Information on Tree Growth
The principal raw material yielded by trees is wood, which can he used in many ways and for many purposes and which, along with coal – the product of trees of earlier geological periods – made possible the smelting of ores and the development of all branches of industry.
Trees grown for their wood are cultivated in forests. Unlike other raw materials where the supplies are exhausted after a time, if felling is wisely planned, the supply of wood in a forest remains constant and the felled wood is replaced by new wood in the form of new growth.
In the mild climate of central and western Europe, the annual increment per hectare, depending on the site, type of soil and prevailing species, averages from three to ten cubic metres of wood that can be cut without decreasing the supply and production of further wood. With systematic care and fertilization this increment can be increased even further, as is shown by the plantations of cultivated hybrid poplars with an annual increment of fifteen to twenty- live cubic metres of merchantable wood.
Felled wood is processed in two ways: mechanically, whereby only the shape is changed, and chemically, whereby not only the shape is changed but also the substance. Wood processed by the first method is used mainly in the building. industry, the joinery trade, furniture making, wheel and waggon making, in mines, on railway lines, etc.
The favoured wood of the building industry is that of conifers: spruce, pine, fir and larch. It is long, light, well suited for beams, columns, sawn wood, doors, window-boxes and in building ships and transport vehicles.
About fifteen years ago a stand of bristle-cone pine (Pious aristata Engelm.) was discovered in the Rocky Mountains of Nevada, in which the oldest trees had 4200 annual rings.
