Presentation Title

Seasonal changes in tissue water relations for eight species of ferns during historic drought in California

Presentation Type

Poster

Keywords

chlorophyll fluorescence; ferns; niche segregation; osmotic adjustment; water utilization; xylem embolism

Department

Biology

Major

Biology

Abstract

California experienced unprecedented drought between 2013 and 2015. During this period we compared seasonal changes in tissue water relations among eight fern species in the Santa Monica Mountains of southern California. Our objective was to elucidate differential mechanisms of drought survival and physiological performance during extreme water deficits.

We monitored seasonal changes in water potential (Ψmd) and dark-adapted chlorophyll fluorescence (Fv/Fm), assessed seasonal changes in tissue water relations including osmotic potential at saturation and the turgor loss point (Ψπ, sat and Ψπ, tlp), measured xylem-specific and leaf-specific hydraulic conductivity (Ks and Kl), and estimated, for two evergreen species, vulnerability of stem xylem to water stress-induced embolism (water potential at 50% loss hydraulic conductivity, Y50).

Although species grew within one watershed, they were spatially separated, occupying narrow microsites and displaying differences in water utilization. Among eight species possessing four life history types, three evergreen ferns displayed the greatest disparity in seasonal dehydration, with riparian species maintaining seasonal water potentials above -2 MPa while an upland species repeatedly declined below -8 MPa. Consistent with this disparity, Ψ50 for riparian ferns were -2.5 MPa compared to -4.3 MPa for the upland species.

Observed differences in physiological performance among eight fern species reflected niche segregation in water utilization and habitat preference associated with distinct life history traits. We predict differential survival among fern species as future drought events in California intensify, with desiccation-tolerant resurrection ferns being the most resistant and evergreen dehydration-tolerant ferns the most vulnerable.

Faculty Mentor

Stephen D. Davis

Funding Source or Research Program

Summer Undergraduate Research in Biology

Location

Waves Cafeteria

Start Date

1-4-2016 2:00 PM

End Date

1-4-2016 3:00 PM

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Seasonal changes in tissue water relations for eight species of ferns during historic drought in California

Waves Cafeteria

California experienced unprecedented drought between 2013 and 2015. During this period we compared seasonal changes in tissue water relations among eight fern species in the Santa Monica Mountains of southern California. Our objective was to elucidate differential mechanisms of drought survival and physiological performance during extreme water deficits.

We monitored seasonal changes in water potential (Ψmd) and dark-adapted chlorophyll fluorescence (Fv/Fm), assessed seasonal changes in tissue water relations including osmotic potential at saturation and the turgor loss point (Ψπ, sat and Ψπ, tlp), measured xylem-specific and leaf-specific hydraulic conductivity (Ks and Kl), and estimated, for two evergreen species, vulnerability of stem xylem to water stress-induced embolism (water potential at 50% loss hydraulic conductivity, Y50).

Although species grew within one watershed, they were spatially separated, occupying narrow microsites and displaying differences in water utilization. Among eight species possessing four life history types, three evergreen ferns displayed the greatest disparity in seasonal dehydration, with riparian species maintaining seasonal water potentials above -2 MPa while an upland species repeatedly declined below -8 MPa. Consistent with this disparity, Ψ50 for riparian ferns were -2.5 MPa compared to -4.3 MPa for the upland species.

Observed differences in physiological performance among eight fern species reflected niche segregation in water utilization and habitat preference associated with distinct life history traits. We predict differential survival among fern species as future drought events in California intensify, with desiccation-tolerant resurrection ferns being the most resistant and evergreen dehydration-tolerant ferns the most vulnerable.