Short-term temporal changes of bare soil CO2 fluxes after tillage described by first-order decay models.

To further understand the impact of tillage on carbon dioxide (CO₂) emission, we compare the performance of two conceptual models that describe CO₂ emission after tillage as a function of the non-tilled emission plus a correction resulting from the tillage disturbance. The models assume that C in the readily decomposable organic matter follows a first-order reaction kinetics equation as and that soil C-CO₂ emission is proportional to the C decay rate in soil, where C_soil( t) is the available labile soil C (g m⁻²) at any time ( t) and k is the decay constant (time⁻¹). Two possible relationships are derived between non-tilled ( F_NT) and tilled ( F_T) soil fluxes: (model 1) and (model 2), where t is time after tillage. The difference between these two models comes from an assumption related to the k factor of labile C in the tilled plot and its similarity to the k factor of labile C in the non-till plot. Statistical fit of experimental data to conceptual models showed good agreement between predicted and observed CO₂ fluxes based on the index of agreement (d-index) and with model efficiency as large as 0.97. Comparisons reveal that model 2, where all C pools are assigned the same k factor, produces a better statistical fit than model 1. The advantage of this modelling approach is that temporal variability of tillage-induced emissions can be described by a simple analytical function that includes the non-tilled emission plus an exponential term, which is dependent upon tillage and environmental conditions. [ABSTRACT FROM AUTHOR]