Dynamics of water transport and storage in conifers studied with deuterium and heat tracing techniques

The volume and complexity of their vascular systems make the dynamics of long-distance water transport in large trees difficult to study. We used heat and deuterated water (D 2 0) as tracers to characterize whole-tree water transport and storage properties in individual trees belonging to the coniferous species Pseudotsuga menziesii ( Mirb.) Franco and Tsuga heterophylla (Raf.) Sarg. The trees used in this study spanned a broad range of height (13.5-58 m) and diameter (0.1.4-L43 m). Sap flow was monitored continuously with heat dissipation probes near the base of the trunk prior to, during and following injec-tion of D20. The transit time for D20 transport from the base of the trunk to the upper crown and the tracer resi-dence time were determined by measuring hydrogen iso