“I will conquer him in his cedar wood and show the strength of the sons of Uruk, all the world shall know of it. I am committed to this enterprise: to climb the mountain, to cut down the cedar, and leave behind me an enduring name.”
-Epic of Gilgamesh
Types of wood
Over 60,000 distinct types of tree cover the earth. Some, like the aspen, have tremendous range and cover continents. Some are limited to fewer than a dozen members of the family. Some live and die in a few short years, while others may have single members older than the human race. All are broadly defined into two groups: Hardwoods are sourced from broad-leafed deciduous trees, which drop their leaves each autumn. Softwoods come from conifers, named for their seed cones, and usually retain their needles year-round. In general, hardwoods are harder than softwoods, though the hardwood balsa and the softwood yew are the best-known exceptions to each case.
Properties of wood
The key characteristics of wood, from an engineering perspective, are density, hardness, elasticity, and rupture strength. All of these properties except density are anisotropic, or different in different directions. Anyone who has chopped down a tree and split it to lumber knows this; because the cells that grow to form a tree align vertically, they are hard to cut across but easy to split along. Most wooden items, therefore, are designed so that the grain of the wood is oriented across the direction requiring the greatest strength. An oar will have the grain run the length of it, for example, so that it will not split when pulled in the current.
Density is important for several reasons, none more important than buoyancy. Some woods, like lignum vitae or ebony, are so dense that they will sink in water. Others, like balsa, float light as a feather. Lower density also often results in lower workability and quality of worked surfaces, and the other properties of interest discussed here more or less scale with density. Hardness matters for maintaining a finish without scratches or dents- important if you would like two pieces of wood to slide on one another. At the same time, however, hard woods dull tools more quickly and are overall more difficult to work. The rupture strength is the actual force required to break the wood, while elasticity quantifies how far a wood will bend before it breaks, which is a quality superior to all others for the production of longbows.
Common trees in diverse biomes
Aspen: (sub)Alpine forest
Pando Aspen Colony, UT
Quaking Aspen is the most widely distributed species of tree in North America. [1] Depending on the local climate, aspen varies greatly in size and shape, from stunted shrubs shorter than a man in the alpine regions, to massive trees of 100 feet/30 meters in wet, cool mixed forest where frequent fires help keep the more dominate conifers from shading out young shoots. Aspen shoots are connected to root systems that are often large and out of sight. Clonal colonies, so-called because what appears to be a forest is actually many shoots of a single genetically identical tree, can survive fires, logging, grazing, and disease before springing forth new life. Utah’s Wasatch Range is home to a single aspen tree that covers over 100 acres of forest. Named Pando, Latin for “I Spread”, the tree is estimated to be at least 10,000 years and perhaps up to 80,000 years old. Each individual shoot lives for perhaps 100 years before its replacement by a fresh member. Such a legendary tree could only be killed by concentrated effort or decisive climatic change. [2]
Cedar: Semi-arid desert
The Cedar of Lebanon was one of the renowned trees of the ancient world. Filling the mountain slopes of the Eastern Mediterranean and Cyprus, is was highly sought after for the construction of temples, ships, and luxury articles of all sorts. Its leaves were distilled into cedar oil, used as a preservative, insecticide, embalmment, and as a base for paint pigments. The Egyptians constructed their war fleet of cedar, and burned the scrap into charcoal.
Yew: Broadleaf forest
Yew grows in mixed forests as an understory to oak or other broadleaf hardwoods. Its wood is harvested for the classic stave of the English longbow; along with a few other woods, it must be in the discussion for which timber has had the most outsized effects on human history. Long, long before English archers routed the French men-at-arms at Agincourt, hunters were stringing bows made of yew. Over five thousand years ago, the man we now call Ötzi (the Iceman) died in the Italian Alps, still carrying his yew-handled copper axe and yew longbow.
Eucalyptus: Savannah
The Cerrado of Brasil is one of the world’s richest savannahs, and Eucalyptus is one of its signature products. Originally native to Australia and rarely found elsewhere, eucalyptus have been transplanted around the world. In Brasil, the fast growing eucalyptus is an incredibly important part of the economy. Eucalyptus plantations greatly reduce destruction of native tree species and rainforest, while providing mass quantities of wood for two important Brasilian industries: pulp for paper and charcoal for steel. The oily leaves can be steam distilled for eucalyptus oil and used for massage, as an insect repellent, or a natural anti-inflammatory or a remedy for cold or fever.
Mangrove: Saltwater mangroves
You can’t have a proper mangrove swamp without mangrove trees, and so that’s what we’ll dig into here. The term mangrove actually is used to designate a special type of tidal wetland that composes some 25% of the tropical coast around the world. The tree roots readily, and farmers use new shoots to reclaim silty tidewaters and to construct living traps for fish and shrimp. Stilt dwellings, wharfs, and various boats and canoes are all still made from mangrove wood, which has high levels of tannin that serves to preserve the wood against decay and borer damage while submerged. The same tannin is extracted from the bark for tanning of leather on all coasts of the Indian Ocean, while the wood supplies high-quality charcoal and the fruit and sap and other parts of the tree are turned to food and wine and medicine. [3]
Bald Cypress: Swamplands
Oaxaca Bald Cypress
The Bald Cypress got its name as a conifer that drops its needles each fall. Like most conifers, its wood is naturally resinous or oily, and this helps to preserve cypress lumber against the elements, rot, and insect attack. Some grow as large as the giant sequoia on the opposite American coast, reaching heights of well over 100 feet over the course of a thousand years. Swamps sometimes yield ancient logs of enormous size, well preserved despite their long immersion.
Brasil Nut: Tropical Rainforest
The Brasil Nut shadows the rain forest canopy of the Amazon with its impressive height, and its roots delve so deep and so wide that the nuts for which it is named have unusually high levels of trace minerals from the soil. The nuts are hidden within a fruit about the size of a coconut, and fall well over a hundred feet to the rainforest floor at speeds approaching 50 miles an hour. Local rodents gnaw them open and move the nuts about like acorns from oaks, and the trees tend to grow in small groves as a result. The nuts are very high in fatty acids and oils, and are often pressed to extract the oil. The lumber is of good quality, though it is no longer legally logged.
Willow: Freshwater wetlands
Willow, and other trees in the same family, are widespread in the Northern Hemisphere, especially near running water. Their flexible young branches are easily bent and woven to form baskets, fish traps, fences, and (when covered in clay or plaster) walls. Wattle and daub, as the construction is called, was the forerunner of the lath and plaster walls that yielded to modern drywall. The bark famously contains salicylic acid, known today as Aspirin, but known from the even most ancient of texts as a cure for fever and pain.
Few trees: Grasslands
Grasslands will have trees along the fringe or near settled areas, but by and large the growth of large flora is hindered by frequent fires. Trees might be imported and thrive in this biome, but would likely be valued for their shade or other useful features if found in a new area.
No trees: Tundra, Steppe, Arid desert
Too cold, too dry, or both, these biomes see very few trees of any size.
A forested world
Some trees may overlap many biomes; some will be unique to one. The combination of properties of a piece of lumber is unique to a species (allowing for minor variation in growing condition), and without ever considering the color, grain or beauty of a piece of lumber, they may provide reason to import wood from afar.
References
[1] J.B. Mitton and M.C. Grant, “Genetic Variation and the Natural History of Quaking Aspen,” Bioscience 46[1] (1996) Link
[2] M. Grant and J.B. Mitton, “Case Study: The Glorious, Golden, and Gigantic Quaking Aspen,” Nature Education Knowledge 3[10] (2010) Link
[3] W.M. Bandaranayake, “Traditional and medicinal uses of mangroves,” Mangroves and Salt Marshes 2 (1998)
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