57 



rotation may, be shorter, because (1) trees appear to grow here faster than they do at the 

 Knysna, perhaps owing to the heavier rainfall in the Natal forest region ; (2) the 

 measurements were taken in a virgin forest where the growth would be sometimes almost 

 stationary, and always slower than that of forest cultivated in accordance with 

 suitable methods of forestry. 



FORMATION OF SERIES. The sustained yield of which a forest is capable, 

 may be determined in each case according to either the area, or the volume of the 

 standing stock. If we take area as our basis, the forest may be divided into as many 

 sections as there are years in the rotation, and we may cut over one of these sections 

 each year. The portion of forest thus included in one working cycle is termed a Series, 

 When basing the annual yield on volume, the rotation may be subdivided into equal 

 periods of 10 or 20 years, and corresponding blocks o? forest assigned to each, one block 

 being worked over during one period and the whole Series during the rotation. The 

 standing stock on the block which is to be worked first, is estimated and its volume 

 divided by the number of years in the period ; the quotient gives the number* of cubic 

 feet that may be cut during each year of the period ; and this cutting may be spread 

 over various areas according to cultural requirements. 



There are cases in which it is necessary to limit the working of a forest to the selec- 

 tion of mature trees. The yield may then be sufficiently limited by being expressed in 

 the number of trees to be cut yearly in the forest. 



CULTURAL TREATMENT. The forests of the country having been divided into a 

 number of Series, and their survey effected, the mode of treatment of each Series ha* 

 to be decided. There are two ways in which trees may be reproduced ; by seed as in 

 High Forest, or by shoots or suckers from the stumps, as in Coppice. Coppice is- 

 unsuited for the production of large timber, and there is no place for the system in our 

 native forests. It is however adapted to plantations designed to supply wattles and poles 

 and in these equal areas may be cut over each year as soon as the plants reach the 

 reqnired size. In High Forest, the principal modes of treatment are the method of 

 thinnings and the Selection method or " Jardinage" 



METHOD OF THINNINGS. This method aims at ensuring a complete natural sowing 

 of the ground, and continually fostering the growth of the timber. These results 

 are achieved by making in each portion of the forest, instead of a single cutting at 

 maturity, a succession of cuttings of different character, at various periods of the rotation. 

 These cuttings are classed as regeneration cuttings and improvement cuttings, the first 

 being designed to ensure reproduction, and the second to improve the growth of the 

 young timber. 



Regeneration cuttings are generally three in number. In dense forests, the primary 

 cutting opens the continuous leaf-canopy just enough to admit sunlight but preserve 



