Dynamics of coarse riparian detritus in a Hawaiian stream ecosystem: a comparison of drought and post-drought conditions

Abstract

AbstractInput, standing crop, and export of coarse (>4 mm2) particulate organic matter (CPOM) was measured in Kaiwiki Stream, a forested stream on the Island of Hawaii. The study was conducted during and after a severe drought associated with the 1997–1998 El Nino/Southern Oscillation event. During the drought, stream discharge was reduced by ∼70% and no spates occurred. Hawaiian streams draining windward mountain slopes normally experience >20 spates per year. During the drought, the mean rate of CPOM export was 8% of the mean input rate; following the drought, the export rate increased to 40% of input. Rates of marked leaf transport within the study area increased 30- to 50-fold following the drought, and rates of stem transport increased 10- to 30-fold. Lower rates of CPOM export and transport during the drought suggested that retention and potential availability to detritivores were increased compared to the post-drought period. Differences in CPOM standing crops during and after the drought were not ...