Vegetation communities and edaphic relationships along a typical coastal saltmarsh to woodland gradient in eastern Tasmania

Abstract

Saltmarsh soils impose harsh selection pressures on vegetation resulting in characteristic plant communities. For our study of the effect of edaphic factors on vegetation we chose Long Point in Moulting Lagoon, Tasmania’s largest saltmarsh, which is dominated by a diverse assemblage of halophytic succulents and graminoids. Three transects were established to sample variations in vegetation along the gradient from saltmarsh to woodland. Soil samples were analysed for summer and winter moisture, pH, and electrical conductivity (EC); a mixed summer and winter sample from each point was analysed for soil organic matter (SOM) and carbon. Additionally, a particle size analysis was carried out on all summer samples. Aspects of soil characteristics were aligned to classified vegetation groups and elevation. Moisture, pH, EC, SOM and carbon were all negatively correlated with elevation; the saltmarsh zone displaying higher levels of all variables than those in the adjacent woodland zone. Clay content decreased and sand content increased from the marine margin of the saltmarsh zone to the woodland zone. Within the saltmarsh zone, soil moisture, EC and carbon had highest values in the low marsh area, with values decreasing towards the upper marsh area. This study deepens our understanding of the roles various edaphic factors play in the floristic composition of coastal saltmarshes.