height measurements, such as the effects of the competition of 

 Artemisia tridentata upon 17 species of range grasses artificially 

 seeded in northern Nevada. In early spring, Agropyron cristatum 

 was only 4 in. tall under intense competition with A. tridentata, but 

 7 in. tall where the competition was lacking. The heights of 

 Agropyron smithii -were 15 and 17 in., respectively, showing that this 

 grass resisted the competition better than the other Agropyron.^'^^ 



The height of the herbage and the depth of the root system 

 often show a relationship. For example, Buchloe dactyloides in 

 Nebraska, with an herbage height of 5.5 in., had a working 

 depth (the depth to which a large number of roots penetrate) and 

 a maximum depth of the root system at 12 and 20 in., respectively; 

 but when the herbage height was 3 in. the root depths were only 

 5 and 9 in., respectively. Another relationship was also noted: in 

 six grass species the width of the third leaf from the ground varied 

 in accord with the diameter of the roots at a depth of 6 in.^^^ 



In comparing the effects of systems of grazing upon the vege- 

 tation, flower stalks were cut at the close of the growing season 

 and taken into the laboratory for making precise measurements. 

 The average length of 100 stalks o^ Agropyron smithii from a de- 

 ferred and rotation pasture in northern Colorado was 23.0 in. and 

 that from an adjoining continuously grazed pasture, 18.7 in.; 

 and the respective heights of Stipa viridula in the same habitats 

 were 32.1 and 24.1 in.io^ 



Height measurements are excellent for showing the effects of 

 clipping species at various heights and frequencies. In eastern 

 Montana Bouteloua gracilis, clipped during the growing seasons 

 from 1938 to 1941, showed the following results in 1942 when it 

 was not clipped: ^^' 



Analytic; CKaracteristics of the Conmnmunity • 107 



