Bristlecones grow slowly to survive millennia

By Jeff Mitton

Bristlecone pines are emblematic of the highest and windiest peaks in the west, the last refuges of wilderness.

Their iconic status is, I suppose, attributable to our fascination with superlatives: biggest, smallest, highest and deepest. Great Basin bristlecone pines, Pinus longaeva, are the oldest living trees clinging to the highest mountains.

Bristlecones are restricted to high elevations, between 9,500 and 11,500 feet in California, Nevada and Utah. Within this range, they occupy drier sites. For example, they do not occur on the western side of the Sierra, which receives abundant precipitation when relatively warm, moist air from the Pacific rises over the peaks.

But bristlecones are found in the rain shadow of the Sierra, in the White Mountains of eastern California and on the highest peaks of the Great Basin.

While they may cover an elevational range of nearly 2,000 feet, the majestic trees, the biggest and oldest, are restricted to the very highest elevations, where thin, rocky soil collects between patches of exposed bedrock and solid outcrops. They grow larger and survive longer in these harsh, well-drained sites than at lower elevations, where winds are less destructive, soils are deeper and moisture is more abundant.

Three sites are famous for trees exceeding 4,000 years of age. In the White Mountains of eastern California, east of Bishop, ancient trees endure in the Schulman Grove at 10,000 feet and the Patriarch Grove at 11,200 feet. In the Snake Range of eastern Nevada, a bristlecone grove extends from 9,500 feet to over 11,000 feet on Wheeler Peak in Great Basin National Park.

At 10,750 feet, a tree only 17 feet tall had a circumference of 21 feet and the extraordinary age of 4,900 years. It is astounding to appreciate that these trees were seedlings when the Bronze Age was beginning in China and Stonehenge was under construction.

I ate my lunch in the shade of the Patriarch in Patriarch Grove in September, while watching Clark's nutcrackers probe bristlecone cones for the last seeds of the season. The Patriarch is noted as the largest of the bristlecone pines, with a modest height of 41 feet but an immense girth of 37 feet.

However, a realization came over me that day -- the Patriarch is not a single tree, but a number of stems that have grown together. I suspect that seedlings from several Clark's nutcracker seed caches coalesced into a dense growth, fusing to resemble a single tree. Nevertheless, it is a grand structure and its oldest stems might be ancient.

I mentioned superlatives and described bristlecones as oldest and highest, but I will offer another, with little or no hope of consensus. Ancient Great Basin bristlecones are the most beautiful trees in North America.

They are short and thick with numerous tortured, twisting branches and dark green foliage flecked with resin. But that is their initial form, before centuries or millennia of the vicissitudes of life on talus slopes beneath fracturing cliffs. The occasional rocks ricocheting downhill damage trunks or splinter branches.

Lightning strikes boil the resin and explode the bark, exposing naked wood. Then grit or ice crystals blown by wind sculpt and polish the wood to enhance delicate textures and reveal lustrous hues ranging from cream through yellow to deep reddish brown and black.

Many of the larger trees survive with most of the bark missing from the trunk and just a single strip of bark ascending to nourish a growing branch producing resinous cones.

These immense, ancient trees, enduring in harsh and extreme environments in starkly and intricately sculpted forms, evoke serenity and awe. A quiet stroll in an ancient grove turns one's thoughts inward and far back in time and instills something akin to reverence.

Jeff Mitton (mitton@colorado.edu) is a professor in the Department of Ecology and Evolutionary Biology at the University of Colorado. This column originally appeared in the Boulder Camera.

February 2012