|Bradford, James - Jim|
Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2005
Publication Date: 2/1/2006
Citation: Sims, P.L., Bradford, J.A. 2006. Moderate and heavy grazing impacts on carbon flux in a southern plains mixed-grass prairie [abstract]. Society for Range Management 59th Annual Meeting, February 5-11, 2005, Vancouver, Canada, Abstract No. 334. p. 219. 2006 CDROM. Interpretive Summary: Not needed.
Technical Abstract: Grasslands are important terrestrial ecosystems that, along with other rangeland resources, comprise about 50 percent of the earth’s land area. Even though rangelands dominate much the world’s landscape, knowledge of their role in global carbon budgets is limited. In addition, heavy grazing pressure occurs on much of these lands. Our objective was to compare changes in vegetation structure and CO2 flux on sustainably and abusively grazed mixed-grass prairie at the Southern Plains Experimental Range, Woodward, OK. Both study areas were on Deep Sand ecological sites and in near excellent condition at the beginning of the study. We measured CO2 flux, calculated at 20-minute intervals, yearlong from 1999 through 2004 using Bowen ratio/energy balance instrumentation. Plant measurements included aboveground and belowground biomass, leaf area, and canopy height. We grazed one site at about 53 animal unit days (AUD) ha-1 while the other site was grazed excessively at about 100 AUD ha-1. For the sustainably grazed site, carbon accumulated at an average of 3.6 g C m2 d-1 across the 5 years, 2000 through 2004, and ranged from a loss of 2.3 in 2002 to a gain of 11.3 in 2003. The heavily grazed site lost an average of 2.6 g C m2 d-1 over the 5-year period. These losses ranged from a low of 0.2 g C m2 d-1 in 2004 to a more than 6.1 g C m2 d-1 in 2002. Heavy grazing markedly increased the magnitude and constancy of carbon loss on this prairie.