Pando is a single tree, albeit a tree that is a forest of growing international reputation. Five or six species of aspen (upland Populus) reach around the entire northern hemisphere between about 30°-65° north latitude. They harbor vast amounts of biodiversity. As goes aspen, so goes dependent plants and animals; a cascading effect that may be exacerbated by a warming climate. Can the lessons learned – and answers derived – at Pando shine a light on global-scale aspen conservation?
The fourth and last part of Paul C. Rogers’ Pando series is about the importance of taking the first step:
Why they are slowly slaying this giant
Environmental stewards have a long history of treating the symptoms while avoiding the difficult cures. And often, such as here, there’s good reason for that, frustrating as it may be. Thorny issues, particularly those with significant social components, often contain short-term easy fixes, with long-term difficult solutions left unattended. These so-called “messy problems” are actually quite common, though it is somewhat rare that they occur in a very contained geography, such as that of the Pando clone. This comprehensible scale may provide an advantage. Based on the previous discussion, it is clear that there are too many mule deer and cattle for the current situation at Pando. Cattle are there for only a short time. Deer stay much longer and do appear to be overabundant based on their outsized impact. But it is the combined browsing habits of these two animals that are slowly slaying this giant.
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Pando enters triage
To date, we have successfully fenced only a small portion of this famous grove near Fish Lake, Utah. A significant investment in fencing out deer above the highway is so far proving futile: our data clearly show the animals are finding ways to get in and eat all the new growth. With additional resources we can likely fortify entry points and begin healing another section of Pando. Still, if fencing is going to be our prime strategy for recovery (a.k.a., the easy fix) more than half the clone remains unprotected. Broader questions persist, however: 1) Do we really want a fenced forest? 2) Will fencing provide the long-term solution we desire (i.e., a self-sustaining Pando)? Ideally, we wish to facilitate ecosystem balance where moderate browsing by animals allows a portion of the aspen regrowth to thrive and one day replace dying older trees. Fencing is triage for Pando to prevent large herbivores from browsing. This promotes maximum regeneration for a short period with the intention of moving the forest to a more resilient state.
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“It will be complex, messy, and time consuming”
The more difficult solution requires working with people. In the United States interest groups, such as hunters and livestock growers and protectionists, have significant influence on politicians and government agencies that implement policy. Near Pando, there are also private vacation homes and a seasonal tourist industry. All of these groups have a stake in which methods or restrictions will be instigated to achieve desired outcomes. In particular, actions to regulate wild and domestic animal numbers can sometimes take years to work out with the respective bureaucracies. For example, a proposal to reduce mule deer numbers at Pando requires that State-employed sharp shooters must be approved by several of the above parties, plus a State wildlife commission. Similarly, changing grazing use agreements for cattle would have to be negotiated at several levels involving the federal Forest Service and livestock growers before actual changes could be enacted. If all of this sounds futile, it really isn’t. But it will be complex, messy, and time consuming, and it will certainly never happen if someone doesn’t take the first step.
All of this fuss for a single tree, albeit a tree that is a forest of growing international reputation. These aspen forests have a global reach. Five or six species of aspen (upland Populus) reach around the entire northern hemisphere between about 30°-65° north latitude. Crucial to their sustaining presence is the fact that they harbor disproportional amounts of biodiversity. As goes aspen, so goes dependent plants and animals; a cascading effect that may be exacerbated by a warming climate. Can the lessons learned at Pando shine a light on global-scale aspen conservation?
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“Do we have the will?”
While some questions remain unanswered for now, we do have a strong conception of Pando’s present plight. Mature trees, some nearing 30 meters in height and a half meter in diameter, are succumbing to age-related mortality; their bones litter the forest floor. Meanwhile, generations of this aspen community—normally represented by diverse tree sizes and heights—are nearly absent. With this skewed demography, we’re left asking ourselves, do we have the will as a society to replace the missing age groups of Pando?
We may imagine Pando as being a mirror; a reflection of our larger engagement with the planet we depend on. In our modern world, we aspire to be ecologically and adaptively attuned to our surroundings: meaning that when systems appear to be unraveling, course corrections will be implemented and checkpoints put in place. While we know we have difficult issues to tackle at Pando, tangible actions can be taken now to give this magnificent being some breathing space.
Inspired by Pando
Toward this end, you may consider a visit to Pando or a special forest near you. Earth’s generosity in sharing lessons such as Pando’s long and large existence benefit us every day. This not only takes the form of wonder and visual pleasure. Practical design elements such as biomimicry are being “harvested” by humans time and again. If we are to successfully live as an ecologically adapted civilization, the inspiration of Pando is there for the taking.
Author: Dr. Paul C. Rogers is Director of the Western Aspen Alliance, Ecology Center Associate, and Adjunct Associate Professor, Wildland Resources Department, Utah State University.
|| The author waived his salary for the text. topos donates the amount to the Western Aspen Alliance to contribute to the preservation of Pando.
|| Maybe you also consider a donation to help save Pando and further our knowledge of aspen ecosystems worldwide: support Pando here.
First part of the Pando series.
Second part.
Third part.
Paul C. Rogers has published a compact version of his text in the topos 103 “Trees” – have a look.
Pando is a single tree, albeit a tree that is a forest of growing international reputation. Five or six species of aspen (upland Populus) reach around the entire northern hemisphere between about 30°-65° north latitude. They harbor vast amounts of biodiversity. As goes aspen, so goes dependent plants and animals; a cascading effect that may be exacerbated by a warming climate. Can the lessons learned – and answers derived – at Pando shine a light on global-scale aspen conservation?
The third part of Paul C. Rogers’ Pando series is about the cumbersome offspring of Pando, the human influence on nature and the possible collapse of this forest-tree:
New recruits have been missing
I first strode into the Pando grove over a decade ago. With each step I was not only jarred by the immensity of the plant, but also by the scale of the task ahead. Visually, the area is stunning! But even a casual visitor can see that something is awry. This forest seems to be made up of only mature trees, a sprawling portico of stems overtopping gaping voids. Moreover, these senior citizens of the forest community are now more than 100 years old…and age is taking its toll. Mortality in aspen forests is common at that age, but the lack of successful regrowth is not. In fact, new recruits to the clone have been missing for decades. Envision a gallery of trees similar to an urban park, botanical garden, or cemetery. While those places may be beautiful in their own way, they are not predominantly governed by processes of nature.
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A team for Pando
To gain a better understanding of what was causing the alleged imbalance at Pando a team of conservationists, foresters, wildlife managers, and livestock professionals developed a plan to fence a small (seven hectare) portion, experimentally alter subsets of this area, and monitor how they responded. As the lead scientist of this effort, it was my job to design the follow-up measurements and interpret the results. The group agreed to place 28 monitoring plots in and around the newly fenced area, taking care to arrange these plots so they sampled all conditions, including the ambient state of Pando outside the protective fencing. Over a three-year period, with significant help from field assistants, we measured the size and condition of old trees, as well as the number and height of new aspen suckers. All regrowth was checked for signs of recent browsing. The team also counted deer and cattle scat to see what ungulates were visiting and how abundant they were. Results of all of this effort indicated that deer and cattle were both contributing to chronic browsing of young aspen, that almost no aspen were progressing in height because of herbivory, and that fencing greatly aided in protecting new growth. We also found that different forms of treatment—burning, removing shrubs, cutting 50 percent of mature trees—made little difference in the regrowth of aspen; all were successful. Even fencing without alterations provided ample regrowth! These aspen suckers were trying to grow all along, they just needed a respite from chronic browsing.
Following initial success a second 15-hectare fence was erected within Pando. Unfortunately, early results from a follow-up study indicate that this newly protected area is not facilitating regeneration. What’s the difference between the two adjacent areas? It appears that use of a 25-year-old fence as a portion of the larger exclosure, as a cost saving measure, may have been a mistake. Sections of this older fence seem to be allowing deer to access the site and prevent new aspen suckers from growing. While fencing may seem a simple solution, it is expensive and requires regular maintenance as falling trees commonly breach even the strongest of materials allowing animals to enter and eat young aspen.
“The real issue is the regulation, by nature or humans, of ungulate population numbers and movement”
We should note that determined ungulates, such as deer or elk in the western US, will often find ways to reach the highly nutritious aspen stems, as appears to be the case at Pando. The problem isn’t really that wild animals browse on aspen. That phenomenon has occurred without degradation for eons. The real issue is the regulation, by nature or humans, of ungulate population numbers and movement. In the absence of significant predators, and with economic incentives to maintain game species at high levels, browsers may remain in certain areas for extended periods where previously they were kept moving by threats of attack. Additionally, laws to protect public safety prohibit hunting activities near roads and cabins, both of which are present at Pando. Thus, a virtual sanctuary exists where deer are safe from the few predators and restricted hunters. Deer appear to learn this very quickly and take advantage of their de facto refuge. The upshot of all of these factors is that there is likely an unsustainable concentration of herbivores based at the Pando clone. As complicated as the explanation is, the solution is equally tangled.
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Pando may be collapsing
Over the past 10 years I’ve traversed these 43 hectares known as Pando measuring and musing over what all this data means. Wildlife and plants and people intermingle here at a several levels: ranchers need cattle; hunters need deer; people hike, camp, and build homes; and forests need intact processes or concerted intervention to survive. Current practices for both wildlife and forests favor recreating ecological processes rather than rebuilding historic species compositions. In short, an approach where managers focus on replacing ratios of each species to a conjured past state is not only very challenging, it is likely feudal in the sense that there is no model period to recreate and, even if we could, it may be impossible (and overly manipulative!) to reach that goal. Rather, it is thought, if we can focus on maintaining key processes—disturbance cycles, predator-prey-plant interactions, community rejuvenation—than we can avoid never-ending manipulation of forests such as Pando. Even with that lofty long-term goal, present circumstances refocus our efforts on the immediate crisis at hand. Pando may be collapsing.
To be continued…
First part of the Pando series.
Second part of the Pando series.
Please consider a donation to help save Pando and further our knowledge of aspen ecosystems worldwide: support Pando here.
Paul C. Rogers has published a compact version of his text in the topos 103 “Trees” – have a look.
Pando is a single tree, albeit a tree that is a forest of growing international reputation. Five or six species of aspen (upland Populus) reach around the entire northern hemisphere between about 30°-65° north latitude. They harbor vast amounts of biodiversity. As goes aspen, so goes dependent plants and animals; a cascading effect that may be exacerbated by a warming climate. Can the lessons learned – and answers derived – at Pando shine a light on global-scale aspen conservation?
The second part of Paul C. Rogers’ Pando series is about the growth ability of pando and the added value of its existence for science and for humanity in general:
How did this giant clone survive for thousands of years?
The ability to proliferate from existing root stock is crucial to understanding how large aspen clones thrive. After mature trees, or entire stands, of aspen are injured or die, their predominant mechanism for self-preservation is to reproduce profusely from asexual root suckering. This process involves a hormonal signal (auxin), which suppresses most primordial root buds from suckering until that signal is interrupted by tree damage or death. Reduction in auxins is closely related to increases in root cytokinins that promote new shoot growth. Dramatic examples depicting thousands of new aspen suckers following fire-, disease-, or tree cutting-mortality are common in the western US. However, this process of waiting only for new growth to emerge as a result of catastrophic disturbance paints an incomplete picture. In aspen forests where such stand-replacing disturbances are less common, there is also continuous regrowth where resources, such as water and sunlight, are available in modest measures.
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Stable aspen qualities
Nearly a century ago the forester Frederick S. Baker spoke of aspen’s “two races.” He was referring to what we now call aspen “functional types” : one being very dependent on intense disturbance for regeneration and another that favors small-scale and continuous new stem growth. The latter of these is also found in nearly pure composition—without competing conifers—that provides modest protection from wildfire. Such monotypic aspen forests are called “stable aspen” due to their propensity for remaining in a single-species cover for many generations. Pando exhibits stable aspen qualities. To understand how this giant clone survived for millennia one must invoke knowledge of long-term asexual reproduction within the context of continuous tree replacement, rather than the single-aged stem cohorts commonly found in forests subjected to abrupt upheaval such as wildfire. What I refer to as ‘traditional aspen ecology’ focuses almost solely on aspen intermixed with conifer species and, through a process called succession, transitions over decades-to-centuries from early aspen domination to crowding out by longer-lived conifers. Returning to Pando, we may consider some ideas about competition, sans significant conifer encroachment, which may favor one clone over another.
A little big mystery
What do we really know about aspen growth and survival in the context of giant clones such as Pando? It turns out, very little. We may speculate, however, using our current understanding of potential environmental factors that likely influenced Pando’s success. If you look at the pattern of aspen genotypes on the ground today you see that the giant is surrounded by a few moderate-size clones and many small clones. Thus, we theorize that perhaps Pando may have simply outcompeted adjacent clones. The moniker “I spread” draws from this line of thinking, but there may be more to the story. Conceivably it does just grow faster, or is more environmentally suited to conditions there, or has characteristics of persistence that allow it to endure the wide range of climatic epochs that have occurred during its life (i.e., more effectively than others). Another hypothesis asserts important plant-animal evolutionary traits. As a triploid (having three chromosome sets), Pando appears to have a more rapid growth ability that favors some young stems reaching beyond browse height before ungulates nip their apical buds. Additionally, as much as 30% of leaf matter is comprised of chemically defended phenolic glycosides that “taste bad” to them. It may be that Pando, in an evolutionary trade-off, has invested energy in growth capacity at the expense of chemical defense. While this may not have impeded growth for most of its long life, 20th century human disruptions in the form of predator eradication, road building, livestock introduction, recreational impacts, and forest cutting seem to have disrupted the balance in this system; a balance that may be difficult to recover without additional interventions.
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A barometer of sorts for broader problems
As a global citizen, is it important to invest time and resources in the fate of a single clone, even one as singular as Pando? Why fixate on the “biggest” or “oldest” of anything? After all, nature is not a competition; a cataloging of world records, is it? Why not just focus on the everyday business of conservation? Do we need such icons as Pando to grab the headlines or shake our neighbors from indifference? These questions are not unreasonable given the overwhelming array of environmental issues swamping us; not least of which, a human-induced warming planet, poses serious threats to our collective future. The short answer to these concerns was voiced succinctly by the American conservationist, Aldo Leopold, some 70 years ago: “If the biota, in the course of aeons, has built something we like but do not understand, then who but a fool would discard seemingly useless parts? To keep every cog and wheel is the first precaution of intelligent tinkering.” If a natural feature is very large, for example, perhaps it brings needed attention to many other issues of import; a barometer of sorts for broader problems.
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What Pando teaches us…
Though small at the global scale, Pando illustrates how we might first observe, measure, understand, then take actions in a manner more compatible with the planet. For instance, aspen forests worldwide are known for their outsized influence on regional biodiversity: in the Rocky Mountains they harbor more species than the dominant conifer forests and in Europe many Red List species are aspen obligates. If we can help Pando, dependent species will benefit and so on at regional and even global scales. If our monitoring and tinkering at Pando can preserve this iconic grove, such lessons may be shared around the world for the benefit of the earth’s biota as a whole. To achieve such a lofty goal, we must start at a manageable scale, meticulously measure, take restorative actions, carefully monitor forest responses, make additional adjustments, and share what we’ve learned with others.
To be continued…
Click here for the first part of the Pando series.
Please consider a donation to help save Pando and further our knowledge of aspen ecosystems worldwide: support Pando here.
Paul C. Rogers has published a compact version of his text in the topos 103 “Trees” – have a look.
Pando is a single tree, albeit a tree that is a forest of growing international reputation. Five or six species of aspen (upland Populus) reach around the entire northern hemisphere between about 30°-65° north latitude. They harbor vast amounts of biodiversity. As goes aspen, so goes dependent plants and animals; a cascading effect that may be exacerbated by a warming climate. Can the lessons learned – and answers derived – at Pando shine a light on global-scale aspen conservation?
The first part of Paul C. Rogers’ Pando series is about the origin of pando and the investigation of its sexual reproduction by scientists:
I know this guy. Let’s say, he’s a bit unusual. You see, Pando lives solely in the wild, is completely immobile, and never utters a word. Given this reclusive existence, one would think he is miserable, but that conclusion couldn’t be farther from the truth. He not only thrives in nature, but he spends most of his time helping other plants and animals survive. This guy is quite friendly, too, as he is forever waving to all who will notice. This curious habit, often referred to as trembling or quaking, is common among his peers. Pando’s also immensely stout; in fact, weighing nearly 6,000 metric tons, Pando is thought to be the largest living organism on earth! This interconnected grove of aspen trees may be among the oldest living beings, as well. While extreme heft and age are often a recipe for pending death, it’s not these symptoms that are killing Pando…he’s actually being eaten alive! Let me explain.
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A forest of one tree
Pando challenges our way of thinking about the individual and the community. Human societies and forests presume complexity and plurality; myriad entities interacting, sometimes for their very survival. People, like Pando, tout their uniqueness, their independence. They are simultaneously reliant on community connections. Even in the American West, where the myth of the isolated pioneer or lone gunslinger has fueled many cinematic legends, far-flung settlements were exceedingly dependent on communal support to survive harsh conditions. Likewise, the ecological “strategy” of large aspen clones is to support one another. No stem is truly separate from the larger clone. In the words of my friend Rich Binell, Pando is “a forest of one tree.”
Iconic “clone” spread from a single stem
In southern Utah, USA, the world’s largest known organism comprises some 43 hectares of genetically identical stems—what most of us would call “trees”—that are linked by a subterranean root system. The name Pando derives from the Latin meaning, “I spread,” attesting to the predominant means of aspen regeneration where new stems sprout asexually from established roots rather than from seeds like most trees. Aspen may also originate from sexual reproduction (seeds) and, in fact, all multi-stem clones at one point did germinate from a seed. Over centuries, likely even millennia, this iconic “clone” spread from a single stem to its current extent with an estimated 47,000 joined trees. (While current science is unable to determine Pando’s age, logic suggests that it is unlikely to be older than the most recent glacial epoch or about 13,000 years before the present.) Since aspen are dioecious, they bear male or female reproductive parts on separate plants. Thus, each genetically uniform aspen clone must be either male or female, and Pando is a very big gent indeed.
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One Pando, many scientists
We came to know Utah’s forest giant through a series of scientific steps. Botanists have known that aspen in both Europe and North America can reproduce via asexual “suckering” for centuries, but it was Burton Barnes from the University of Michigan who began a concerted study of aspen clonality based on physical characteristics. Dr. Barnes “discovered” Pando in the late 1960s by closely examining leaf shape and color differences between this giant clone and adjacent aspen stands. During the 1980s University of Colorado scientists Michael Grant and Jeffry Mitton further explored the grove’s size and condition, and actually provided the name Pando. At this same time, US Forest Service personnel initiated some small clear cuts and soon realized that stems were not growing back unless they were fenced off from browsing ungulates such as deer, elk, or cattle.
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There are many questions regarding the origin
As the new millennium began it became evident that not only were young suckers not reaching maturity, but also the oldest trees were beginning to die en masse. A group of forest geneticists, headed by Utah State University professor Karen Mock, decided to test Barnes’ original demarcation of the clone with modern micro-satellite techniques. Their findings: the 43 hectare Pando was nearly the exact size that Barnes outlined, but they also discovered that there were many surrounding aspen clones, some comprised of as few as two stems. While these results were notable, many questions remain as to the origin, age, and ecological development of this clone. For instance, did Pando start as equal size to its neighbors and simply outcompete them via superior traits? Or, perhaps it was the “original” forest in this area and others colonized its edges at varying intervals contingent on specific environmental conditions, such as climate changes, wildfires, animal influences, or even aboriginal actions?
Click here for the second part of the Pando series.
Please consider a donation to help save Pando and further our knowledge of aspen ecosystems worldwide: support Pando here.
Paul C. Rogers has published a compact version of his text in the topos 103 “Trees” – have a look.
