10 BULLETIN 4, U. S. DEPARTMENT OF AGRICULTURE. 



The studies were originally confined to 15 main plots having an 

 average area of about -1 acres, of which 10 were in the whitebark 

 pine and 5 in the lodgepole pine zone. Both in the spring and 

 autumn of 1908. 1909. and 1910 several additional small plots were 

 seeded to grasses and clovers at high and medium elevations. 



CLIMATIC CONDITIONS. 



The amount of precipitation during the growing season was nota- 

 bly greater in the high mountains than at lower levels. In 1909. 

 which was about an average season, the mountain bunch-grass ranges 

 in the whitebark pine zone (elevation about 7.500 feet) received 7.15 

 inches of precipitation during the main growing season, which, at 

 that altitude, is about three months long, mainly July. August, and 

 September. The lands of medium elevation, about 1.500 feet, in 

 the lodgepole pine zone, a region which enjoys a growing season of 

 about four and one-half months, received during July. August, and 

 September 5.51 inches precipitation. On the ranges of the yellow- 

 pine zone (elevation about 3.000 feet), the precipitation received 

 during the same period was 3.63 inches. In subsequent seasons the 

 relative amounts were about the same. 



The temperature in the whitebark pine zone as compared with the 

 two lower zones was found lower by several degrees : the evaporation 

 also was less, and consequently the transpiration demand on the 

 vegetation was less. 



DESCRIPTION OF THE PLOTS. 



The largest plot. 20 acres in area, was selected on a severely over- 

 grazed tract, on what is known as Stanley Range, lying at an alti- 

 tude of about 7.300 feet on a ridge which at one place broadens out 

 into a plateau about a mile in width. The area was seeded to a 

 mixture of timothy, redtop. and Kentucky blue grass. The amount 

 of seed sown per acre was as follows: Timothy. 8 pounds: redtop. 

 3 pounds: and blue grass. 1 pounds. -The seed was worked into the 

 ground by driving a band of sheep in a compact body twice over the 

 area. 



As shown in figure 2. the topography is smooth, and the whole area 

 slopes westerly from 3° to 6°. The soil is a light clay loam, having 

 a depth of from one to several feet, underlain by a layer of basaltic 

 rock mixed with more or less soil. In places this rocky layer is 

 exposed, forming small ,; scabs " or " scablands." The water-reten- 

 tive power of this soil is good, though the surface layer becomes 

 rather dry early in the season. 



The whole area was originally covered with mountain bunch- 

 grass (Festuca viridvla)^ but it is now almost barren. The most 

 abundant perennial plant now is sickle sedge (Cavex umbellata brevi- 



