Come along with Tidbits as we admire the intelligence of trees!
• In 1630 a physician named Jean Baptista van Helmont went against the word of Aristotle, who insisted that trees grow by consuming soil. To prove this theory wrong, he planted a 5-lb. willow sapling in a pot containing exactly 200 lbs. of dirt. For the next five years, he added nothing but water. Then he weighed the tree and the soil again. The willow weighed 169 lbs. The dirt weighed only two ounces less than it had originally. He concluded that trees do not consume dirt, and he was correct. However, he wrongly guessed that trees receive all their nourishment from water. It was years before scientists discovered photosynthesis, the process whereby plants turn sunlight into energy.
• Foresters working to thin overcrowded beech forests in Germany noticed that the more they thinned the forest, the worse the remaining trees fared. This was the opposite of what they expected to find. Wouldn’t each tree benefit from the extra sunlight, the additional space, and more room for roots? Researchers set out to discover why beech forests thrive then the trees are crowded together, but falter when they are spread apart. • What they found surprised them: trees share. Twined together, the roots pass nutrients from one tree to another using a network of fungus that interconnect all the neighborhood trees by tapping into the hair-like 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 as possible. A single ounce of forest soil may contain two 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.
• One type of fungus is able to release a toxin which kills tiny insects in the vicinity. When these insects decay, they give off nitrogen which the fungus absorbs and shares.
TREE DEFENSE SYSTEMS
• When giraffes start feeding on the leaves of umbrella thorn acacia trees, the acacia trees start pumping toxic substances into their leaves making them taste bad. The giraffes move off to other trees, but they always move to trees that are either upwind or quite a distance away. This is because the acacia trees also release ethylene gas that warns neighboring trees that the giraffes are in the neighborhood, and those neighboring trees pump their leaves full of the toxins before a giraffe arrives to even take a single nibble.
• Some trees can identify the specific type of insect feeding on their leaves through compounds in the bug’s saliva. The trees then release pheromones that attract beneficial predators, which arrive and feast upon the marauding invaders.
• In tropical countries, leaf-cutting ants can strip a tree of its leaves in a single night. They take the leaves back to the nest where they chew them into pulp and use them as compost to grow fungus, which they eat. To protect itself from being defoliated, the acacia tree secretes droplets of sweet sap near the base of its leaves. A different type of ant loves to eat the sap, and they set up colonies in the large, hollow thorns of the tree. Any time the leaf-cutting ants come around, they are driven away by the sap-eating ants.
• Some trees have leaves that fold up and droop whenever they are touched. Researchers theorize that when an animal takes a bite of the leaves, the tree reacts this way in order to look less appetizing. The leaves become nearly invisible to the eye when they are tightly folded up.
• Mimosa trees have brackets of leaves that snap closed whenever they are disturbed. One researcher designed an experiment where drops of water fell on the leaves at regular intervals. The leaves closed immediately at first. But after a while, the leaves stopped reacting to the drops and remained open, having apparently “learned” that the water drops represented no harm. Even more surprising was that the mimosa “remembered” this and repeated the behavior weeks later, even though no drops had fallen on the leaves in the meantime.
• The blossoms of the bird cherry tree contain both male and female parts inside each bloom. The flowers are pollinated by bees. When bees are traveling from flower to flower in the crown of a single tree, they tend to spread the pollen of that same tree to its own stigma. Yet when the pollen travels down the tube of the stigma, the tree tests the DNA of the pollen grain, and if it’s a genetic match, the stigma is blocked off and the ovary does not get pollinated, thus preventing inbreeding.
• When researchers placed sensitive microphones against the ground in a forest, they recorded sounds coming from the roots that registered at 220 hertz. This in itself was not all that unusual, but they subsequently found that when they played the recorded noises back, all of the root tips from surrounding trees slowly turned in the direction of the sound.
• It benefits the entire forest to keep as many trees alive as possible, for if trees die and fall, that leaves gaps that affect the microclimate negatively. The hot sun and drying winds disrupt the humidity level and raise the temperature, drying out the forest floor, and leaving the remaining trees far more vulnerable to drought and insects.
• In one experiment, a researcher sprayed an insecticide on one of the largest and oldest trees in a forest and collected the insects that fell dead into collection nets. There were 257 different species of insects living among the boughs of the tree. A similar study in New England showed that 167 different kinds of insects and small animals were living in a single rotting log on the forest floor.
• Researchers in New York state removed forest soil to a depth of one inch and studied it. They found an average of 1,356 living things present in each square foot of dirt (microscopic creatures not included). Some 95% of insects live in the soil at one point or another during their life stages.
• Researchers found when studying a group of women that when they took a walk through a forest, their blood pressure dropped, their lung capacity expanded, and the elasticity of their arteries improved. When taking a walk of identical length through town, none of these benefits were noted.