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1 July 2018 Post-Fire Ecophysiology of Endemic Chaparral Shrub Seedlings From Santa Catalina Island, Southern California
Anna L. Jacobsen, R. Brandon Pratt, Diana Alleman
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Island systems are generally more sensitive to the introduction of non-native species than comparable mainland systems and are particularly vulnerable to disturbances that create opportunities for invasion. We examined the impact of browsing by introduced deer on seedling establishment and physiology in three obligate seeding (i.e., non-resprouting) species on Santa Catalina Island for two years following a large fire in 2007: Arctostaphylos catalinae P. Wells (Ericaceae), Ceanothus arboreus E. Greene (Rhamnaceae), and Ceanothus megacarpus Nutt. var. megacarpus (Rhamnaceae). Four post-fire sites were established, with each site containing 12-20 plots exposed to browsing and 12-20 control plots protected from deer browsing. Browsing did not significantly affect seedling survival or physiology in C. arboreus, the only species to experience significant browsing; browsing did, however, significantly reduce seedling height. Predawn and midday water potentials, stomatal conductance, and growth differed among species during their first post-fire dry season. Arctostaphylos catalinae experienced the lowest dry season predawn water potentials (-3.3 MPa compared to -1.7 MPa for C. arboreus and -2.2 MPa for C. megacarpus). Ceanothus arboreus and C. megacarpus exhibited relatively high seedling survival (56% and 69%, respectively) and high resistance to xylem cavitation of stems (P50 = -6.0 and -6.7 MPa, respectively), compared to A. catalinae which had lower seedling survival (30%) and was less resistant to cavitation (P50 = -4.2 MPa). Browsing significantly impacted seedling height, which could impact stand structure. Differential browsing pressure and seedling resistance to water limitation may have important consequences for long-term distribution and abundance of these island endemics on Santa Catalina Island.

Anna L. Jacobsen, R. Brandon Pratt, and Diana Alleman "Post-Fire Ecophysiology of Endemic Chaparral Shrub Seedlings From Santa Catalina Island, Southern California," Madroño 65(3), 106-116, (1 July 2018).
Published: 1 July 2018

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