(0:00) What is the oldest tree in the world?

(0:04) Well, when you start talking about the oldest or biggest or almost any other superlative in nature, you're unlikely to find a cut and dry answer.

(0:10) There are in fact two contenders for oldest tree and it depends on how you define the term.

(0:20) The oldest know individual tree was discovered in 2012 in the white mountains of east central California, a Great Northern Bristlecone Pine that's 5063 years old, that's older than the pyramids!

(0:33) Here is a photo of a similar Bristlecone Pine, now it doesn't look exactly alive and that may be part of it's secret to success.

(0:40) The high cold arid climate of the White Mountains turns out to be the perfect environment for fostering these ancient trees.

(0:46) 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.

(0:56) Not only is the average rainfall in the White Mountains less than 30cm per year, but most but most of the trees are growing on Dolomite, a type of limestone in highly alkaline soil with very few nutrients.

(1:07) But over time, Bristlecones have adapted to this alkalinity unlike other trees which has left them free to grow without much, if any, competition.

(1:14) Bristlecones also don't expend a lot of energy of their growth, in a good year the tree's girth will increase by about 0.25mm, so instead they can make the most of their meager resources.

(1:25) 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 aren't many other trees around which makes it less likely that they will fall victim to a forest fire over the millennia.

(1:38) Researchers are able to determine these tree's 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 a timeline that goes back thousands of years.

(1:52) For our second contender, we are going to Fishlake National Forest in south central Utah.

(1:57) Here lives a clonal colony of Quaking Aspen that may very well be the oldest living thing on Earth.

(2:03) It's been named 'Pando' and every tree or stem as they are called in the half square kilometer colony is genetically identical, although no individual tree in the colony is older than 200 years, they are all connected by a single root system that is at least 80,000 years old and possibly much older.

(2:20) At over 6,000 metric tons, it also holds the distinction of being the heaviest known living organism on Earth!

(2:26) So, how did Pando get so old?

(2:28) Clonal colonies like Pando can reproduce either by flowering and producing seeds or by producing a clone of themselves.

(2:34) In this case cloning just means extending the enormous 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.

(2:45) Recent studies have found that Pando hasn't reproduced sexually in more than 10,000 years, that's quite a dry spell!

(2:52) 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.

(3:00) So thanks for the evolutionary tips worlds oldest trees! I'll be sure to keep them in mind when I turn 5,000 years old and want to go for another 5,000.

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