Pando (tree)

Pando ( ) is the name of a quaking aspen (Populus tremuloides) clone located in Sevier County, Utah, United States, in the Fishlake National Forest. A male clonal organism, Pando has an estimated 47,000 stems (ramets) that appear to be individual trees but are genetically identical parts of a single tree connected by a root system that spans . As a multi-stem tree, Pando is the world's largest tree by measures of weight, landmass and species, and is generally held to be the world's single largest organism by weight. Systems of classification used to define large trees vary considerably, leading to some confusion about Pando's status. Within the United States, the Official Register of Champion Trees defines the largest trees in a species-specific way; in this case, Pando is the largest aspen tree (Populus tremuloides). In forestry, the largest trees are measured by the greatest volume of a single stem, regardless of species. In that case, the General Sherman Tree is the largest unitary (single-stem) tree. While many emphasize that Pando is the largest clonal organism, other large trees, including redwoods can also reproduce via cloning. Pando being the heaviest tree and the largest tree by landmass, while also being the largest aspen clone, leaves it in a class of its own.…

]] Pando ( ) is the name of a quaking aspen (Populus tremuloides) clone located in Sevier County, Utah, United States, in the Fishlake National Forest. A male clonal organism, Pando has an estimated 47,000 stems (ramets) that appear to be individual trees but are genetically identical parts of a single tree connected by a root system that spans . As a multi-stem tree, Pando is the world's largest tree by measures of weight, landmass and species, and is generally held to be the world's single largest organism by weight. Systems of classification used to define large trees vary considerably, leading to some confusion about Pando's status. Within the United States, the Official Register of Champion Trees defines the largest trees in a species-specific way; in this case, Pando is the largest aspen tree (Populus tremuloides). In forestry, the largest trees are measured by the greatest volume of a single stem, regardless of species. In that case, the General Sherman Tree is the largest unitary (single-stem) tree. While many emphasize that Pando is the largest clonal organism, other large trees, including redwoods can also reproduce via cloning. Pando being the heaviest tree and the largest tree by landmass, while also being the largest aspen clone, leaves it in a class of its own. Friends of Pando and the Fishlake National Forest partner to study and protect Pando, working alongside the Utah Division of Wildlife Resources. Notable organizations that also study and advocate to protect Pando's care include the Western Aspen Alliance and Grand Canyon Trust.

Discovery, naming and verification

The Pando tree was identified in 1976 by Jerry Kemperman and Burton V. Barnes. A posthumous biography by Barnes's colleague, Daniel Kashian, details Pando's discovery: As a part of his aspen work in the West, Burt began to examine an extremely large trembling aspen clone southwest of Fish Lake, Utah, in the late 1960s and early 1970s. Using aerial photography and the same morphological differentiation techniques he developed for aspen at UMBS for his dissertation, Burt concluded that the aspen forest that covered about 106 acres was a single aspen clone, quite possibly the "world's largest organism." Other than a single publication about aspen clone size and another great story to tell his students, Burt's studies on the Fish Lake clone were relatively obscure. Work by Fishlake National Forest to understand and protect the tree began in 1987, according to interviews and articles written by Fishlake Forest as well as accounts gathered by Friends of Pando. Based on Barnes and Kempermans's 1976 paper noting Pando's discovery, Michael Grant, Jeffrey Mitton, and Yan Linhart of the University of Colorado at Boulder re-examined the clone in 1992 and described Pando as a single male aspen clone based on its morphological characteristics such as pollen production, leaves, and root structure. Michael Grant named the tree "Pando" which is Latin for "I spread" in an editorial which was later published in Discover Magazine. A large-scale genetic sampling and analysis was published in 2008¹ by Jennifer DeWoody, Karen Mock, Valerie Hipkins, and Carol Rowe. The research team's genetic study confirmed morphological analysis by Barnes and Kemperman as well as Mitton, Grant and Linhart, thus verifying Pando's size and scale of operation.

Size and age

Most agree, based on Barnes's work and later work, that Pando encompasses , weighs an estimated or 13.2 million pounds, and features an estimated 47,000 stems, which die individually and are replaced by genetically identical stems that are sent up from the tree's vast root system, a process known as "suckering". The root system is estimated to be several thousand years old, with habitat modeling suggesting a maximum age of 14,000 years and 16,000 years by the latest (2024) estimate. Individual stems do not typically live more than 100–130 years. Pando's landmass spreads from 2,700 m (8,900 ft) above sea level to approximately 2,813 m (9,230 ft) above sea level along the western side of a steep basin wall. Mitton and Grant summarize the development of stems in aspen clones:

Range of age estimates

Due to the progressive replacement of stems and roots, the overall age of an aspen clone cannot be determined from tree rings. Speculations on Pando's age have ranged between 80,000 and 1 million years. Many news sources list Pando's age as 80,000 years, but this claim derives from a now-removed National Park Service web page, which redacted that claim in 2023 and was inconsistent with the Forest Service's post ice-age estimate. Glaciers repeatedly formed on the Fish Lake Plateau over the past several hundred thousand years and the mountains above Pando's landmass were crowned by glaciers as recently as the last glacial maximum. Ages greater than approximately 16,000 years therefore require Pando to have survived climate conditions during the Pinedale glaciation, something that appears unlikely under current estimates of Pando's age and modeling of variations in local average temperature and climate. According to multiple studies, in order for the Pando seed to germinate, would have required soil temperatures of at least while soil temperatures of at least would be needed for suckering to begin and for Pando to have spread. During the time glaciers were present in the area, temperature models indicate Pando's homeland would have been 7‒25 °F (4‒14 °C) cooler, with the warmest month, July, which today has an average temperature of for the high, and for the low. A 2017 paper by Chen Ding et al. seems to support US Forest Service claims that Pando could not be older than the last Glacial Maximum in the area based on paleo-climate models and genetic traits of aspen sites throughout North America. A 2024 paper by Pineau et at first indicated the age could be between 16,000 and 80,000 years based on the first somatic mutation model of the tree, but, that research did not pass peer review, while mass media outlets continue to push an unverified claim. A revised draft by the researcher in 2026 tacked the age at between 16,000 years old and upwards of 37,000 years old , but again, did not pass peer review making it hard to situation the claims. Thus, charcoal studies published in 2022¹ place the lower end of Pando's potential age range at around 9,000 years, while the somatic mutation models' most conservative estimate, which seems climatically and geologically possible of 16,000 years, awaits replication, or a process where new material and methods might bring more clarity. Estimates of Pando's age have also been influenced by changes in the understanding of the establishment of aspen clones in western North America. Earlier sources argued that germination and successful establishment of aspen on new sites were rare in the last 10,000 years, and that Pando's root system was therefore likely greater than 10,000 years old. More recent observations, however, have shown seedling establishment of new aspen clones is a regular occurrence and can be abundant on sites exposed by wildfire. These findings are summarized in the U.S. Forest Service's Fire Effects Information System:

See also

Auxin Basal shoot Cytokinins Largest organisms List of individual trees List of oldest trees Posidonia australis Rhizome Vegetative reproduction

References

Additional references

External links

Friends of Pando "A Guide to All Things Pando"

Text derived from https://en.wikipedia.org/w/index.php?oldid=1378542374 under CC BY-SA 4.0; modifications have been made.