Energy and CO2 exchanges over vineyard using micrometeorological techniques

The contribution of soil and vegetation CO2 fluxes to global carbon balance in tree and vine crop ecosystems needs investigation. In the last decade, the eddy covariance (EC) technique was accepted as a standard for estimating carbon and water vapour exchanges by all international flux networks. EC provides a direct measurement of energy and mass flux that uses high frequency measurements of scalars and the vertical component of wind speed. The newer surface renewal (SR) method, however, offers an alternative technique to measure fluxes. This paper reports the results from flux experiments conducted during 2005 over a vineyard ecosystem located in Tuscany (central Italy) during the fruit set and veraison phenological stages. Half-hourly measurements of carbon dioxide (Fc) and latent heat (LE) fluxes were made using an EC system. Estimates of Fc and LE fluxes were also obtained using the SR method. In addition, net radiation (R n) and soil heat flux (G) density data were collected, and the energy balance closure was good. Partitioning of available energy into sensible heat flux H and LE was related to weather conditions and irrigation applications. The Bowen ratio values varied from 0.3 to 0.5 indicating that the plant water status was good. Daytime F c values ranged between -5 and -8 ?mol CO2 m-2 s- 1, and the daily net C budget was positive, showing that the vineyard was a sink for C over the period studied.