64 Journal of Agricultural Research voi.xix. No. j 



side of the river shows by the character of the soils and the rocks that lie upon or near 

 the surface that the great continental glacier was once here. Toward the west the 

 belt fades out and becomes indistinguishable from the land farther west over which 

 the ice did not pass, but the eastern part of the belt is sufficiently modified as to the 

 soils and the landscape features to be readily recognized. 



The soils, therefore, in the belt bordering the Missoiu'i River on the west constitute 

 a transition type from the glacial soils of the eastern portion of the State to the non- 

 glaciated or residual soils of the southwestern portion of the State. 



CLIMATE 



The United States Weather Bureau Station at Bismarck has made con- 

 tinuous meteorological observations since 1875. Bismarck is located on 

 the east side of the Missouri River, only about 5 miles distant from Man- 

 dan. Observations were begun at the Mandan Field Station during 191 3. 

 From 1875 to 1914, inclusive, or 40 years, the mean annual precipitation 

 was 17.41 inches. The greatest annual amount during this period was 

 30.92 inches in 1876, while the lowest was 11.03 inches in 1899. During 

 191 7 the record at the Mandan Field Station was 10.31 inches. The 

 mean seasonal precipitation from April i to July 31, inclusive, was 9.91 

 inches during the 40- year period. The month of maximum precipitation 

 is June, with a mean of over 3.5 inches, and the month of minimum pre- 

 cipitation is February, with less than 0.5 inch. 



The temperature is extreme in both winter and summer. The lowest 

 recorded to date was 45° F. below zero in January, 1916, while the high- 

 est was 107° above zero in July, 1910 and 1917. The average dates of 

 killing frosts in spring and autumn are about May 15 and September 15, 

 respectively, but frosts have occurred as late as June 7 and as early as 

 August 23. The average frost-free period is 128 days. The prevailing 

 wind direction is from the northwest. The average wind movement 

 near the ground is about 6 miles per hour. 



PLANT FORMATION 



According to a map of "Plant Formations of the United States," by 

 Shantz and Zon,* this region would come within the "short-grass forma- 

 tion." However, Dr. F. E. Clements, who visited the field station during 

 the summer of 191 7, is of the opinion that it would be more properly 

 placed in the "long-grass" or "prairie formation," because of the long 

 grasses and other plants which are typical of a prairie formation. 

 From actual determinations in the field the percentages of short-grass 

 and long-grass cover have been found to be nearly equal, so that the for- 

 mation could be put in either class, according to the viewpoint of the 

 observer. If the secondary plant layer is considered as the determining 

 factor, the region falls in the long-grass formation. The vegetation in 

 this particular area might be considered as in a transition zone, since 

 the dominating species are typical of both formations. 



'Shantz, H. L., and Zon, R. plant formations of the united states. Paper presented before the 

 Ecological Society of America at its annual meeting in New York in 1916. The map will appear in the 

 Agricultural Atlas. 



