| Crop-fallow is a major cropping system used to conserve soil moisture and maintain stable yield in semi-arid regions, but there is still uncertainty about net CO2 exchange by this ecosystem. Examining the energy and CO2 transfers within this cropping system is therefore important for calculating agricultural sources and sinks of carbon. The objective of this paper is to study the energy and CO2 transfers, carbon balance, soil carbon dynamics over a barley-fallow rotation in Lethbridge. Simultaneous measurements of net radiation, sensible heat, latent heat and CO2 fluxes were made by two Bowen Ratio systems, which were used to test modeled results from the ecosystem model ecosys. Long-term soil carbon dynamics was predicted using ecosys, through which the effects of land use change and climate change on soil carbon were examined. Results indicates that crop-fallow is a net C source in drier years while a small sink in wetter years before harvest, but soil loses C in both cases after harvest, causing a negative NBP. |
