048: What's The Oldest Tree in the World?

What is the oldest tree in the world?

Well, when you start talking about the oldest, the biggest or almost any other superlative nature, you're unlikely to find a cut and dry answer. There are in fact two contenders for oldest tree, and it depends on how you define the term.

The oldest known individual tree was discovered in 2012 in the White Mountains of east central California, a great northern bristlecone pine that's 5.063 years old. That's older than the pyramids, here's a photo of a similar bristlecone pine, now it doens't look exactly alive and that may be part of its secret to success. The high cold arid climate of the white mountains turns out to be the perfect environment for fostering these ancient trees. Strangely, the higher you go in those mountains, the older the trees get and several studies have suggested that the longevity of pines there, is directly related to how bad the growing conditions are. Not only is the average rainfall on the White Mountains less than 30 centimeters per year, but most of the trees are growing on dolomite, a type of limestone in highly alkaline soil with very few nutrients. But over time bristlecones have adapted to this alkalinity unlike other trees which has left them free to grow without much if any competition.

Bristlecones also don't expend a lot of energy on their growth and in good year the tree's girth will increase by about 0.25 milimeters. So instead they can make the most of their meager resources. As a result bristlecones tend to have a pretty high proportion of dead to live wood, but this has its advantages too, reducing respiration and water loss, and it also helps that there are many other trees around, which makes it less likely that they'll fall victim to a forest fire over the millenia.

Researchers are able to determine these trees precise age thanks to a process called cross dating, which involves taking core samples from both living and dead trees and then matching up the patterns of their rings to come back with the timeline. That goes back thousands of years.

For our second contender, we're going to Fish Lake National Forest in south central Utah. Here lives a clonal colony of quaking aspen that may very well be the oldest living thing on earth. It's been named Pando and every tree or stem as they're called in the half square kilometer colony, is genetically identical. Although no individual tree in the colony is older than 200 years, they're all connected by a single root system that's at least eighty thousand years old and possibly much older. At over 6.000 metric tons, it also holds the distinction of being the heaviest known living organism on earth. So, how do Padon get so old? Clonal colonies like Pando can reproduce either by flowering and producing seeds or by producing a clone of themselves. In this case cloning just means extending the enourmous network of roots and forcing a new stem up through the ground, because the heart of Pando, is so far beneath the ground, it can't be killed by a forest fire. Recent studies have found that Pando hasn't reproduced sexually in more than 10.000 years. That's quite a dry spell, and not that surprising given its age. That just means that it's up to the root system to continue producing clones and letting forest fires burn to keep invading conifers at bay.

So thanks to the evolutionary tips, world's oldest trees, I'll be sure to keep them in mind when I turn five thousand years old and wanna go for another five thousand, and thank you for watching this episode of SciShow. If you have any questions or comments or ideas, write down on the comments bellow and on facebook and twitter, and if you want to keep getting smart with us here at SchiShow, you can go to youtube.com/scishow and subscribe.