224 Studies in Forestry [CHAP. x. 



was the motive, and enhanced increment on the parent 

 standards the effect; in the latter, enhancement of annual 

 increment is the object, and simultaneous natural reproduc- 

 tion of shade-bearing kinds of trees is the result of this 

 sylvicultural operation. 



Rules for the Conduct of Partial Clearances. 



With the light-demanding species of trees, when they are 

 not grown in mixed forests along with shade-bearing species, 

 underplanting is almost a necessity after heavy thinnings or 

 partial clearances, in order to maintain the productive capacity 

 of the soil. The manner in which this method of treatment is 

 applied to the various chief genera of our light-demanding 

 forest trees Oak, Pine, and Larch is as follows : 



Oak. When pure forests of Oak have passed through the 

 regular processes of thinning, and approach the time for a partial 

 clearance taking place, their canopy is in general somewhat 

 light and thin, although perhaps not broken ; and the under- 

 growth is usually already beginning to form canopy for itself 

 below the older crop. To avoid the formation of twigs and 

 shoots from the dormant buds along the stem, often leading 

 to ' stag-headedness V the partial clearance should not be made 

 by one fall, but is better attained by one or two heavy thinnings 

 conducted to the extent deemed advisable for each individual 

 crop. The time at which it should take place is also dependent 

 on the special circumstances of each crop, special regard being 

 given to the time of underplanting and the development 

 of the undergrowth, the energy of growth of the trees, and 

 the nature of the soil and situation. As, however, the efficacy 

 of this method of treatment is all the more apparent the earlier 



1 In his Lehrbuch der Baumkrankheiten, 1889, p. 14, R. Hartig remarks 

 that : ' Oaks, which have grown up in close canopy along with Beech and 

 have only a slightly-developed crown of foliage, acquire a predisposition 

 towards a drying-up of the top of the crown (stag-headedness) when they 

 become fully exposed to light and air ; whilst, under similar conditions, trees 

 with well-developed crowns do not suffer from this disease.' 



