An exceptional dataset for over 12,000 Carnegiea gigantea collected by the Arizona Department of Game and Fish over two field seasons on a restricted military reservation was released to the authors for analysis, including a variety of variables for which little empirical evidence exists. Data on epidermal browning, physical damage due to fire, lightning, gunshot or topping, rodent girdling, bird cavities and other variables were assessed using primarily chi-square analysis. The main findings of this study include: (1) Plants with high amounts of epidermal browning were rather evenly distributed across height classes, although the very smallest plants (0–0.9 m) had substantially less epidermal browning. (2) Although past work has shown that epidermal browning is surely a function of solar radiation receipt, other variables (bird cavities, girdling, damage, branching) are statistically linked with browning, raising the possibility that other biotic and abiotic factors may hasten browning. (3) Bird cavities are better predicted by height than branches, likely due to decreased visibility and exposure to thermally tempering winds caused by branches, and improved defensive position and reduced exposure to heating from the surface associated with taller plants.
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1 January 2014
Relationships Between Epidermal Browning, Girdling, Damage, and Bird Cavities In a Military Restricted Database of 12,000 Plants of the Keystone Carnegiea gigantea In the Northern Sonoran Desert
Taly Dawn Drezner
Vol. 61 • No. 1
Vol. 61 • No. 1