Graduation Date

Fall 2020

Document Type



Master of Science degree with a major in Natural Resources, option Forestry, Watershed, & Wildland Sciences

Committee Chair Name

Lucy Kerhoulas

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Rebecca Hewitt

Second Committee Member Affiliation

Community Member or Outside Professional

Third Committee Member Name

Jasper Oshun

Third Committee Member Affiliation

HSU Faculty or Staff

Subject Categories



Water is often the most limiting resource in a plant’s environment. Plants that can maximize their ability to acquire water improve their chances of success. Outside of the traditional soil-plant-atmosphere continuum, plants can alternatively acquire water via foliar uptake of water and hydraulic redistribution (HR) of deep water. This study used greenhouse-based experiments to investigate water use and physiology in four conifer species native to the western U.S.: Picea sitchensis (Bong.) Carriére (PISI), Pseudotsuga menziesii (Mirb.) Franco (PSME), Sequoia sempervirens (D. Don) Endl. (SESE), and Thuja plicata Donn ex. D. Don (THPL). First, this work investigated the capacity for foliar water uptake using two different measurement methods (submersion in water versus exposure to water vapor in a fog chamber). Second, mesocosms were used to evaluate the capacity for HR of water and the possible effects of HR water on tree physiology. Analyses found that foliar uptake rates measured using a fog chamber were roughly three times greater than uptake rates measured using the submersion method. All species were capable of foliarly absorbing water; PSME generally had the greatest foliar uptake values while THPL had the lowest uptake capacity. Findings also suggested that PISI and SESE are capable of hydraulically lifting water and that this HR water can sustain plant water potential and stomatal conductance during drought, even for neighboring trees. Collectively, this work provides a methodological comparison of two commonly-used methods to measure foliar water uptake capacity and also demonstrates that two important western conifer species (PISI and SESE) are capable of hydraulically redistributing water to enhance physiology (water potential and stomatal conductance) in the trees lifting water as well as in neighboring trees. The use of waters that have been foliarly absorbed and/or hydraulically lifted and redistributed may become increasingly important for trees in the western U.S., as climate models project that this region will likely continue to warm and dry in the coming decades.

Citation Style



Thesis/Project Location