Skip to main content
ARS Home » Pacific West Area » Tucson, Arizona » SWRC » Research » Publications at this Location » Publication #169007
Title: ASSESSING THE CONTRIBUTION OF SEMI-ARID SOILS OF THE SOUTHWESTERN US TO AMELIORATION OF GLOBAL WARMING 1649

Author
item McLain, Jean
item Martens, Dean

Submitted to: Soil Science Society of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2004
Publication Date: 10/30/2004
Citation: Mclain, J.E., Martens, D.A. 2004. Assessing the contribution of semi-arid soils of the southwestern us to amelioration of global warming. [abstract} In: Proceedings of the Soil Science Society of America Annual Meeting, October 30 - November 4, 2004, Seattle, Washington. p. 1.

Interpretive Summary: Semi-arid ecosystems represent 25% of the Earth's land area and are increasing due to desertification. Moisture limitations have led to the belief that these soils are not significant consumers or producers of trace gases and thus, they are often largely overlooked in greenhouse gas inventories. We are using long-term (100-yr) grazing exclosures to study the influences of grazing management on trace gas (CO2, N2O, and CH4) production and consumption in rangelands of southeastern Arizona. Trace gas fluxes were negligible on all sites prior to the arrival of the summer monsoon rainfalls. Following precipitation input, CO2 production was equal on the grazed and non-grazed sites, averaging 310 mg m-2 h-1, but soil N2O production in grazed areas (32 'g m-2 h-1) was higher by 45% than in the non-grazed enclosures (18 'g m-2 h-1). Soil CH4 consumption during the summer monsoon averaged 20 'g m-2 h-1 in the non-grazed sites, but only 3 'g m-2 h-1 in the grazed treatments. Chemical and physical mesquite control measures also decreased CH4 consumption by more than 50%. This work suggests that semi-arid rangelands represent a significant terrestrial CH4 sink and a seasonal source of N2O, and that grazing practices impact the climate change mitigation potential of semi-arid soils.

Technical Abstract: Semi-arid ecosystems represent 25% of the Earth's land area and are increasing due to desertification. Moisture limitations have led to the belief that these soils are not significant consumers or producers of trace gases and thus, they are often largely overlooked in greenhouse gas inventories. We are using long-term (100-yr) grazing exclosures to study the influences of grazing management on trace gas (CO2, N2O, and CH4) production and consumption in rangelands of southeastern Arizona. Trace gas fluxes were negligible on all sites prior to the arrival of the summer monsoon rainfalls. Following precipitation input, CO2 production was equal on the grazed and non-grazed sites, averaging 310 mg m-2 h-1, but soil N2O production in grazed areas (32 'g m-2 h-1) was higher by 45% than in the non-grazed enclosures (18 'g m-2 h-1). Soil CH4 consumption during the summer monsoon averaged 20 'g m-2 h-1 in the non-grazed sites, but only 3 'g m-2 h-1 in the grazed treatments. Chemical and physical mesquite control measures also decreased CH4 consumption by more than 50%. This work suggests that semi-arid rangelands represent a significant terrestrial CH4 sink and a seasonal source of N2O, and that grazing practices impact the climate change mitigation potential of semi-arid soils.