干旱区生态环境知识资源中心

A correct determination of actual evapotranspiration (ET) is known to be a key factor for establishing irrigation strategies in semi-arid areas. Vineyards are a challenging crop at this point since water use is controlled by plants and the soil surface. A better understanding of the contributions of the vine transpiration (T) and soil evaporation (E) to the total ET is then required. Two-source energy balance models (TSEB) allow for this partition using component radiometric temperatures, together with ancillary meteorological data, as inputs. Even though widely applied and validated in terms of total fluxes, the lack of measures of isolated components made it difficult to draw conclusions about the performance of TSEB models in terms of ET partition into soil E and canopy T. An experiment was conducted in a vineyard in Barrax, Central Spain, in 2013 with the aim of testing the potential of TSEB models to predict plant transpiration. A set of thermal-infrared radiometers (IRTs) were mounted in the middle of a row, standing on a 9-m(2) monolithic weighing lysimeter. In a first phase of the experiment the soil surface below the vines remained covered by a waterproof canvas to annul soil evaporation. Ancillary information of air temperature, humidity, wind speed and solar radiation was also registered, and all data were collected and stored in 15-min averages. Hourly and daily energy fluxes were calculated. Results showed an average estimation error of 0.7 mm d(-1) in vine transpiration. In a second phase, comparison between ET measures and modeled transpiration gave some insight into the ratio E/T once the canvas was removed.