12 A MANUAL OI< FORESTRY 



lific of discussion among foresters, as to whether pure or mixed 

 forests are more profitable. 



Naturally there are advantages in a mixture of deep and 

 shallow-rooted trees, since a greater store of soil moisture and 

 fertility is thus made available. So also different trees having 

 somewhat different requirements as to chemical or physical 

 properties of soil can abstract more from a given area than could 

 one species, and a mixture of trees having different degrees of 

 shade endurance can dwell more closely and form a heavier stand 

 per acre. But the chief advantage of a mixture is in case of some 

 ratastrophe which devastates one species but spares the others. 

 The tamarack may suffer from insect ravages, as was the case 

 twenty years or more ago. If other species are in mixture they 

 remain to take up the area, to reproduce, and also, to some extent, 

 to present a barrier to the invasion of insects. In case of a 

 severe windstorm, the more shallow-rooted trees may be over- 

 turned in exposed situations, unless protected by a mixture of 

 wind firm varieties. So against all forest enemies a mixture 

 forms a safeguard. There is also a financial advantage in raising 

 mixed forests. The length of time required to grow timber is 

 so great that it is impossible to predict what species will be more 

 valuable by the time of maturity. In Europe the first forestry 

 measures were induced by a scarcity of fuel wood in the vicinity 

 of the large cities. Hardwoods were, therefore, cultivated in 

 these early operations, but to-day when railroad transportation 

 has brought coal to the cities from long distances and manu- 

 facture is given an impetus, the demand is for softwood lumber 

 and the systems of management have been changed to produce 

 it. A mixed forest provides against such changes of the market 

 by furnishing different classes of timber. On the other hand, 

 pure forests have now well-recognized advantages, the primary 

 one being the simplicity of management. While the chances 

 for injury are greater than with mixed forests, the profits are 

 also greater if such injury is avoided, for a pure forest of trees 

 adapted to a situation will produce more valuable timber than 

 a mixed one. 



