Tuesday, November 14, 2006

Patterns in Ecosystem Respiration: First Year Responses to Elevated CO2 and Irrigation from the High Plains Global Change Experiment.

Sarah Bachman and Elise Pendall. Univ of Wyoming, 1010 Beaufort, Laramie, WY 82072

Future responses of ecosystem respiration to global climate change remain a major gap in our present understanding of ecosystem physiology.    In semi-arid ecosystems, precipitation patterns govern net ecosystem production and consequently ecosystem respiration.  Precipitation inputs occur in pulses, regardless of annual averages however.  Here we present ecosystem respiration from an irrigation event in the first year of elevated CO2.  On the day prior to irrigation (day -1), average ecosystem respiration by elevated CO2 plots (EC) was already approximately 38.5% greater than ambient CO2 plots (AC).  We established non-watered control plots (C) for comparison, and on day -1 ecosystem respiration in these plots was not significantly different from ambient plots.  Respiration peaked one day following irrigation, and the response was greater in elevated plots.  By seven days following irrigation, ecosystem respiration was approximately 62% greater in elevated plots, yielding an overall pattern of ecosystem respiration similar to control and ambient CO2 plots, but greater in magnitude and longer in duration.  In modeling carbon cycling, ecosystem respiration responses to precipitation pulses will be critical to accurately predicting whether ecosystems act as net sources or sinks of CO2.