Getting to the Roots of Tree Communication- by John Canoles
Baltimore County’s Country Chronicle newspaper was kind enough to let us share this article by local naturalist John Canoles.
Getting to the Roots Of Tree Communication
by John Canoles
Cheer up. Winter is half over. That’s why we celebrate Groundhog Day, the official mid-point of winter. The crass, modern ritual of yanking a hibernating rodent from its dark underground burrow into the bright daylight is just Punxsutawney Phil’s way of celebrating Candlemas which is just the Catholic Church’s way of usurping various western European pagan customs.
Those heathen celebrations acknowledged the halfway mark between the winter solstice and spring equinox signaling the awakening of the earth when all things new were hailed with sacred fires. Vestiges of those primitive customs exist still in some Christian nations as Candlemas marks the official end of the Christmas season when nativity scenes are to be removed and all the candles in the church are to be lit to chase away winter’s darkness.
(By the way, the name woodchuck has nothing to do with wood or chucking but is thought to be derived from the Algonquin word for the animal, wuchak.)
Truth is that while winter may persist officially until March 20 according to the 2017 calendar, local signs of spring will begin to emerge soon. The amount of daylight each day has been lengthening and the sun’s warming rays are growing stronger every day. Soon, vernal pools will fill from the winter rain and snow creating the critical habitat needed for our local amphibians to breed.
Skunk cabbage will be poking through icy wetland seeps while wood frogs and spotted salamanders will venture out on rainy winter evenings to start a new generation in these woodland pools. Soon, too, the trees will begin to pump sap from roots to branches fueling the growth of next summer’s leafy canopy.
Though most people define the forest by the trunks, limbs, branches and leaves that they can see, the underground network of roots that support the visible forest are critical to its survival. Recent and ongoing scientific studies have begun to reveal that this support system is even more important and more complicated than had been previously understood.
The root system of a tree provides two obvious and understood functions. A tree’s root network provides support for the tree, anchoring the tree in place against the pull of gravity and the power of the wind. Many of our canopy trees have large tap roots that bury down deeply into the soil and all trees have a network of strong lateral roots that spread out around the tree to help stabilize the support the trunk.
Growing out of these large supporting roots is a network of fibrous roots that function to gather water and nutrients from the soil. Adding to this fibrous network of roots are mycorrhizal fungi. These fungi grow in and around the fibrous root systems of the trees and improve the tree roots’ abilities to collect moisture and nutrients from the soil.
The fungi cells are much smaller than the tree roots, allowing the fungi to reach into tiny crevices within the soil. The fungi cells also have a much greater surface area which allows for much more efficient absorption. In addition, the chemical composition of the fungi allow them to absorb and process certain chemicals that trees cannot process themselves.
The mycorrhizal fungi help in the process and storage of phosphorus and nitrogen, both of which are critical to a tree’s survival. In exchange for these services, the fungi receive sugars from the tree roots that they cannot produce. This is a mutualistic relationship that generally benefits both participants.
Unravel the relationship
Scientists have begun to further unravel the relationship between trees and fungi and have discovered that the network of mycorrhizal fungi may provide even more benefit to the forest.
The underground network of roots was long understood to be complex and physically interwoven. In this scenario, the root of one tree may grow in and around the roots of another tree, adding to the support function but not providing any true connection between the two trees.
However, with recent studies, it is becoming evident that the fungi within the network allow for a type of communication between the trees of the forest.
Previous studies have shown that trees and other plants react to insect attack by releasing chemicals within their cells to make the plant less attractive to the insect. These studies also showed that adjacent trees and plants would begin producing their variety of insect repellent when a nearby tree or plant was being attacked.
It was assumed, and shown to some degree, that chemical compounds released into the air were providing the “communication” that warned the nearby trees of possible insect infestation.
More recent studies have shown that there also may be chemical communication between the roots systems of neighboring trees. The mycorrhizal fungi provide a connection between the roots systems of adjoining trees and this connection allows the roots to transfer chemical cues between the trees. This allows a tree to “warn” its neighbor of an impeding insect attack.
Through this connection, the individual trees within a forest begin to act as one, reacting to an insect attack as a unit and not just individually as the insect invasion moves through the forest. The benefit to the forest is that trees can prepare their chemical defenses before the insect attackers actually reach their branches, affording them greater protection.
The root connections created by the mycorrhizal fungi also have been shown to transfer nutrients and moisture between individual trees. This creates an unprecedented possibility that the healthy trees can actually help support a weaker tree, nursing it
through an insect attack, storm damage or drought.
Some researchers have suggested that mature trees help to nurse saplings in the understory by providing them with sugars that they cannot produce in the shaded understory.
Though the term “community” always has been used to describe forest resources, scientists appear to be finding that the level of communal interaction may go well beyond the typically intended meaning.
Like birds joining into mixed flock for mutual survival, the trees of the forest may be joined by a network of mycorrhizal fungi that communicates danger and shares in support to preserve the forest as a whole. This gives new and interesting meaning to the concept of united we stand, divided we fall.
The next time you walk through or drive passed a forest, take a moment to imagine the complex web of interaction going on below the ground. Communication, sharing and support between oaks and poplars and pines, all working together to preserve the forest community so that there will be somewhere for future generations to live.
Perhaps one day, we humans will better learn this lesson from our forest neighbors.
John Canoles is a principal in the Glen Arm-based Eco Science Professionals, Inc., an environmental consulting firm that, among other things, helps create backyard habitats and enhance stream bank stabilization. John welcomes your comments and questions. He may be reached at 410-967-0959 or email him at firstname.lastname@example.org.