62 



BULLETIN 791, U. S. DEPARTMENT OF AGRICULTURE. 



tion lias manifested itself, however, the less hardy palatable plants 

 have been killed. In such serious instances of physiological weak- 

 ness, the aerial development of the remaining vegetation is often 

 well-nigh lacking; yet the buds at the crowns of the plants, as well 

 as a considerable portion of the root systems, may survive. So long 

 as the factor disturbing the physiological balance of the vegetation 

 persists, most of the buds at the plant's crown remain dormant, only 

 an occasional aerial shoot being produced to elaborate food and 

 nourish the plant. Where a considerable portion of the vegetation 

 is alive, yearlong protection, or grazing after seed maturity, will 

 greatly promote revegetation. In figure 26 is indicated the effect of 

 protecting yearlong a moderately depleted range. The unprotected 

 area represented has been grazed moderately by sheep and cattle 

 before seed maturity each year during the period of the test, and 

 corresponds to the grazing practice in vogue prior to the experiment. 

 When the protected areas shown in the figure were fenced in 1913, 

 the vegetaticn appeared identical with that outside in character, 

 density, and vigor.^ The difference in 1917 in these particulars is 

 summarized in Table 7. 



Table 7. — C'o'nvparative height and density of vegetation on plot protected from 

 gracing for fire successive years and on unprotected adjacent range grazed 

 annually l)y sheep, usually ivell in advance of seed maturity} 





Density per square foot. 



Relative height (physiological 

 index). 



Plant. 



On pro- 

 tected 

 plot. 



On open 

 range. 



Per cent 

 differ- 

 ence. 



On pro- 

 tected 

 plot. 



On open 



range. 



Per cent 

 differ- 

 ence. 





45.6 

 1.6 



28.2 

 1.4 



.7 



38 

 12 



1.47 

 3.06 



0.85 

 1.20 



42 



Slender wheat grass {Agropyron tenerum) . 

 Androsace (^Androsace diffusa) 



61 





3.2 



45.6 



.8 



3.2 



100 

 63 



2 75 

 34 



1.20 

 1.90 

 5.20 

 1.70 









16.9 

 1.4 

 2.1 

 5.6 



12.7 

 1.4 

 4.9 



4.2 

 3.5 

 0.8 

 2r8 

 1.4 



1.03 

 4.40 

 1.20 



46 



Tall larkspur {Delphinium harheyi) 



Low pea vine {LatJiyrus leucanthus) 



15 

 29 











1.20 





Plantain (Plantago tvecdyi) 



.8 

 4.8 



12.0 

 7.2 

 4.0 

 2.4 



4.0 



2 75 



22 



65 

 51 

 80 



2 17 



65 







2. 82 

 2.56 



2.13 

 1.18 



24 



Small mountain porcupine grass (Stipa 



54 









2.92 

 1.95 



2.92 

 0.96 







Spiked trisetum ( Trisetum spicatum) 



Tongue-leaved violet ( Viola linguaefolia)... 



51 









1 The figures here given were compiled from a bisect 16 feet long and 1 inch -wide'and outside of the pro- 

 tection plot. Owing to the unwieldiness of such a sketch, only half of its length is shown in figure 26. 



2 Indicates more individuals per square foot on the unprotected range than on the protected range. 



In the density of the vegetation per square foot, the difference in 

 the percentage figures for the highly palatable perennial plants is 



1 Comparative average height growth of the different species on the fenced and un- 

 fenced areas is here iised as an index of physiological vigor, of which it is believed to be 

 a reliable criterion. 



