三种方法测定高寒草甸生态系统蒸散比较

利用涡度相关技术(Eddy covariance technique)、小型蒸渗仪(Mini-lysimeter)和波文比-能量平衡法(BREB)对2005年和2006年夏季(7～8月份)青藏高原海北高寒草甸生态系统的昼间蒸散(E)变化进行了对比观测研究.在观测期间,存在能量不闭合现象,涡度相关系统测定的湍流通量相当于有效能量的73%.3种不同方法测定的蒸散量之间具有较好的相关性,涡度相关系统与小型蒸渗仪测定的蒸散量相关系数达0.96,与波文比法的结果相关系数为0.95.然而,波文比法计算的蒸散量最大,比涡度相关系统的观测值高43%;小型蒸渗仪法的测定值次之,比涡度相关法的观测值高19%;涡度相关法测算的蒸散值最小.研究结果表明,利用涡度相关技术测定该高寒草甸生态系统的潜热通量,可能会过小评价该生态系统的蒸散量.

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.