Wednesday, November 15, 2006

Nutrient Dynamic Differences in Former Wetland Soils Following 80+ Years of Agriculture.

A. Puanani Borges1, Keith A. Johnson1, Carl J. Bernacchi2, Kelly McConnaughay1, Eldor Paul3, Rich Conant3, and Sherri Morris1. (1) Biology Dept, Bradley Univ, 1501 W Bradley, Peoria, IL 61625, (2) Illinois State Water Survey, 2204 Griffith Drive, Champaign, IL 61820, (3) Natural Resource Ecology Lab, Colorado State Univ, Ft. Collins, CO 80523

Soil C content and nutrient dynamics are important factors to developing plant communities and can be altered by moisture regimes.  This study examines soil differences between two former wetlands that existed for 50 and 1,000+ years and a current wetland that also existed for 1,000+ years.  Both former wetlands were disturbed by soybean/corn cultivation for 80+ years, and are part of a large-scale restoration project along a major river system.  Composite cores from 0-10, 10-25, and 25-50 cm depths were taken from two former wetlands and an adjacent undisturbed wetland.  Soils were analyzed for bulk density, total and resistant carbon and nitrogen, and net nitrogen mineralization rates determined using two 30-day incubations.  Carbon, nitrogen, and C/N did not differ between former wetland soils.  Resistant C, resistant N and the RC/RN ratio were higher in the younger former wetland at 10-25 cm. However when summed to 50 cm, resistant C/N was higher in the older former wetland.  Percent resistant carbon was higher in former wetland soils than the adjacent wetland.  Nitrogen mineralization, nitrification, and percent nitrification were significantly higher in 0-10 cm current wetland soils following 30 days incubation.  After 60 days, current wetland soils had significantly greater N mineralization and nitrification at 0-10 cm.   However, the older former wetland had higher nitrogen mineralization and nitrification at 10-25 cm.  These results suggest that nutrient content and nitrogen turnover currently differ between the former wetland sites and the adjacent wetland. We predict that restoration will result in changes in soil carbon dynamics and increased nitrogen turnover as sites are returned to wetlands.