Communication Among Trees

By Len Phillips

Can trees really “talk” to each other like people communicate? Of course not, but they do communicate among themselves by linking their roots together and using a fungal network in the soil. But mankind has not yet learned their language.

People communicate by voice, writing, and by electronic means. Trees in the forest communicate by various means sent through their root network connected to other tree roots and also by underground hair-like fungal roots also linked to the fungi attached to adjacent trees, all of which can spread twice the distance of the branch crown. This information is sent by electrical impulses as well as by chemical compounds and hormonal signals to determine which trees need more nitrogen, phosphorus and carbon, and which trees have extra to share. However, the process is extremely slow and can take hours for a message to be transmitted even though the messages move through a “fiber-optic” type network scientists are now calling the “wood-wide-web”.

Researchers have also determined that trees communicate many other messages. For example, when something smells nice, people are attracted to it, but when it smells bad, they stay away. Trees have a sense of smell and can identify a pest by the smell of the saliva left on a partially eaten leaf. If the pest is harming the tree, the tree will produce toxins to make the leaves smell bad or have a bitter taste or kill the pest. When leaves are being eaten by pests, the tree also gives off an ethylene gas that warns other trees in the forest of the danger. These other trees pump toxins into their leaves to discourage the pests from coming to their tree. On the other hand, all trees know that the sweet smelling perfume in a flower will attract bees to pollinate their flowers and ensure the tree's survival for many generations to come, and this is good communication.

People go to the store or their gardens to obtain the food they need. This food is surplus produced by other people called farmers. Water is shared by everyone in a city through a network called the municipal water supply. Trees with abundant food and water will transmit messages between trees, expressing an interest in sharing water, food, and information with those in need. Tree roots often continue to live after a tree dies or is cut down because the roots are connected to other living trees and the sugars from the live trees are shared with all the trees connected to the underground network. There are many examples discovered by scientists that tree roots have transferred carbon and carbon products from living trees through living tree stumps, which continue the transfer of products to other living trees.

People work to provide food and shelter for their families and when one person dies, there are others to replace them and the family continues to survive. Trees also have families around them in the form of seedlings and sometimes suckers from their roots. In addition, the tree family members are all available to survive the mother tree when she dies. As soon as there is an opening in the forest canopy that allows the sunlight to reach these family members, there is a major growth spurt from all the family members as they race to be the first tree to reach the opening. Once the hole in the canopy is filled the trees that did not make it, die or decrease their growth rate while they wait for the next opening to appear.

People deal with bad weather by seeking shelter and staying inside. People can not individually alter the weather. However, by working together, people have invented air conditioning and heaters to alter the temperature and level of humidity in their buildings. People who experience high temperatures will also seek relief by moving into the shade, being submerged in water, or go inside for air conditioning. People also sweat when they become overheated and the evaporating moisture on the skin, cools the body down. Forest trees can also deal with weather changes through communication. In the forest, besides creating shade with their leaves, a group of trees working together can create an ecosystem that can moderate the weather (heat and cold) and move water to alter the level of humidity and temperature. As water is pumped out the leaf stomata, the evaporating moisture cools the forest and brings the temperature down. As water passes through the trees faster than normal, the trees become cooler internally as well as helping to lower the temperature within the forest. In addition, all the trees working together will release terpenes into the atmosphere above the forest on hot summer days. These terpenes act as a natural form of cloud seeding. These clouds help to block sunlight and cool the forest.

The houses that shelter people are likely to be damaged less within the congestion of a city than in a single home by itself. Houses built in areas of high winds are built with concrete and steel. An individual tree that is subject to high winds on the whole tree are more likely to be damaged than trees in a forest where all the trees act as a unit and if any problem occurs it is just the tree tops or individual limbs that might be damaged while most of the trees remain intact. Trees also have certain weak branches that are attached with co-dominant crotches so when there is a severe wind storm, one of the two branches break away to reduce wind resistance and damage to the entire tree.

People who live alone are not as healthy nor live as long as those who live and communicate within a community. People need people to be happy and help others in need. Trees that are planted in cities have roots that were damaged when the tree was dug and trees that were planted in proximity to city sidewalks, are surrounded by soil that is so compact that roots can not penetrate it. These isolated trees are subject to pests and diseases without the warning that the trees in the forest provide each other. These situations prevent trees from being happy and developing a communication network with other trees. Trees growing in the forest are happy and healthy because they are part of the forest communication network and are likely to live twice as long as the same trees living in a city.

People have skin. It sheds as we grow from childhood. It is formed as an inner layer of skin and as new inner layers are made, the outer layers fall off in flakes. It is flexible and conforms to our bones and muscles. It prevents our bodies from drying out. It keeps pests and diseases from invading our body. It protects all our inner organs so our bodies can function. Trees also have skin that functions the same way, except we call it bark. Bark prevents the tree from drying out and protects the tree's inner functions. Insects and fungi would thrive if there were a low moisture level in the wood and it is unappealing to pests because they will suffocate in high moisture levels of wood with bark intact. A tree contains almost as much liquid as people do. Trees will also communicate with other trees if they are being attacked, so the neighboring trees can establish defenses before they are attacked.

Trees expand their diameter without breaking the bark the same way that people grow without breaking their skin. The bark originates near the cambium which makes the bark on the exterior surface the oldest. The newly formed bark is not broken, which keeps the high moisture levels inside the tree. The breaks on the older bark, which is at the surface, may crack, but it does not harm the tree. A break or cut in the bark is as uncomfortable for the tree as a break or cut in the skin is for people. Skin is harmed by an excess amount of sunlight making it become sunburned. Bark is also harmed by an excess of sunlight and making it become hard and inclined to crack, causing injury to the tree. This is why some nurseries put a dot of paint on the north side of the tree, so when the tree is transplanted, the person planting the tree can orient the dot to the north, thus preventing sun damage to the tree. If the nursery did not identify north, the tree planter should see which branches are the largest in diameter. These are the limbs that were facing southwest in the nursery and this is how a tree communicates to people about the best orientation for the tree to be planted. The southwest direction provides the most intense sun and it is the side that the tree has developed its thickest, toughest bark.

As people get older, they begin losing their hair in the same manner that the highest tree branches in the forest begin to thin out when the tree gets past middle age. About the same time, the trees also redirect their growth to lower branches making the tree wider. (This increase in width around the middle is another parallel to people.) The twigs on many branches of a very old tree also begin to die off, just like many very old people lose body mass. The communication links however do not seem to change between trees as the trees get older. They may not be as fast as a young tree, but the roots do keep transmitting messages, even after death.

Like people, trees are extremely social creatures, dependent on each other for their survival. And, as it is with us, communication is key.

Source

      Wohlleben, Peter, The Hidden Life of Trees, Greystone Books, 2015.