Pando
Pando — a single name, whereas plants as a rule have two names, one for the genus and one for the species — is a quite large organism. Covering more than 100 acres, it weighs in the order of 6,000 tons.
It lives in south-central Utah, in the Fishlake Forest, at the western edge of the Colorado Plateau, at 2,700 m (8,850 ft) above sea level. It can be described as a colony of 47,000 aspens (Populus tremuloides). The individual trees are connected by their roots. Their trunks average 130 years in age, as revealed by the tree rings. Aspen establishment from seeds has probably not occurred in the United States since the last glaciation, about 10,000 years ago. Pando’s last flowering may have occurred at that time.
It is a single male quaking aspen, as indicated by identical genetic markers. During forest fires from lightning strikes, Pando survived underground. Its root system is estimated to be 80,000 years old. The comparison with archeology is irresistible, with both Pando and archeological sites the soil serves as a conservatory.
Pando’s existence and age appear to negate, even ridicule, the legendary tale of Mormons, in their westward migration, bringing small quaking poplars with them. The legend contends they planted these. The imported trees became aspens if one is to believe the tale.
Pando’s roots, like those of many other trees, are closely associated with fungi. Such an interaction is symbiotic, i.e., mutually beneficial. The fungus gains access to sugars such as glucose and fructose. The plant gains the advantage of being able to draw on the mycelium for its sustenance, much superior to its own root system. This mycelium is much better able to obtain from the soil water and other nutrients, being much smaller in diameter than the smallest root. Comparable to blood capillaries, it can drain a much greater volume of soil, with a far greater absorption capacity.
Aspens such as Pando’s are predominantly ectomycorrhizal: this long word only means that the fungal mycelium remains external to the plant root cells — their friendly symbiosis remains totally respectful. The fungi act towards the quaking aspens in the manner of a wet nurse, to use an anthropomorphic comparison.
Forest fires were mentioned above in connexion with Pando’s underground survival. Other hazards are bacteria, blights, insects and foragers. They can wipe out the above ground portions of plants, while the underground rhizome endures.
But not always. Think of volcanic eruptions. A lava flow, a field of pumice can destroy and render an entire area sterile. A pumice plain extending over 20 km2 was created by the May 18 1980 eruption of Mount St. Helens. This is extremely nutrient-poor soil. By 1998, mycorrhizae had yet to assist the resettling of plants in that harsh environment. Underground vegetation can be extremely durable, but it has first to be established.