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In studying soil or subsoil in relation to tree growth, the degree of porosity 

 and its water-retaining capacity is of far greater importance than chemical com- 

 position. 



The chemical composition of soil and subsoil is of far less importance in for- 

 estry than in agriculture, for trees as a general rule take only about one-twelfth 

 of the mineral substance required for the successful growth of field crops. Trees 

 have their likes and dislikes, but few soils are so poor that they cannot support 

 a crop of some species or other of tree. For example, Pinus pinaster (Cluster 

 pine) will grow practically anywhere except on limestone, whereas Pinus halepensis 

 (Aleppo pine) nourishes on the poorest of limestone ridges. 



The only safe method of assessing the quality of a locality is by a close study 

 of the trees which have previously grown on the same area and the conditions 

 under which they have developed. 



The forester may decide that in order to fulfil his objects of management more 

 than one species of tree are necessary, in which case he has the alternative of grow- 

 ing the different species in "pure forest" on separate areas, or together in a "mixed 

 forest" on the same area. In the case of a mixed forest the management is more 

 difficult and great care must be taken to see that one species does not outgrow and 

 suppress another. Certain species known as "light demanders," require full en- 

 joyment of direct sunlight. Other species, known as "shade bearers," are content 

 with much less light, and will flourish under the shade cast b}^ a light-demanding 

 species. 



Method of Begeneration. — If the forester has decided to continue growing a 

 species already established on the area, he will seek to establish the new crop by 

 some system of "natural regeneration." It is more economical and satisfactory 

 to start a fresh crop of trees with seed from "mother trees" already established on 

 the area than to employ "artificial regeneration." If it is necessary to resort to 

 artificial regeneration, then the seed must be collected, and it may be sown directly 

 on to the area where it is desired to establish the new crop, or it may be sown in 

 a nursery and the young plants carefully tended until they become large enough 

 to plant out. 



In this country the forester is often blamed for sowing or planting his trees 

 too close together, but in this he is simply following the example set by Nature. 

 In a virgin forest from which fires are excluded Nature fills up open spaces with 

 many thousands of seedlings to the acre; as they develop, the stronger suppress 

 the weaker, and this struggle goes on throughout the whole life of the forest. The 

 forester steps in and, working on the principles laid down by Nature, causes a 

 struggle between the individual trees in order that they may grow into fine straight 

 timber trees without side branches, but hastens their development by thinning out 

 the crop at intervals. 



A "sylvicultural system" sets out the method by which the formation, regenera- 

 tion, tending and exploitation of the woods which compose a forest are effected. 

 Every forest requires individual treatment, so that the sylvicultural system only sets 

 out the general lines of working. The main consideration in the management of 

 any forest is to ensure that the sylvicultural system adopted will at least main- 

 tain the fertility of the soil on which the forest is growing. Herein lies the great 

 distinction between forestry and the general practice of agriculture. Field crops 

 rob the soil of essential mineral salts and make the use of fertilisers and manures 

 necessary. Forest crops, if properly managed, increase the fertility of the soil by 

 returning to it rich organic matter in the form of humus. 



