Once again I find myself reading Bernd Heinrich’s work The Trees in My Forest. It’s a great story of tree biology and a masterful piece of natural history writing. And I find myself enjoying his interpretation of wood and the role it plays in the tree system.

It’s true that as tree climbers and arborists we think about wood; the strength of it and if it can support our anchors and our rigging, or the tree structure as a whole. But the importance of wood as a byproduct of a tree’s physiological and biological processes has nothing to do with tree climbers. Although it does have a lot to do with support in a very symbiotic sort of way.

Wood is built in order to support leaves. Leaves have an incredibly lasting effect on tree growth, even with their impermanent quality (especially deciduous trees). The opening and closing of stomates is what draws water up tracheid walls. “The water molecules adhere to one another. They are anchored to other water molecules and also to the cellulose molecules of the tracheid walls. Each time a water molecule evaporates from the top of the chain through a leaf stomate, it pulls the rest of the chain behind it…Evaporation from the leaf surface drives movement of the water column,” (Heinrich, 70). Wood (tracheids) is what frames the chains of water columns, or rather the hollow, stacked cells is what, as Bruce Lee might say, the water becomes. And so we see how important the relationship between wood and water and leaf is. But leaves do much more than just pump the pipes.

They also make sugar. And guess what the cellulose molecules are made of? That’s right, glucose. So the leaves make the sugar that’s the wood that moves (or rather guides) the water. Back to Bernd, “There are about 2 billon (2,000,000,000) cellulose chains in one tracheid or wood fiber. Each tracheid cell thus contains the equivalent of 2,000,000,000,000 sugar molecules, which are the primary product of photosynthesis,” (Heinrich, 71). So then, photosynthesis doesn’t just make oxygen, it builds wood too.

Wood doesn’t just support leaves either, it supports the process of carbon sequestration, which is the primary way in which trees battle global warming. And guess what, it’s partly due to glucose and how it’s is built on a molecular level.

Heinrich writes that, “glucose is a sugar composed of six carbons, requiring six carbon dioxide molecules to make, hence one tracheid cell takes up to the equivalent of 771,600 (# of glucose units per second per tracheid cell for thirty days) x 6 = 4.6 million carbon dioxide molecules per second,” (71).

And that’s just the capability of one tracheid cell, on average, that’s 7 mm long by .2 mm wide (70).

Imagine you are sitting on the public toilet, perhaps on lunch break from a good crown cleaning, business as usual, and you reach for the toilet paper but the paper is no more. Now you have a better idea of the populace’s dependency on wood fiber, from a climber’s perspective on lunch or not, and more specifically, sugar.

“Like paper, cotton, linen, rayon and cellophane are also nearly all pure cellulose, that is they are long chains of sugar molecules attached end to end,” (72).

I can just hear Elaine from the other stall, “but can’t you spare just one square!?”

No matter what anyone tells you, if you are a tree climber or not, your life depends on sugar.