TY - JOUR
T1 - Effects of sample size on sap flux-based stand-scale transpiration estimates
AU - Kume, Tomonori
AU - Tsuruta, Kenji
AU - Komatsu, Hikaru
AU - Kumagai, Tomo'omi
AU - Higashi, Naoko
AU - Shinohara, Yoshinori
AU - Otsuki, Kyoichi
PY - 2010/1
Y1 - 2010/1
N2 - In this study, we aimed to assess how sample sizes affect confidence of stand-scale transpiration (E) estimates calculated from sap flux (Fd) and sapwood area (AStree) measurements of individual trees. In a Japanese cypress plantation, we measured Fd and AS-tree in all trees (n = 58) within a 20 × 20 m study plot, which was divided into four 10 × 10 subplots. We calculated E from stand AS-tree (A S-stand) and mean stand Fd (JS) values. Using Monte Carlo analyses, we examined the potential errors associated with sample sizes in E, AS-stand and JS using the original AS-tree and F d data sets. Consequently, we defined the optimal sample sizes of 10 and 15 for AS-stand and JS estimates, respectively, in the 20 × 20 m plot. Sample sizes larger than the optimal sample sizes did not decrease potential errors. The optimal sample sizes for JS changed according to plot size (e.g., 10 × 10 and 10 × 20 m), whereas the optimal sample sizes for AS-stand did not. As well, the optimal sample sizes for JS did not change in different vapor pressure deficit conditions. In terms of E estimates, these results suggest that the tree-to-tree variations in Fd vary among different plots, and that plot size to capture tree-to-tree variations in Fd is an important factor. The sample sizes determined in this study will be helpful for planning the balanced sampling designs to extrapolate stand-scale estimates to catchmentscale estimates.
AB - In this study, we aimed to assess how sample sizes affect confidence of stand-scale transpiration (E) estimates calculated from sap flux (Fd) and sapwood area (AStree) measurements of individual trees. In a Japanese cypress plantation, we measured Fd and AS-tree in all trees (n = 58) within a 20 × 20 m study plot, which was divided into four 10 × 10 subplots. We calculated E from stand AS-tree (A S-stand) and mean stand Fd (JS) values. Using Monte Carlo analyses, we examined the potential errors associated with sample sizes in E, AS-stand and JS using the original AS-tree and F d data sets. Consequently, we defined the optimal sample sizes of 10 and 15 for AS-stand and JS estimates, respectively, in the 20 × 20 m plot. Sample sizes larger than the optimal sample sizes did not decrease potential errors. The optimal sample sizes for JS changed according to plot size (e.g., 10 × 10 and 10 × 20 m), whereas the optimal sample sizes for AS-stand did not. As well, the optimal sample sizes for JS did not change in different vapor pressure deficit conditions. In terms of E estimates, these results suggest that the tree-to-tree variations in Fd vary among different plots, and that plot size to capture tree-to-tree variations in Fd is an important factor. The sample sizes determined in this study will be helpful for planning the balanced sampling designs to extrapolate stand-scale estimates to catchmentscale estimates.
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U2 - 10.1093/treephys/tpp074
DO - 10.1093/treephys/tpp074
M3 - Article
C2 - 19822581
AN - SCOPUS:77950358510
SN - 0829-318X
VL - 30
SP - 129
EP - 138
JO - Tree physiology
JF - Tree physiology
IS - 1
ER -