The stump of a kauri, a New Zealand conifer, is kept alive by feeding from the roots of trees that transmit water and nutrients to it. The story of a wood wide web or a tree company linked by a root network.
It was known that the trees that make up a forest communicated with each other in the face of invaders such as insects or diseases. They can transmit chemical signals through a network of fungi that connects their roots.
Scientists Martin Bader and Sebastian Leuzinger from the Auckland University of Technology have shown that underground root networks can also keep a strain of kauri (Agathis australis) alive from neighboring trees of the same species.
- There are between 60,000 and 100,000 species of trees on Earth.
- The kauri is similar to the California redwood, although it is on average a little less high.
- It can reach 50 meters in height and 16 meters in circumference.
- It takes about 800 years to reach its maximum size, and can live beyond 2000 years. Some specimens would even be 3000 years old.
A hike, a discovery
The two colleagues were walking through a forest in the Waitakere Mountains, on the northern island of New Zealand, when they saw a strain of kauri that looked strangely healthy despite the lack of branches and leaves. It should normally show signs of decomposition.
The duo then decided to push their investigations, and to try to establish if the surrounding kauris could play a role in its survival. They decided to measure the flow of sap and water in both the strain and its neighboring congeners.
At first, they determined that the strain was still alive and that it was physiologically linked to neighboring trees by a network of roots.
In a second step, their experiments showed that the flow of water in the strain increased as the water flowed from the surrounding trees, suggesting that the strain was drinking from the trees that surround it.
Scientists believe that trees in this forest share water and other nutrients.
This changes how we view tree survival and forest ecology.
Root communication can thus be formed between trees when they recognize that a neighboring root tissue, although genetically different, is sufficiently similar to allow the exchange of resources.
To date, scientists have identified about 150 species of trees, such as Oregon pine in North America, that communicate and exchange nutrients from the roots.
The present works are the first to demonstrate the existence of this type of communication among kauris.
This new knowledge could, in a time of climate change, encourage scientists to conduct more research in the field, particularly with respect to the impact of longer and longer droughts in the future.
For example, trees that have direct access to water could help others. This interconnectivity could, however, allow the spread of diseases such as kauri dieback, an incurable and deadly disease.
One thing is certain, the researchers believe that we must review our perception of trees as individuals and rather consider them as forest ecosystems, real superorganisms.
There are still a few questions that remain unanswered. Why do healthy trees keep their “grandfather” alive when it does not seem to provide any benefit for the whole?
One of the explanations advanced by the authors of this work published in the journal iScience is that the network of roots formed before one of theirs collapses, when it was still alive. Then, after the disappearance of the main part of the tree, the strain continued to extract nutrients and water from its neighbors.
The New Zealand team now wants to better understand the biological processes involved, and to study in more depth the root systems that bind the kauris together.