418 Forestry Quarterly 



S3^tem has made most progress and the selection system has 

 almost vanished, being replaced by the group and the shelter- 

 wood methods. 



But that does not mean that the natural school had no adherents 

 or in any way gave up the controversy. Gayer, Ney, Burkhardt, 

 Borggreve, followed by Wagner, Mayr, Duesberg, Dittmar, and 

 others have championed its cause during the last 30 years (88). 

 And in so doing they have given the world some of its most sugges- 

 tive and most original silvicultural literature. They have tried 

 to solve the problem, each in an original way. By making use of 

 the latest ecological investigations they have endeavored to show 

 why the natviral system should replace a thoroughly artificial one. 

 For a time the controversy between the two theories was eclipsed 

 by the painstaking research towards the study of the natural laws 

 imderlying the two silvictiltural systems. 



Wagner (83) prefers natural reproduction because this produces 

 a race of trees adapted to the site and gives rise to mixed stands. 

 His practice is to cut the forest in narrow strips running east and 

 west, beginning at the northern edge of the forest, a narrow strip 

 being thinned in advance of cutting to start the natural reproduc- 

 tion. Mayr's ideal (59) is quite the opposite: a small pure stand 

 in which species are mixed as smaU stands, not as individuals. 

 It can be reproduced by artificial or by natural means and soil 

 production is secured by tmderplanting. Wagner's method has 

 been tested in the forest; Mayr's is based upon piu"ely theoretical 

 grounds. Both claim universal application for their method. 



Other men have limited their observations and reflections to 

 local conditions and are willing that their results should be applied 

 only to those conditions. In the west we find van Schermbeck, 

 Grabner and Erdmann; in the east Godberssen, Dittmar, Reuss 

 and Duesberg. Van Schermbeek's problem was to rejuvenate 

 run-down pine lands in the heath country of Holland which had 

 become sour due to the exposure and the presence of pure pine 

 stands. It was essentially a problem in the biology and chemistry 

 of the soil and a classic among ecological investigations. His 

 warning was to avoid pure stands of pine. Erdmann had a similar 

 problem on heath lands. He studied the changing relations be- 

 tween the soil and the stand on heath soils and came to the con- 

 clusion that mixed stands and the avoidance of clear cutting was 

 the only way to prevent the deterioration of the soil. Godberssen 



