by Laura and Amy
We recently read The Overstory, by Richard Powers, a Pulitzer Prize winning novel that looks at human and tree relationships from a poetic, yet gripping perspective – we loved it.
Some of the information about trees was so mind-boggling that we thought you might be interested in it. We confirmed these facts from the novel with science/forestry websites to be sure it wasn’t all fiction.
Fact 1: Trees build themselves out of air! You’ve probably all heard that forests are carbon sinks, storing carbon from carbon dioxide (CO2) in the air. But what we didn’t realize is that all the wood of a tree is made from that CO2. Trees get water and nutrients from soil, but studies have shown that there is no depletion of soil from a tree growing in it, so all the carbon comes from the air.
Here’s the science of how that happens. The amazing process of photosynthesis is where chlorophyll (the green part of plant leaves) uses light energy to break water (H2O) into oxygen (O2) and hydrogen (H). The pores of the leaves (stomata) take in CO2 from the air – that CO2 is broken into more O2 and carbon (C) which binds with the H from the water to make various carbohydrate (CH) chemicals. Trees use those carbohydrates to stay alive, reproduce, and build their structures, including the roots, trunk, branches, stems, leaves, and seeds, including fruits and nuts. The O2 is released from the pores into the air, and we breathe it in. Plants and plankton in the oceans are what made the O2 that allowed the earth to be habitable for animals, including us.
Fact 2: Aspen trees’ root systems can live for thousands of years! The trees above ground can live 150 to 200 years, but as we learned on last year’s tree educator walk, aspens are a colony of genetically identical shoots off a common root mass, which is a single organism. These root masses can often live from 5,000 to 10,000 years, according to the US National Park Service, and what is thought to be the oldest living root colony in the world, in Utah’s Bryce Canyon National Park, is 80,000 years old. Our aspen root masses in Calgary are not likely to be more than about 10,000 years old as that is roughly the end of the last ice age here, and they would have moved north from warmer areas over time.
Fact 3: Trees can communicate with each other and occasionally other creatures through the air. Using pheromones and other scent signals released into the air, some trees can emit signals to surrounding trees or even protect themselves against predators. An example of this is a tree called the wide-crowned umbrella thorn acacia that can emit a distress signal in the form of ethylene gas that, in high enough quantities, has the capabilities of sickening or even killing the large giraffes that snack on its leaves. Another example: elms and pines can detect caterpillar saliva and in response, release a pheromone that attracts a specific kind of wasp to eat the caterpillars, thus protecting the trees from decimation. A recent study also shows that some trees know the “taste” of deer saliva and in response to the animals making a meal of the tree, can release a chemical to make their own leaves taste bad. Trees, it turns out, are not at the mercy of their environment but are in fact active participants.
Our Tree Book Club, though small, is keen, and will be reading The Hidden Life of Trees, by Peter Wohlleben next. We don’t have a fixed schedule; we just meet for a walk to discuss the book once we have finished it. If any of you would like to read The Hidden Life of Trees and discuss it with us, contact us at [email protected].
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