Scaling sap flux measurements to whole-tree water use or stand-level transpiration is often done using measurements conducted at a single point in the sapwood of the tree and has the potential to cause significant errors. Previous studies have shown that much of this uncertainty is related to (i) measurement of sapwood area and (ii) variations in sap flow at different depths within the tree sapwood. This study measured sap flux density at three depth intervals in the sapwood of 88-year-old red pine (Pinus resinosa) trees to more accurately estimate water-use at the tree- and stand-level in a plantation forest near Lake Erie in Southern Ontario, Canada. Results showed that most of the water transport (65%) occurred in the outermost sapwood, while only 26% and 9% of water was transported in the middle and innermost depths of sapwood, respectively. These results suggest that failing to consider radial variations in sap flux density within trees can lead to an overestimation of transpiration by as much as 81%, which may cause large uncertainties in water budgets at the ecosystem and catchment scale. This study will help to improve our understanding of water use dynamics and reduce uncertainties in sap flow measurements in the temperate pine forest ecosystems in the Great Lakes region and help in protecting these forests in the face of climate change.

中文翻译：

---

温带红松人工林木质部液流径向变化

将树液通量测量缩放到整棵树的用水量或林分蒸腾量通常是使用在树边材中的单个点进行的测量来完成的，并且有可能导致重大错误。以前的研究表明，这种不确定性大部分与（i）边材面积的测量和（ii）树边材内不同深度的液流变化有关。本研究测量了 88 年树龄红松 (Pinus resinosa) 边材中三个深度间隔的液流密度，以更准确地估计南部伊利湖附近人工林的树木和林分用水量加拿大安大略省。结果表明，大部分水分运输（65%）发生在最外层边材，而只有26%和9%的水分运输在边材的中部和最深处。这些结果表明，如果不考虑树木内汁液通量密度的径向变化，可能会导致蒸腾量被高估高达 81%，这可能导致生态系统和流域规模的水预算存在很大的不确定性。这项研究将有助于提高我们对水资源利用动态的理解，减少五大湖区温带松树林生态系统液流测量的不确定性，并有助于在气候变化面前保护这些森林。