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 best species of trees for this purpose are various pines, larches, and, in sub-tropical regions, members of the genera Agathis, Shorea and Canarium. Similar methods are used in the case of certain tropical, broad- leaved trees to obtain caoutchouc and latex, which are of importance in the rubber, textile and food industries - trees of the genera Hevea, Castilloa, Mimusops, Achras, etc.
The leather industry could not function without tannins, another product of many woody plants. In some trees, these are obtained from the bark (spruce, oak), in others from the wood and bark (chestnut, false acacia), and in still others from the leaves (staghorn sumach) or fruits (sapan). Before the day of synthetic dyes, trees were also an important source of natural dyes. - 15266
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 best species of trees for this purpose are various pines, larches, and, in sub-tropical regions, members of the genera Agathis, Shorea and Canarium. Similar methods are used in the case of certain tropical, broad- leaved trees to obtain caoutchouc and latex, which are of importance in the rubber, textile and food industries - trees of the genera Hevea, Castilloa, Mimusops, Achras, etc.
The leather industry could not function without tannins, another product of many woody plants. In some trees, these are obtained from the bark (spruce, oak), in others from the wood and bark (chestnut, false acacia), and in still others from the leaves (staghorn sumach) or fruits (sapan). Before the day of synthetic dyes, trees were also an important source of natural dyes. - 15266
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Garden planning for the urban front garden often has to provide parking space. While it is difficult totally to hide parked cars, sensible planting can offer partial screening.
