Document: ELI-3-34-1

How will invasive and less-invasive plant species perform in a high-CO2 world? Projections from ecophysiological data on four grass species.

FARNSWORTH, E.J.*

Smith College, Northampton, MA 01063 USA ¹

Abstract:
I ask if rising atmospheric carbon dioxide concentrations will alter the capacity of invasive species to outcompete non-invasives in wetland assemblages and hence modify rates of invasive spread. The replacement of native assemblages by invasives may in turn alter future carbon budgets of wetlands, with feedbacks on climate. I report 2 seasons of field data from four Connecticut tidal marshes (2 freshwater and 2 saline). I address the hypothesis that four dominant, perennial, monocot species ranging along a life-history continuum from highly invasive (Phragmites australis) to less invasive (Typha angustifolia) to non-invasive in the east (Leersia oryzoides and Spartina alterniflora) differ consistently in their phenology, carbon assimilation and respiration, C:N ratios, water-use, and architecture, with implications for their responses to increased carbon availability. Biomass allocation, phenology, photosynthetic rates, and water use differ among the species. Specifically, efficient growth in the early season enables the more invasive species to establish and enforce early competitive superiority via shading and to attain higher total biomass than less-invasive species in both marsh types. Rising sea level accompanied by water stress may select against the more invasive species, especially Phragmites that shows lower growth rates and more negative water potentials than other species in salt marshes and relative to its performance in freshwater marshes. Season-long, comparative measurements suggest that rising CO2 will alter both species composition and carbon budgets of tidal wetlands.

Keywords: invasive species, carbon, physiology, climate change, wetlands

This abstract is being presented at: 3:45 PM in session:
Oral Session #30: Effects of Elevated Carbon Dioxide.