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Accueil du site → Master → Etats Unis → 2020 → Evergreen, Semi-evergreen, and Deciduous Woody Plants in a Semi-arid Savanna : Photosystem Energy Dynamics and Near-canopy Remote Sensing with CCI/PRI

Texas A&M University (2020)

Evergreen, Semi-evergreen, and Deciduous Woody Plants in a Semi-arid Savanna : Photosystem Energy Dynamics and Near-canopy Remote Sensing with CCI/PRI

Raub, Harrison Donald

Titre : Evergreen, Semi-evergreen, and Deciduous Woody Plants in a Semi-arid Savanna : Photosystem Energy Dynamics and Near-canopy Remote Sensing with CCI/PRI

Auteur : Raub, Harrison Donald

Université de soutenance : Texas A&M University

Grade : Master of Science (MS) 2020

Résumé partiel
Woody encroachers have transformed the Southern Great Plains across its semi-arid regions. Little is known how these encroachers—particularly the drought tolerant Juniperus—may be vulnerable to hotter temperatures and water limitations in future climate projections and how that will affect their light utilization for photosynthesis and dissipation of excess energy. Additionally, photosynthetic changes in drylands are not adequately captured with remote sensing partly due to use of greenness indices in the presence of evergreens. Responses among three co-occurring encroachers to seasonal water-limitations were compared using photosynthetic rates, energy partitioning of absorbed light, and sustained energy dissipation, while the recently created Chlorophyll Carotenoid Index (CCI) was tested to track the photosynthetic phenology of trees varying in leaf persistence. Declining stem water potential (-5 MPa) during the summer dry period elicited strong photochemical stress in J. ashei. The actual quantum yield for PSII decreased to 4%, regulatory light-induced energy dissipation increased to 84%, while the maximal quantum yield of PSII in a dark-adapted condition (Fv/Fm) declined to 75% from sustained dissipation. Photochemical stress was less severe in the drought avoiders with neither decreasing in Fv/Fm, while regulatory light-induced dissipation increased to 43% in Prosopis glandulosa and Quercus fusiformis remained near 50%. Consequently, water stress elicited stronger photochemical stress in J. ashei relative to the other two drought avoiders.

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Page publiée le 24 mai 2021