PARENT SESSION
Poster Session #21: Riparian and Wetland Restoration.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Effects of carbon additions on desired native and undesired weedy plant establishment in wetland prairie.

DAVIS, KIMBERLY¹, WILSON, MARK^*,2, ¹ Oregon State University, Corvallis, Oregon² Oregon State University, Corvallis, Oregon

ABSTRACT- Soil carbon additions could be an effective site preparation tool in restoration if they reduce soil nitrogen levels via enhanced microbial immobilization, which in turn controls nitrophilous weedy plants. Previous studies have mostly been limited to upland ecosystems and have yielded mixed results. We tested experimentally the effect of three levels of sugar and sawdust additions to a wetland prairie in western Oregon's Willamette Valley. Carbon additions resulted in significantly reduced levels of soil nitrogen (up to 75% reduction in ammonium, up to 97% reduction in nitrate). Carbon additions and the resulting drop in nitrogen availability led to significantly lower first-year aboveground biomass of unsown exotic grasses and a cosmopolitan weedy grass, and significantly higher aboveground biomass of the dominant native bunchgrass Deschampsia cespitosa sown into treatment plots. The significant increase in overall native plant biomass (562 g/m² with high carbon additions compared to 152 g/m² in untreated controls) stemmed from reduced competition by weedy, undesired grasses (231 g/m² with high carbon additions compared to 521 g/m² in untreated controls). These results demonstrate the potential of carbon additions as an effective tool in restoring degraded wetland prairies.

KEY WORDS: carbon additions, plant establishment, prairie restoration, reverse fertilization