Radiolab: From Tree to Shining Tree


Three guests: Suzanne Simard, a professor of forest ecology and teacher at the University of British Columbia, Jennifer Frazer, a science writer that has a blog called The Artful Amoeba, and Roy Halling, a mycologist.

The connection between trees

  • Normally trees from different species are competitors.
  • Suzanne noticed that by cutting a birch tree, the fir tree next to it dies.
  • She leads an experiment to test it out.
    • She sealed trees into plastics bags and injected radioactive gas.
    • The trees sucked up the gas.
    • Where does isotopes go after?
      • They are shared between trees.
      • 1 tree was connected to 47 other trees.
      • The bigger and older the tree is, the more connected it is.
      • Trees have a complex communication network.

Wood Wide Web

  • The communication is not only made by the main roots.
  • The feeder roots that communicate too.
    • There are little white threads attached to the roots, smaller than an eyelash.
    • They’re everywhere and some even go on for 7 miles.
    • Not really plants, but a fungus.
    • They’re hollow, like tubes.
      • A fungi freeway.

Why are fungi creating this network and why do trees need it?

  • The tree has something the fungus needs and the fungus has something the tree needs.
  • A tree turns inorganic carbon into organic carbon.
    • CO2 into sugar.
  • If they only had that mechanism, trees wouldn’t be tall.
  • They need minerals
    • Nitrogen
    • Phosphorus
    • Magnesium
    • Potassium
    • Calcium
    • Copper
  • For example, nitrogen is used in DNA and in lignin cells, which make the tree rigid.
  • Fungus can draw water and nutrients from the soil.
  • Trees can only absorb nutrients from the tip of its roots.
    • That’s not enough.
  • Fungus takes sugar from the trees to build their bodies.
  • They communicate through chemical signals.
    • Fungus tells the tree to soften their roots so they can enter.

How is the fungus getting the minerals?

  • It hunts, fishes and strangles.
  • They developed a system for mining.
    • They worm their way back and forth until they reach a rock.
    • They secrete acid and dissolve the rock.
    • They suck up the minerals.
  • They can also hunt.
    • There are some insects living in the soil, called springtails.
    • Fungi eat them.
      • They have a way of telling if the insect is dead or alive.
      • They pierce them and suck the nutrients out of them.
    • They can even absorb the nutrients from carcasses of animals that seeped into the soil.
      • In some trees, 75% of their nitrogen comes from fish.

How much sugar do the trees give to the fungus?

  • The estimate, which depends on each ecosystem, is from 20% to 80%.
  • Trees that don’t need sugar right now give it to the fungi.
    • When they need it, the fungi can give some back.
    • It’s like a bank system.

Alerting the forest

  • Trees can also send danger signals through the network to other trees.
  • So the other trees start producing chemical that tastes bad to prevent insect from eating them.
  • If a tree is dying, he’ll send his carbon to his neighbours.
  • Maybe it’s the fungi that decides who gets what.
  • Food ends up with new trees that are better at adapting.
  • This is the intelligence of the forest.
  • Forests act like one big organism.
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