SILVICULTURE, PROTECTION AND EXTENSION 



The statement has long been accepted in 



Production silvicultural discussions that mixed stands 



in produce more than pure stands because 



Mixed Stands they are capable of more fully utilizing the 



factors of site. This dictum has had no 



other basis than general observation until now Dr. Schwappach 



has undertaken a careful investigation of the subject and here 



gives some of the current results of his as yet unfinished work. 



There are many inherent difficulties in the investigation. 

 Actual production in mixed stands must be compared with the 

 average production of pure stands of the component species on 

 the saine site class as read from yield tables. While such a scheme 

 is open to theoretical objections the concordance of the results 

 secured speaks for its practical value. 



Mixtures of oak and beech and of pine and spruce are compared 

 with pure stands on the basis of fourteen and thirteen examples. 

 Three spruce-beech mixtures are studied and one stand of pine and 

 beech. 



Mixtures of pine and spruce under eighty years of age yield less 

 than is produced when the two species are segregated into pure 

 stands, but after the eightieth year the production of the mixed 

 stand becomes greater. Such behavior, of course, indicates that 

 such mixed stands call for management on a longer rotation than 

 is demanded by pure stands of either component. Although this 

 appears to be generally true, local conditions are not without their 

 influence. In dry, sandy soil, an underwood of spruce with its 

 superficial root-system may absorb the entire precipitation during 

 critical periods of the year and seriously reduce the growth of the 

 pine. Again in mountainous regions where the spruce is much 

 more at home an admixture of pine may not be beneficial. 



The solitary pine-beech mixture reported shows one-third greater 

 current growth at one hundred and fifteen years than yield tables 

 indicate for pure stands. 



Mixed stands of oak and beech show in every instance but one 

 a greater increment than is indicated for pure stands of the two 

 species segregated. There is some indication that a portion of 

 this at least is due the silvicultural care given the mixed stands 

 under investigations. 



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