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 dCsoil(t)/dt = -kC(soil)d(t) 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 (FNT) and tilled (F-T) soil fluxes F-T F-NT + a(1) e(-a2t) (model 1) and F-T a(3)F(NT) e(-a4t) (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. t 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. t 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.