GRAZING AND FOEAGE PRODUCTION ON NATIONAL FORESTS 



31 



ing from the five harvestings. There was a slight decrease from 

 year to year in the number of mountain brome and mountain dande- 

 lion plants on the plots harvested twice in the season. In the former 

 case it is believed that the loss was caused by frost upheaval, and 

 in the latter pocket gophers cut the taproots. There was also a 

 noticeable decrease in the yields of Letterman needle grass and 

 mountain brome on these plots. Inasmuch as these plants are bunch 

 grasses it is believed that some of the previous year's growth may 

 have been included with the first cutting in 1920. The difference 

 in the growth potentialities of the seasons is no doubt responsible 

 for some variation in the yields. 



Number of P/onts Treated 



Crams 

 S320, 



AferocpeY/e/d perTreotec/ P/onf 



~W 



Toto/ r/e/c/ ofPtolS 



i 



Leoend 

 ■■i Harvested fi W times in season 

 I I Horvested two times in season 



Fig. 11. — Effect on vitality and yield of frequency of harvesting. Cropping as 

 often as five times in a season not only causes a loss in plants but lowers the 

 yield of those surviving 



The results with mountain brome and violet wheat grass har- 

 vested four times, at monthly intervals, the first harvesting ap- 

 proximately one month after the beginning of growth; twice, the 

 first harvesting at seed maturity and the second at the close of the 

 growing season; and once only, at seed maturity, are shown in 

 Table 7 and Figure 12. 



The increasing yield of violet wheat grass and the maintenance 

 of the yield of mountain brome when harvested once or twice in 

 the season compares strikingly with the bare maintenance of vigor 

 in the wheat grass, and the excessive loss in the brome, when har- 

 vested four times. In contrast to the death of all the mountain 

 brome plants in the first year when harvested five times, as shown 

 in Tables 5 and 6, many of those harvested four times, monthly, 



