Pando (tree)

Pando (Latin for "I spread"), the world's largest tree, is a quaking aspen tree (Populus tremuloides) located in Sevier County, Utah in the Fishlake National Forest. A male clonal organism, Pando has an estimated 47,000 stems (ramets) that appear as individual trees, but are connected by a root system that spans 106 acres. Pando is the largest tree by weight and landmass and the largest known aspen clone. Pando was identified as a single living organism as each of its stems possesses identical genetic markers. The massive interconnected root system coordinates energy production, defense and regeneration across its expanse. Pando spans 0.63 miles by 0.43 miles of the southwestern edge of the Fishlake Basin in the Fremont River Ranger District of the Fishlake National Forest and lies 0.43 miles to the west of Fish Lake, the largest natural mountain freshwater lake in Utah. Pando is located at an elevation of 2700 m above sea level.

Pando occupies approximately 43 ha and is estimated to weigh collectively 6000000 kg, or 13.2 million pounds, making it the heaviest known organism. Systems of classification used to define large trees vary considerably, leading to some confusion about Pando's status. In contrast to the General Sherman Tree, the largest single stem tree, Pando is often characterized as an "organism" or "plant". Pando, however, is a tree and commonly known as the "Pando Tree".

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. While many emphasize that Pando is the largest clonal organism, other large trees, including Redwoods can also reproduce via cloning. This leaves Pando in a class of its own being the largest aspen tree, largest tree by weight and, the largest by land mass, combined.

Since the early 2000s, little information has been adequately corroborated about Pando's origins and how its genetic integrity has been sustained over a long period time (between 9,000 and 12,000 years). Researchers have argued that Pando’s future is uncertain due to a combination of factors including drought, grazing, and fire suppression. Each claim has met with controversy considering how little time the tree has been the subject of concern. In terms of drought, Pando's long lived nature suggest it has survived droughts that have driven out humans for centuries. In terms of grazing, a majority of Pando's land mass is fenced for permanent protection and management as a unique tree. What's more, grazing is only permitted 10 days a year in October in a small edge of Pando's boundary along the waters of Coots Slough, part of Fish Lake. In terms of fire suppression, research published in 2022 by Jan Novak et al. seems to suggest Pando has survived conflagrations that would have likely leveled the tree many times, after which Pando regenerated itself from the root system. That paper suggest such large scale fire events are infrequent, which may be owed to the fact that aspen are water heavy and so, are naturally fire resistant earning them the name "asbestos forest" by Canadian Forest Ecologist Lori Daniels. Regardless of controversies and how little is known today about Pando, there is broad consensus that protection from deer and elk who feed on the new growth faster than they can reach maturity is critical. However, such protection systems are only meaningful if they are coupled with ongoing management and restoration efforts which are under way.

Today, Friends of Pando and the United States Forest Service are official partners working to study and protect Pando and work alongside Utah Division of Wildlife Resources to care for and protect the Pando Tree. Notable organizations that also study and advocate to protect Pando's care include 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 Burton V. Barnes' 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 of 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 2008 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.



Research and protection
In late 1987, Fishlake National Forest began work to remove diseased trees and promote new growth using coppicing, mechanical stimulation, to simultaneously remove diseased stems while stimulating regeneration. In 1993, Fishlake National Forest began work on the "Aspen Regeneration Project", installing fences to help control deer and elk who threatened to destroy the productive results of the regeneration project. Today, 53 acres of Pando is protected by 8-foot fences to control populations of mule deer (Odocoileus hemionus) and elk (Cervus canadensis), and to control human uses, such as permitted grazing by domestic cattle (Bos taurus).

Regeneration rates in portions of the "Aspen Regeneration Project" which started in the 1990's, and was expanded in 2014, showed promise based on photographic evidence and repeated survey plots by land managers, scientists and conservation groups between 1993 and today. Despite this, many have argued more work needs to be done to control wildlife, as Pando is surrounded by 700 square miles of de facto wildlife preserve managed by people, groups and agencies who do not have Pando's sustainability as a central concern in their land management policies. Paul Rogers and Darren McAvoy of Utah State University completed an assessment of Pando's status in 2018 and stressed the importance of reducing herbivory by mule deer as critical to conserving Pando for the future. In 2019, Rogers and Jan Šebesta surveyed other vegetation within Pando besides aspen, finding additional support for their 2018 conclusion that interactions between browsing and management strategy may have had adverse effects on Pando's long-term resilience to change. In 2023, a team of researchers, land managers, wildlife biologists and citizen scientists groups began long term programs to monitor deer and elk using GPS collars and wildlife cameras to better understand wildlife, as well as deer and elk browsing on the tree.

Size and age
Most agree, based on Barnes' work and later work, that Pando encompasses 42.89 ha, weighs an estimated 6000 metric ton 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. Individual stems do not typically live more than 100–130 years.

Mitton and Grant summarize the development of stems in aspen clones: "... 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 above-ground 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."

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. In Pando's case, ages up to 1 million years have therefore been suggested. An age of 80,000 years is often given for Pando, 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 mountain above Fish Lake Basin occupied by Pando was crowned by glaciers as recently as the last glacial maximum. Ages greater than approximately 16,000 years therefore require Pando to have survived at least the Pinedale glaciation, something that appears unlikely under current estimates of Pando's age and modeling of variation in Pando's local climate. A 2017 paper by Chen Ding et al. seems to support US Forest service 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.

Estimates of Pando's age have also been influenced by changes in the understanding of establishment of aspen clones in western North America. Earlier sources argued germination and successful establishment of aspen on new sites was rare in the last 10,000 years and therefore, Pando's root system was likely over 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: "Kay documented post-fire quaking aspen seedling establishment following 1986 and 1988 fires in Grand Teton and Yellowstone National Parks, respectively. He found seedlings were concentrated in kettles and other topographic depressions, seeps, springs, lake margins, and burnt-out riparian zones. A few seedlings were widely scattered throughout the burns. In Grand Teton National Park, establishment was greatest (950–2,700 seedlings/ha) in 1989, a wet year, but hundreds to thousands of seedlings established each year despite drought conditions in 1986–1988 and 1990–1991. Seedlings surviving past one season occurred almost exclusively on severely burned surfaces."

Pando in popular culture

 * In 2006, the United States Postal Service published a stamp in commemorating Pando which was designed by artist Lonnie Busch, calling it one of the forty "Wonders of America".
 * In 2013, Pando featured as the backdrop and the subject of a music video for a successful campaign led by 4th graders of nearby Monroe, Utah, United States, to have the State of Utah's Tree be changed from Colorado Spruce to the Quaking Aspen. The song the children sang was written by Utah folk artist and songwriter, Clive Romney.
 * In 2018, the Pando Aspen Clone figures as a central figure in the life of the character Patricia Westerford in Richard Powers' novel The Overstory.
 * In 2021, childrens book author Kate Allen Fox published "Pando: A Living Wonder of Trees" earning her a School Library Journal Award for the work.
 * The 2022 Disney film Strange World has a creature named "Pando" which bears similarities with the actual Pando Tree.
 * In 2022, an episode of NBC TV Show "The Blacklist" entitled "The Trembling Giant" (a nickname for Pando) features a scene where central character Raymond 'Red' Reddington details the tree's operation.
 * In 2022, Friends of Pando published audio works by sound conservationist and artist Jeff Rice documenting the tree's subterranean workings for the first time.
 * In 2022, Pando was the subject of an issue of the webcomic xkcd published on December 23 (two days before Christmas), which facetiously suggests adding to Pando's many world records that of world's largest Christmas tree by running a 9,300-foot-long string of Christmas lights through the branches along its perimeter.
 * In 2024, the Hallmark Channel had a movie titled, Branching Out, set in Utah, in which a young girl searches for the paternal side of her family, as her mom had used a donor for an IVF conception. The girl's mom and the donor fall in love. At the film's conclusion, as the girl presents her "family tree" project to her class, she explains her family tree is a Pando, as the newfound family and her are all interconnected, like the Pando tree.
 * In 2024, Intel Computer Chip Corporation named a novel quantum computing control chip "Pando Tree". While many technology organizations have utilized "Pando" in terms of its Latin meaning for "spread", the naming is the first to explicitly honor the Pando Tree itself.