GRAZING AND FORAGE PRODUCTION ON NATIONAL FORESTS 45 



Some of the plots were remapped yearly, others every few years, 

 with a view of noting the changes in the vegetation. 



The data have been grouped to show for the first and last map- 

 pings (1) the number and names of species, (2) the density of the 

 cover, (3) the average palatability of the cover, and (4) the com- 

 parative quantity of the forage. 



The true comparative quantity of the forage is expressed by the 

 forage factor, which may be defined as the numerical value, or 

 index figure, obtained by multiplying the density of the cover (ex- 

 pressed in tenths or percentage of a complete cover) by the aver- 

 age palatability (expressed in percentage) of the type concerned. 

 In other words, it is that figure which when multiplied by the 

 surface or gross acres of a type gives the forage acres which the 

 type contains. 10 



In order to apply the forage factor to the plot study it was first 

 necessary to record the palatability of each species that occurred 

 on the selected areas. This was done by careful observation of the 

 actual quantity of each species which was utilized by cattle and 

 sheep on various range types and at different times of the season 

 with a view of determining the average quantity taken by each 

 class when the range as a whole was properly used. The percent- 

 ages of palatability of the species as given in Table 13 are believed 

 to be reasonable averages for the locality, types, and conditions 

 concerned. 



The following compilations aim to show the comparative rate 

 of revegetation and forage increment on plots protected yearlong 

 as compared with those grazed in general according to the deferred 

 plan. Ordinarily the latter plots were grazed more closely than 

 was desirable, and they were not always deferred as late as was 

 advisable. The grazed plots were so selected as to represent, as 

 closely as possible, average conditions on the range adjacent to the 

 inclosed plots. 



The most impressive changes are the remarkable increase in num- 

 ber of species, density, and comparative value on all of the plots, 

 regardless of whether they were protected yearlong or grazed. 

 By reference to Tables 14, 15, and 16, giving conditions in Bear 

 Creek Canyon, it will be noted that in 1921 the density and forage 

 factor of the grazed plot were approximately equal to those of the 

 protected plots. These plots were on an area extremely depleted in 

 1916, with inferior soil, infertile, and of poor tilth. Nearly all the 

 invading species, therefore, were annuals or short-lived perennials. 

 The Horseshoe Flat plots, recorded in Tables IT and 18, are lo- 

 cated on range which was less depleted than the Bear Creek Canyon 

 area in 1915 and supported at that time a small number of species, 

 but several valuable grasses fairly high in the successional develop- 

 ment. Spiked trisetum, Letterman needle grass, and violet wheat grass 

 were fairly well represented. By 1921 these species had increased 

 appreciably on both the protected and grazed plots, and by far 

 the greater proportion of the vegetation consisted of perennial 

 plants. 



10 A forage acre is represented by a surface acre supporting a complete ground cover of 

 vegetation (10/10 density) within reach of livestock and which is entirely (100 per cent) 

 palatable to livestock. 



