Periodical Literature. 459 



they were to move only in the subordinate stand. Within the last 

 20 years ideas opposed to this teaching which does not recognize 

 the dominant stand have asserted themselves, and under various 

 names {Plenterdurchf orshmg, Kopf durchforstung, Durchforstung 

 im Herrschenden, freie Durchforstung) systems of thinning in the 

 dominant (the French eclaircie par le haut) in juxtaposition to 

 thinning in the subordinate {Niederdurchforstung, eclaircie par le 

 has) have been developed. 



The object of thinnings in general is the production of the 

 largest and at the same time most valuable wood quantities in 

 shortest possible time. 



It has been recognized that the largest volume is dependent on 

 a certain degree of density of stand. What degree, is still un- 

 solved, although we are nearer its solution. Volume is the re- 

 sultant of the work of crown and root, a combination of the ra- 

 diating energy of the sun and the chemical energy of the soil. 

 We have learned through Wiesner, that not all, and not the direct 

 light, but certain rays and of the diffused light — only a certain 

 part of the light surrounding the crown is active. It may be 

 asserted that the useful light — the so-called relative light enjoy- 

 ment (Lichtgenuss) — becomes the smaller in amount, the more 

 effective the crown density. But since root activity has also to be 

 considered, a limitation results. Not the densest crown cover rep- 

 resents the optimum, although here the largest amount of foliage 

 and light are interacting, but root energy is reduced especially 

 by retaining precipitation in the foliage and lower temperature.. 

 Considering various degrees of density the optimum must have- 

 passed when after interruption of crown cover the soil covers; 

 itself with a green vegetation, which withdraws part of the total 

 growth energy from wood production. 



The working hypothesis, then, may be formulated that the 

 largest increment occurs when a minimum of foliage is pervaded 

 by the largest amount of utilizable light. The optimum will be 

 at hand, theoretically, just before other vegetation appears, prac- 

 tically when the crown cover is slightly opened. Hence a severer 

 opening of the crown cover means decrease of volume production 

 (not of the single stem, but of the stand) ; except temporarily 

 when through more rapid humification the soil energy is increased. 

 But this is merely anticipating the use of the fertile elements 

 which would be otherwise distributed in time. 



