Leaf Litter Breakdown of Native and Invasive Riparian Trees in Hawaii (Mackenzie
Channel: Ronald Cannarella
Date: 2012-06-07

Presentation at the Hawai`i Conservation Conference 2007 by Richard MacKenzie (Richard MacKenzie1, Nicole Cormier1, Francis Kinslow2, Tracy Wiegner2; 1Institute of Pacific Islands Forestry, Hilo, HI, 2University of Hawai‘i Hilo, Hilo, HI) on "Leaf Litter Breakdown of Native and Invasive Riparian Trees in Forested and Developed River Reaches on the Island of Hawai‘i". Hawaiian flora communities are often dominated by invasive plants, especially at lower elevations where human impacts (i.e., agriculture, urbanization) are also greatest. While this threatens Hawaiian biodiversity, invasive N-fixing plants, like Falcataria moluccana (Albizia) threaten ecosystem function through alteration of nutrient budgets and cycling. To examine the effects of invasive plants and land use on riverine organic matter dynamics, we compared leaf breakdown of albizia and native Metrosideros polymorpha (‘ōhi‘a) trees in forested and developed reaches of the Wailuku River during wet and dry seasons (2005-2006). During 2005, breakdown rates of albizia leaves were significantly faster than ‘ōhi‘a (1.5 – 2X), which was attributed to greater initial fungal colonization. However, by the end of the experiments, fungal biomass on ‘ōhi‘a was similar to and often exceeded that on albizia litter. Breakdown rates of litter from both species did not differ between forested and developed reaches of the river. Breakdown rates were greatest during dry seasons for both litter types, which was attributed to increased river flow (100-500X) resulting from storms. Replacement of native riparian forests by invasive albizia forests could dramatically alter organic matter and nutrient dynamics in Hawaiian rivers and their downstream coastal areas.

Hawaii Conservation Alliance
Executive Producer: Ronald Cannarella