH, electrical conductivity, organic carbon, nitrogen content and the presence of sulfidic materials. Results indicate that mangrove soils exhibited the highest concentrations of chromium reducible sulfur (CRS), while saltmarsh and paperbark forest soils displayed varying levels of acid neutralising capacity (ANC), largely influenced by seawater intrusion and organic matter decomposition. Net acidity was highest in mangrove and deeper saltmarsh layers, indicating a significant potential acidification risk if disturbed. This study highlights the spatial variability in ASS characteristics and acidification risks across different vegetation zones in temperate coastal environments. The findings underscore the need to consider management strategies in conservation areas to mitigate acidification hazards, particularly in light of ongoing sea-level rise and climate change, which may alter the distribution of coastal vegetation and the formation of ASS. These insights provide critical baseline data for the conservation and management of temperate coastal ecosystems in southern Australia.