CHAPTER XI 



THE PRACTICAL EFFECTS OF UNDERPLANTING 



THE conservation of the productive capacity of the soil is 

 one of the first fundamental principles of Sylviculture ; for the 

 sustained yield of the best classes of timber can only reasonably 

 be expected when measures are taken to safeguard all factors 

 determining the quantity or quality of the food-supplies avail- 

 able for the root-systems. One of the first practical steps in 

 this direction consists in the protection of the soil against 

 insolation, and against loss of soil-moisture, by means of the 

 maintenance of a good, close leaf- canopy and the consequent 

 thicker layer of dead leaves. This both forms humus or mould 

 for the benefit of the soil, and also acts mechanically to prevent 

 evaporation from drying winds. Beech, Spruce, Douglas and 

 Silver Firs, and Black Pines species of trees that are densely 

 foliaged and therefore naturally capable of bearing shade well 

 are endowed with good soil-protective qualities throughout the 

 whole period of their development until they attain their 

 technical and financial maturity ; but most of our other valu- 

 able forest trees, Oak, Ash, Maple, Birch, Larch, and Scots 

 Pine, lose their power of conserving the productive capacity 

 of the soil long before they attain their maturity, owing to the 

 natural demands they exhibit for increased growing-space and 

 relatively greater coronal development when once they have 

 nearly completed their main growth in height. These latter 

 species, in fact, prove themselves light-demanding in place of 



