NOTES ON THE DISTRIBUTION OE LODGEPOLE AND 

 YELLOW PINE IN THE WALKER BASIN. 



By H. S. Kerr. 



During the summer of 1912 an area of approximately four 

 hundred square miles on the Paulina National Forest was cov- 

 ered by extensive reconnaissance. In connection with this work 

 notes were taken on the distribution of Lodgepole and Yellow 

 pine. Some of the ideas brought out by this study are given 

 here. 



The topography of this region is of rather an unusual form 

 and, since it is so vital a factor in the matter of tree distribu- 

 tion, should be discussed briefly. 



At one time the ocean extended eastward as far as the Blue 

 Mountains. Later the Cascade Range was elevated above its 

 surface. Lava flows took place along the broken folds and spread 

 over the country, now known as the Walker Basin. In the inter- 

 vals between the later flows, and continuing after they had ceased 

 altogether, were heavy showers of volcanic ash or pumice. This 

 dust cover is thickest near the mountains and gradually becomes 

 thinner as the distance from them increases, until at sixty or 

 seventy-five miles it disappears altogether. 



During the time that the Cascade Mountains were forming, 

 the region to the eastward was also rising. However, it was 

 not until the volcanic disturbances had subsided to a great extent 

 that it became dry land, as it is evident that much of the pumice 

 was deposited under water. Gravity, aided by wind, rain and 

 snow, slowly worked the pumice cover down from the lava piles 

 and cinder cones into the depressions between them until, at the 

 present time, the general form of the topography is that of a 

 nearly level plain with many small lava buttes and cinder cones 

 rising abruptly from it. Occasionally also one may find a por- 

 tion of the old ocean floor which has been thrust up by some 

 local volcanic disturbance. A good example of this is the flat 

 topped butte in Sections 13 and 14, of Township 24 S.. Range 

 13 E. This butte, which covers a half section or more, rises to an 

 elevation of about two hundred feet above the surroundinsf coun- 



