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Force Project Description

Abstract Presentation

Within the macroaggregate structure (center) fungi (top right) and bacteria (bottom right) reside, but have a lower activity than when they would live outside of the macroaggregate due to factors such as reduced diffusion rates of oxygen and nutrients. Within these macroaggregates, microaggregates (top left) are formed around particulate organic matter (bottom left) and these microaggregates physically protect the organic matter incorporated in them. More intensive management in conventional tillage (CT) versus no-tillage (NT) agroecosystems increases the dynamics of macroaggregates, which inhibits the incorporation of organic matter in newly formed microaggregates and consequently reduces the sequestration of organic matter in CT agroecosystems.

     Soil acts as both a sink and source of atmospheric CO₂. Future mitigations of high CO₂ levels will have to: 1) lower net fluxes from the soil due to disturbance, and 2) increase the soil sink capacity. This requires a knowledge of the factors affecting soil C stabilization, e.g., information on soil C pools and fluxes. Also required is information on effects of various management practices such that future decisions in this regard can be made.

     In this project we study dynamics of soil C in the eastern deciduous forest region. Millions of acres of formerly agricultural sites have reverted to forest in this region. We sampled associated native forest, present agricultural sites and reforested plots to determine total C and N storage. Acid hydrolysis in conjunction with ¹⁴C dating is used to determine the resistant old soil C pool. Long-term incubations and curve fitting of the CO₂ evolved are used to assess the size and turnover of the active and slow C-pools. The effect of physical protection exerted by aggregates is determined by measuring aggregate size distribution and particulate organic matter (POM) fractions associated with the aggregates. A differentiation between POM within versus between aggregates is made.

     Decision making involves information on past and future effects of various management scenarios. We use the data base from our sites and the improved Century model to predict realistic effects of management on future soil C and CO₂ levels. These include effects of tillage, decreased fallow, CRP land, cover crops, increased crop residues and roots from higher yielding crops attributable to fertilization, improved genetics and higher CO₂. From this we can make much better predictions to be used by decision makers responsible for possible mitigation options. Funded by the Department of Energy.