PARENT SESSION
Poster Session #13: Restoration Ecology.
Tuesday, August 7, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Soil carbon addition for weed control in tallgrass prairie restoration.

BLUMENTHAL, DANA¹, JORDAN, NICHOLAS¹, ¹

ABSTRACT- Soil nitrogen enrichment, and consequent vigorous weed growth, is thought to hinder the restoration of tallgrass prairie. Adding carbon to the soil may facilitate prairie restoration by inducing immobilization of plant-available nitrogen. Early attempts to use this method, however, have had mixed results. Success of carbon addition depends on two assumptions: that problematic weeds are nitrophilous relative to prairie species, and that carbon addition results in nitrogen immobilization large enough in magnitude and duration to change the outcome of weed/prairie competition. We tested these assumptions by comparing productivity of 10 weeds and 10 tallgrass prairie species under 18 levels of carbon addition, ranging from 200 to 8000 g m^-2. Carbon (sawdust and sucrose), was tilled into the soil prior to planting. To control for non-nitrogen effects of carbon addition, nitrogen was added to a subset of plots. Relative to untreated plots, the highest level of carbon addition resulted in an 86% decrease in available NO₃-N, a 15-fold increase in early-season light availability, a 54% decrease in weed biomass and a 8-fold increase in prairie biomass. Nitrogen addition reduced or reversed all of these effects. Significant species-specific responses to carbon addition included decreased biomass for five annual weeds and increased biomass for six prairie species, one annual weed, and three perennial weeds. Results suggest that carbon addition may be a useful tool for restoring nitrogen-limited plant communities.

KEY WORDS: invasion, nitrogen immobilization, weed competition