Tree bark specific weight: density of dry and wet bark

We usually call the outer, cracked, easily separated layer of a trunk or root tree bark. In a broader biological sense, bark is a set of special plant tissues that move nutrients from the leaves to the roots. Bark is present on old branches, the trunk and roots of a tree, as well as on very fresh shoots.

Structure and functions

The main structural components of bark are:

• Cork - the outer part of perennial shoots, consisting of dead layers of phloem and primary bark. Some woody plants do not have cork, while in others it is clearly expressed. It may be ring-shaped, as in grapevine, or scaly, as in oak.

• Periderm - an anatomical and topographic zone of stems of higher plants, represented by a complex of tissues. This bark layer performs gas exchange functions and protects internal tissues from overheating and moisture loss.

• Primary and secondary bark, phloem - the conductive tissue of a plant, consisting of sclerenchyma and parenchyma cells, as well as sieve elements: living cells through which phloem sap is transported.

The main chemical components of bark include:

• Cellulose. The percentage of this substance in dry bark is approximately 16-23%. Cellulose is a carbohydrate whose molecules are arranged in a dense thread and have no side branches. This substance gives woody tissues high mechanical strength and elasticity at the same time.

• Lignin. A polymer compound that makes up the main mass, up to 33%, of lignified plant cell walls. Cellulose and lignin can be compared with reinforcement and strong concrete, which form durable organic structures.

• Extractive substances or extracts, up to 30% of the total bark mass, are viscous liquids or dry substances consisting of alcohols, esters, water or carbon dioxide.

Weight of tree bark

Parameters such as thickness, moisture content and density of bark differ between tree species. They depend on age, the bark’s position on the trunk and the growing conditions of the plant.

Use of bark

The area of bark use in industry and household applications is quite broad. It is used not only for making crafts and decorative containers.

• Bark is used to produce tar, tanning substances, latex, many medicinal substances and spices.

• Bark is an important source of useful substances for many animal species, and for some it is the main source of food.

• In gardening, bark is actively used as mulch, and some types of bark can be eaten.

• Shredded tree bark, as a waste product of the woodworking industry, is used in the production of fiberboard.