Tree Talk: the language of the forests and what we can learn from it.
Trees have been found to talk with each other using a complex network of underground fungi, and we’ve been using this knowledge for new technologies. But with hotter and drier climates, how will this change?
Spanning from the tips of tree roots to all throughout the soil, there is a lattice of fungi. We’ve known for a long time that this fungal network—termed mycorrhiza—provide trees with water and nutrients, like phosphorus and nitrogen, in exchange for sugar that the tree creates during photosynthesis. Trees can end up giving 30% of the sugar they create to fungi.
But trees use this fungal network to communicate with other trees.
This network is like the postal system. Through the post, we are connected to people and places across a vast distance; we send each other information through letters, and sometimes we receive packages with things we need or asked for.
Similarly with trees, the way they ‘talk’ is by giving and receiving chemical, hormonal and slow-pulsing electrical signals through this lattice of buried fungi.
Communicating through the ‘wood-wide web’
In every forest that is not too damaged or degraded, each tree is connected to all others. Chemical signals can be sent to nearby trees to alert them of dangers, such as disease or insect attacks. When a neighbouring tree receives this signal, their behaviour changes.
For example, scientists injured Douglas fir saplings that were planted next to ponderosa pines and two things happened. Firstly, nutrients and water were transferred from the Douglas fir saplings to the ponderosa pines via the fungal network. Secondly, and most interestingly, stress signals were sent along the same network, resulting in an increased production of defensive enzymes in the ponderosa pine.
These two things did not happen when the fungal network was severed.
Since researching this underground arboreal information highway more intensely, we now also know that trees can also recognise their genetic relatives.
How this has changed the way we look at trees
Prior to this discovery, forest ecology was built around the simple idea of competition driving forest structure. But it’s not just about competition between saplings and mature trees; the ecosystem also requires cooperation. A sapling in a shaded part of the forest would otherwise be as good as dead if it weren’t for the fungal network allowing nutrients to flow from one tree to another.
And this knowledge has impacted the way we understand reforestation and species reintroductions.
While trying to save a critically endangered tree species (of which there are only 76 left), Chinese scientists found that the presence or absence of this fungal network in their transplanted saplings was really important for sapling survival. Grown with fungi, saplings had an 80% chance of surviving when transplanted to the forest. But without fungi, survival dropped to 46%.
Going back to your roots
Ecologists are gaining a greater appreciation for the importance of microbes (fungi included) in the functions of ecosystems. Like how we better understand how human gut microbes are affecting our health and behaviour, ecologists are beginning to understand how microbes are affecting the earth.
This increased understanding has led to improvements in reforestation activities, contaminated water clean up, pest and disease control and commercial forestry.
The omnipresent spanner in the works: climate change
However, this new knowledge of how microbes affect the earth is limited. With increasing temperatures and more erratic weather, the impact on microbes is poorly understood.
If microbes cannot survive in this changing world, how will trees, animals or even humans?
Despite this bleak outlook, there’s a positive outcome from all this research. It has shown us that, instead of looking at trees as habitat for a wide range of animals, we should instead see the diverse network of fungi and bacteria under the soil as habitat for trees. If we can better understand and harness these interactions between microbes and their trees, perhaps there’s a way of saving the forests from climate change.
If you would like to know more about the intricacies of ‘tree talk,’ I recommend you read this interview with Suzanne Simard, one of the first scientists to discover the importance of mycorrhizae to forest health.