September 20, 2016

Radiolab: From Tree to Shining Tree

LISTEN

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.