Soils play a vital role in dealing with the environmental impacts of rising atmospheric carbon levels — primarily carbon dioxide — from natural and human activities. Clemson University soil scientists are studying soil types, ranking them on their ability to hold carbon and preventing it from returning to the atmosphere for eons.
The Earth’s carbon budget — its balance between carbon used for plant growth and excess carbon stored — is a dynamic process. As carbon is released through fossil-fuel burning and changing land use, scientists are seeking a more accurate understanding of carbon storage and cycling.
The Earth holds carbon in what scientists call pools: reservoirs of carbon stocks stored in and on the Earth and oceans as organic and inorganic matter. Simplistically, organic carbon compounds are connected to plants or animals while inorganic carbon compounds are often linked to minerals or rocks. Soil is second only to the oceans as a carbon sink: pools into which more carbon flows in than out. Soil scientists have a better picture of soil organic carbon — soil containing decaying plant and animal matter — than soil inorganic carbon. Scientists are now studying soil inorganic carbon, theorizing it may be a key area for forming and holding carbon, preventing it from returning to the atmosphere for eons.
A team of Experiment Station scientists from Clemson University and Virginia Tech analyzed the 12 major soil groups in the continental United States, ranking them for their potential ability to form new soil inorganic carbon based on average annual atmospheric wet deposition of calcium, or the amount of ionic calcium present in rainfall. The results were first presented at the Soil Science Society of America Annual Meeting in November 2007 in New Orleans and recently have been published in the May-June 2009 issue of the Soil Science Society of America Journal.
The study evaluated average annual atmospheric wet deposition of ionic calcium from 1994 to 2003 in the continental United States by soil order using spatial analysis of ionic calcium wet deposition data obtained from the National Atmospheric Deposition Program and the State Soil Geographic Database from the Natural Resources Conservation Service of the U.S. Department of Agriculture. Using geographic information system (GIS) software, spatial data layers were developed and averaged to create a final iconic calciu wet deposition map layer. The total deposition per soil order was calculated by combining the final average ionic calcium wet deposition map layer with the generalized soil order data layer.
Results from the study revealed that the total wet deposition of ionic calcium was 8.6 × 108 kilograms, which would be equivalent to the maximum theoretical formation of 2.6 × 108 kilograms of carbon as soil inorganic calcium, barring losses due to competitive processes, such as plant uptake, erosion and deep leaching. The soil orders receiving the highest area-normalized total wet deposition of ionic calcium were Alfisols and Mollisols, non-arid soils that typically are associated with the “bread-basket” regions of the United States.
Research team member Elena Mikhailova, a soil scientist at Clemson who originally conceived the research approach, stated, “Formation of new carbonate minerals in soils — what scientists call pedogenic carbonates — represent a pathway by which atmospheric (carbon dioxide) can be sequestered. Maps of potential (soil inorganic carbon) formation and storage based on wet (ionic calcium) deposition can aid in understanding terrestrial ecosystem inorganic carbon dynamics and the way it can be manipulated to decrease (carbon dioxide) concentrations in the atmosphere.”
The research is part of an ongoing project at Clemson to study soil carbon, particularly inorganic carbon stocks, and its role in the global carbon budget. Studies will measure, profile and identify the soil carbon characteristics and regional distribution to understand conditions and develop predictive models for future soil inorganic carbon research.
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