Azimuthal and radial variations in sap flux density and effects on stand-scale transpiration estimates in a Japanese cedar forest

Yoshinori Shinohara, Kenji Tsuruta, Akira Ogura, Fumikazu Noto, Hikaru Komatsu, Kyoichi Otsuki, Toshisuke Maruyama

研究成果: Contribution to journalArticle査読

41 被引用数 (Scopus)

抄録

Understanding radial and azimuthal variation, and tree-to-tree variation, in sap flux density (Fd) as sources of uncertainty is important for estimating transpiration using sap flow techniques. In a Japanese cedar (Cryptomeria japonica D. Don.) forest, Fd was measured at several depths and aspects for 18 trees, using heat dissipation (Granier-type) sensors. We observed considerable azimuthal variation in Fd. The coefficient of variation (CV) calculated from Fd at a depth of 0-20 mm (F d1) and Fd at a depth of 20-40 mm (Fd2) ranged from 6.7 to 37.6% (mean = 28.3%) and from 19.6 to 62.5% (mean = 34.6%) for the azimuthal directions. Fd at the north aspect averaged for nine trees, for which azimuthal measurements were made, was obviously smaller than F d at the other three aspects (i.e., west, south and east) averaged for the nine trees. Fd1 averaged for the nine trees was significantly larger than Fd2 averaged for the nine trees. The error for stand-scale transpiration (E) estimates caused by ignoring the azimuthal variation was larger than that caused by ignoring the radial variation. The error caused by ignoring tree-to-tree variation was larger than that caused by ignoring both radial and azimuthal variations. Thus, tree-to-tree variation in Fd would be more important than both radial and azimuthal variations in Fd for E estimation. However, Fd for each tree should not be measured at a consistent aspect but should be measured at various aspects to make accurate E estimates and to avoid a risk of error caused by the relationship of Fd to aspect.

本文言語英語
ページ(範囲)550-558
ページ数9
ジャーナルTree physiology
33
5
DOI
出版ステータス出版済み - 5 2013

All Science Journal Classification (ASJC) codes

  • 生理学
  • 植物科学

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