The interstitial environment of coastal dune slacks

Abstract

Slack sands were fine, well to very well sorted and slightly coarse skewed. There was a significant increase in water table depth from west to east across a series of 37 slacks, with the mean water table depth ranging from 48 cm in the west to 82 cm in the east. The mean salinity of the groundwater was 2·3%o. The mean organic content of the sand was 0·69% and decreased linearly with an increase in sand depth. Mean organic content across the main study slack was highest where sand deposition and climax plant populations occurred. Sand moisture content increased with an increase in sand depth, the sediment being moist at the surface (8·6% water by mass), and reached saturation point (21%) at depths as shallow as 30 cm and never deeper than 100 cm. The sand porosity increased from 20·8 to 21·4% with an increase in sand depth. Fungal abundance was relatively constant across the main study slack, reaching highest values in the middle and decreasing towards the landward end of the slack and across the slack series from west to east. Fungal abundance decreased linearly with an increase in sand depth, but fungi were still present 60 cm below the surface. No correlation was found between fungal abundance and total sand organic content.