204 Alaskan Science Conference 



Although the number of degree days in the Tanana valley 

 for growing grains is much lower than in the temperate zone 

 of Europe and America, nevertheless grains are growing here 

 quite successfully by the use of acclimated varieties and strains. 

 The fact that days in the high latitude sub-arctic regions are 

 much longer than in temperate zones having more hours of 

 solar and sky radiation, particularly during the month of 

 June, has a profound effect on plant growth and its pheno- 

 logical phases. Length of the solar radiation hours during the 

 day in June is essential for native and cultivated plants which 

 are in the blossoming phase at this time. During the month of 



Table 4.— Normal number of the solar and sky radiation units in gram calories 

 per square centimeter (gmcl/cm 2 ) Fairbanks, Alaska 



Daily Total 



Month mean per month 



May 477 i4.7 8 7 



June 499 14,970 



July 447 !3>857 



August 314 9,734 



September l 7&b 5> 2 95 



Total per 5 months 58,943 



Mean per month 478 



June solar and sky radiation recording began in Fairbanks at 

 4: 00 a.m., while in Madison, Wisconsin, at 10: 00 a.m. and con- 

 tinued to 7:30 p.m. However the total number of solar and 

 sky radiation units is higher at Madison than in Fairbanks 

 (Table 4 and Fig. 3). 



Our phenological observations in this region during the 

 last six years indicate that most of the native sedges (Eriophorum 

 sp. Carex sp.), grasses (Poa arctica, Calamagrostis canadensis, 

 Bromus arcticus, Bromus pumpclianus) and legumes (Astragalus 

 sp.) have completed their blossoming during this month. Our 

 perennial fire weed (Epilobium augustifolium) blossoms in the 

 first part of July, coinciding with the beginning of heading of 

 our barley and wheat. 



