Intra-storm evaporation as a component of canopy interception loss in dryland shrubs: observations from Fowlers Gap, Australia

Interception losses from the canopies of dryland plant taxa remain poorly understood, especially the relative contributions of intra-storm and post-storm evaporative losses. Employing a new measuring apparatus, this study uses low-intensity simulated rain, matched to the properties of local rain, to explore interception processes in bluebush shrubs at an Australian dryland site. Five shrub specimens were exposed to simulated rain for 60-90 min. Experiments were repeated at three rainfall intensities (10, 15, and 20 mm h(-1)). Canopy evaporation was found from the difference between the flux of water delivered to the shrub and the flux of throughfall, once equilibrium had been established. The results show that evaporation from the wet foliage during rain proceeds at an average rate of 3.6 mm h(-1). This figure is for relatively cool spring-season conditions; evaporation rates in hot summer conditions would be larger. Intra-storm evaporation is shown to exceed post-rain evaporation from interception storage on the shrubs, and this differentiates dryland shrub interception processes from those of the better-studied wet forest environment. Implications of the high dryland shrub canopy evaporation rates for aspects of dryland ecology are highlighted. Copyright (c) 2007 John Wiley & Sons, Ltd.