Stand-scale transpiration estimates in a Moso bamboo forest: (I) Applicability of sap flux measurements |
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Authors: | Tomonori Kume Yuka Onozawa Hikaru Komatsu Kenji Tsuruta Yoshinori Shinohara Toshihiro Umebayashi Kyoichi Otsuki |
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Affiliation: | 1. School of Forestry and Resource Conservation, National Taiwan University, Taipei 106-17, Taiwan;2. Kasuya Research Forest, Kyushu University, Sasaguri, Fukuoka 811-2415, Japan;3. Fukuoka Prefecture, Hakata-ku, Fukuoka 812-8577, Japan;4. National Agricultural Research Center, Kannondai, Tsukuba, Ibaraki 305-8666, Japan |
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Abstract: | The applicability of sap flux (Fd) measurements to bamboo forests has not been studied. This study was undertaken to establish an optimal and effective design for stand-scale transpiration (E) estimates in a Moso bamboo forest. To this aim, we validated Fd measurements in Moso bamboos in a cut bamboo experiment. In addition, we analyzed how sample sizes affect the reliability of E estimates calculated from Fd and conducting culm area (AS_b). In the cut bamboo experiments, we found that Fd measurement using a 10 mm probe was a valid means of determining the water-use behavior of a Moso bamboo, although a specific correction was needed. Furthermore, we calculated E from stand AS_b (AS_stand) and mean stand Fd (JS). Employing Monte Carlo analysis, we examined potential errors associated with sample size in E, AS_stand, and JS using an original dataset with AS_b and Fd measured for 40 and 16 individuals, respectively. Consequently, we determined the optimal sample size for both AS_stand and JS estimates as 11. The optimal sample sizes for JS were almost the same under different vapor pressure deficit and soil moisture conditions. The optimal sample size for JS at the study site was less than that of a coniferous plantation in the same region probably owing to small individual-to-individual variations in sap flux in the Moso bamboo forest. Our study concludes that sap flux measurements are an applicable technique for assessing water use in Moso bamboo forests. |
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Keywords: | AG, Ground area AS_stand, Sectional area of stand culms AS_b, Sectional area of individual culms CV, Coefficient of variation Dmax, Daily maximum VPD dCV/dn, Changes in CV in accordance with n dTmax, Maximum temperature difference between the two probes E, Stand-scale transpiration ΔE/E, Potential error in E estimate due to sample size DBH, Diameter at breast height Fd, Sap flux Fd_ave, Specific sap flux averaged over culm area (= Q/AS_b) Fd_up, Sap flux calculated from water uptake measured in cut bamboo experiments JS, Mean stand sap flux LAI, Leaf area index n, Sample size PDF, Probability density function Q, Whole bamboo sap flux Rs, Solar radiation SD, Standard deviation VPD, Vapor pressure deficit |
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