Tree are the largest of all living plants and are the oldest of all known living things. Babies and small children are often entranced by the beauty of trees and many are occupied for ages lying in their prams looking up at the waving branches. Older children like to climb trees and build tree houses. This affinity that humans have for the beauty of trees may well be instinctive and evolved in us over countless millennia.
Trees are among the most important plants used by people and now provide us with food, wood and timber for tools and buildings, medicines, fuel, and paper. They are therefore an important economic resource and source of employment. The forestry industry in Canada alone employs about 840,000.
However, trees would also once have been an important source of sanctuary from animal predators as well as being a place in which to hide from human enemies or to hunt from. They were also an important source of weapons for ancestral man-spear, bows, and arrows and foraging and later farming implements such as the digging stick. They were (and are) an important source of material for utensils, furniture, and building materials. Obviously, many wooden artifacts will have perished over time. One of the oldest known is a wooden spear point found in Clacton Essex and dating back between 360,000-420,000 years ago. Spears 400,000 years old have been found in Germany. Planks of wood have been found dating back thousands of years. A willow plank, with one deliberately polished surface, has been fond in the Jordan Valley in Israel and dated anywhere from 240,000 to 750,000 years old.
Trees figure prominently in the myths and religions of different peoples. Think of the Tree of Knowledge and the Tree of Life in the Garden of Eden. After the climate warmed and the last Ice Age ended much of prehistoric Europe was covered in forest as was England. Trees were sacred and holy places to many of the European tribes as they were also to many of the Indian tribes of North America. It is very difficult for us in these days of science and the Internet to understand the ‘mindset’ of peoples for whom the whole universe is animate. Not only do animals have souls, have ‘personhood’, but plants and especially trees may have spirits in them and these spirits needed to be thanked when the tree was used. Some even believed that trees uttered cries of pain when cut. Trees come alive in stories. Think of Tolkien’s Lord of the Rings.
The age of trees fascinates us. Trees are one of the few natural, living things which lives longer than man. Trees, unlike many other plants, grow for a very long time-some for thousands of years. The affinity we have for trees clearly has its roots in the early dawn of our ancestral past. And trees help replenish our atmosphere and help us breathe. Wood from trees is used in art to express human creativity and religious belief.
One of the oldest species of tree is the ginko. Once thriving with various kinds in abundance only one species remains today. a native of Asia, it now is also grown in parts of Europe and the US where is is sometimes called a maidenhair tree. The bristlecone pine tree of California is probably the oldest tree alive being dated as over 4,600 years old.
There are approximately 20,000 species of tree which are grown around the world today and are divided into six different groupings. These include broadleaf, needleleaf, monocotyledons, cycads, tree ferns, and ginkos.
Some parts of the world support dense forests while other climates are too inhospitable for tree growth. A few trees grow in the Arctic or in Greenland where bitter, cold and long winter months produce the few stunted trees that will grow. At least two months of a year without frost is required to support tree life and that is the reason no trees grow in Antarctica. While some trees can survive hot, dry, desert climates most trees require 40-50- cm. of rain a year.
The European need for timber linked with the vast abundance of it in the New World was one of the motivations for the colonization of North America. The tree usually has a single wooden stem or trunk which after a few feet up tends to branch out.
The British Royal Navy had a great need for tall wooden masts and the pine tree fit the bill. This is because of the way in which the trunks of pine trees and other conifers grow-extending straight to the tip of the conical crown and with branches which are comparatively slender and extending from the trunk at right angles. The first shipment of white pine from America to England was in 1634. Pines and other conifers evolved in this manner in order to survive in cold and snowy climates. Leaves contain moisture and so the thin needle-like leaves are less vulnerable to freezing in the cold and contain a protective waxy rind. The downward slope of the branches allows snow to slide off rather than a heavy weight of snow to accumulate and break branches.
Each tree has its typical shape which is composed of the trunk of the tree and its crown where the branches spread out. The two primary sources of nourishment for trees are the air through the leaves and the soil through the roots. The roots also help to anchor the tree into the ground. How trees get their nourishment is quite an amazing process. Atmospheric carbon dioxide is turned by the cells of the leave with the aid of the sun’s energy and chlorophyll into the organic material of the tree. From water, obtained through the roots in the soil, the tree gets necessary minerals.
These are fed through the tree through the branches to the leaves by tubes to the leaves. When the temperatures cool in autumn the green pigmented chlorophyll of broad leafed trees is drawn from the leaves and they begin to turn colour giving the glorious cavalcades of colour. As can be seen from the photo of the maple leaf the ‘tubes’ which carry the moisture through the leaves look remarkably like the veins in animals which carry blood.
Trees need minerals for nourishment and these are obtained from ground water but in order to get the necessary minerals trees absorb far more water than they need. The excess is disposed of through a process called transpiration by which the surplus water is evaporated through the leaves and into the atmosphere which also helps to keep the leaves cool