ARS | Publication request: Long-term measurements of CO2 flux and evapotranspiration in a Chihuahuan desert grassland

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 2004
Publication Date: September 15, 2004
Citation: Mielnick, P., Dugas, W.A., Mitchell, K., Havstad, K.M. 2004. Long-term measurements of CO2 flux and evapotranspiration in a Chihuahuan desert grassland. Journal of Arid Environments. 60:423-436

Interpretive Summary: The increasing levels of atmospheric CO2 are a concern due to possible effects on global and regional climates. Plants remove CO2 from the atmosphere and deposit CO2 through their roots and residues into the soil. These CO2 deposits can remain in the soil, or sequestered, for long periods of time. Since approximately 1/3 of the world’s land surface is rangeland, there has been interest in understanding how much CO2 can be stored by rangeland plants. This study looked at CO2 fluxes (the change in CO2 from soil storage to release into the atmosphere) for plant sin the northern Chihuahuan desert in southern New Mexico. Because this desert region received limited rainfall, during most of the year, more CO2 is actually released into the atmosphere than is sequestered. However, these net values were quite low. These desert regions may not be likely to sequester atmospheric CO2.

Technical Abstract: We measured CO2 and evapotranspiration (ET) fluxes above a Chihuahuan desert grassland from 1996 through 2001. Averaged across six years, this ecosystem was a source (positive flux)of CO2 in every month. Over that period, sustained periods of carbon uptake (negative flux)were rare. Averaged across all months, we estimated that CO2 was being released into the atmosphere at a rate of +1.5 g CO2 m-2 d-1 (+0.40 g Cm-2 d-1) or +533 g CO2m-2 yr-1 (+145.3 g Cm-2 yr -1). Average ET was 299mm yr -1 with a monthly range of 0.15mm d-1 in December to 2.15mm d-1 in August.