CARBON DIOXIDE FLUX DURING THE FIRST YEAR FOLLOWING SWITCHGRASS ESTABLISHMENT

Authors: Skinner, Robert; Adler, Paul

Submitted to: Eastern Native Grass Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 9/27/2006
Publication Date: 10/13/2006
Citation: Skinner, R.H., Adler, P.R. 2006. Carbon Dioxide Flux During the First Year Following Switchgrass Establishment. In: Sanderson, M.A., Adler, P., Goslee, S., Ritchie, J., Skinner, H., Soder, K., Proceedings of the Fifth Eastern Native Grass Symposium, October 10-13, 2006, Harrisburg, Pennsylvania. p. 56.

Interpretive Summary: An interpretive summary is not required.

Technical Abstract: Perennial grasslands managed for biofuel production could provide additional environmental benefits by sequestering carbon in the soil. An eddy covariance flux tower was used to quantify the net carbon dioxide flux during 2005 for a switchgrass (Panicum virgatum L) field that had been planted in 2004. The summer of 2005 experienced significant drought with deficit moisture conditions existing from mid-April through late-October. Switchgrass height was only 56 in. when plants reached physiological maturity in mid-August. Plots were harvested in April 2006. Poor growth during the summer combined with leaching and lodging losses during the winter resulted in an average yield of only 837 lb dry matter ac**-1. The field experienced a net loss of carbon dioxide due to soil and plant respiration until mid-April when photosynthetic uptake became great enough to offset respiratory losses. Initial early-season uptake during late-April and early-May was due to weeds since switchgrass did not begin active growth until mid-May. Switchgrass rapidly accumulated carbon dioxide from mid-June until seed heads appeared in early-August. Little additional net uptake occurred during seed filling. September 15 was the last date that net uptake was observed. Respiratory loss after September 15 offset about 69% of the total uptake during the growing season so that net flux for the year was -603 lb CO2 ac**-1. When the carbon dioxide-equivalent of the biomass removed in April 2006 was subtracted from the total flux, the field became a net source to the atmosphere of 1843 lb CO2 ac**-1. The combination of a dry year and relatively immature switchgrass stand meant that the field was not able to sequester carbon during 2005. Measurements will continue for several more years to determine the carbon sequestration potential of more mature stands under a range of environmental conditions.