Comparison of three methods for measurement of evapotranspiration in an alpine meadow

The daytime evapotranspiration(E) was measured using the eddy covariance(EC) technique,the mini-lysimeter method,and the Bowen ratio-energy balance(BREB) method,in an alpine meadow ecosystem on the Qinghai-Tibetan plateau during the growing season of 2005 and 2006(Jul.-Aug.).The energy imbalance with a slope of 0.73 was found in this study.Results showed a significant correlation between the E measured with the three methods,with the correlation coefficient of 0.96 between the EC technique and the mini-lysimeter method,and 0.95 between the EC technique and the BREB method.However,the value of E measured by the BREB was the largest,which was 43% higher than that by the EC;whilst the E measured with the mini-lysimeter had the medium value,which was 19% higher than that by the EC.The results suggest that the E may be underestimated using the EC in this alpine meadow on the Qinghai-Tibet Plateau.