| Water can be stored in trees for days to months, but the precise duration of long-term stored water, and how it is linked with tree physiology is not known. I studied water movement in two tree species at the East Fork of Mink Creek Nordic Center in Southeastern Idaho by injecting deuterated water into conifer and deciduous trees, Pseudotsuga menziesii (Douglas fir), and Populus tremuloides (quaking aspen), respectively, to compare how long the tracer remained in trees of different hydraulic strategies. To do this, leaves were collected daily to weekly for several weeks after tracer water injection during the summer. The leaf water was then analyzed for hydrogen isotopes. As a follow-up study, I collected branch tips from two Douglas fir and two aspen at sub-daily timescales and analyzed those samples for hydrogen isotopes. For the first experiment, I hypothesized that the tracer would remain in both species for about a month, and that the tracer would have a longer residence time in the isohydric Douglas fir trees. For the subdaily study, I hypothesized that enrichment in D2O would occur in the middle of the day. In the first study, I found that the tracer resided in the trees for 7-11 days. The tracer reached the canopy leaves of aspen sooner and remained in them for a longer period of time compared to Douglas fir trees. In addition, tracer velocity and time to peak tracer concentration was faster in the aspen. Furthermore, there was no correlation between tracer velocity and sap flow. I found a pattern of enrichment at the midday measurement in the leaves in both species for the sub-daily study. |