All About Trunks

All About Trunks

By Madison Nef

The trunk is a very important part of a tree. It harbors the special tissues that move food and water throughout the tree, and serves a storage space for extra carbohydrates that can be used later in case of a drought or other form of natural catastrophe. It also provides good structural support for the leaves, branches and limbs of the tree.

The most visible part of the trunk is the bark. The bark is the harder outer layer meant to protect the tissues inside of the trunk. Bark is rough, tough and like armor- and it comes in many different consistencies and colors depending on the type of tree. Just beneath the bark layer are the cork cells- they are very important to the tree because they protect the rest of the tree if the bark gets damaged.

The next layer, below the bark and cork cells, is called the phloem. The phloem is responsible for transporting the food created and stored in leaves throughout the tree. It moves up, down, and in circular motions. The next layer in the trunk is called the cambium- it is only a single cell layer thick, but it is largely important because it produces the phloem cells to the outside of the tree and the xylem cells to the inside.

Without the cambium, the cells would not be able to replenish when they get damaged… therefore they would wither and die. If these vital cells die, then the whole tree dies… thus, without the cambium, the tree would die. Even though the cambium is just one cell thick, it is quite possibly the most important part of the tree.

Each spring, the cambium produces new xylem and phloem cells. This process starts and moves rapidly in the spring, slowing down in the summer and fall and coming to a complete stand-still in the winter. This creates the annual rings of a tree, which are visible when looking at the cross-section of a tree trunk (when the tree is cut down, and you look inside the stump). You can also tell how old a tree is if you count these rings- since they reproduce every year, it gives a good age. The condition of the rings can also tell you about what kind of life the tree has had, if you know what they mean.

Different types of trees react differently to different climates and weathering. For example, lots of rain often results in faster and more efficient growth, which leads to larger, wider rings. Drought, on the other hand, leads to slower growth and much narrower rings.

Narrow rings can also be caused by crowding from neighboring trees. If you ever see a tree with narrow rings on half the side of the trunk, and wider rings on another… the side with the narrower rings is the side that the tree was crowded on.

Old and non-functioning xylem cells are called heartwood. This wood is used as structural strength for the tree and also provides storage space for food and nutrients in the form of starches. If you chop a tree in half lengthways, you will see long rays running down the interior of it. These lines are called ray cells, and they are used as sewer lines, of a sort.

These ray cells are responsible for cleaning the tree out and disposing of all the waste, propelling it downward and out of the tree so the tree can survive healthily.

In most trunks, you can find knots in the wood. These knots are created when a tree grows around a branch, leaving this marking where the branch still is- just inside the tree.

Many trees are damaged and killed every year because of damage caused by humans. It is extremely harmful to remove the bark of a tree, as it kills the phloem and bark… which as we know are the two important protective layers of a tree. Carving initials of messages into the trees also kills the phloem, and gouging the bark with lawn mowers and string trimmers also deal a lot of damage, killing trees or causing them not to be able to grow properly.

While trees cannot be gouged or cut into without killing it, they have no trouble growing around objects. This process does not damage the tree in any way, as it can meld to whatever the object is. If ever you pass a tree with a weird piece of metal or anything else jutting out from it, this is likely what happened.

Even though heartwood does help to make a healthier tree, trees CAN live and survive with hollow centers. These hollows serve as homes for a lot of wildlife and animals- but the hollows are quite dangerous, as they are lighter and easily knocked down in the wind and bad weather.

The trunk is, indeed the body of a tree- largely important to its survival and crucial to its development.