Effects on catchment water balance from the management of Pinus plantations on the coastal lowlands of south‐east Queensland, Australia

Abstract

AbstractA paired catchment study was conducted over a 10‐year period on the hydrology of an exotic Pinus plantation in the coastal lowlands of south‐east Queensland, Australia. Each catchment was instrumented with a stream monitoring station, tipping bucket rain gauge, and a network of piezometers to monitor the shallow perched water table. After a 6‐year calibration period a harvest treatment was imposed on one catchment (Review): clearfelling approximately 90% of the catchment area, which contained a mature (44‐year‐old) Pinus elliottii plantation. This subsequently was re‐established with a second rotation plantation of a hybrid of P.elliottii × P.caribaea var. hondurensis. The control catchment (Crayfish) contained a P. elliottii plantation similar to that clearfelled at Review. The post‐harvest period was monitored for a further 4 years.Evapotranspiration was found to be the major output flux, with stream flow only a minor component of the study catchments' water budget. Areas with gleyed podzolic soils were found to remain waterlogged for periods up to 7 months following the seasonally high summer rainfall period, with other soils having water logging periods of only a few months. Little change was observed in waterlogging characteristics following harvesting, in contrast to stream flow which increased for 3 years but with evidence of a decline after 5 years.The perched‐watertable piezometric surface indicated that its lateral drainage differs from that of surface flows; the perched‐watertable drainage fluxes from the study catchments seem minor and off‐site movement of solutes (e.g. nutrients and contaminants) via them would be limited. It was identified that the interaction between the perched and deep aquifers was poorly understood, as well as the relative importance of the soil moisture storage of the aquitard clay layer between them. It was concluded that there is a need to undertake more detailed analysis using modelling, and to obtain additional field data on soil‐layer properties and piezometric levels of the deep aquifer. Copyright © 2002 John Wiley & Sons, Ltd.