Pando (tree)

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Pando (or The Trembling Giant^[1]) is a clonal colony of a single male Quaking Aspen (Populus tremuloides) tree located in the U.S. state of Utah, all determined to be part of a single living organism by identical genetic markers,^[2] and one massive underground root system. The plant is estimated to weigh collectively 6,000 tonnes (six million kilograms),^[3] placing it as the heaviest known organism in existence.^[4] The root system of Pando is estimated to be the oldest known living being in existence at 80,000 years of age.^[5]

Contents 1 Name 2 History 3 Size and age 4 Debate 5 Location 6 Trivia 7 See also 8 References

[edit] Name

The name "Pando" was chosen because it is Latin for "I spread",^[1][6] while the nickname "The Trembling Giant" can be attributed to the common name of Populus tremuloides, the trembling aspen, whose leaves frequently rattle.

[edit] History

Pando is thought to have grown for much of its lifetime under ideal circumstances: frequent fires have prevented its main competitor, conifers, from colonizing the area, and climate change, transitioning from a wet and humid weather pattern to semi-arid, has obstructed widespread seedling establishment and the accompanying rivalry from younger aspens.

During intense fires, the organism survived by its root system, sending up new stems in the aftermath of each wildfire. Due to its age, the climate into which Pando was born is markedly different from that of today, and it may be as many as ten millennia since Pando's last successful flowering, according to an OECD report:

	Clonal groups of P. tremuloides in eastern North America are very common, but generally less than 0.1 ha in size, while in areas of Utah, groups as large as 80 ha have been observed (Kemperman and Barnes 1976). In the semi-arid western United States, some argue that widespread seedling establishment has not occurred since the last glaciation, some 10,000 years ago (Einspahr and Winton 1976, McDonough 1985). Indeed, some biologists feel that western clones could be as old as 1 million years (Barnes 1966, 1975). It has been claimed that a single clone, nicknamed "Pando" (Latin for I spread), covers 43 hectares, contains more than 47,000 stems and weighs in excess of 6 million kg, making it the largest known organism (Grant et al. 1992, Mitton and Grant 1996)
—OECD, Consensus Document on the Biology of Populus L. (Poplars)[3]

Pando was discovered in 1992 by Michael Grant of the University of Colorado at Boulder.

[edit] Size and age

The clone encompasses 43 hectares (107 acres) and has around 47,000 trunks, which continually die and are renewed by its roots. The trunks are connected together by its root system. The average age of Pando's trunks (or technically, stems) is 130 years, as deciphered by tree rings. Michael Grant in BioScience said:

...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 aboveground appearances the new stems look just like individual trees. The process is repeated until a whole stand, of what appear to be individual trees, forms. This collection of multiple stems, called ramets, all form one single, genetic individual, usually termed a clone.

In comparison to Pando's most widely held total age of 80,000 years, the most accepted view among current anthropologists is that Homo sapiens first migrated out of Africa to Eurasia and Oceania only 40,000 years ago, and finally to the Americas 10,000 years ago.^[7]

[edit] Debate

Some experts speculate that Pando's reign since 1992 as the heaviest and oldest organism in existence may be short-lived. Candidates for the titles include many theoretical scenarios: less well-studied Quaking Aspen in Utah that may be 80 ha in size and one million years in age, a clonal colony of at least 7 Coastal Redwood that could weigh more,^[8] possibly older fungal mats in Oregon, or older Creosote Bushes. Other scientists feel that portions of Pando's root system may be dead and might have led the plant to split into separate groups (and thus would not be one organism), though the collective groups would remain the same singular genetic individual.

Tree experts also note that the organism's age cannot be determined with the level of precision found in tree rings; some claim Pando's age is closer to 1 million years^[4]. Its current 80,000 years designation is based on a complex set of factors including the history of its local environment such as, the evidence indicating that there are few if any naturally occurring new aspens in most of the western United States since a climate shift took place 10,000 years ago and eliminated favorable soil conditions for seedlings, the rate of growth (including the differences of rates in distinct climates when accounting for its local climate history, that males grow slower than females, and that aspen grow slower at higher elevations with Pando at 2697 m or 8,848 ft above sea level), its size, and its genetic code in comparison to the mutations found among aspens born in the modern era. Michael Grant summed it thus:

Despite enormous crops of viable seeds, successful seedling establishment appears to be a rare event in the semiarid West, but the establishment of new trees from seeds appears to be common in the moist, humid forests of New England... aspen establishment from seeds probably has not occurred in the western United States since the last glaciation, some 10,000 years ago... Part of the rationale behind current age estimates for aspen clones is that sexual reproduction is effectively frustrated by the rarity of a favorable suite of conditions in semiarid environments... High levels of genetic variation and excesses of heterozygotes are found in [the aspen of] semiarid environments... Clonal reproduction is more common in arid environments... Heterozygotes often exhibit superior longevity in forest trees [across many species]... growth rate of aspen decline with elevation, steepness of slope, age of the ramet, and exposure to wind... growth rate decreased dramatically with elevation... The researchers reported that the area of the female clones was 41% greater than males, the number of female ramets 52% greater, and the basal area of females 56% greater [when compared at the same age and environment]...

[edit] Location

Pando lives in the Wasatch Range of the Rocky Mountains in Utah near Fish Lake and Bryce Canyon National Park.

[edit] Trivia

• The United States Postal Service has made a stamp in commemoration of the aspen, calling it one of the forty "Wonders of America".^[9]
• Alternate claimants to the title of largest and longest lived include Posidonia oceanica, a seaweed off the island of Ibiza and Armillaria ostoyae, a fungus in the Blue Mountains of eastern Oregon.

[edit] See also

• Largest organism
• Stolon
• Vegetative reproduction

[edit] References