Asking the pikas politely…
There is a need to better understand how mountain vegetation uses water to better predict both forest health and downstream water availability in a more drought-prone future. We use state-of-the-art high frequency stable isotope measurements to identify how rain and snowmelt infiltrate into and move through the soil, as well as how this water is taken up and used by plants, in the East River, Colorado. In June 2022, we installed an in-situ measurement system based on vapor probes to observe 2H, 18O, and 17O ratios of water in the soil, plants, and air. Specifically, we measured these isotope ratios at sub-daily frequency along three soil profiles down to 90 cm depth and in six trees (3 aspen and 3 Engelman spruce) using a cavity ring down spectrometer in the field. This sub-daily isotope data is unprecedented for the studied ecosystem and the very first application of the in-situ system in North America. In addition to this novel isotope technique, we instrumented the site with matric potential sensors along two soil profiles to observe subsurface water availability and the three investigated trees were equipped with sap flow sensors to measure transpiration flux. Meteorological data were gathered at nearby weather stations and by the SAIL campaign, a DOE ARM site close to our instrumented forest.