Stand-scale transpiration estimates in a Moso bamboo forest: (I) Applicability of sap flux measurements

Abstract

The applicability of sap flux ( F d ) 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 F d measurements in Moso bamboos in a cut bamboo experiment. In addition, we analyzed how sample sizes affect the reliability of E estimates calculated from F d and conducting culm area ( A S_ b ). In the cut bamboo experiments, we found that F d 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 A S_ b ( A S_stand ) and mean stand F d ( J S ). Employing Monte Carlo analysis, we examined potential errors associated with sample size in E, A S_stand , and J S using an original dataset with A S_ b and F d measured for 40 and 16 individuals, respectively. Consequently, we determined the optimal sample size for both A S_stand and J S estimates as 11. The optimal sample sizes for J S were almost the same under different vapor pressure deficit and soil moisture conditions. The optimal sample size for J S 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.