If you look at the treetops in some forests, you may notice what looks like channels between the outer branches of the trees above your head, and they overlap together in what looks like a paper puzzle, in a phenomenon that has long attracted the attention of photographers and scientists alike, and has been called “crown modesty.”
Since the 1920s, scientists have been interested in documenting and studying this phenomenon, but until now there is no agreement about the causes of its occurrence, but its importance for these trees is clear, as one of the most important goals of plants is optimal exposure to the sun, which is extremely important for the process of photosynthesis, and thus This phenomenon prevents any possible shading of trees or parts of them.
Mutual pruning
A team of researchers believes that wind causes branches to collide with their nearby neighbors, causing damage to their leaves and buds. As a result, trees limit the growth of their limbs in these locations to avoid further damage. This means that there is “mutual pruning” between trees in forests.
In 1955, it was conducted study On eucalyptus trees in northeastern Australia, where strong winds often cause trees to rub against each other, the resulting erosion kills the limbs of sensitive developing trees, causing them to move apart, but this was not evident in all trees.
In 1984, other research on mangrove trees showed a close result, as it appeared to the researchers that the “crown modesty” is the result of a battle between the upper limbs of the trees during the blowing of the wind, so each of them cleans a small area surrounding its limbs, and in the end this wonderful shape is created.
Proponents of this hypothesis cite that the phenomenon of “crown shyness” is particularly observed in conditions favorable to this pruning, including windy forests and resilient tree groups.
Sensor Kings
Another team of scientists assumes that the matter is more complex than just the movement of tree limbs, as each tree can sense nearby plants from a distance, and thus grow to the extent that it does not expose them to contact with other tree limbs, so as not to shade them, block them from the sun, or prevent their growth.
This team relies on the fact that it has been previously proven that tree leaves can sense distant light that bounces back on them after colliding with nearby trees. Other research has also proven that trees have a specialized sensor system to detect chemicals emitted by nearby neighbors, meaning that plants use this. Means to determine the distance between it and a nearby plant, and then grow to a level that prevents contact.
In confirmation of this hypothesis, a team of Malaysian researchers concluded: study Dryopalanops aromatica, the growing tips were sensitive to light levels and stopped growing when approaching neighboring foliage due to the shadow created by their approach.
The wonderful world of trees
But in the end, it appears that “crown modesty” has great adaptive importance. In addition to allowing different trees to get the best exposure to sunlight, it also leaves gaps for light to pass down to smaller plants and animals that need light.
In addition, “crown modesty” in one way or another resembles a degree of social distancing, as it can contribute to reducing the spread of diseases among plants, especially epidemics that spread in forests just as they spread among human masses.
In any case, the world of trees is not very different from the animal world or the world of us humans, where its individuals compete or cooperate in different contexts.
For example, trees of different species, or even the same species, can exchange carbon, nitrogen and phosphorus through root networks, and this cooperation supports the health and resilience of the forest as a whole.
Through these underground networks, trees can also send warning signals to other trees about threats such as insect infestation, allowing other trees to prepare their defenses by producing protective chemicals.
But it’s not always that peaceful. Tree species spread their roots into the ground to compete with their neighbors for nutrients in the soil. Some trees quickly rise to the highest possible point among a group of trees to get sunlight. Some trees – such as black walnuts – release chemicals into the soil. It inhibits the growth of nearby plants, reducing competition.
