SYLVICULTURE. 



The administrative and the sylvicultural management of mixed 

 woods is more difficult and hence more expensive than that of 

 pure woods. 



In America logging expenses are much increased where only 

 one species can be utilized in mixed forests. Logging for Spruce 

 on " Black Spruce Slopes " in the Adirondacks is relatively cheaper 

 per thousand feet board measure than logging for Spruce where 

 Spruce forms only one-third of the growing stock. This objection 

 does not hold good, of course, where all species are marketable at 

 the same time. 



E. Rules governing the composition of a mixture and rules for 

 treating mixed forests (holding good for artificial and semi-arti- 

 ficial forests) : 



I. Species selected for a mixture must improve one another. 



II. Each species should occupy that section of ground on which 

 it thrives best. 



III. The mixture should at least maintain the productiveness 

 of the soil. 



IV. A light-demanding species mixed with a shade bearer must 

 either be given an advance in age or else must naturally possess 

 an advantage in rapidity of height growth; otherwise it soon 

 disappears. This relative height growth is not a fixed quantity; it 

 usually differs according to the soil and to the climate. 



V. The. denser the forest cover is, the earlier and the more 

 intense must be the help given to the species likely to be suppressed 

 (Sassafras and Locust in mixture with Chestnut). 



After Henry Mayr: species which are botanically different from 

 the most natural mixture (Oak and Pine at Biltmore; Birch and 

 Spruce in Balsams; White Pine, Linden and Elm in Michigan). The 

 exceptions to this rule are many (Norway and Jack Pine in Michi- 

 gan; Red Firs and White Firs in the Pacific Coast States). 



Paragraph VIII. Dr. Henry Mayr's (Munich) fundamental prin- 

 ciples of Sylviculture. 



A. Forest is possible only where the mean temperature of 1.1n^ 

 four months of most active growth averages 50 degrees Faht. or over 



B. A mean summer temperature (May to August) of 53 to 59 

 degrees Faht. produces the Fir and Spruce zone of Europe, Asia and 

 America. A ' mean summer temperature of 59 to 64 degrees is 

 productive of Beech, also of White Oak, Maple, Hemlock and Cham- 

 aecyparis. A knowledge of the summer mean is essential when 

 introducing exotics. A knowledge of the possibilities of forest 



36 



