Abstract Detail

Pteridology

Holmlund, Helen [1], Lekson, Victoria [2], Gillespie, Breahna [3], Nakamatsu, Nicole [4], Burns, Amanda [5], Sauer, Kaitlyn [4], Pittermann, Jarmila [6], Davis, Stephen [4].

Differential Response of Eight Fern Species to Severe Drought in California.

Southern California has experienced unprecedented drought for the last three years. During this time, we characterized seasonal water relations in eight fern species in the Santa Monica Mountains. We predicted differential water utilization among the eight fern species based on differences in microhabitat and life history traits.
We monitored seasonal changes in midday water potential and midday dark-adapted chlorophyll fluorescence, and also compared pressure-volume parameters, including osmotic potential at saturation and osmotic potential at the turgor loss point. We further compared stipe hydraulics and vulnerability to xylem cavitation in two evergreen species occupying moist and dry microsites (xylem-specific conductivity, leaf-specific conductivity, and water potential at 50% loss of conductivity).
Significant differences in water relations were observed among the eight species examined. Seasonal water potential and fluorescence indicated four life history types relative to frond water utilization: evergreen, summer deciduous, fall deciduous, and resurrection. Evergreen species maintain functional fronds all year. Summer and fall deciduous species experience frond dieback at the beginning of the summer and fall, respectively. The fronds of the resurrection ferns abruptly desiccate at the onset of the dry season and revive following small rain events, as little as 5 mm. The two evergreen species exhibited the greatest difference in seasonal water utilization, with dehydration-tolerant Dryopteris arguta repeatedly exceeding midday water potentials of -8 MPa and dehydration-sensitive Woodwardia fimbriata never dropping below -2 MPa. These two species also showed significant differences in resistance to water stress-induced embolism of stem xylem. The water potential at 50% loss of conductivity was -4.3 MPa for D. arguta and only -2.5 MPa for W. fimbriata (P < 0.01).
These differences in the water relations, life history traits, and microhabitats appear to facilitate coexistence of the eight species in the same watershed in the Santa Monica Mountains. We anticipate differential mortality among these 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.

1 - University of California, Santa Cruz, Ecology and Evolutionary Biology, 1156 High Street, Santa Cruz, CA, 95064, USA
2 - Pepperdine University, Natural Science, 24255 Pacific Coast Highway, Malibu, CA, 90263
3 - San Diego State University, Ecology, 5500 Campanile Dr, San Diego, CA, 92182
4 - Pepperdine University, Natural Science, 24255 Pacific Coast Highway, Malibu, CA, 90263, USA
5 - Berea College, Biology, 101 Chestnut Street, Berea, KY, 40403
6 - University Of California, Integrative Biology, 1156 High Street, Santa Cruz, CA, 95064, USA

Keywords:
chlorophyll fluorescence
ferns
niche segregation
osmotic adjustment
water utilization
xylem embolism.

Presentation Type: Poster
Session: P, Pteridological Section/AFS Posters
Location: Exhibit Hall/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 5:30 PM This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PPD001
Abstract ID:133
Candidate for Awards:None