why do trees live longer than humans

Dear Dr. Universe: How long can trees live? б
-Jessy, 8, Seattle, WA What kinds of trees are in your backyard? Do they have pinecones? Colorful leaves? Pods withб seeds? Tell us more or send a picture toб. Dear Jessy, As I was hiking through the bristlecone pine forests of the Sierra Nevada recently, I stumbled upon a tree barely six inches tall. It was growingБslowly, but surely. I was surprised to find this tiny pine tree was already about 40 years old. Some trees will stop growing once they reach that age. But others live much longer. In fact bristlecone pine trees arenБt just the oldest trees, they are some of the oldest living things on our planet. They can live for about 5,000 years. БThese trees were growing when the Egyptians were building the pyramids,Б said my friend Kevin Zobrist, a forester at Washington State University. Zobrist knows a lot about different trees and told me a bit about bristlecone pine trees. By the time the pines are about 5,000 years old, they will stand 60 feet tall with a trunk that is nearly five feet around.


If we were to cut into the trunk, we could look at its growth rings. Each ring would signify a year of its life. We would have a lot of counting to do. Click to zoom in. On my hike, I noticed some of the treesБ young pinecones were purplish-pink. Eventually they would turn brown and fall to the ground. I spotted a few old cones by the tree. They had that fresh pine scent. I looked up at the branches that twisted and stretched like arms up to the sky. I wondered how on earth these trees were able to live such long lives. Zobrist explained that bristlecone pine trees are tough and have adapted to their environment. They are equipped to deal with drought, extreme climates, and insects that might cause serious damage if they attack. For example, the tree can actually shut down or go dormant for a while, if conditions are too harsh. This helps the tree survive for thousands of years. БThey teach us that nature is resilient,Б Zobrist said.


БThey teach us that nature can carry on. Б Of course, not all trees live quite as long as these pines. But many live longer than humans and us cats. The redwood trees of California are about six times taller than the bristlecone pines. Some of them have been around for nearly 2,000 years. Even when a tree dies, it finds a new life. Creatures and plants on the forest floor are counting on the trees to get old, die, and fall. They can use the fallen trees as their home or for food. ItБs been said that trees are our planetБs lungs. They help make the oxygen we breathe and keep life thriving on our planet. I took a deep breath of the mountain air and said a quick thank you to the trees before heading down the trail, on to the next adventure. Sincerely, Dr. Universe Trees are not exactly built to last forever. For example, ailanthus trees are very pithy and prone to weathering, so they typically only live to be 30-70 years. All species of trees have a general lifespan due to the integrity of their structure and the effect of the environment.


You can say in a perfect world, there is the potential for them to live forever, but it could never happen on earth. Even if you got rid of insects, kept the tree free from damage and weathering, made sure to give it everything it needed, it could still grow too big to exist because the atmospheric pressure would prevent nutrient flow and it would die. Thus it s kind of a moot point. Meristematic tissue is very important, though, like you said. It s believed to be able to produce more tissue indefinitely if conditions are right, so a tree s lifespan is generally though of as a guideline and not definite. There is always an outlier. Meristematic growth is more applicable to cloning and grafting and not distinct trees. The fact that there are cultivars of apples that have existed since the 1600 s due to grafting is a good example of this. The thing is, even if the tree itself dies, if meristem tissue remains, they can sprout back from the same root system and it s hard to say if it s the same organism or not.


A good example of this is Pando out in Utah. It s a colony of aspens that continues to send up shoots from an extensive interconnected root system that is believed to have existed for around 80,000 years. The trees themselves only live up to 150 years, but the root system lives on possibly indefinitely. So the real issue is if you define the organism by the tree or not. If you define it by the tree structure itself, as far as we know trees can t live forever on earth, though maybe in some hypothetical eden that we can t test. If you define the organism by the meristem tissue, it can potentially live forever even on earth. In general, things like pando are considered a clonal colony and not a discrete organism. So technically trees don t live forever, but clonal colonies can. In a perfect situation, perhaps both could live forever, but we ll probably never know.

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