Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/1996
Publication Date: N/A
Interpretive Summary: Increasing global concentration of CO2 in the atmosphere has led to concerns regarding its potential effects on the environment, such as the possibility of global warming. The increased CO2 comes largely from the use of fossil fuels, such as gasoline in cars. On the other hand, plants need CO2 to grow and remove CO2 from the atmosphere. A highly debated hypothesis is that the increased levels of CO2 in the atmosphre is being removed by plants and is being stored in soil in the form of organic carbon. Understanding how C02 is cycled is important if we are to determine its potential impact to the environment. This study examined carbon storage in soil as it is affected by growing crops in elevated atmospheric C02. The data from this study indicated that there is a potential for carbon from atmospheric C02 to be stored in soil under agriculture production systems, but the potential storage of carbon may be different for different crop species.
Technical Abstract: Increasing global atmospheric CO2 concentration has led to concerns regarding its potential effects on the terrestrial environment. Attempts to balance the atmospheric carbon (C) budget have met with a large shortfall in C accounting (÷1.6 X 1015 g C yr-1) and this has led to the hypothesis that C is being stored in the soil of terrestrial ecosystems. This study examined the effects of CO2 enrichment on soil C storage in C3 soybean (Glycine max L.) Merr. and C4 grain sorghum (Sorghum bicolor L.) Moench. agro-ecosystems established on a Blanton loamy sand (loamy siliceous, thermic, Grossarenic Paleudults). The study was a split-plot design replicated three times with two crop species (soybean and grain sorghum) as the main plots and two CO2 concentration (ambient and twice ambient) as subplots using open top field chambers. Carbon isotopic techniques using ë13C were used to track the input of new C into the soil system. At the end of two years, shifts in ë13C content of soil organic matter carbon were observed to a depth of 30 cm. Calculated new C in soil organic matter with grain sorghum were greater for elevated CO2 vs. ambient CO2 (162 and 29 g m-2, respectively), but with soybean the new C in soil organic matter were less for elevated CO2 vs. ambient CO2 (120 and 291 g m-2, respectively). These data indicate a potential for soil C storage in agro-ecosystems, but the mechanisms for C storage are different for different crop species.