The Growing of Mine Props on the High Veld, 263 



over a long" period of years, noting- the behaviour of each species 

 during a variety of seasons and in all manner of situations, will 

 enaljle the planter to avoid climatic traps and pitfalls. The results 

 of study and experience up to the present time are given under the 

 heading- " sylvicultural notes," each species being- dealt with 

 separately. 



E SPA CEMENT. 



Espacement has an important bearing- not only on the successful 

 establishment of a stand of trees, but on its future development, the 

 quality of wood produced, and tiie general economy of manag-ement. 

 Too often tho-se intending- "^0 g-o in for afforestation are under an 

 impression that planting espacement is a common factor which can 

 be applied to any species, situation, or circumstances, and that some 

 day they will harvest approximately the same number of trees that 

 were originally planted. Such is far from being- the case. Nature's 

 method is to regenerate in more or less dense mass formation which, 

 when unassisted by man, has to undergo a slow process of survival 

 of the fittest before final development is leaclied. The science of 

 forestry, evolved by man, consists in hastening this process to secure 

 his needs more quickly. We cannot, however, afford to discard 

 nature's example entirely, and must base our sylvicultural methods 

 on certain fundamental natural principles. One of tiiese principles 

 is to secure what is technically known as "forest conditions" at an 

 early stage. In a young stand this condition is reached when it is 

 sufficiently dense to ex(dude weed-growth without necessity for 

 further cultivation, and no stand on the high veld can be considered 

 established, or safe against damage from frost, drought, and fire, 

 until then. To attain this end most economically, the planting 

 espacement has to be varied .according to differences in rate of growth 

 and individual habits of species, such as natural erectness or other- 

 wise of stem, density of lower branches, etc. 



Having secured " forest conditions," the forester's attention is 

 next concentrated on maintaining what is known as a "normal 

 stand " throughout the remainder of the rotation. By '' normal 

 stand" is understood that particular density which, without 

 sacrificing " forest conditions," will maintain noimally vigorous 

 growth in the best stems. Everything- depends on maintaining this 

 density. A too open stand is exposed to the dangers of understocking, 

 and, if too dense, loss of increment takes place. As the stand 

 develops the correct density is maintained by a process of thinning 

 whereby espacement is constantly increased and the number of stems 

 to the acre reduced. This operation is of the utmost importance, 

 and demands great skill and experience. The lungs and stomach of 

 a tree lie in its crown, hence it must be >^een to that the crowns of 

 those individuals intended for the main crop are properly developed 

 and not allowed to deteriorate. Every species has its own individuality 

 of habit which must be taken into account when thinning. Further- 

 more, its habit varies according to situation and age, and whether 

 it is growing pure or in mixture with other kinds. Where, as in 

 this country, many hundreds of species have to be dealt with in 

 scores of different situations and mixtures, the number of combina- 

 tions that have to be studied may be more readily imagined than 

 calculated. But one thing should be remembered, an error of 



