– by Dr Bharti Raizada
July 17, 2017: People all over the globe believe that trees, particularly big and old trees- are a symbol of forgiveness, gratefulness, wisdom, strength, endurance. Some of these trees in different countries and religions are- Bodhi tree in India, The Major Oak in England. The Great Sugi in Japan, The Baobab in Africa, Tane Mahuta in New Zealand, El Tule in Mexico. In Hinduism, some trees are considered eternal and wishful filling or Kalpvriksh.
Recently, I visited Sequoia National Park in California, USA. George Stewart led the movement to create Sequoia National Park and in 1890 Congress agreed to this idea.
Sequoia trees are mainly found in Sierra Nevada mountain range between 5,000- 7,000 feet. Above 7,500 feet temperature is too cold and below 5,000 feet it is too dry for Sequoias to grow. These trees are protected resource. Sequoia trees are conifers but it differs from other conifers in that its trunk remains thick far up the tree giving it a columnar shape and huge bulk. This large volume makes them world’s largest trees.
Sequoia trees can grow up to 311 feet tall and 40 feet in width at base, 52,500 cubic feet volume, 1385 tons in weight i.e. more than four fully loaded jumbo jet airplanes. They live up to 3,200 years. Sequoias can grow in groups. The Three Graces and The Four Guardsmen are group of three and four sequoias respectively. These Sequoias are of same age.
Tiny male cones grow near tree tops. Late in winter, they release mists of yellow pollen onto the female cones hanging below. Female cones, small when pollinated, grow bigger and each cone holds 200 seeds tightly between its scales. 455 cones contain 91,000 seeds or one pound of seeds.
Mature sequoias carry thousands of female cones. About 2,000 new cones may grow each year. Cones can hang on the tree, sealed, for up to 20 years until something opens them. Thousands of seeds sprout in the ashy soil left by the fire. This soil absorbs and holds moisture well.
New roots easily penetrate it because it is loose and crumbly. The odds of a single tree to grow into a big sequoia are extremely small. The hazards to seed are—too deep forest litter preventing seed to reach soil, seed can land in bad spot and never sprouts, seed eaten by ground squirrel, seedling starts in shade and withers, if seeds are too crowded then they wither, fungus in soil kills seedling, if there is not enough rain then seedling dries out, cone with seeds taken home by someone. Sequoias produce million of seeds to increase the chances that a few will grow to maturity. Damage from ozone pollution shows up as a yellow spot on seedlings and this reduces the tree’s ability to create nutrients through photosynthesis.
Each tree ring marks one year of growth and records fire and weather conditions. The wider the ring the better the growing conditions- sun, water, and nutrients were plentiful. Tree growth is measured in rings per inch. Sequoias need frequent fires to reproduce. Their survival depends upon conditions created by natural processes. To grow Sequoia need moist, but not soggy soil throughout the summer. Most Sequoia saplings that grow in dense groups will die. Competition for light and moisture is too great. When fire thins these dense groups the survivors fill out.
Fire kills some sequoias but benefits many others-
- Heat opens cones on sequoias and seeds rain down
- Seeds land on clear soil fertilized by ash
- Heat kills insects and fungus that may attack seedlings
- Trees that compete for sunlight, moisture, and nutrients are killed
- Once burned, an area is less flammable for several years, giving seedlings a good start
Sequoia trees live for 3,000 years. Adaptation makes then live this long. The bark of the tree is up to two feet thick protects the living layer underneath it. The tannin, a reddish chemical, present in high concentrations in Sequoia bark, gives the Sequoia resistance to rot, boring insects, fungus, and fire. Thick bark with many air pockets insulates the wood from heat. The high branches hold foliage well above most fires. The sap is watery and not very flammable, so does not burn easily. When injured the tree heals and keep growing. Curved healing rings grow over wounds restoring the trees protective surface. Some trees may be burned hollow but survive for centuries. Rapid growth often occurs after fire. With competing trees burnt away, the surviving sequoias get more light, moisture, and nutrients. Trees may grow thicker annual rings for as long as 100 years. Tons of leaves, branches and tree trunks pile up on the forest floor each year. For tiny sequoia seeds, this dry and impenetrable deep layer is a sure death. They can not even start to grow. Fires clear this natural litter and leave behind better conditions for sequoia regeneration. Repeated ground fires usually leave a large triangular scar on the trunks. These scars limit the flow of water to the crown. The top dies, leaving a dead snag above massive branches and abundant foliage. Heat from fire dries out hanging Sequoia cones leading to cones opening and falling of millions of seeds.
Giant Sequoias need an enormous amount of water. By growing near the meadow but not in it, they can benefit. Their roots capture moisture as it drains toward the meadow. Sequoias shallow roots can support a giant tree in less than three feet of earth by spreading out far from the trees. Interlocking roots throughout the forest help to support the Sequoias. As Sequoias grow taller, they loose lower branches due to fire or lack of Sun. Once the trees rise above the rest of the forest canopy, their pointed crowns round off. Dead tops mark the oldest Sequoias. Once mature they grow no taller, but continue to grow thicker.
Foot traffic wears away topsoil exposing shallow Sequoia roots. Most large sequoias die by falling after root damage, soft soil, heavy snow or the wind.
Giant sequoia groves are portions of Sierra Nevada mixed conifer forest that contain giant sequoias. In most groves, giant sequoias are fewer in number than other tree species but are the most visually striking and dominant in size. Within park boundaries, park staff distinguishes approximately 40 different giant sequoia groves, ranging from one to tens of thousands of sequoia trees per grove. Giant Forest is a large sequoia grove, set on a rolling plateau between the Marble and Middle Forks of the Kaweah River in Sequoia National Park. It is the largest of the unlogged giant sequoia groves, and it contains more exceptionally large sequoias than any other grove. It hosts the largest living sequoia, the General Sherman Tree. In this grove, visitors can see the effects of decades of prescribed burning: open forest conditions and clumps of giant sequoia seedlings that establish after fire.
Grant Grove is located in Kings Canyon National Park. This grove has numerous exceptionally large sequoias grouped in a 90-acre area. A higher percentage of this grove’s mature sequoias reach sizes of ten, fifteen, and twenty feet (3, 4.5, or 6 m) in diameter than in any other grove.
Redwood Mountain Grove is a very large grove of a spectacular old growth sequoias and a diversity of plants on the forest floor. In the spring, the colorful mix of wildflowers along the ridge trail and near Redwood Creek will delight hikers as much as the giant sequoias. In the fall, the dogwood shrubs turn a deep red color, and the fall light provides good photo opportunities.
Redwood Mountain Grove is the largest grove in total area, has the largest area of old growth giant sequoias, and contains more mature sequoias than any other grove. This grove was one of the first areas where Sequoia and Kings Canyon National Parks started prescribed burning to reduce fuels and stimulate giant sequoia reproduction. The large fire scars on some of the monarch giant sequoias are a testament to the presence of fire over many centuries in sequoia groves. Today, the open stands of trees and the growth of young giant sequoias at Redwood Mountain Grove illustrate successful outcomes of the parks’ fire program
The Sugar Bowl Grove is one of few examples of a nearly pure giant sequoia forest, rather than the typical mix of giant sequoias with other types of trees.
Some interesting facts:
- General Sherman, the name was given by James Wolverton in 1879, after the leader he served under during the Civil War, is the largest tree by Volume and weight. General Sherman, in the US, has a girth of 109 feet around on the ground and is 36.5 feet in diameter at the base.
2. El Tule in Mexico is largest by thickness in the world.
3. Coast Redwood is the tallest tree in the world. It is 367 feet tall and 10 feet in diameter.
4. Sugar Pine is biggest and tallest pine tree. It is 216 feet tall and 10 feet in diameter.
5. General Grant, in Kings Canyon National Park, USA, is the largest tree by width.
6. Centennial stump in California National park is 24 inch in diameter. Eastern people in Philadelphia did not believe that such a giant tree existed and called it a “California Hoax”.
7. Sentinel Tree, a Sequoia in Sequoia National Park, is 2,200 years old.
- Giant Forest, named by John Muir, in Sequoia National Park hosts four of world’s five largest trees. In Giant Forest Sequoias grow bigger than anywhere else, and Round Meadow is one of the best Sequoia habitat within Giant Forest.
The above information is from Park website and display boards in National park.