EANGE AND CATTLE MANAGEMENT DURING DROUGHT. 19 



proper grazing will be agreed to readily as the major factors re- 

 sponsible for variation in forage production. Other factors, such as 

 " spotted " rainfall, soil, and character of vegetation necessitate ad- 

 justments in any general program of production. These adjustments 

 are of little purpose, however, unless they are part of a compre- 

 hensive plan calculated to meet the conditions resulting from drought 

 and from grazing use. 



VARIATION DUE TO DROUGHT. 



It is somewhat difficult to determine from, data available the per- 

 centage of depreciation of the range as a direct result of drought, 

 because records of changes in vegetation on areas protected against 

 grazing have been collected only for the period 1915 to 1919, in- 

 clusive, and because part of the protected areas being studied were 

 rendered unreliable by sand blowing on them in amounts sufficient to 

 create unnatural conditions. However, the data available are im- 

 portant because they show, at least approximately, the changes which 

 occurred in the main vegetation types during the drought of 1916 to 

 1918, and indicate the changes which will probably occur during a 

 similar period in future years. , 



WINTEE OE YKAELONG EANGE. 



For the winter or yearlong type of range figure 5 indicates the 

 annual change in density of good perennial forage grasses during 

 the period 1915 to 1919, inclusive, with the annual precipitation for 

 the same period. The actual amounts of good perennial forage 

 grasses, inferior perennial grasses, long-lived weed'"' vegetation, and 

 short-lived plants per unit of area are given in Table 6. Only the 

 good perennial forage grasses, mainly black grama and red three- 

 awn, are used in establishing the curve indicating the change in con- 

 dition of the vegetation, since these species represent the main graz- 

 ing values of the range and are the ones most important to maintain. 

 The vegetation curve is basecj upon quadrat chartings and observa- 

 tions on two representative areas of grama grass range, one pro- 

 tected against grazing from, 1913 to 1919 and one protected from 1916 

 to 1919, inclusive. The protected areas were examined frequently 

 each year, and quadrats were charted twice annually in 1915 to 1919, 

 except 1918, when only one charting Avas made because of lack of 

 vegetative growth early in the year. 



1° " Weeds " as used in this publication mean all herbaceous vegetation other than 

 grasses or grasslike plants. 



