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Bayou-Diversity (17 November 2019) BARK In humans and other animals a covering of skin serves various functions including protecting the body within. In trees and other woody plants bark can be considered analogous to skin. Like skin, bark is comprised of several layers, some living and some non-living. The outermost layer is called cork and does not consist of living cells. It is usually impermeable to water and gases. Moving inward, specialized layers of living cells perform critical functions including the transport of nutrients. The nutrients are manufactured via photosynthesis in the leaves or needles and flow through sieve-like tubes throughout the rest of the plant.

Humans have been using bark products for thousands of years. The inner bark of some plants is edible. The spice we call cinnamon is finely ground bark of the cinnamon plant. Latex and resins are bark products used in chemicals. Tannin from oak bark was used to tan animal skins for centuries. Lifesaving medicines such as quinine and aspirin were made from bark. As a construction material bark is used as shingles and flooring. Native Americans made birch bark canoes, and today we grind it up to use as landscape mulch.

This discussion of bark would be incomplete without mentioning how we thoughtlessly abuse it even while cherishing the plant it protects. The invention of the gasoline-powered string trimmer has resulted in the unintentional and untimely deaths of countless landscape trees and shrubs. If a string trimmer has been used in your yard, I challenge you to look closely at the base of your woody plants. There is a very good chance they have been partially or completely girdled. Once the bark of a plant has been seriously damaged, the plant will never thrive to reach its potential and will often die. Besides destroying the nutrient transporting cells, bark wounds are prime entryways for pathogenic bacteria, viruses, and insects.

To view another bark-related travesty in our region, visit a public campground and consider the nearby trees that we love for their shade and aesthetic values. Most will likely be hacked, scored, burned, or carved with initials. Beech trees in particular are condemned if they are so unfortunate as to germinate in a public area. Considering the many benefits that we have reaped from bark over the centuries, what does this unnecessary destruction say about us? (Adapted from “Bayou-Diversity – Nature & People in the Louisiana Bayou Country,” LSU Press)


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