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31 August 2020 Dendrochronology of a Rare, Long-Lived Mediterranean Shrub
Ellis Q. Margolis, Keith Lombardo, Andrew Smith
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Ceanothus verrucosus (CEVE) is a globally rare, long-lived, chaparral shrub endemic to coastal southern California (CA) and northern Mexico. There is concern for CEVE persistence because of habitat loss, fire, and climate change, yet little is known about basic features of the plant, including whether it contains annual rings, plant age, and climate–growth response. Growth-ring analysis was challenging because of semi-ring-porous structure, false, and missing rings. We successfully crossdated CEVE annual rings, primarily from Cabrillo National Monument, CA, using a nearby Pinus torreyana chronology. The oldest living individual had 116 rings; the oldest inner-ring date was 1873; and most of the plants established between 1894 and 1905, all older than previous estimates. CEVE mortality occurred during a dry period from the late 1940s through the early 1960s. Correlations between age and stem measurements were weak to moderate (r = 0.10 to 0.56) posing challenges for field-based estimates of plant ages, which are important for population modeling. Variability in CEVE ring width had a strong positive correlation with prior cool-season (October–April) precipitation, yet 2- to 7-day warm-season precipitation events were recorded as rare false rings in multiple years, indicating extreme plasticity in cambial phenology and growth response to moisture.

Copyright © 2020 by the Tree-Ring Society
Ellis Q. Margolis, Keith Lombardo, and Andrew Smith "Dendrochronology of a Rare, Long-Lived Mediterranean Shrub," Tree-Ring Research 76(2), 61-73, (31 August 2020).
Received: 26 March 2020; Accepted: 15 May 2020; Published: 31 August 2020

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