WATER-LOGGING AND RELATION TO A DEEP WEATHERINGPROFILE: A CASE STUDYFROM NORTH TUAN STATE FOREST,QUEENSLAND, AUSTRALIA

摘要

Plantation forests are a major landuse within the coastal plains of southeastern Queensland. In low-lying areas such asrnthe north Tuan State Forest, one of the biggest issues for forest management is about wet-season water-logging. Here we report on arnstudy focused on a perched water table formed at the top of a deep weathering profile.rnDeep weathering profiles typically consist of horizons including soil, (ferricrete), mottled zone, pallid zone and bedrock. Thernsoil mainly consists of quartz sand, which overlies ferricrete or clayey mottled zone at shallow depths. Hydraulic conductivity dropsrnquickly from the soil to ferricrete or mottled zone. Because of the flat topography, water drainage is impeded and under high rainfall,rnperched groundwater forms above the mottled saprolite and water-logging occurs consequently.rnDuring the last wet season, water-logging started after the highest rainfall in December and finished as the wet season ended.rnThe highest water level was observed either in December or January depending on site drainage conditions. Water-logging risk map,rnwhich was derived from subtraction of interpolated highest-recorded water table from DEM, shows that the closer to waterways, thernhigher the risk is. This supports the preference of maintaining native vegetation in these buffered zones rather than economicrnplantations.