title: Seasonal changes in tissue-water relations for eight species of ferns during historic drought in California.
abstract: California experienced severe drought between 2012 and 2016. During this period, we compared seasonal changes in tissue-water relations among eight fern species in the Santa Monica Mountains of southern California 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 tissue-water relations including osmotic potential at saturation and the turgor loss point (Ψπ, sat and Ψπ, tlp), and measured, for two evergreen species, xylem-specific and leaf-specific hydraulic conductivity (Ks and Kl) and vulnerability of stem xylem to water stress-induced embolism (water potential at 50% loss hydraulic conductivity, Ψ50).
  
  
  
  Species grew in either riparian or chaparral understory. The five chaparral species had a wider range of seasonal water potentials, root depths, and frond phenological traits, including one evergreen, two summer-deciduous, and two desiccation-tolerant (resurrection) species. Evergreen species were especially diverse, with an evergreen riparian species maintaining seasonal water potentials above -1.3 MPa, while an evergreen chaparral species had seasonal water potentials below -8 MPa. In those two species the Ψ50 values were -2.5 MPa and -4.3 MPa, respectively.
  
  
  
  Observed differences in physiological performance among eight fern species reflected niche partitioning in water utilization and habitat preference associated with distinct phenological traits. We predict differential survival among fern species as future drought events in California intensify, with desiccation-tolerant resurrection ferns being the most resistant.
authors.affiliation: Pepperdine University 24255 Pacific Coast Highway, Malibu, California 90263 USA helenireneholmlund@gmail.com.
authors.forename: Helen I
authors.initials: HI
authors.lastname: Holmlund
authors.affiliation: Pepperdine University 24255 Pacific Coast Highway, Malibu, California 90263 USA.
authors.forename: Victoria M
authors.initials: VM
authors.lastname: Lekson
authors.affiliation: San Diego State University, 5500 Campanile Drive, San Diego, California 92182 USA.
authors.forename: Breahna M
authors.initials: BM
authors.lastname: Gillespie
authors.affiliation: Pepperdine University 24255 Pacific Coast Highway, Malibu, California 90263 USA.
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Nakamatsu
authors.affiliation: Berea College, 101 Chestnut Street, Berea, Kentucky 40403 USA.
authors.forename: Amanda M
authors.initials: AM
authors.lastname: Burns
authors.affiliation: Pepperdine University 24255 Pacific Coast Highway, Malibu, California 90263 USA.
authors.forename: Kaitlyn E
authors.initials: KE
authors.lastname: Sauer
authors.affiliation: University of California, Santa Cruz, 1156 High St, Santa Cruz, California 95064 USA.
authors.forename: Jarmila
authors.initials: J
authors.lastname: Pittermann
authors.affiliation: Pepperdine University 24255 Pacific Coast Highway, Malibu, California 90263 USA.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Davis
mesh_terms: D002140:California; D057231:Climate Change; D003890:Desiccation; D055864:Droughts; D017753:Ecosystem; D029624:Ferns / Q000378:metabolism*; D012621:Seasons; D013045:Species Specificity; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water
keywords: chlorophyll fluorescence; ferns; niche segregation; osmotic adjustment; pteridophyte; water utilization; xylem embolism