Girdling is one of the most common methods of controlling tree populations and has been in use for thousands of years. Although the method is quite simple, it has quite interesting effects on the physiology of a tree. Let’s take a look at everything you need to know about girdling trees including how to do it properly.
Girdling or Ringbarking is the removal of a ring of bark including the cork, cambium, phloem, and in some cases even the xylem layers from a tree. Girdling cuts off the supply of food and nutrients from the foliage to the roots. Nutrient deficiency in roots will lead to the eventual death of the tree.
What is Girdling?
Girdling is the act of removing a ring of bark including the cork, cambium, phloem, and in some cases, even the xylem from the tree. Doing so has an immediate impact on the transport of water and other nutrients within the phloem tissue.
Removing the xylem layer will further affect the transpiration processes within the tree. Girdling stops the transportation of nutrients resulting from photosynthesis in the foliage, to the roots, and vice versa.
Is There a Difference Between Girdling and Ringbarking?
While girdling and ringbarking are often used interchangeably, botanists differentiate between the two quite clearly. While the latter is defined as removing a ring of bark including the cambium layer, the former suggests removing the xylem layer along with the cambium.
What Are the Physiological Effects of Removing the Phloem Layer of a Tree?
For ease of understanding, both ringbarking and girdling will be used interchangeably. But it is important to understand the different impacts removing both cambium and xylem layers will have on the tree.
If you only remove the cambium layer, this will only stop the translocation of nutrients within the phloem tissue, but water and nutrient transport will continue within the xylem tissue.
The phloem tissue is majorly responsible for transporting complex organic molecules like amino acids, sugars, and hormones along with other substances mixed with the phloem sap. This will stop the transport from both roots to the foliage and from foliage to the roots.
The impact of removing the phloem layer can differ based on the season and type of tree. During the seasons when the tree is going through active growth, the level of photosynthesis is very high in the tree. During this time, the transportation of nutrients and water is often basipetal. In other words, flows from foliage to the roots.
Similarly, if you are dealing with deciduous trees coming out of the winter season, the nutrient transportation is usually acropetal (in other words, flows from the roots to the foliage). This is because the sugars stored in the roots are being utilized for new leaf and bud growth.
Immediately after girdling, any nutrients or hormones made in the roots are unable to reach the foliage and vice versa. This does not mean that you will see an immediate stop in the growth of the tree.
For a short while after girdling, the existing nutrients and sugars made in the foliage have nowhere to travel. This often leads to an increase in the foliage and trunk size above the girdled area. A similar thing is observed in the roots, the roots will have enough carbohydrate reserves within them to stimulate root growth for some time after gridling.
Over time, this growth ceases and the roots begin to starve which affects the water and nutrient uptake. This leads to an eventual weltering of the foliage followed by the tree’s death.
For larger trees, removing the phloem layer will lead to their death over a 2–5-year period unless affected by environmental stresses like drought.
What Are the Physiological Effects of Removing the Phloem and Xylem Layer of a Tree?
There is a huge difference in the physiological changes in a tree when you remove the xylem layer. This will not only affect the translocation processes but transpiration as well. Unlike removing only the phloem layer, the effects of removing the xylem can be seen almost immediately.
Because the transport of water is completely stopped, you can see the wilting of the canopy within a day, especially if you live in a hot and humid area. Permanent damage to the foliage and the trunk of the tree can be seen within 24-48 hours.
What Are The Causes of Girdling?
Girdling is majorly caused either intentionally by humans or unintentionally through other environmental stresses, or even animals like moose, or beavers.
Either partial or complete girdling is often caused by animals through grazing, fungal infections, and pest infestations. For example, horses are known to girdle by eating the bark of trees.
Over the years, humans have been using girdling both as a means of population control in large areas, and to boost the fruit production in certain trees. Girdling has the advantage of being cheap and easy to perform which is one of the biggest reasons for its widespread use.
Should You Fell a Tree or Girdle It?
If you have to get rid of a tree, then the question occurs whether you want to cut it down or kill it through girdling. There are a few factors which you need to take into account.
If you want to get rid of the tree in a hurry, then felling it will be the best option. On the other hand, felling a large tree can cause significant damage to the surrounding area and property.
Killing a tree using girdling can take a long time, sometimes up to 3-4 years. It is useful if you have to get rid of a large number of trees as girdling is much easier and faster as compared to cutting a tree down. The dead wood can be later used as firewood as it will dry while standing. This is one of the biggest reasons why girdling has been in use for generations for controlling tree growth in forests and farms.
Girdling is also useful when you have to reduce the canopy size of a large tree that is surrounded by desirable smaller trees. Cutting the tree down in this instance can end up killing the surrounding trees as well.
As a downside, girdling has the disadvantage of uncertainty. Once a tree has been girdled you cannot predict when it will completely die, fall down or in which direction it will fall down. Large-scale girdling does pose a safety risk.
What is the Use of Girdling?
Other than controlling the tree population in forests and farms, girdling or ringbarking has also been used by fruit plantations to artificially increase the size and quantity of fruit production over a season. This is due to the stored carbohydrates in the canopy of the trees. Although there are no studies that reflect its impact on the long-term growth and survival of trees.
Can You Save a Tree Which Has Been Girdled?
If your tree has been accidentally girdled either by humans or by animals, there are a few things that you can do to either prolong its life or save the tree.
- The first and the easiest thing which you can do is immediately replace the bark in the affected area. This method is also known as bark patch grafting. The thing to keep in mind here is speed. You need to place the new bark on the affected area as soon as possible before the exposed area dries out.
- The other method you can use is known as bridge grafting. This technique has been used historically for protecting orchard trees. Usually, bark tissue from the same specimen or from a clone is used or inserted into the bark of the affected tree. This allows the xylem and the phloem to form channels for the transport of nutrients and water.
- Injecting sucrose into the soil is also known to work in some cases. Sucrose facilitates the growth of fine roots in established trees. It should be noted that the results are not definite and largely depend on the species you are dealing with and the concentration of sugar of a given species.
One thing which you need to make sure of to save a tree after girdling is to protect the tree from further environmental stresses. This includes scenarios such as animal attacks, pests, insects, fungal infections, lack of nutrients and water in the soil, and waterlogging near the tree.
How to Girdle or Ringbark a Tree?
Girdling or ringbarking is quite easy to perform. All you will need is a tool such as a chisel, an ax, or a chainsaw. Any tool which you can use to cut into the tree in a controlled manner can be used.
Using the tool of your choice, remove a complete ring from around the tree’s trunk about 4-6 inches wide. If you are not sure how deep to make the cut, about 1 inch is more than enough. 1-inch depth will avoid any confusion regarding whether the process will be successful or not.
Do not make the ring too narrow because trees tend to form callous over them which can help them survive the process. Removal with should be at least 4-6 inches.
In some cases, it is even recommended to use herbicides like Tryclopyr, Garlon RTU, or Tordon RTU to increase the effectiveness of the girdling method.
Improper girdling by removing narrow strips around 1-2 inches wide can be survived by the trees. With larger and wider wounds, the tree will only be callous around the edges of the cut.
Do You Need to Completely Remove a Ring of Bark to Kill a Tree?
Trees are known to have survived with 50% vascular tissue removal. Some species such as Eucalyptus camaldulensis, Platanus orientalis, and Acacia melanoxylon have even survived from 60, 75, and even 90% of tissue removal.
It has been observed that trees can survive even till 90% of tissue removal and with 20% remaining vascular tissues, they can even have a full healthy canopy.
Can You Use Girdling for Removing Selective Branches?
Girdling can be used to control the growth of unwanted branches of a tree without damaging the tree’s health. If there are a couple of branches in a tree that you want to either remove to stop growth, you can girdle near the base of the branch to stop its growth.
Girdling is one of the most cost-effective methods for controlling vegetation growth. Removing a ring of bark including the phloem and the xylem cuts off the transport of nutrients from the roots to the foliage and vice versa. This eventually leads to the tree starving to death. One of the downsides of Girdling is that it takes a really long time to be effective.
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