ARS | Publication request: Nitrogen and carbon cycling in a grassland community ecosystem as affected by elevated atmospheric CO2

Submitted to: International Journal of Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 2012
Publication Date: April 24, 2012
Repository URL: http://handle.nal.usda.gov/10113/54112
Citation: Torbert III, H.A., Polley, H.W., Johnson, H.B. 2012. Nitrogen and carbon cycling in a grassland community ecosystem as affected by elevated atmospheric CO2. International Journal of Agronomy. Article ID 817343, 5 pages, 2012. doi:10.1155/2012/817343.

Interpretive Summary: Increasing global atmospheric CO2 concentration has led to concerns regarding its potential effects on grasslands and the long-term storage of C and N in soil. This study examined responses to elevated CO2 in a grass ecosystem invaded with a leguminous shrub. Seedlings of Acacia along with grass species were grown for 13 months at three different levels of atmospheric CO2 concentrations. Elevated CO2 increased both C and N inputs from plant growth which would result in higher soil C from litter fall, root turnover and excretions. Results from the incubation indicated an initial (20 days) decrease in N mineralization which resulted in no change in C mineralization. However, after 40 days, an increase in both C and N mineralization was observed. These increases would indicate that increases in soil C storage may not occur in grass ecosystems that are invaded with Acacia over the long-term.

Technical Abstract: Increasing global atmospheric CO2 concentration has led to concerns regarding its potential effects on terrestrial ecosystem and the long-term storage of C and N in soil. This study examined responses to elevated CO2 in a grass ecosystem invaded with a leguminous shrub Acacia farnesiana (L.) Willd (huisache). Seedlings of Acacia along with grass species were grown for 13 months at CO2 concentrations of 385 (ambient), 690, and 980 µmol mol-1. Elevated CO2 increased both C and N inputs from plant growth which would result in higher soil C from litter fall, root turnover and excretions. Results from the incubation indicated an initial (20 days) decrease in N mineralization which resulted in no change in C mineralization. However, after 40 days, an increase in both C and N mineralization was observed. These increases would indicate that increases in soil C storage may not occur in grass ecosystems that are invaded with Acacia over the long-term.