Measuring and modeling rainfall interception losses by a native Banksia woodland and an exotic pine plantation in subtropical coastal Australia

Abstract

Rainfall loss by canopy interception and subsequent evaporation to the atmosphere can be a significant portion of water loss from forested ecosystems. To quantify and compare interception losses from two forest types (exotic pine plantation vs. displaced native Banksia woodland) on Bribie Island in subtropical east coast Australia, we measured gross rainfall, throughfall and stemflow over a one-year period (May 2012–April 2013). Interception losses from both forests were also simulated by the revised Gash’s analytical model (RGAM) and the WiMo model. The results show that the annual interception loss in the Banksia woodland was lower (16.4% of gross rainfall) than that in the pine plantation (22.9% of gross rainfall) over the study period, which can be explained by the lower canopy storage capacity and higher aerodynamic resistance of the Banksia woodland. Using fixed parameters obtained from wet season (November–April), the optimized RGAM and WiMo models predict the interception losses from both forest stands reasonably well, with an underestimation of 8.5–12.7% for the dry season (May–October), and a total underestimation of 5.2–8.2% for the entire year. The results indicate the development of commercial pine plantations in these areas would result in an increase in interception losses and thus reduce the net rainfall input in these forested ecosystems.