98 



BULLETIN 1333, U. S. DEPARTMENT OF AGRICULTURE. 



encourage pines in some degree. These and other relations will be 

 further analyzed in the following discussions of the types. 



(1) The yellow pine sites — M-l at 7,200 feet elevation and F-2 

 1,700 feet higher — show nearly the same soil temperatures at all 

 seasons, although the constant difference between the two is even 

 greater than the difference in air temperatures near the ground. 

 These two stations are almost in a class by themselves. However, 

 it is to be noted that F-l, the control station, practically measures 

 up to yellow pine standards, its 4-foot mean being as high as that at 

 Station F-2. Stations F-l 2 and F-4, bo'th representing sites in 

 which the yellow pine tends to give way to Douglas fir and limber 

 pine, show soil temperatures a little below the 3-ellow pine standard. 



That the growing-season temperatures indicated above as being 

 favorable to yellow pine will not fall far short of those occurring in 































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Fk;. 7.— Relation of soil and air temperatures on opposing slopes. 



any of the yellow-pine sites of this region is indicated by numerous 

 measurements made in the Black Hills region in 1914, when, during 

 June, July, and August, soil temperatures at 1 foot ranging from 

 56° to 65° were continually encountered. 7 Although measurements 

 are lacking, there is little doubt that winter soil temperatures are 

 kept up fully as high as in the Pikes Peak region, notwithstanding 

 much lower air temperatures, through the agency of a heavy snow 

 blanket in the Black Hills. Larsen (13) shows an August mean of 

 65° at 1 foot, for the Idaho western yellow pine site, as compared 

 with about 03° at Monument in July. Pearson (19) gives May to 

 October values ranging from 53.1° to 66.2° for a number of pine 

 sites in the Soul Invest. 



In the typical western yellow-pine sites the soil temperature at I 

 feet dot^s not, for any 10-day period, go so low as 32°. At Station 



7 Five mee urn ment j In three Quality I pine sites, between June ~\ and July 8, showed an average tem- 

 perature of 67.7°. i j lower than Station I- 1 for the same period: Thirty observations in 11 Quality 11 

 . gave a mean temperature of .v.:-, i..v higher than the control station. Twenty- 

 two oh - rvationsin 10 Quality III sites gave a mean of 58.9 . or UPabove the control station for the period 

 inly n to Ahl'ii i 3. From this ii appears thai the moister and better sites are appreciably cooler than 

 i the rikes Peak region. This difference may be due wholly to denser stands In the 

 On the whole, the two localities are more similar than mighl be expected. The a 

 i f all Blai k lliii observations, June 22 to August 3, was 60.2 , and for the control station 57.9°. 



