Institute of Ecosystem Studies

2007 BES Annual Meeting Presentation and Poster Abstracts

Effects of abundant non-native earthworms on plants and soil dynamics
McCormick, Melissa
Co-Authors: Melissa K. McCormick, Katalin Szlavecz, Kenneth Parker, Timothy R. Filley, Dennis F. Whigham
Abstract: The interaction of invasive species with site history has the potential to affect ecosystem processes. Non-native earthworms have long been present in the mid-Atlantic region and their abundance in forests differs across a gradient of forest age. Non-native earthworms are more abundant in successional forests compared to mature forests and they are more abundant in urban forests compared to rural forests. We hypothesized that abundant non-native earthworms could affect successional trajectories by altering soil organic matter dynamics and directly affecting vegetation by ingesting seeds, affecting their viability, and burying seeds too deep to germinate or have access to appropriate mycorrhizal fungi. We further hypothesized that native and non-native earthworms would have different effects on seed germination and resulting plant distribution. We tested these hypotheses at the Smithsonian Environmental Research Center, MD because 1. uniform geology would not confound possible earthworm effect, and 2. the land use history of the site is well documented. We used litter decomposition and earthworm exclusion bags to examine soil carbon dynamics and used feeding experiments and mesocosms to examine the effect of two non-native and one native earthworm species on seed viability and burial in the native orchid Goodyera pubescens. Abundant non-native earthworms altered the chemical composition and rate of leaf litter decomposition. All three earthworm species decreased seed viability but differed in their propensity to consume and bury seeds. This suggests that 1. abundant non-native earthworms can decrease colonization and 2. native and non-native earthworms function differently in different-age forests.