Variability of total soil respiration in a Mediterranean vineyard

Total soil respiration (TSR) is the major component of the CO2 global flux. The knowledge of the temporal-spatial variability of TSR allows for a better interpretation of a critical component of global greenhouse gas flux measurements. The objective of the research was to evaluate the TSR dynamic over a long measurement period in a vineyard in the South of Italy. A static home-made automatic system was used to measure TSR for a three year period. A portable gas analyser (Li-Cor 6400-09) was used to study TSR spatial variability. A non-invasive geophysical technique (Electromagnetic Induction – EMI) was applied to search for a significant relationship between apparent soil electrical conductivity (ECa), the EMI signal and TSR. Long-term measurements of TSR enabled to study its temporal dynamics. CO2 rates ranged from 0.78 to 43.7 g CO2 m–2 day–1. TSR increased during spring and decreased by 45–50% during the mid-summer. The daily trend of TSR showed differences between the seasons studied reporting a clearly variation among TSR measured on row and inter-row positions. The supplemental irrigation significantly affected (P < 0.001) CO2 soil effluxes which showed a weekly mean increase of 300%. Significant inverse relationships were found by interpolating TSR values and ECa (coefficient of correlation ranging from –0.43 to –0.83 at P < 0.001). The spatialisation of TSR at field scale was performed using the linear regression between TSR values and EMI signals. TSR spatialisation gave a more detailed view of CO2 emissions distribution within the vineyard. EMI technique could be a useful tool to compute accurately the global CO2 emissions which are a complex and hard to measure component of the agrosystem carbon balance.