California's Superlative Trees: The Oldest

California is exemplified by many different landscapes: its sunny beaches, rolling vineyards, granite mountain cathedrals, and vibrant cities, to name a few.  But it is also home to a wide array of forests, which contain a few of the world's most amazing types of plants.  To me, it wouldn't be California without the trees!

While California's Coast Redwoods (Sequoia sempervirens) have earned the title of the world's tallest trees, and Giant Sequoias (Sequoiadendron giganteum) of the Sierra Nevada are the world's most massive, hands down the winner for the world's oldest trees - and indeed the world's oldest living single organism - goes to the White Mountains' ancient Great Basin Bristlecone Pines (Pinus longaeva).

While bristlecone pines are found across the Great Basin in parts of Nevada and Utah, the oldest specimens, many of which exceed 3,000 years, grow in the harsh conditions of eastern California's White Mountains.  The Methuselah Tree held the record, at 4,847 years of age, until another, older tree was discovered nearby in 2012 and found to be 5,065 years old.

To reach these venerable elders of the plant kingdom, Eric and I took a trip to the eastern side of the Sierra earlier this month.  From our home in the Great Valley, we traveled more than 9,000 vertical feet up and over Sonora Pass, winding leisurely up the gradual western slope before descending 3,000 feet down the steep eastern slope into the Great Basin (being thankful all the while we were not in a covered wagon, like the first pioneers of that pass!)  A couple hours of scenic driving south from Bridgeport on Highway 395 takes travelers past Mono Lake, June Lakes and Mammoth Lakes (our favorite place to camp and stay!), through Bishop to the small town of Big Pine, which sits at approximately 4,000 feet above sea level in the Owens River Valley.  Heading east out of Big Pine, the White Mountains loom large in front of travelers on Highway 168.  Just over 20 miles of paved road separates Big Pine from the Ancient Bristlecone Pine Forest, but don't be deceived: it is 20 of the most brutal miles of asphalt I have ever driven.  Because in those 20 miles, that steep, narrow, winding road gains 6,000 feet in elevation as it rises through pinyon-juniper woodlands, soaring to 11,000 feet above sea level.  I use the word "soar" intentionally: there were moments when a quick glance down into the valley below looked exactly like the view from an airplane, coming in to land!  Google Maps says the drive should take 45 minutes; it felt like it took us hours.  (Although, we did stop twice along the way to take in the incredible views.  And, birds.  No explanation required!)

After nearly an hour of crazy-steep, winding road, the pavement ends at the parking lot for Schulman Grove and the Ancient Bristlecone Pine Forest Visitor Center.  (The visitor center is temporarily closed due to COVID-19, but the bathrooms are still open; bring your own drinking water though.)  Those with stouter hearts and sturdier vehicles may wish to continue on to the Patriarch Grove, accessed via 13 additional miles of dirt road, which continues on past the Visitor Center.

We were content to park our car in the paved parking lot and set off to explore the Shulman Grove on foot.  Visitors with sturdy footwear and plenty of water can choose between the Discovery Trail, a one-mile loop, and the Methuselah Trail, a 4.5 mile loop that includes 900 feet of elevation gain.

The line between dolomite soils that support bristlecone pines is apparent in this photo. 
On the distant hill is more favorable soil for dense, shrubby alpine plants which prevent
bristlecone pine seedlings from establishing.

Here, at an elevation nearing 11,000 feet, the bristlecone pines that stand today have grown for several millennia on thin, nutrient poor dolomite soil.  Pale in color, dolomite is what gave the White Mountains their name.  A type of limestone, dolomite rocks were born around 650 million years ago as sediments settled on the floor of an ancient shallow sea, before they were gradually uplifted to create the mountain ranges of today.  Soil derived from dolomite is highly alkaline, making it inhospitable to most other plants.

Not only is the soil poor at these high elevations in the White Mountains, but the climate is also harsh.  Drought is extreme here, with annual average precipitation amounting to less than twelve inches, most of which falls as snow during the long winter.  The growing season of favorable temperature is very short, and almost completely dry.  Winters are frigid, with freezing winds whipping across the mountains, and summers are blazing hot, especially on the rocky south-facing slopes.  The white rocks reflect sunlight, which cools the underlying soil slightly but produces considerable glare.  (Wear your sunglasses!)

Bright white dolomite gave the White Mountains their name.

Bristlecone pines don't grow here because they like it; they grow here because in the fierce world of plant competition, they have little other choice.  Able to thrive where other plants cannot, bristlecone pine seeds germinate against all odds, sending up seedlings in an otherwise barren landscape where they can grow without becoming shaded out by other plants, and where other plants will not out-compete them for scarce water and soil nutrients.  A lack of understory around bristlecone pines also translates to a lack of fuel for wildfires.  The rocky, barren slopes surrounding these ancient trees provide a natural firebreak, protecting them from the ravages of lightning-ignited fires.

In fact, it is the harsh climate itself that enables bristlecone pines to attain such great ages. 

When researchers began searching for the very oldest of these ancient trees, they drew on experience from the western Sierra Nevada, where the oldest Giant Sequoias, those that were the tallest and most massive, were found in sheltered locations on moist north-facing slopes.  Searching similar areas in the White Mountains yielded curious results.  It turns out, the oldest bristlecone pines are found not in sheltered pockets of favorable climate and soil, but in the harshest conditions of the entire range: the highest elevations on south-facing slopes of thin, rocky soils where they receive blistering solar radiation, months of freezing cold, very little moisture, and fierce winds that blast the trees with either sand or ice nearly year-round.

But bristlecone pines stand in the face of all the trials of nature, and grow slowly on, turning adversity to advantage. 

Furthermore, the oldest bristlecone pines are not actually those that are the tallest or largest.  The oldest trees are those that are shorter, twisted, gnarled, and weather-beaten.

The oldest gnarled ancients seem to know that nothing good happens in a rush, and so they grow at exceedingly slow rates, putting on the smallest amount of new growth each year.  100 annual growth rings may be contained within one inch of wood, each ring no wider than a quarter of a millimeter!  But the wood they do produce is extremely hard, filled with resin, and resistant to fire, disease, insects and rot.  The trees that establish themselves in more favorable conditions (relatively speaking) grow faster, put on more wood annually, and attain greater heights, but they die at a younger age, succumbing to the disease or insects their ancient forefathers wisely grew to withstand.  (I feel like there's a good life lesson in there somewhere.)

The tiny, densely packed rings of an ancient Bristlecone Pine - with my index finger for scale.

In addition to the bristlecone pine's ability to withstand and even thrive in the harshest of climates, and the wisdom of growing slowly, these ancient survivors have a few other tricks up their sleeves that aid them in attaining mind-boggling lifespans.  The first of these adaptations for survival is the bristlecone pine's ability to conserve energy by retaining individual needles up to ten times longer than other pine trees.  While a typical pine might shed and regrow each needle every 4 to 6 years, bristlecone pines can hold on to individual, living, photosynthesizing needles for up to 40 years!

While most trees will die if the majority of their bark is removed, bristlecone pines are one of the few tree species that can continue to grow with just a small strip of life-giving bark connecting roots to limbs.  Up to 90% of a tree's bark may be removed and the tree will go right on growing, for centuries!  Many of the bristlecone pines in the Schulman Grove look dead, like bleached white sculptures of twisted wood: but they are not dead.  Look closely around the weathered trunk and you will spot a strip of living bark, running up the length of the tree and supplying water and nutrients to a remaining tuft of living branches.

Consistent with the trees' mantra of grow slow, grow old, the female cones of bristlecone pines take two years to mature.  After they are fertilized in their first year, second-year cones turn purple (or green, on some trees, showing genetic variation) and exude large amounts of sticky, sparkling sap.

While many plants growing in arid environments grow deep tap roots, reaching far down into the soil to access moisture buried below, the roots of bristlecone pines are quite shallow.  The shallow root system enables bristlecone pines to quickly capture soil moisture near the surface before it evaporates.

Perhaps the one disadvantage of growing so slowly bristlecone pines have encountered is the natural phenomena of erosion.  For such slow-growing and long-lived trees, the incremental erosion of soil throughout the many long years becomes a real threat.  If they live long enough, most of these trees will see the ground pulled out from underneath them by the forces of wind, water, ice, and gravity.  Scientists believe that once the shallow roots of these old trees are exposed, they become susceptible to disease and insect infestation.  It is supposed that erosion is the leading cause of death in the most ancient of trees.

But even dead trees are beautiful in their form, fascinating in their study, and valuable in providing scientists and dendrochronologists with a wealth of information.  By matching up the annual growth rings in living trees with those in dead trees and even dead wood (which decomposes extremely slowly), a continuous chronology has been laid out that stretches back 10,000 years or more into human history, nearly to the last ice age!  Tree ring data provides information on radio carbon dating and how the climate has changed in the past.  It also sketches a history of fire and floods, air quality changes, volcanic history, weather patterns, and more.  Tree ring data from bristlecone pines has enabled scientists to recalibrate radio carbon dating methods and determine more exact dates for ancient civilizations.  For example, these recalibrated dates show that metal working in Europe occurred even earlier than previously estimated.

An informative sign at the Schulman Grove illustrates how dendrochronologists match up tree rings
in living trees, dead trees, and dead wood to create a timeline of events stretching back over 10,000 years.

If you're hoping to snap a photo of the world's oldest living tree, aged just over 5,000 years, quell your expectations: no signs denote the oldest trees, in order to protect them from vandalism.

Content yourself with the knowledge that the world's oldest living organism is indeed out there, probably in front of your very eyes, if not somewhere just beyond the next white rocky ridge.  Take a moment to rest in the shadow of these ancient trees - I almost want to call them ancient "creatures," or even "beings," which I know they are not, but if you visit for yourself you might understand what I mean.  Take a moment to feel their bark, try to count their minuscule rings.  Pause to think about the harshness of the climate and the thousands of winter snows these elders of the plant kingdom have experienced, all the moonlit nights, blazing hot summer afternoons, rock slides, bird songs, and thunderstorms.

Think about all that these great trees have witnessed during their lives, quietly observing the long years of human history, storing the wisdom of the ages in their solid trunks.  Then again, the view from where these trees sit hasn't changed all that much through the millennia; perhaps they have watched the glaciers that lay between distant Sierran peaks shrink and diminish, as the trees have gazed west across the Owens Valley from their lofty perch in the White Mountains, but that's about it!

Like the trees, time slows to a near stand-still in the White Mountains, moving as slowly as the gnarled old sentinels that stand watch atop them.