Over time, changes in plant growth and litter production caused by rising CO2 and O3 concentrations could impact the storage and cycling of carbon in soil organic matter. DOE’s decade-long investment in a multi-factor Free-Air CO2 Enrichment (FACE) experiment in Rhinelander, Wisconsin, enabled scientists from Argonne National Laboratory and two Midwest universities to observe that elevated CO2 changed the trajectories of three soil organic matter pools characterized by extent of decomposition. As the experiment progressed, relatively undecomposed particulate organic matter fragments built up more rapidly in the soil of plots exposed to elevated CO2, while the amount of carbon found in more highly processed mineral-associated organic matter pools declined under elevated CO2 but not in ambient soils. Thus, elevated CO2 appears to have increased the cycling of carbon and nitrogen in the soil organic matter of the sandy soils at this site. In contrast, elevated O3 tended to have the opposite effect, reducing both detritus inputs and the cycling of soil carbon and nitrogen. The effects of O3 occurred regardless of atmospheric CO2 concentration. Although forest community composition altered the magnitude of the responses, enhanced turnover of soil organic matter could limit the potential for long-term soil carbon sequestration in the northern deciduous forests of an elevated CO2 world.
References: Hofmockel, K. S., D. R. Zak, K. K. Moran, and J. D. Jastrow. 2011. "Changes in Forest Soil Organic Matter Pools After a Decade of Elevated CO2 and O3," Soil Biology and Biochemistry 43, 1518-1527.
Contact: Mike Kuperberg, SC-23.1, (301) 903-3281, Daniel Stover, SC-23.1, (301) 903-0289
SC-23.1 Climate and Environmental Sciences Division, BER
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