28 PROTECTION OF PLANTS, 1921-22 



has been removed, but not neailj- as good as they should be in order to produce 

 a succession of future crops. You will see at once that in order to harvest a 

 crop of trees on the same area, let us say at intervals of ten j^ears, a sufficient 

 number of trees must be ready at each interval to pay the lumberman for 

 cutting them. When he cuts the 12 inch trees, for example, enough 11 inch 

 trees should be left to furnish the next crop, enough 10 inches trees to yield a 

 profitable crop at the third cutting, and so on down through the diameter 

 classes, but with an increasingh' larger number of trees in each diameter class 

 downwards because the highest death rate is among the smaller trees. This 

 is what foresters call the proper gradation of diameter classes and it is the basis 

 of successive j-ields on the same area. Now, investigations have demonstrated 

 that such proper gradation cf diameter classes, especially in the smaller diameter 

 classes, is lacking in the cut-over pulpwood forests of the mixed tj'pe (hard- 

 woods and softwoods mixed) in Ontario, Quebec and New Brunswick, as revealed 

 by intensive stud}' of small representative areas. The trees that remain after 

 the first, second and even third cutting belong to the virgin forest. They 

 might be called the virgin surplus. When the lumberman cuts over an area 

 ten years after his first cut, he thinks he is cutting the growth that has accu- 

 mulated in the meantime, but he is not; he is simply cutting the virgin surplus, 

 a part of the virgin forest that he did not take the first time because it wasn't 

 profitable for him to take it. In fact, since the lumbering operations began 

 in this mixed hardwood-softwood forest, say 50 or 60 years ago, there has not 

 been enough regeneration of spruce eventually to replace what has been 

 removed. In other words, the spruce as a tree of future commercial importance 

 is being gradually crowded out of this mixed hardwood-softwood forest. ' 



Under normal conditions forest trees die of disease. Very few die of old 

 age. There is scarcely a healthy tree in a mature forest. Unfortunately, 

 lumbering methods have been such as to increase rather than to decrease the 

 susceptibility of trees to disease. Periodically^ there comes a combination of 

 man-made and nature-made conditions that produces an epidemic in the forest. 

 Just now the Eastern forests are being swept by a real scourge, the spruce 

 budworm, which has alreadj^ destroyed, according to the estimate of Dr. 

 J. M. Swaine, 30 years' supply of pulpwood at the present rate of production. 

 The destruction of wood material through such epidemics, however, cannot 

 be adequatelj^ measured by the trees killed at the time because the after effects 

 continue for years. The weakened trees becomes susceptible to fungus diseases 

 to which they were pre^douslJ• resistant. The fungus bodies are like cancers. 

 They dissolve away the tissues of roots or stem at the base of the tree until it 

 is overturned by the wind. 



Our forests, particularly the older stands, are rotten with fungus diseases. 

 The number of trees that die before their allotted time is enormous and this 

 has an important economic significance. This is an enormous waste of sawlog 

 and pulpwood supplies that will be largeh' eliminated when conditions are such 

 that our forests can be reallj^ 'managed. Balsam is one of the most susceptible 



