study of trees



study of trees defined in 1944 year

study of trees - Study of Trees;
study of trees - Forestry is usually ranked as an applied science, perhaps because the study of trees, as an end in itself, has been much neglected in Britain. The botanist studies trees up to a certain point, but as the scope of his researches embraces the whole vegetable kingdom, his work is usually concerned with the tree as a flowering plant, not with the tree as a seedling, as a log of timber, or as a unit in a great forest. Therefore, whilst precise knowledge concerning the systematic botany or evolutionary classification of all known trees is available, and the general anatomy and physiology of trees is widely understood, there are still gaps in our knowledge which demand the attention of students and research workers.

To start at the first stage of the life history, most trees bear seed only at intervals of years. Why? Does this habit assist them, or is it forced upon them? Is it connected with climate, weather, or is it a definite rhythm in the life of the tree? Why, for example, does the oak bear seed one year and the beech the next, seldom if ever in the same year? This is a question that seldom occurs with herbaceous plants; most annuals must seed yearly or perish.

Following on the seed, the survival of the seedling next attracts attention. Every forester dealing with the natural regeneration of trees will notice that there are times when, and places where, the seedlings come away from the start freely and unaided; at other times and on other areas they hang back perhaps for years, or fail entirely. The factors governing this, which must have affected the spread or retrogression of trees all over the world, are still but little known.

The growing tree may be studied in relation to any of the varied elements of its environment, soil, climate, competing or complementary flora, and animals which attack it or assist it. The geologist, meteorologist, and zoologist must all lend assistance here, but at times the trail can only be followed by the specialist in another field of botany. Thus, symbiosis, or living together of the tree with a fungus or bacterium for their mutual benefit, is found in many trees - how many and how frequently we do not know. Such common trees as alder and laburnum cannot thrive without the aid of the right bacteria; many conifers demand the help of fungi.

In all these cases the student is faced with a double problem. Not only must he discover how a fungus affects a tree, but also how the tree affects the fungus. Trees are physically so large that a similar dual problem arises in respect of soil, surrounding flora and fauna, and even, to some extent, climate. Not only does the soil decide which trees will grow, but the trees decide in what way the, soil that supports them shall develop from its parent rock.

After the tree is felled, its timber attracts the attention of the wood technologists. They may be interested in it as a biological unit, a source of chemicals, or as a physical entity. The trunk reveals the life history of the tree, and a smaller portion of the wood, when cut into sections along the three chief planes - across the axis, along a radius, or tangentially to the cylinder, will show features under the microscope which enable the parent tree to be identified by this evidence alone.

The wood chemist will want to know what substances have been elaborated within the wood, such as gums, oils, or resins. He may wish to extract them because of their value, as with turpentine, or again he may wish to extract them because they impair the useful properties of the timber for some purpose such as paper-making. On the other hand, he may desire to treat the timber chemically with some new substance, to mate it resistant to fire, decay or insect attack. The wood itself yields raw material for chemistry; thus its cellulose may be transformed into the unlikely form of artificial silk.

The wood physicist is concerned with the mechanical properties of the timber, its reaction to bending and cutting, the loads needed to crush or break it, and its suitability for constructional work. On his findings depend the utilisation of new timbers in place of old and well-tried ones that may be in short supply.

The timber merchant, carpenter, shipwright, and cabinet maker must also take a keen interest in ^rood and ultimately in the tree as the source of its supply. Their demands take financial effect in the import and export of quantities of timber and manufactured goods, which bring in the statistician and economist, who show how the tree's products affect the trade of the country.

To return to the living tree, the distribution of each species across the world provides a fascinating study. Why are some genera, such as the pines, found right across the northern hemisphere, whilst others, such as Sequoia, are confined to one continent? Why do certain species vary at different points in their range, - is it due to climate or to evolutionary history? Again, is a given species of tree expanding its range or becoming more restricted in spread? Some of these questions may be solved by the palaeontologist, who studies fossil tree remains in rocks and peat-bogs. Others are the concern of the present day, or even of the future, since they help to decide where trees can be planted anew with prospects of success.

Allied to plant geography, the study of forest ecology, or the living tree in relation to its environment, is of first importance to the forester. Vegetation tends to form groups, of which the grasses of the dry plains and the, sedges of the marshland are examples; and of these groups, the high forest is the climax, representing the greatest domination of plant life over its environment. Natural forests are rare in Britain, and such few as remain merit careful study. In few cases is the forest static, either it is expanding by encroachment over the plain or it is being beaten back by grazing animals, or unregulated fellings. Such forests vary widely in composition, and may be made up of one species or several. Often there is a succession of species. Thus, on bare downland, wild roses, brambles, and juniper may appear, followed by spindle tree, blackthorn, and wayfaring tree. Amongst this shrubby growth, birches will spring up, followed and ultimately surpassed by slower- growing oaks. Then, in the shade of the oaks, beech seedlings may take root, outlasting the oaks after many years and, since oak seedlings cannot grow in the dense shade of the beech, ultimately replacing them as the climax form. Such changes take years and centuries, and can only be observed stage by stage. But they clearly show just what conditions are needed by trees to ensure their effective growth, and so provide information of the greatest value in practical forestry.

Forestry, considered as a craft, may be concerned with vast natural forests found in the tropics and the less developed countries of the temperate zones, or, as in Britain, with artificially established plantations. It is concerned with the ordered growth at all stages of all trees providing timbers useful to man, and with their utilisation as soon as they have attained their most profitable stage of development. The forester sows what he cannot hope to reap, and must foresee the needs of the future whenever he plants a tree or carries out a thinning. In return, he has the privilege of reaping what he has not sown, and the duty of utilising what others before him have planted, to the best advantage at the present day. Moreover, he can see his work persisting and growing on throughout his lifetime and beyond. Long after the farmer has forgotten the crops of his boyhood, the forester finds that the trees he planted in his youth are growing still, becoming every year of greater value, and furnishing each season products of utility from their thinnings, such as the humble but essential pitprop, to enrich the life of himself and his neighbours.

This work has mainly been concerned with the identification of trees at all stages, and with the essential facts governing their growth and utilisation; it deals only with the trees of one country. The study of trees leads on into broader fields, into other lands, back into history, and on into the future. It reaches wide as the world, and longer than the life of man.

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