44 BULLETIN 1170, U. S. DEPARTMENT OF AGRICULTURE. 



native vegetation. They also indicate the effects of grazing upon 

 species that grow in mats or small bunches. From these maps it is 

 clear that the quantity of Stipa comata has been reduced by the over- 

 grazing in the 30-acre pasture. 



The list quadrats used in these experiments are of great value 

 in keeping a record of the number of plants of different species. 

 These quadrats show that Artemisia frigida has increased in ex- 

 tent under the heavy grazing in the 30-acre pasture. The vigor 

 of the individual plants of this species has been favored by the 

 reduction of the competition of other species in the small pasture. 



The clipped quadrats used in the experiment were designed to 

 facilitate the study of the effects of frequent and infrequent removal 

 of the vegetation upon its subsequent growth and also to determine the 

 period of greatest growth. In the frequently clipped quadrats Stipa 

 comata has disappeared, other species have been weakened, and the 

 total production has been reduced. Bouteloua gracilis is the one 

 species that appears to respond to frequent clippings better than 

 any other species. The greatest growth of the vegetation occurs 

 early in the season at the time the cattle make their greatest gains. 



Photographs of the plants growing in the different pastures have 

 been taken from the same points each year. These form permanent 

 authentic records that can not be obtained in any other way. 



Areas known as " isolation transects " were set aside in the 100- 

 acre and 30-acre pastures and in one division of the rotation pasture. 

 Units are annually closed to grazing on one side of the transect and 

 opened to grazing on the other, while the central units are never 

 grazed. The units that are annually closed to grazing in the 30- 

 acre pasture contain about five times as many plants of Artemisia 

 frigida as those that are never grazed. The plants of this species 

 are also more vigorous in the units closed in 1920 and 1921 than in 

 those closed previous to 1920. 



General field notes are kept each year upon 27 different species of 

 plants that are common on the prairie. These notes show that the 

 prairie has turned green in the spring as early as April 15 and as 

 late as May 20, while it has started to " dry up " as early as June 15. 



A mowing experiment was undertaken to determine the effects of \ 

 the annual and biennial removal of the vegetation upon the total 

 production. The yields also furnish data from which the quantity 

 of forage available for grazing may be determined. 



Field germination tests show that the seeds of many of the most 

 valuable range grasses are low in vitality. 



Each year a number of trials have been made to grow cultivated 

 forage plants sown in the native sod without breaking. The results 

 show that it is almost impossible to get the plants to grow in a 

 vegetation of such density. 



Soil-moisture determinations show that the first foot of soil in all 

 pastures is well filled with water at the beginning of each season. It 

 was not until 1919 that the moisture of the sixth foot of soil was 

 greatly reduced. The sixth foot of soil in the 30-acre pasture has 

 not been reduced to the same degree as in the other pastures. 



The grasses of this region make up about 50 per cent of the dry 

 weight of all species of plants. It is estimated that 90 per cent of 

 them are palatable and therefore afford excellent grazing for cattle. 



