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The atmospheric CO2 concentration has been increasing since the industrial revolution. A proposed mitigation strategy is sequestering carbon (C) in terrestrial ecosystems, either in plant biomass or soil organic matter. The litter-C pool is the second largest C pool in agroecosystems post-harvest, and the amount of litter-C loss has been correlated with ecosystem respiration. Yet, the potential importance of the litter pool as one of the major C pools in a system is relatively unknown. We do, however, know that the size of the litter pool can be affected by increases or decreases in both litter-C production and decomposition, respectively, and is therefore a highly dynamic C pool. With the increase in productivity, and the decrease in litter burial and soil disturbance in agroecosystems, the propensity for substantial litter build up is likely and yet the magnitude and temporal dynamics of litter-C accretion is generally unknown. Therefore, in order to understand ecosystem carbon dynamics, and make accurate predictions of C sequestration, careful quantification of litter-C production, losses, and accretion is essential. In this dissertation, I detail my exploration of litter-C dynamics in maize-based agroecosystems. I first investigate the impact of management on the decomposition of one annual maize litter cohort and examine potential changes in litter tissue quality, decomposition rates, and the changes in this annual litter-C pool over three years of in situ decomposition (Ch.2). I then report changes in litter-C production and decomposition for four annual litter cohorts of both maize and soybean litter to examine litter-C accretion under different management regimes (Ch.3). Thirdly, I investigate the effect of inorganic nitrogen additions to litter and how this influences litter and soil organic matter decomposition with both field and laboratory incubation conditions (Ch. 4). Finally, I finish with a study about how the addition of charred plant material impacts litter and soil organic matter decomposition and whether it is an effective sequestration strategy in prairie ecosystems (Ch.5).
Adviser: Johannes M.H. Knops