Pando: The Heaviest and Oldest Known Organism

Pando (Populus tremuloides), which is also known as the trembling giant is the heaviest and oldest known organism. It is a clonal colony of a single male quaking aspen determined to be a single living organism by identical genetic markers and assumed to have one massive underground root system. Pando was discovered in 1968 by researcher Burton V. Barnes.

The heaviest known organism is estimated to weigh 6,000,000kg, covering 43 hectares (106 acres) and having over 40,000 stems which die individually (but have an average lifetime of 130 years) and is replaced by new stems growing from its roots. The trembling giant achieved the climax of being the oldest known living organism when its root system was discovered to be about 80,000 years old (although some biologist claimed it to be about 1 million years old). According to Michael Grant in Bioscience:

“…quaking aspen regularly reproduces via a process called suckering. An individual stem can send out lateral roots that, under the right conditions, send up other erect stems; from all the above ground appearances the new stems look just like individual trees, forms. This collection of multiple stems called ramets, all form one, single genetic individual, usually termed clone.”

Its survival had been enhanced by some ideal circumstances which are: prevention of its main competitor, conifers through frequent forest fires. A climate shift from wet and humid to semi-arid has obstructed seedling establishment and the accompanying rivalry from younger aspens.

P. tremuloides survived underground during intense fire, but after each of the wild fire, its root system sends up new stems.