What actually is Vascular Cambium? Why does it matter?
Vascular cambium is the tissue that gives rise the formation of both xylem and phloem tissues. The xylem, vascular cambium, and phloem, along with their supporting tissues are arranged in vascular bundles. These vascular bundles form a continuous connection between the furthest root and the tip of the highest branch. When these bundles become severed or interrupted as in this feeding damage over the winter by rodents, the tree can die.
The xylem is responsible primarily for moving water and dissolved nutrients from the roots through the stems and into the leaves so photosynthesis can take place. Photosynthesis is a complex two-step process within the chloroplasts where sunlight, carbon dioxide and water are transformed by a system of enzymes into glucose (a simple sugar) and oxygen. The phloem translocates the sugar made in the leaves into either developing organs like buds or fruits or down to the roots to fuel both growth and storage of energy.
In the case of Emerald Ash Borer that attacked Green Ash, the borer entered through the bark and created galleries in the vascular tissue.
If the insect infestation completely infests the vascular tissue around the entire trunk, the tree will die as indicated in this post:
https://bygl.osu.edu/node/1012
While the function of these vascular tissues is the same for all vascular plants the arrangement differs. In monocots, like grasses, the vascular bundles scattered throughout the stem of the plant. In dicots, the typical arrangement of the bundles is for the phloem to be oriented toward the outside of the plant, the xylem to the inside with the cambium in between. Herbaceous dicots have a ring of discrete vascular bundles, like in this celery.
While in woody plants, these bundles form into rings.
In a healthy tree, typically the phloem tissue, just under the bark, is replaced annually. From the vascular cambium, a new ring of phloem tissue is produced to the outside and a new ring of xylem is produced to the inside.
Depending on the growing conditions and tree species, the thickness of the xylem ring can be highly variable. Under good growing conditions the rings will be wider while narrow rings can be indications of drought or other stressful conditions.
In autumn, trees and other perennial plants will transport sugars down to the roots for the winter. The roots store these carbohydrates and then when conditions are favorable the xylem transports water and sugars back up the trunk to resume growth. A great example of this is in the form of sap collected in the early spring from maple trees. The carbohydrates stored in the roots are carried back up the tree to begin growth. This sap can be collected in late winter, and boiled down to make maple syrup.
It takes 40 gallons on sap to create 1 gallon of maple syrup.
The process of maple syrup is demonstrated here:
https://bygl.osu.edu/index.php/node/2091
But what happens when this vascular tissue becomes disrupted? The tree will suffer and may even die.
This vascular interruption can happen in a number of ways. Girdling roots can cause the vascular tissue to become constricted and may cut off the flow of water and carbohydrates to and from the roots.
Pictures of girdling roots are shown in the article “A Girdle you Hate to See”:
https://bygl.osu.edu/index.php/node/1215
Also, a tree that is constricted as it grows, as in the case of this maple will eventually die.
Damage to the trunk can occur from a tree being hit by a lawnmower.
In this Crimson King Norway Maple, the side of the tree that was damaged, stunted and probably headed for death.
As you can see, the damaged side of the tree is showing canopy decline.
Once the tree begins to rot and decay, secondary organisms like saprophytic fungi,
or insects can be observed.
Another common way to damage the trunk of a tree is to run a weed eater.
This tree was damaged around the base of the trunk with a weed whip. You may also notice a girdling root to the right.
This damage cut through the phloem and damaged the vascular cambium where growth was inhibited, and the Redbud died.
In addition, damage to vascular tissue can happen through volcano mulching.
Adventitious roots can begin to form above the basal flare of the tree as vividly demonstrated in the post below:
https://bygl.osu.edu/index.php/node/2347
Also, this mulch can hold moisture against the trunk of the tree and can create an environment where rot can set in.
It’s important to remember that just below a tree’s bark is living tissue. Any damage to this bark can hurt the tree.
Vascular Cambium is important. Do your part to take care of trees.
