Persistence of Lodgepole Pine Forests in the Central Sierra Nevada

Parker, Albert

I examined the age and size structure of six stands of lodgepole pine (Pinus contorta ssp. murrayana) across the species' elevational range (2000-3000 m) in the central Sierra Nevada. For all six stands I found strong positive correlations between diameter and age, plus diameter class distributions that closely fit a negative exponential curve. The horizontal pattern of stems, measured by Morisita's index of dispersion, indicates random dispersion of trees but strong aggregation of seedlings in small clumps (10-80 m2). The scale of this clumping suggests that tree-falls may often create regeneration sites for lodgepole pine. Pinus contorta apparently persists indefinitely in these stands by continuous successful establishment despite the virtual absence of crown fires. These features of the size and age structure contrast with the relatively even-aged structure and unimodal or bimodal diameter distribution commonly reported for lodgepole pine (P.c. ssp. latifolia) in the Rocky Mountains. Such differences in stand structure between mountain ranges may be related to regional differences in site productivity as well as in the scale and frequency of disturbance (tree-fall gaps in the Sierra Nevada vs. crown fires in the Rocky Mountains.

Persistence of Lodgepole Pine Forests in the Central Sierra Nevada

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