ARS | Publication request: ELEVATED CO2 IMPACTS ON MICROBIAL ACTIVITY AND SOIL ORGANIC MATTER IN A SOUTHEASTERN U.S. SOIL

Submitted to: International Soil Conservation Organization Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 10, 1999
Publication Date: May 10, 1999
Citation: Stott, D.E., Rogers Jr, H.H., Prior, S.A. 1999. Elevated CO2 impacts on microbial activity and soil organic matter in a southeastern U.S. soil. International Soil Conservation Organization Conference Proceedings. p. 91.

Technical Abstract: The continuing rise in atmospheric CO2 has important implications for terrestrial carbon processes. Plant growth is typically stimulated by elevated CO2 because CO2 is the substrate for photosynthesis and water use efficiency increases. Stimulation of root system development associated with increased growth immediately lead to hypotheses of changes in soil and rhizosphere microbiology, as related to the C flow within the soil. Enhanced plant growth suggests greater delivery of C to soil, and potentially greater soil C storage in terrestrial ecosystems. We studied the C storage and changes in microbial activity in two agroecosystems, soybean and sorghum, a C3 and a C4 crop respectively. The soil used was the Blanton Loamy Sand located in Auburn AL. Treatments consisted of 360 ppm CO2 in ambient atmosphere, 360 ppm CO2 in open-top chambers and 720 ppm CO2 in open-top chambers. oil was sampled after the sixth year. Cores were divided into 4 depth samplings: 0-5 cm, 5-10 cm, 10-15 cm and 15-30 cm. Microbial enzymatic activities measured included: B-glucosidase, arylsulfatase, phosphatase, amidase and fluorescein diacetate hydrolase. In addition total C and N, dissolve organic C and carbohydrate C was measured. Susceptibility to crusting and surface sealing was determined using the Griffith fall-velocity tube. While differences in activity with depth were significant, with the surface layer having the greater activity and C sequestration, differences between CO2 treatments were minimal. Despite exposure to elevated CO2, this loamy sand from the southeastern United States was unable to sequester addition C, probably due to the warm climate and rapid organic C turnover.