PERIODICAL LITERATURE 



SILVICULTLKE. I'KoTECTK )X. AND EXTENSION 



Statistics in rc-^'ard to rL'!ati\c lit,'lit rc'(inirc- 

 Diffcrcnt Tree mciits and rate of height growth for cUlfcrcnt tree 

 Species ill sjjecies in Sweden show that the culmination of 



Szcedoi height growtli occurs earher in the "light-de- 



manding'' than in the "shade-enduring" species. 

 The most "light-demanding" species such as larch, birch, and pine, 

 attain their maximum rate of height growth at 10-15 years, while in 

 the most "shade-enduring"' species, such as spruce and beech, the 

 maximum is reached at 30-40 years. This relation does not always 

 hold in comparing trees growing on different sites and under different 

 climatic conditions. Such discrepancies, however, are apparent rather 

 than real, due to the fact that under unfavorable growing conditions 

 the age of a tree as expressed in calendar years is not a true index 

 of its progress in the life cycle of the species. Height growth cul- 

 minates later, as measured in years, in a tree growing under un- 

 favorable conditions, than in a tree of the same species growing under 

 favorable conditions. It is also commonly accepted that trees grow- 

 ing under unfavorable conditions have higher light requirements than 

 trees of the same species growing under favorable conditions of soil 

 and climate. The author concludes that if proper standards of com- 

 parison are utilized the relative light requirements and the culmination 

 of height growth remain the same for a given species under varying 

 conditions of site and climate. G. A. Pearson. 



.■\milon, J. A. Hdjdtillvdxtens forlopp hos triid iiied oliha liusbchov. Skogs- 

 v&rdsforeningens Tidskr., 17:95-108. 1919. 



In portions of Norrland. Sweden, the pine 



The Pine Heaths forests (Pin us syk'estris) reproduce themselves 



of Norrland with such difficulty as to cause serious concern 



among foresters. The ground is usually covered 



with a dense mat of lichens, mainly Cladina alpcstris, which grow to a 



height of more than a decimeter. The lichen mat apparently does not 



seriouslv interfere with germination because young seedlings are 



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