Anthony Ambrose photo
Giant sequoia grows in roughly 75 scattered groves between 5000 and 7000 feet on the west slope of the central Sierra Nevada. The Giant Forest grove in Sequoia National Park is at 6800 feet elevation and includes four of the five largest sequoia specimens, including the General Sherman tree, the world's largest tree.
In Giant Forest there are significant swampy meadows. The moisture and moderate climate provide optimal conditions for this tree. The largest trees I saw were found in flattish spots (that
figures, less runoff).
In a recent trip to Giant Forest (June 2018), I was fortunate to meet two forest ecologists who were taking core samples for the purpose of learning how water stress affects the health of giant sequoias. Over 4000 trees have been surveyed and 49 trees are being studied in depth. Relatively few giant sequoias died in the recent drought, and most of those in Giant Forest seem to be quite resilient. Of what I saw this year in the Sierra however, white firs (Abies concolor) and sugar pines (Pinus lambertiana) have fared the worst in these last few years of drought and fires.
For more about the study:
Excellent and dramatic post with more details about this program:
New egg-sized cones are green, while older brown cones also remain on the tree. Illustration is from Forest Trees of the Pacific Slope.
For many years it was believed necessary to suppress forest fires, but starting in the 1960s forestry professionals started to recognize that fires were a part of forest ecology, and were necessary to clear the forest floor and provide nutrients for seedlings. This is particularly true for giant sequoias. The trees' 1–2 foot thick, non-resinous bark protects them from all but the fiercest fires. Additionally they contain tannic acid, a chemical used in fire extinguishers (Arno), which also makes them undesirable to insects and fungi. All of the large, old trees have fire scars which often hollow out part of the base. They remain standing and vigorous, though ultimately, over centuries, the weakened base, coupled with storms, can topple the trees.
Giant sequoias can attain huge girth and great height (to 290 feet, though not as tall as coast redwoods), and can live over 3000 years. Their immense size is hard to comprehend when standing beneath or walking around. Likewise, I found it hard to get good photos of an entire tree, and even including people for scale proved inadequate.
Curiously, the wood of giant sequoia is very light, weak and brittle. Since it is highly resistant to decay, these gigantic and magnificent trees were cut down for shingles and fenceposts. Even worse, the trees often shattered when they fell to the ground.
A carpet of white ashes in a controlled burn east of Roads End in Kings Canyon National Park