Calibration of sap flow techniques using the root-ball weighing method in Japanese cedar trees
Calibration of sap flow techniques using the root-ball weighing method in Japanese cedar trees
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DOI：
10.1007/s00468-022-02325-w
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发表时间：
2022-07
期刊：
影响因子：
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通讯作者：
S. Iida;S. Takeuchi;K. Shinozaki;M. Araki
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文献类型：
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作者：
S. Iida;S. Takeuchi;K. Shinozaki;M. Araki
sap流量技术采用根球称重法，在不切割茎的情况下评估实际蒸腾。我们的结果与切割段实验相似，这意味着茎切割对校准的影响有限。近年来，越来越多的研究报道了使用液流技术的低估。这些研究使用了切割的茎段和由水柱或真空泵产生的人工树液通量密度，这表明实验室校准结果与活树之间可能存在差异。本研究采用根球称重法对两种杉木幼树的热耗散法（TD）和热比法（HR）的液流技术进行了校正。将根系挖出并用一层不透水的薄膜包裹，然后使用大型电天平通过每棵树（包括根球）的日失重量来测量日蒸腾量。虽然在根球形成过程中，截根会减少蒸腾，但其对标定性能的影响可以忽略不计。根球称量法在适宜的供水条件下，可以测量出5 ~ 3个月的日蒸腾量。考虑到伤口效应是仔细估计的，HR法测量的树液通量密度有5.8%的轻微低估。TD方法低估了树液通量密度61.4%，利用新建立的校准曲线可以合理地修正。此外，新的校准曲线与先前报道的针叶树校准曲线一致，这意味着以前的切段校准可能适用于活树。进一步的根球实验是必要的，以提供全面的了解种内和种间差异的校准液流技术。
Key messageSap flow techniques are calibrated by root-ball weighing method evaluating actual transpiration without stem cutting. Our results are similar with cut-segment experiments implying limited effects of stem cutting on calibrations.AbstractIn recent years, an increasing number of studies have reported underestimations using sap flow techniques. These studies used cut stem segments and artificial sap flux density generated by water columns or vacuum pumps, which suggests the possible differences between the laboratory calibration results and living trees. Here we used the root-ball weighing method to calibrate the sap flow techniques of the thermal dissipation (TD) and the heat ratio (HR) methods for two young Japanese cedar trees (Cryptomeria japonica). The root systems were dug out and wrapped by an impermeable sheet, then the daily amount of transpiration was measured by the daily weight loss of each tree (including the root ball) using a large electrical balance. Although transpiration was reduced by cutting the roots during root-ball creation, its effect on the calibration performance was negligible. The root-ball weighing method could measure the daily amount of transpiration for > 3 months with suitable water supplies. Given that the wound effect was carefully estimated, the HR method measured the sap flux density with a slight underestimation of 5.8%. The TD method underestimated the sap flux density by 61.4%, which can be reasonably corrected using the newly established calibration curve. Moreover, it was confirmed that new calibration curve was consistent with previous calibration curves reported for conifer species, thus implying that the previous calibrations with cut segments are likely applicable for living trees. Further root-ball experiments are necessary to provide comprehensive understanding of intra- and interspecific differences in the calibration of sap flow techniques.