Distinguishing Root from Soil Contributions to Soil Respiration: Exploration of a New Approach

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Over recent decades concentrations of CO2 in the atmosphere have increased steadily, primarily due to the combustion of fossil fuels. This finding has generated substantial debate concerning the possible consequences for our global environment, since CO2 is a greenhouse gas. Of the CO2 emissions from fossil fuel combustion and cement manufacture, about 30% is absorbed by the oceans and about half remains in the atmosphere. The remaining 20% is assumed to be absorbed by plants and soils. Since that process is not well understood, a major gap in understanding how Earth will respond to increasing atmospheric CO2 concentrations exists. To fill this gap, we need a better understanding of the processes of plant growth and decomposition in soils. That need remains because of our perpetual lack of tools for investigating robustly that dark, dirty, and obscure world belowground. We have developed a new approach that takes advantage of precise measurements of isotopes of carbon, physiological differences among plant species, computer modeling, and a combination of experimental field and laboratory studies, to divide the belowground ecosystem into its major components. We propose that we can distinguish, and thus investigate independently, the separate but simultaneous processes of plant (root) growth and organic matter decomposition, and thus provide a new tool for understanding what we cannot see. Living soils are where organisms, land, water, and atmosphere interact the most. By shedding light on this murkiest of ecosystems, we expect to advance significantly our capacity to investigate a host of biogeochemical processes that influence our waters, our air, the productive capacity of our land and, potentially, our climate.