Carbon Sequestration Potential in Midwest Agricultural Land Compared to Restored Grasslands
Roser Matamala, Argonne contact (matamala@anl.gov)
Carbon dioxide fluxes and stocks in terrestrial ecosystems are key measurements needed to constrain quantification of regional carbon sinks and sources and the mechanisms controlling them. This information is required to produce a sound carbon budget for North America. The purpose of the proposed project is to examine CO2 and energy fluxes from agricultural land and from land in the Conservation Reserve Program (CRP) and to compare the carbon sequestration potentials of these lands. Our study integrates eddy covariance measurements with biometric measurements of plant and soil carbon stocks for three systems in Northeastern Illinois: (1) long-term cultivated land in corn-soybean rotation with conventional tillage (a common agricultural practice on the highly productive soils of the Corn Belt region of the Midwest), (2) a 15-year-old restored prairie that represents a long-term application of CRP conversion of cultivated land to native vegetation and, (3) a newly planted switchgrass field (a biofuel crop, planted summer 2008) after the removal of pasture grasses. The primary objectives of the study are to (1) compare net ecosystem production derived by integrating eddy covariance estimates of net ecosystem exchange over time with independent biometric measurements of ecosystem carbon stocks, (2) examine how factors such as climate, vegetation and management practices affect net ecosystem production (NEP) and soil C sequestration and, (3) Partition of NEE into assimilatory and respiratory fluxes and partition of soil respiration into its heterotrophic and autotrophic components. The study is contributing to the North American Carbon Program by providing information on the magnitude and distribution of carbon stocks and the processes that control carbon dynamics in cultivated and CRP-restored land in the U.S. Midwest.
Research progress:
In the first year (2005), the prairie restoration was a strong C sink with a NEP 438 g C m-2, despite a pronounced spring drought. In the second year (2006), with normal precipitation, a Melilotus alba invasion dramatically reduced NEP by half, reducing the C sink strength capacity of the restoration. The mechanisms for this reduction appear related to the loss of species and functional diversity that resulted from the dominance of M. alba, which led to a 42% reduction in the length of time when the vegetation was photosynthetically active, as compared to the previous year. In 2007, a year when M. alba was present but not dominant, plant diversity remained low and NEP was 43% lower than 2005 and very similar to 2006 NEP. These results suggest that biotic limitations to NEP may outweigh the effects of abiotic limitations at some sites and that biotic factors can also exert large memory effects on plant diversity and productivity.
Biometric and annual NEE estimates of NEP correlated extremely well at the prairie site, resulting in 5.5 Mg C h-1 y-1 in the year 2005. At this site, about 14% or 0.8 Mg C h-1 of NEP remained in the soil, with climate and vegetative growth exerting the greatest controls on C sequestration.
Project personnel:
Roser Matamala, Argonne National Laboratory
David R. Cook, Argonne National Laboratory
Julie D. Jastrow, Argonne National Laboratory
Miquel A. Gonzalez-Meler, University Illinois at Chicago
Postdoctoral Research Associate: Nuria Gomez-Casanovas, University of Illinois at Chicago
Links:
Project Webpage: http://www.atmos.anl.gov/FERMI/Information/index.html
North American Carbon Program:http://www.esig.ucar.edu/nacp/