Saturday, October 13, 2012

Exploring Giant Sequoia Trees

When we first entered Sequoia National Park, we stopped at the first sight of some extraordinarily large and tall sequoia trees along  highway 198 going south to Sequoia. We were amazed by the sheer height and size of the giant sequoia trees -it was extremely hard to take a good full picture of those big trees. We explored approximately ten big trees for about 30 minutes!

Quickly Justin and Nicholas were bored of the seemingly same big trees everywhere in the park, despite the fact that we saw bigger trees later, such as the 275 ft tall, 2200 year old General Sherman Tree, the largest tree by volume, or the 267 ft tall, 2000 year old General Grant Tree, the largest tree by width. It was really hard to appreciate all these world records then and there because the surrounding trees are almost just as big.

However, observation and curiosity made it interesting and fun for  Lily and me.

Giant Sequoia Tree Bark color

Very quickly we noticed that there are differences in color of the barks between the smaller sequoia trees and larger one. The large sequoia trees have a reddish, relatively smooth barks, while the smaller sequoia trees barks are more like regular trees, grey, and fragmented. It was interesting. But I did not think about it further until Lily raised the questions about why there was such a difference.

I hypothesized that it was because that the older trees experienced fires and the surface grey barks were burnt. We tried to find an answer at the Giant Sequoia Museum, but could not. So Lily went to ask a ranger at the information desk. We were told that Sequoia trees' barks change color at around 500 years of age due to chemical produced in the trees - tannin, it is a mechanism for the trees to be more fire resistant and pest resistant....(upon web search at the time of writing - I found another explanation - sequoia tree barks contain tannin. When the lower portion of sequoia trees' bark were burnt, the tannins from upper portion of the trees leaked to coat the surface of the burnt area, giving it the reddish color) . We were really excited to find the answer, and felt like we got a peek at secrets of nature!!

Shallow roots for very tall trees

Most giant sequoia trees are so straight, so it was peculiar to see some leaning trees, especially around Big Tree trail. We saw some fallen trees. Based on my common sense, the very tall trees have very deep roots. How could such big trees just fall?

From the exhibit along the trail I was surprised to find out that Giant Sequoia Trees actually have very shallow roots, 3 feet deep on average for trees 200 - 300 ft tall. But the root system extended extensively in horizontal directions, it can stretch out for 300 ft near the soil surface to take water and nutrients.

 The big tree trail is a trail on the perimeter of a meadow - wet land. As the wet land grows, the sequoia trees used to be far enough from the water's edge gets closer, water flow induce soil erosion. The Giant Sequoia trees lean or fall due erosion of soils in their immediate surroundings.

It is also a wonder that giant sequoia trees can pump water and nutrient 200 ~ 300 ft above its root system. It turns out that "trees draw water from the soil upwards. Their foliage is the main motor driving this movement. During photosynthesis, leaves open their stomata and allow water to evaporate into the air.This transpiration creates suction, which extends to the xylem in the leaf veins. From one cell to its neighbor, then across the xylem, suction draws the water."  All trees pump theie water up in the same mechanism  but I did not give it a thought on how it could be, took it for granted, until now.

Fire helps Giant Sequoia trees
People try hard to fight forest fires by all means. I heard comments on why we should allow some fires to burn but did not really investigate it. At the visitor center's exhibit, I found a specific example of fire's role in giant sequoia's life, from seed germination, seeding,  to pests control, from nutrient creation to kill competitors, ...."Fire is the dynamic process that allows minerals and energy to recycle faster within the ecosystem's operation. In theory, similar decomposer functions are performed by fungal and bacterial action. But these processes are far slower than fire, and it is doubtful whether these organisms have ever played the complete decomposition role without fire. "   Artificial fire fighting slowed the process, and caused some of the biggest fires we ever see!!
Longevity of Giant Sequoia Trees

It is absolutely amazing to see giant sequoia trees can live 2000 ~ 4000 years.

When one gives it a bit thinking, one realizes that  the longevity relates to 1 ) their genetics, which definitely play significant roles; 2) external conditions, such as soil type, precipitation, weather patters, temperature, altitude ..., which must have played almost an equally important role as genetics, based on the facts that not all giant sequoia trees live to 1000+ years; no 1000+year old giant sequoia trees outside the limited areas.

All these mental activities at Sequoia helped me to peek into nature's secrets and to have enormously satisfying and exciting experiences.

1 comment:

  1. I Love Giant Sequoias,they are, the largest living thing in the world : Sherman 1400 tons! 10 blue whales.