Quaking Aspens – one forest, one organism

To carry on the tree theme, I thought I would draw your attention to one of the most interesting forests in the world. A forest of Quaking Aspens or Populus tremuloides in Utah known as Pando.

Source: scottks1 [Flickr]

It looks pretty standard in forest terms but this forest has a secret. It is one organism. A forest of clones.

Discovered in the 1970’s by Burton V. Barnes, the forest covers 106 acres and has 47,000 trees which are all linked by an immense root system underground. It is thought to weigh over 6 million kilograms and so qualifies as the heaviest known organism! At an estimate 80,000 years old, it began to grow when the first humans were beginning to move out of Africa. It has lived through ice ages and innumerable forest fires in that time.

In hindsight it can be quite easy to spot a clonal forest, especially in the spring or autumn. The trees all have the same internal signals so all make leaves or change colour at the same time, which can give some spectacular patterns in the landscape (see below).

Fishlake Forest, Utah. Source: Public Domain

These trees are all male. But they cannot produce viable pollen for sexual reproduction like other male trees because they are triploids. This means that they have three copies of their genetic code in each cell. So they can only reproduce by making new shoots which come from its root system.

But this forest is being threatened. Living in a dry climate, these trees take a long time to reproduce. The average age of the trees in the forest is 130 years old, which is coincidently the age they are expected to die. If a large proportion of the trees in this wood die of old age, there will not be enough energy in the root system to bring up new stems. And even if they do, there is a big problem with herbivores, such as elk and deer which are eating the vast majority of seedlings.

On top of this, one of the main problems with being a clone is that you all have the same genetic information. That means that it will be much harder to survive the arrival of a new threat. As I am sure you are aware, the climate is changing. A change in conditions or the arrival of a new disease or pest could spell disaster for these trees as they will most likely be unable to adapt to these new pressures.

Efforts have been made to reduce the number of tree seedlings being eaten but it is the unpredictable changes that are most worrying. These trees have survived for thousands of years so here’s hoping they can cope with the latest difficulties being thrown at them.

To find out more about this forest and trying to save it, here is a podcast from Living on Earth: