114 SUGAR PINE TYPE 



in the sequoia type while the Douglas fir type on the north has a 

 shorter growing season but much more precipitation. To be 

 specific, sugar pine and its associates thrive best with an annual 

 precipitation of at least 40 inches altho they can endure a mini- 

 mum of 20 inches. Likewise, the largest trees, 10 feet in diameter 

 and 200 feet in height and scaling over 25,000 feet, are only found 

 where the growing season is at least seven months long. Like 

 the rest of CaHfornia the heat of summer in this type is unrelieved 

 by showers. Fully four-fifths of the precipitation falls during 

 the early spring, late fall and winter. 



As was seen in discussing the location and extent of the type 

 it is essentially a mountain form of vegetation. The valleys are 

 too hot and dry to allow tree growth. At the other extreme 

 sugar pine does not reach the summits of the Sierras, at least as 

 a commercial tree, because of the cold. The type may, therefore, 

 be characterized as a middle slope type. From this it naturally 

 follows that the soil is of medium depth because great accumula- 

 tions of alluvial soil are not found on mountain slopes but still 

 the grades are gradual enough so that the bed rock is covered in 

 most places with a moderate layer of soil. As with other forms 

 of tree growth the chemical composition of the soil has Kttle 

 effect upon the growth of sugar pine and its associates. The 

 physical characters of the soil are the controlHng factors, reason- 

 able depth, good drainage and good capillarity. 



By composition the type may be divided into two subtypes or 

 cover types, the sugar pine-yellow pine subtype and the sugar 

 pine-fir subtype. The former is the more abundant in the 

 southern part of the type's range since it is an association of trees 

 which are well suited to the hot, dry summers of the middle and 

 southern Sierras. The important species in order of their abund- 

 ance are as follows: 



Per cent by volume 



Sugar pine 25 



Western yellow pine 20 



White fir 15 



Douglas fir 15 



Incense cedar 10 



Jeffrey pine 10 



Sequoias 5 



100 



