Collaborative Research: Quantifying the amount and functional significance of long-term stored-water in trees

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Accurate modeling of water storage and fluxes in both natural and human-altered ecosystems is critical to managing global water resources under current-day and projected future climates. One important step towards accurate modeling involves determining how much water trees store, and how the amount of stored water varies through time and within tree organs. Another important step involves determining how stored water, and variations in stored water, affect the physiological behavior of individual trees and larger ecosystems. The investigators in this project will measure the amount of water stored in different organs of trees, determine how long water resides in these organs, and evaluate how long-term stored water affects whole-tree water use. The data collected will reveal novel information about how trees store and manage water, which will ultimately allow prediction of tree water storage and water movement through ecosystems in current and future climates. The study site in Idaho broadly represents many landscapes across the Intermountain West. Results from this study will be shared with local communities in the Snake River Plain region, and activities will involve students and faculty members from Tribal Colleges in the Pacific Northwest.Most models assume steady-state water flow through the soil-plant-atmosphere continuum. However, there is substantial storage of water in trees, and the residence times of water inside trees ranges from days to months. The total amount of stored water in trees and broader ecosystems, how long water resides in plants, and the ecohydrological implications of tree water storage are still not completely understood. Characterizing the duration of water storage and its impacts on tree ecohydrology are critical for improving hydrological models. The data collected in this study will be used to test the hypotheses that: (1) Water is stored in trees for many days, with differences in residence time correlating to species- and size-specific sapwood architecture and water-management strategies; (2) Stored water will buffer declines in water transport as soil moisture availability declines, at daily and seasonal timescales; (3) Inter-species differences in water storage and transport-buffering strategies will translate to differential responses in whole-tree water balance and fluxes due to changing climate in modeled scenarios. The work combines stable isotope tracers (deuterium), gas exchange, and hydraulic functional trait data collected in the field with process- and trait-based modeling to determine residence times of water in tree organs, how trees manage water storage and transport among organs, and how water storage regulates whole-tree water relations at hourly to monthly timescales.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.