Grantee Research Project Results

2002 Progress Report: An Experimental Study of Biological Invasions in Forests of the Eastern United States.

EPA Grant Number: R828900
Title: An Experimental Study of Biological Invasions in Forests of the Eastern United States.
Investigators: Gurevitch, Jessica , Howe, Katherine , Hyatt, Laura , Lerdau, Manuel
Current Investigators: Gurevitch, Jessica , Lerdau, Manuel
Institution: The State University of New York at Stony Brook
EPA Project Officer: Packard, Benjamin H
Project Period: September 20, 2001 through February 19, 2004 (Extended to September 19, 2005)
Project Period Covered by this Report: September 20, 2001 through February 19, 2002
Project Amount: $451,553
RFA: Exploratory Research to Anticipate Future Environmental Issues (2000) RFA Text |  Recipients Lists
Research Category: Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration , Water

Objective:

One of the major environmental problems facing the United States in the 21st century is the invasion of native ecosystems by exotic species. These invasive species have the potential to reduce biodiversity, disrupt ecosystem function, and cause severe economic and social problems. One of the objectives of this research project is to test hypotheses about what makes different habitats more or less likely to become invaded by exotic species. To address this problem, we are conducting research in a range of invaded and uninvaded forests in eastern Long Island, NY. Although some forests here are heavily invaded by nonnative plants, some mesic hardwood forests and nearly all pitch pine-dominated woodlands seem to resist the establishment of exotic, invasive species. We are taking an experimental approach to major test factors hypothesized to limit invasibility of forest ecosystems in the Eastern United States: litter depth, light, nitrogen, and calcium availability. The second objective is to examine the ecosystem impacts of invasions by measuring the dynamics of litter decomposition (mass and nutrient loss), comparing litter from native and invasive species. It is thought that invasive species will have higher rates of mass and nutrient loss than natives, and that these differences will swamp site-specific effects. This work is the first experimental study of factors regulating invasibility of forest ecosystems, bringing community and ecosystem approaches together.

Progress Summary:

During the past year of the project, we have made substantial progress on both of our objectives. We experimentally tested the hypothesis that low resource availability prevents exotic species from invading pine barren forests through a series of field manipulations. We planted seedlings of common native and exotic species into invaded and uninvaded forest types on Long Island (all seedlings were diligently removed at the end of the growing season). Overall, exotic species were more likely than native species to become established and grow, a result that supports the hypothesis that successful invaders are more vigorous than natives. However, adding nutrients did not enhance survival or growth for exotics or natives. Under nutrient addition, particularly with nitrogen, exotic species were more likely to shrink in size, although native species were more likely to die. We suspect this pattern is partly because of the interaction of selective herbivory by insects and mammals and study species' defense mechanisms. On average, plants grew better in gaps. Surprisingly, on average, across all treatments and sites, natives grew more than exotics.

Preliminary results from our experiment on evaluating litter decomposition have yielded some interesting findings. Although exotic and native species litter mass has decomposed at similar rates in uninvaded habitats, litter mass decomposition of exotic species has been much more rapid than native species in invaded sites. Not surprisingly, litter decays more rapidly in higher nutrient, moister hardwood forests than in pine barrens sites, but litter also decayed more rapidly in invaded than in uninvaded hardwood forest sites. These results suggest that invasion may alter ecosystem characteristics such as litter decomposition, affecting invasive and native species differently.

This work has helped us to develop auxiliary hypotheses and already is revealing intriguing insights into the process of invasion.

Future Activities:

We will continue to test factors hypothesized to limit invasibility of forest ecosystems in the Eastern United States. In addition, we will continue to examine the ecosystem impacts of invasion by measuring the dynamics of litter decomposition and comparing litter from native and invasive species.

Journal Articles:

No journal articles submitted with this report: View all 35 publications for this project

Supplemental Keywords:

forests, Eastern United States, ecosystem services, invasion prevention, invasion mitigation, ecological impacts, nitrogen deposition, calcium loss, anthropogenic changes, global change., RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Ecological Risk Assessment, Ecosystem Protection, Forestry, Biology, Ecosystem/Assessment/Indicators, Futures, Monitoring/Modeling, Exp. Research/future, Ecological Effects - Environmental Exposure & Risk, exploratory research, invasive species, biodiversity, endangered species, forest, Eastern U.S., emerging environmental problems, extinction risk, forests, ecological dynamics, ecological exposure, biopollution, futures research, rainfall, runoff

Progress and Final Reports:

Original Abstract

2003 Progress Report

2004 Progress Report

Final Report