title: Structural determinants of increased susceptibility to dehydration-induced cavitation in post-fire resprouting chaparral shrubs.
abstract: It is well established that transpiration and photosynthetic rates generally increase in resprouting shoots after fire in chaparral shrublands. By contrast, little is known about how plant hydraulic function varies during this same recovery period. We hypothesized that vascular traits, both functional and structural, would also shift in order to support this heightened level of gas exchange and growth. We examined stem xylem-specific hydraulic conductivity (Ks) and resistance to cavitation (P50) for eight chaparral shrub species as well as several potential xylem structural determinants of hydraulic function and compared established unburned plants and co-occurring post-fire resprouting plants. Unburned plants were generally more resistant to cavitation than resprouting plants, but the two groups did not differ in Ks. Resprouting plants had altered vessel structure compared with unburned plants, with resprouting plants having both wider diameter vessels and higher inter-vessel pit density. For biomechanics, unburned plants had both stronger and denser stem xylem tissue than resprouting plants. Shifts in hydraulic structure and function resulted in resprouting plants being more vulnerable to dehydration. The interaction between time since disturbance (i.e. resprouting versus established stands) and drought may complicate attempts to predict mortality risk of resprouting plants.
authors.affiliation: Department of Biology, California State University, Bakersfield, 9001 Stockdale Highway, Bakersfield, CA, 93311, USA. ajacobsen@csub.edu.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Jacobsen
authors.affiliation: Department of Natural Sciences, University of Houston-Downtown, One Main Street, Houston, TX, 77002, USA.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Tobin
authors.affiliation: Department of Biology, California State University, Bakersfield, 9001 Stockdale Highway, Bakersfield, CA, 93311, USA.
authors.forename: Hayden S
authors.initials: HS
authors.lastname: Toschi
authors.affiliation: Department of Biology, California State University, Bakersfield, 9001 Stockdale Highway, Bakersfield, CA, 93311, USA.
authors.forename: Marta I
authors.initials: MI
authors.lastname: Percolla
authors.affiliation: Department of Biology, California State University, Bakersfield, 9001 Stockdale Highway, Bakersfield, CA, 93311, USA.
authors.forename: R Brandon
authors.initials: RB
authors.lastname: Pratt
mesh_terms: D001696:Biomechanical Phenomena; D003681:Dehydration / Q000378:metabolism; D005390:Fires; D057446:Hydrodynamics; D010788:Photosynthesis; D018526:Plant Transpiration; D010944:Plants / Q000033:anatomy & histology / Q000378:metabolism*; D013997:Time Factors; D052584:Xylem / Q000378:metabolism
keywords: chaparral; embolism; modulus of rupture; pit area; pit membrane; vessel density; vessel diameter; vessel element length; vessel length; vulnerability to cavitation