30 Forest Club Annual 



pecially near the surface, is extremely low. The temperature of 

 the surface of the soil is very high .commonly being as high as 

 140 degrees F. in summer. These then are the climatic and 

 the edaphic factors which the seedlings must overcome if the 

 species is to encroach upon the plains. It is well known that 

 such seedlings grow best if somewhat shaded. In the above 

 places they are exposed to the direct glare of the drying sun. 

 The result is that the grasses win over the pine seedlings in the 

 competition upon the fine soil and consequently the trees are 

 kept out by the developing sod. It is the relation of all these 

 factors to germination and the development of the seedling 

 rather than to the mature trees which must be studied. This 

 reasoning may not be entirely conclusive, but it may be sug- 

 gestive to the student. I might suggest that some experiments 

 be planned in reference to this problem, because it is one which 

 would lend itself nicely to experimentation. Here is where 

 the forest ecologist or the worker in silvics might solve some very 

 interesting practical problems. 



2. The Foothill Forest Zone. 



In relation to altitude, this, the first distinctly forest zone, 

 begins at about 6,000 feet and extends upward to about 8,000 

 feet. Within this belt occurs most of the bull pine. As I have 

 already indicated it may migrate to lower levels, and it may 

 also go somewhat higher though the bulk of the species is to be 

 found within the above limits. Bull Pine forms a very open 

 forest. The widely scattered individuals give a park-like effect 

 to the landscape. Grasses, woody herbs, and bushes of various 

 species are found in the open areas. On the hillsides Sabina 

 scopulorum occurs in mixture with the pine. The bull pine is 

 found on dry and on moist slopes, on tops of ridges and in canon 

 bottoms. The tree is not exacting as to soil requirements, 

 growing in soils from glacial drift and volcanic ash to deep loose 

 sands and rather tenacious clays. It is most chacteristic how- 

 ever on dry, well drained rocky or gravelly soils. It may live 

 and thrive in a soil with very low water content, its deep roots 

 enabling it to grow in nearly as dry soils as those occupied by 

 the Pinon. The tree is a frequent and an abundant seeder 

 after the age of twenty-five years has been reached. Seedlings 

 meet with many of the same difficulties here that they do lower 

 down in the plains grass zone. For efficient germination and 

 seeding fresh, well-drained soils are required along with a mod- 

 erate daily range of temperature and not too strong light. The 

 older trees demand much light, but the seedlings must be shaded 

 for a number of months. Seedlings commonly occur beneath 





