Periodical Literature 99 



Mixtures of spruce and beech also appear more productive than 

 pure stands although comparison can here be secured only by- 

 extrapolation of the yield tables. The value production falls with 

 the rise of the proportion of beech in this mixture. 



An investigation of the relative proportions of the two species 

 in these mixtures at successive stock-takings shows the tendency of 

 the beech (or spruce) to increase in volume, number of trees, and 

 basal area. The absolute changes found depend of course on the 

 particular silvicultural treatment the stand has received. 



The practical advantages of indigenous mixtures over artificial 

 pure stands is clearly shown in the Silesian districts of Breslau and 

 Oppeln where the managed forests are almost entirely Scotch 

 pine with an understory of spruce in the lower country and of 

 spruce with very little pine in the moimtains. Careful search, 

 however, reveals many isolated small areas where larch, beech, 

 oak and fir, and even other species occur in amoimts large enough 

 to affect the stand and their effect is always favorable. Here 

 measiirements merely confirm what the eye recognizes at first 

 glance. 



Untersuchungen in Mischbesldnden. Zeitschrift fiir Forst und Jagdwesen. 

 Aug. 1914, pp. 472-491. 



The fimction of thinning in stands in 



Influence which the height growth has culminated is 



of to promote diameter growth. "Thinnings" 



Thinnings in this discussion by Oelkers is used in the 



sense of Michaelis' "Bramwalder Anleitung. ' ' 



While the effectiveness of thinning may indeed depend upon the 



manner in which it is carried on, it remains none the less dependent 



upon the severity of the thinning. 



Thinning admits simlight, precipitation and wind to the stand. 

 Precipitation affects chiefly the soil and roots and Metzger has 

 shown the influence of wind on the bole. Light affects crown, 

 bole and forest floor. While we know considerable of photo- 

 synthesis in the green leaf, we know nothing of the influence of 

 direct simlight on the bole. The investigations so far made of 

 the influence of sunlight on the flora, the faima and the physical 

 structure of the forest soil have proven very enlightening. 



