GLOBAL CHANGE AND BELOWGROUND PROCESSES IN AGRICULTURAL SYSTEMS
Location: National Soil Dynamics Laboratory
Title: Effects of Elevated Atmospheric Carbon Dioxide on Soil Carbon in Terrestrial Ecosystems of the Southeastern U.S.
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: May 1, 2008
Publication Date: March 9, 2009
Citation: Runion, G.B., Torbert III, H.A., Prior, S.A., Rogers Jr, H.H. 2009. Effects of Elevated Atmospheric Carbon Dioxide on Soil Carbon in Terrestrial Ecosystems of the Southeastern U.S. In: Lal, R. and Follett, R.F. (eds.). Soil Carbon Sequestration and the Greenhouse Effect (2nd Edition). SSSA Special Publication No. 57. Agronomy Society of America-Crop Science Society of America-Soil Science Society of America, Madison, WI. pp. 233-262.
Interpretive Summary: In today’s world, it is important to enhance soil C sequestration. Using plants to extract C from the atmosphere and store it in soils represents a great opportunity to help mitigate potential climate change. However, since soil C sequestration is a slow process, long-term studies are needed to assess how management soil C buildup. Given the CO2-induced increases in biomass observed within terrestrial ecosystems of the southeastern U.S. (crops, forests, and pastures), there is little doubt that these systems have a potential for increased soil C storage. Within this chapter, we have shown that both plant species and N cycling within plant/soil systems are critical factors controlling C storage. Our objective continues to be to increase our understanding of how we can best manage these systems to maximize soil C sequestration, while also providing food and fiber to a growing population.
Plants depend on carbon dioxide (CO2) as the substrate for photosynthesis; they remove CO2 from the atmosphere and use it for tissue production, respiring a portion back to the air. A portion of the carbon (C) fixed by plants enters the soil via root exudation and as plant litter (both aboveground tissues and roots). Once in or on the soil, plant tissues decompose; during this process, another portion of the C fixed by plants is lost to the atmosphere via respiration of insects and microbes responsible for decomposition. The amount of C able to be sequestered in soil is a sum of plant biomass inputs minus that lost during decomposition. The fact that the concentration of CO2 in the atmosphere is increasing is important not only for it’s effects on plants, but also because it is thought to be a major contributor to global warming. Can terrestrial ecosystems help mitigate global warming by removing C from the atmosphere and storing it in soils? And, can we manage these ecosystems to enhance the amount of C being removed? Terrestrial ecosystems of the Southeastern U.S. (row crops, forests, and pastures) are important not only for the raw materials they provide, but also due to their potential for soil C storage. It is well known that, for most plant species, elevated CO2 leads to increased biomass production. Greater amounts of biomass suggest that more C could enter the soil system. Rising levels of atmospheric CO2 have also been shown to alter plant tissue chemistry; these alteration might also lead to increases in the amount of C entering soil and/or the duration that this C resides in the soil via impacts on decompositional processes. Here, we provide evidence of the potential for terrestrial ecosystems of the Southeastern U.S. to increase soil C sequestration and for this potential to be enhanced through management of these systems. [GRACEnet Publication]