April 1, 1916, to December 31, 1917. Ro- 

 tated with Stations 7-8 and 15, this 

 station being reached the second decade 

 of each month. 



FOREST TYPES IN CENTRAL RQCKY MOUNTAINS. 17 



object of this kind of cutting is to leave at the first cut only such 

 trees as will be merchantable in a few years, and these for the value 

 of their protection to the new growth, whose development deter- 

 mines the time when the old trees shall all be removed. Inasmuch 

 as the original stand was not single-aged, though it was mainly so, 

 this process involved forced cutting of material not merchantable 

 except for fuel. All trees except those of Douglas fir were removed 

 in the cutting, and of the latter about S3 trees of an average diameter 

 of 9.7 inches and an aggregate basal area of 43 square feet were left 

 on the acre plot. This represents just one-fourth the basal area of 

 the original stand. Presumably, therefore, the crown density is not 

 over one-fourth of the virgin crown density nor of that now shelter- 

 ing Station 9. 



Although a few observations of minimum temperatures were made 

 at this point in the fall of 1915, the more important records do not 

 begin until 1916. The equipment used was as follows: 



Maximum and minimum thermometers, in standard shelter, 1 foot above 

 ground, April 1, 1916, to December 31, 1917. 

 Air thermograph, in shelter. 

 Psychrometer. 



Anemometer, 1 foot above ground, 

 With register. 



vaporimeter, inner-cell, Type 2, 

 in 1916. 

 Evaporimeter, inner-cell, Type 4, 



in 1917. 



Evaporimeter, Type 4, January 1, 1918, to April, 1920. 



One and 4 foot soil thermometers, in iron pipes, April 1, 1916, to April, 1920; 

 1-foot iron pipe replaced by wooden tube, April 26, 1918. 



Soil well furnishing samples for moisture determination at depths of 1, 2, and 

 3 feet, from May 23 to end of season, 1916, and also from the surface during the 

 whole season of 1917. 



F-15: Fremont north slope Dour/las fir, half cut. — Elevation, 9,080 

 feet; aspect, N. 8° W.; slope, 28 per cent. This station is only 250 

 feet east of the preceding and practically on the same contour. How- 

 ever, it will be noticed that the slope is slightly less steep, and this 

 location has a very slight bearing to the west of north. The differ- 

 ence in slope, giving somewhat more direct insolation at Station 15 

 than at Station 14, is probably a little more than counterbalanced, 

 for the general area in which Station 15 is located, by a somewhat 

 greater density of cover. At the station, however, the cover is fairly 

 heavy on the east but relatively open to the west and southwest, 

 permitting sun action in the afternoon, and this will fully account 

 for the slightly higher soil temperatures here than at Station 14. 



The plot in the center of which Station 15 Lies, like that surrounding 

 Station 14, has been heavily cut over, but with the object here of 

 leaving trees of all sizes, or in other words, of producing a " selection " 

 forest. Again, this cutting was forced, as the pri and was far 



richer in mature than in immature sizes. This was especially (rue 

 of the Douglas fir, and as the cutting conipL ed all other 



species, the number of healthy young trees left could not be \ 

 great. However, the number of trees is somewhat greater than in 

 the "sherterwood" forest, both of large and small sizes. The princi- 

 pal shortage is in trees 4 to 6 inches in diameter. In the stand 

 left after cutting there are 110 trees of an average diameter of 10.2 



73045°— 24 2 



