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1 April 2006 AGE AND POPULATION STRUCTURE OF JOSHUA TREES (YUCCA BREVIFOLIA) IN THE NORTHWESTERN MOJAVE DESERT
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Abstract

Many desert perennials are long-lived, but there are few data on ages or population structures of desert plants. We used 2 methods to estimate ages of a population of Yucca brevifolia (Joshua tree) in southwestern Utah from a 14-year census of plant sizes. Plant height at the 1st census ranged from 0.08 m to 6.0 m, and trees grew in height at a mean rate of 3.75 cm · yr−1. Plants also increased slowly in basal diameter (0.142 cm · yr−1) and branch length (0.024 m · yr−1), but basal diameter varied greatly from year to year, with many plants decreasing in diameter between sequential censuses. Forms of a nonlinear growth equation (the Richards function) did not fit the data on growth in height, but a simple linear relationship fit the data well. Using height as a linear predictor of age, we estimated that ages of a sample of 69 Joshua trees ranged from <20 to >300 years old, with 75% of the trees between 20 and 100 years and 11% over 150 years old. These data support the assumption that Joshua trees are indeed long-lived.

Kimberly D. Gilliland, Nancy J. Huntly, and J. E. Anderson "AGE AND POPULATION STRUCTURE OF JOSHUA TREES (YUCCA BREVIFOLIA) IN THE NORTHWESTERN MOJAVE DESERT," Western North American Naturalist 66(2), 202-208, (1 April 2006). https://doi.org/10.3398/1527-0904(2006)66[202:AAPSOJ]2.0.CO;2
Received: 16 March 2004; Accepted: 1 June 2005; Published: 1 April 2006
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