Friday, August 2, 2013

Creeping at high altitude: dwarf pine (Pinus albicaulis)

The dwarf pine (Pinus albicaulis) occurs at high elevation— together with the tamarack pine (Pinus contorta) up to a height of 9,500 feet—and often by itself up to 12,000 feet. This pine, also named whitebark pine, is a key species and vital evergreen of high-altitude forest communities of western North America [1]. The extreme, almost alpine conditions, under which trees survive in those exposed locations, find their expression in the bowing, asymmetric or contorted tree sculptures; illustrated by the hemlock spruce (Tsuga mertensiana) and the Sierra juniper (Juniperus occidentalis). John Muir introduced the dwarf pine—found as a group of erect trees at lower elevation and as closer to the ground growing “dwarfs” at higher, frequently exposed sites—as follows [2]:
This species forms the extreme edge of the timber line throughout nearly the whole extent of the range on both flanks [of the Sierra Nevada]. It is first met growing in company with Pinus contorta, var. Murrayama, on the upper margin of the belt, as an erect tree from fifteen to thirty feet high and from one to two feet in thickness; thence it goes straggling up the flanks of the summit peaks, upon moraines or crumbling ledges, wherever it can obtain a foothold, to an elevation of from 10,000 to 12,000 feet, where it dwarfs to a mass of crumpled, prostrate branches, covered with slender, upright shoots, each tipped with a short, close-packed tassel of leaves.
John Muir, 1894.

Often occurring as krummholz, the dwarf pine is also called scrub pine or creeping pine. Small trees of this pine species served Muir as a sheltered campsite, where, during stormy nights, he “often camped snugly beneath the interlacing arches of this little pine. The needles, which have accumulated for centuries, make fine beds, a fact well known to other mountaineers, such as deer and wild sheep, who paw out oval hollows and lie beneath the larger trees in safe and comfortable concealment.” [2]

Keywords: conifers, Pinales, Pinaceae, natural history, Sierra Nevada.

References and more to explore
[1] Even Reed Larson: Status and Dynamics of Whitebark Pine (Pinus albicaulis Engelm.) Forests in Southwest Montana, Central Idaho, and Oregon, U.S.A. Dissertation, University of Minnesota, June 2009 [].
[2] John Muir: The Mountains of California. The Century Company, New York, 1894. Note: see pages 149 to 152  in the Penguin Classics Book print of 1985 with an introduction by Edward Hoagland.

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