Tidbits Appreciates Trees

A DISCOVERY

• In 1630 Flemish physician Jan Baptista van Helmont challenged the ancient writings of Aristotle, who had claimed that trees grow by consuming soil. To prove this theory wrong, van Helmont planted a five-pound willow sapling in a large pot containing exactly 200 pounds of dirt. For the next five years he added nothing but water. Then he separately weighed the tree and the soil again. The willow had grown to a weight of 169 pounds, while the dirt weighed only two ounces less than it originally was. He correctly concluded that trees do not consume dirt for their growth. However, he wrongly assumed that trees receive all their nourishment from water. It was years before scientists discovered photosynthesis, the process whereby plants turn sunlight into energy.

ANOTHER DISCOVERY

• Foresters working to thin overcrowded beech forests in Germany noticed that the more they thinned the forest, the worse the remaining trees seemed to fare. This was the opposite of what they expected. Wouldn’t each tree benefit from the extra sunlight, the additional space for air, and more room for roots? Researchers set out to discover why beech forests thrive when the trees are crowded together, but weaken when they are spread apart.

• What they found surprised them: Trees share and depend on one another. Twined together, the roots pass nutrients from one tree to another using a complex network of fungus that interconnect all the neighborhood trees by tapping into the hairlike fibers of the smallest roots. When one tree is short of water, a nearby tree with extra water to spare will pass some over through the fungus highway. When that tree is short of nutrients, it receives a helpful supply in return from the trees surrounding it. Meanwhile, the fungus keeps part of the nutrients for itself, and constantly expands to connect as many tree roots in the network as possible. A single pound of forest soil may contain miles of fungus strands.

• One researcher injected a radioactive dye into a birch tree and then tracked it as it moved into the network of fungus in the soil and then into a nearby Douglas fir.

• Discover more interesting facts in this week's Tidbits by clicking the image and link below: