Year of Award

2024

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Geosciences

Department or School/College

Department of Geosciences

Committee Chair

Marco Maneta

Commitee Members

Solomon Dobrowski W. Payton Gardner Kelsey Jencso

Keywords

Ecohydrology, soil-plant-atmosphere continuum, ponderosa pine, osmotic potential

Publisher

University of Montana

Subject Categories

Hydrology | Plant Biology

Abstract

Most current ecohydrologic models simplify the hydraulics that are at play in plant-water relationships by assuming that the water content within the plant is static. In reality, plants have a relative water content that varies with time in response to environmental stresses. To some extent, variations in plant relative water content are regulated by changes in the osmotic potential of water within plant cells, which contributes to the resilience of plants during periods of water shortage. We present a model that simulates plant water transport and storage within the soil-plant-atmosphere continuum. The model incorporates the role of osmotic regulation in maintaining cell turgor pressure and reducing water losses via transpiration via a control on stomatal conductance. The model was calibrated and demonstrated for ponderosa pine seedlings (Pinus ponderosa) using data of water availability and plant hydraulic status collected during a greenhouse experiment. The model successfully captured plant water stress metrics like leaf water potential and soil water potential, while also accurately capturing plant water storage dynamics via variations in turgor pressure and relative water content. Further, we used simulated plant relative water content as an indicator of plant water stress and a predictor of seedling mortality. Modeled outputs show that the plant is able to maintain a relative water content of above .77 until extreme drought conditions, which reflects behavior of plants in the wild. Increasing the realism of plant hydraulic processes in ecohydrologic models is a necessary step to improve predictions of landcover change and landscape degradation caused by prolonged droughts and climate change.

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© Copyright 2024 Michael Kurt Kendree Jr.