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

Abstract

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.