Summary
1. Friendships
Scientists have discovered that trees in forests are linked by fungal networks, or interconnected roots that allow them to exchange sugar and by which they can communicate. This provides benefits to each member of the forest. By living in a group, each tree maintains moist soil, a suitable microclimate, and shelter from wind and rain. A tree also benefits from having nearby trees that can help it with energy when it is stressed. Planted trees aren’t able to receive this kind of community assistance because their roots are damaged during planting and can’t form the necessary network.
Need to Know: Trees form “friendships” and these friendships help them stay healthy and live longer. The whole forest benefits when the trees care for each other, because a colony of healthy trees means a better ecosystem for all.
2. The Language of Trees
A tree passes information, such as the presence of insect or fungal invaders, along to neighboring trees. Transmitting these alerts allows other trees to prepare their defenses. Chemical signals are released into the air, and they are passed between trees via their interconnected roots and the network of fungus that spreads between them under the ground. Electrical signals are also sent through this system, what scientist Dr. Suzanne Simard calls the “wood wide web.” Trees also have the ability to communicate with other species, such as when they produce the blossoms and sweet odors that attract bees for pollination.
Need to Know: Trees have a language. Instead of words, they use chemical and electrical signals sent through the air or through an underground system of roots and fungus to communicate with other trees and species.
3. Social Security
Traditional forestry assumes that it is better to grow trees with lots of space between them because it gives each tree a lot of sunlight and water. But researchers at the Institute for Environmental Research at rwth Aachen found that beech trees synchronize their rate of sugar production so that all trees are producing sugar at the same rate. They do this by sharing sugar with each other through their network of roots and fungus. If trees are felled to give the remaining trees more room, the trees that are left are on their own, without the network to exchange sugar. Some have trouble surviving. The mutual assistance trees provide each other is consistent with natural selection for individual fitness because each tree helps the others survive and thrive.
Need to Know: Trees have their own version of social security. A tree that is getting plenty of sun and water and is making more than enough sugar can share with trees that don’t have ideal growing conditions. All the trees benefit, because a forest where all the trees are healthy creates more protection from heat and wind, and because if one of the strongest trees gets sick, it can rely on the trees around it for assistance.
4. Love
Deciduous trees carefully “plan” when they will reproduce based on the levels of their energy reserves, and they communicate with neighbor trees so that they all reproduce at the same time. They synchronize the years they reproduce, which for this species involves producing and releasing seeds. Only producing seeds in certain years helps protect the seeds from herbivores. For example, deer and boar love to eat the seeds in acorns and beechnuts. When trees stop production of these foods, it decreases the populations of these herbivores, increasing the trees’ chances of successful reproduction in the next cycle. Another advantage of deciduous trees reproducing in sync is that the genes from many trees will be mixed, preventing inbreeding.
Trees have several strategies for dispersing pollen and encouraging genetic diversity, including scattering pollen via insects or in the wind. In some species, each particular tree only has one sex. Other types of trees have male and female blossoms that open at different times of the year to prevent self-pollination. A bird cherry tree is actually able to determine the genetic makeup of pollen and block its own pollen from reaching an egg.
Need to Know: Deciduous trees don’t reproduce every year, which helps limit the populations of herbivores that feed on their seeds. In contrast, coniferous trees usually reproduce annually. Although some birds are able to eat the seeds inside these trees’ cones, herbivores aren’t the same threat as they are to deciduous trees. All trees have strategies to promote genetic diversity, which makes the trees healthier.
5. The Tree Lottery
Like effective companies or well-organized families, trees budget their energy. Creating blossoms consumes an immense amount of energy. Species that blossom annually carefully adjust their energy use over the course of the year, while those that blossom periodically need years of recovery after the enormous energy used for bud production. During their blossoming year, these trees are vulnerable to insect infestation because they don’t have the energy to put up their usual defenses.
The energy of blossoming and creating seeds is energy put into producing the next generation of trees. Different species of trees have different strategies for when their seeds sprout. Some seeds sprout right away, some seeds can wait a year or two before they sprout, and some seeds can remain dormant for as many as five years. There are many dangers for the sprouts—hungry animals, bad weather, lack of water. Most don’t survive.
Need to Know: Huge amounts of energy are required for a tree to reproduce, and most seedlings don’t make it. Odds are, a tree will only produce one other viable tree. A poplar, for example, will make over a billion seeds in its lifetime. But statistics say that out of those billions, only one will grow into a mature tree. For a tree, reaching sexual maturity is like winning the lottery.
6. Slowly Does It
Trees usually grow slowly. A young beech tree growing under the canopy of a parent tree will only have access to the limited sunlight that reaches the forest floor, about 3% of the total sunlight. The lack of sunlight limits sugar production, so there isn’t much energy available for growth. But this forced slow growth is actually good for the young tree because it makes its wood dense and resistant to breakage in future storms and attacks b...