科研成果

Partitioning oak woodland evapotranspiration in the rocky mountainous area of North China was disturbed by foreign vapor, as estimated based on non-steady-state 18O isotopic composition

发布时间:2015-02-13点击率:1063

作者:ShouJia Sun, Ping Meng*, JinSong Zhang, Xianchong Wan, Ning Zheng, Chunxia He

期刊:Agricultural and Forest Meteorology

发表时间:2014年

卷.期.页码:184:36-47

摘要:

In terrestrial ecosystems, partitioning ecosystem-scale evapotranspiration (ET) between plant transpirationand soil evaporation remains a technical challenge. In this paper, we used a newly-developedlaser-based isotope analyzer (OA-ICOS) and the Keeling plot approach to partition ET components of a Quercus variabilis plantation in a lithoid hilly area of north China. The results showed that, on day-ofyear(DOY) 254, 257, and 263, the modeled leaf water 18O composition (δL,b) and observed leaf water 18O composition (δL,b) were in substantial agreement and had a significant linear correlation with coef-ficient of 0.96, indicating that Keeling plot approach and Graig–Gorden model can be used in portioning ET between plant transpiration and soil evaporation in a terrestrial forest ecosystem. Isotopic partitionrevealed that the percent contribution of transpiration to total ET increased from the morning, reachedmaximum values at noon, with maximum values of 91.19%, 86.30%, and 85.37% for DOY 254, 257, and263, respectively, indicating the transpiration from Q. variabilis Blum contributed the most to the totalET in this forest ecosystem. On DOY 260, the stability stratification was unstable, which resulted fromthe foreign vapor concentration. The increased vapor concentration led to a 80.83% difference between δsL,b and δL,b. The correlation coefficients between δsL,b and δL,b decreased from 0.96 to 0.43 when dataseton DOY 260 was included, indicating foreign vapor increased the uncertainty in the estimation of δ18O of ET (δET) and δ18O of transpiration (δT) in the forest ecosystem. Path analysis results suggested thatwater vapor concentration was the major factor influencing the partitioning of ET with isotopic approachin the forest ecosystem. Since the increased water vapor concentration and decreased atmosphere δ18O disturbed the estimation of δE, δT, δET, the isotopic approach cannot be used in partitioning ET underthis condition on DOY 260. Therefore, under most circumstances the isotopic approach can be used topartition ET for forest ecosystem in a non-steady state (NSS), while water vapor concentration may causeuncertainties.