Changes in soil carbon are difficult to measure directly because carbon amounts in the soil are large and highly variable, and any expected changes are relatively small. Newer approaches therefore use eddy-covariance measurements to track short-term changes of soil carbon. Mr Puche developed a detailed mechanistic ecosystem model that incorporated detailed representation of photosynthesis, transfers of energy, carbon and nutrients, and farm management practices. The model was designed to test the reliability of these measurements, and to better understand soil carbon behaviour under grazed dairy pastures in New Zealand. After parameterisation, the model achieved good performance that showed that the key biophysical drivers of the system were well modelled. This study then identified systematic omission of carbon losses of considerable magnitude by eddy-covariance measurements when grazing animals were near the measurement tower, which led to biased estimates of the farm’s carbon balance. His modelling work rectified that problem. 