The amount of diversity in this world is absolutely amazing! There are so many skin tones, hair colors (mine is blue and will be purple in a few days…), eye colors, heights, shapes…. you get it – this list could go on and on… Did you know that there is even MORE diversity in the natural world, including trees?
Did you know that North America has 17% of the world’s forests? There are roughly 900 different species of trees, many of which are found in areas of high biodiversity (Florida, Kentucky, Texas, and California). The trees found here in the US are so unique! One may be over 370 feet tall and have reddish bark that attaches to the tree in long strips and another may be only 15 feet tall and have grey, smooth bark with large, horizontal pores. Any idea which trees I mentioned? Hint – One is located in California and is VERY iconic. The other is an ornamental that some people may have in their own yards!
Trees all function differently based on where they live, what their soil is like, and even what the air quality is like! Form meets function and we can examine these differences by looking at tree bark, or skin.
The bark is the epidermal layer of the tree. This layer protects the tree from insects, fungi, bacteria, and other harmful objects, similarly to our skin! It prevents foreign objects from harming it’s important vessels (called Xylem and Phloem which can be compared to our veins and arteries). As the trees continue to grow, that epidermal layer becomes to tight and splits, causing the unique strips, chunks, and lines in the bark -thank goodness our skin is elastic!. In some cases, the tree will actually shed it’s old, tight skin in large swathes. These trees are called “Exfoliating Trees.” An example of these would be River Birches, Sycamores, and Paperbark Maples. In many trees, the splits in the bark form lines that look like ski trails. These lines and paths help to direct rain water down the trunk toward the roots. If the slope of the branches didn’t help funnel rain water towards the trunk, and the bark didn’t direct the rain down to the roots, most of the rain water would either miss the root systems or break the branches from the excess weight!
Trees also have something called lenticels. These are pores in the bark of the tree that help facilitate gas exchange between the air and internal tissues. Leaves have pores as well, called stomata, and are located on the bottom portion of the leaf. Those pores help with respiration. In some trees, the lenticels are small, barely noticeable and in others, like Cherry trees, lenticels are very large and pronounced holes that look like stripes or polka-dots in the bark.
Often, the features of the bark can help us identify the tree! For example, greyish, smooth bark with large lenticels tells us that the tree is a Flowering Cherry. A tree with bark that looks like burnt cornflakes glued onto the trunk is a Black Cherry. A tree with lots of exfoliating bark that’s slightly reddish in color is a River Birch. A tree with long strips of greyish-brown bark, covered in pale greenish-brown lichen, that look like they are about to completely fall off is called a Shagbark hickory. A tree with many tiny, thin strips of slightly exfoliating, reddish-brown bark is an Eastern Red Cedar.
There are many tree species in the world, each with their own unique characteristics! My personal favorite tree is the Betula Nigra, or River Birch. Which is your favorite tree? Let me know in the comments below!
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