24 CONCEPT AND HISTORY. 



continue for a longer period. Three years of complete protection gave about 

 three-fourths of complete recovery for the crowfoot-grama consociation with 

 an annual rainfall of 15 to 18 inches. After 11 years the grazed areas are but 

 partially recovered, though their carrying capacity has increased about 30 

 per cent. 



Reseeding. — Practically all attempts to introduce new species of forage 

 plants or to increase the abundance of endemic species beyond the normal have 

 failed. Alfilaria and some aggressive annuals have given promise, but in the 

 course of a few years the native perennials have crowded them out. 



Carrying capacity. — This has been determined by means of cut-quadrats, 

 hay-cutting, mapping the communities, and by grazing tests of the best part of 

 the reserve. For the latter, the canying capacity is 14 acres per head, while 

 it is 20 acres for the whole reserve. One of the pastures stocked on the basis 

 of 58 acres per head was not noticeably different in condition from adjacent 

 land protected for 11 years, thus indicating a utilization below 50 per cent. 



Jardine and Hurtt, 1917. — In the account of the results obtained on the 

 Jornada Grazing Reserve from 1912 to 1917, Jardine and Hurtt have em- 

 bodied the essentials of the first complete grazing system based upon actual 

 experimental study of the herd as well as of the range. As a consequence, it 

 serves as an excellent model for all ranches large enough to permit the rotation 

 system of pastures and to warrant the segregation of herds by ages and classes. 

 Taken in conjunction with the more intensive grazing experiments such as 

 have been carried on by Sarvis (1919) at Mandan, it furnishes a complete 

 experimental method of range studies. It is especially important in demon- 

 strating how much experimental work and resulting improvement of range 

 and herd can be carried on even under existing economic conditions on well- 

 managed ranches (plate 4, b). 



The authors' most important conclusions are as follows: 



The grama-grass range has improved at least 50 per cent in three years, 

 compared with adjoining unfenced range grazed yearlong. This has been 

 secured by reducing the number of stock during the main growing season from 

 July to October to about half the average number the area will carry for the 

 year, by refraining from overstocking during the other eight months and by 

 better distribution of watering places. The range thus lightly grazed during 

 the growing season has apparently improved as much as similar range pro- 

 tected during the whole year. Where the whole of a range unit is grama, 

 about one-third should be reserved in rotation for light grazing during the 

 growing season for two successive years. 



Fairly efficient utilization of the range is secured by watering places with a 

 2.5 mile grazing radius. When the distance is greater than this, serious over- 

 grazing or actual denudation occurs around the well or tank, while the remote 

 areas are but partially utilized. The carrying capacity of the grama grass is 

 20 to 30 acres, of the tobosa grass 38 to 45 acres, and of the mountain range 

 60 acres. This is based upon carrying stock through the average year in good 

 condition, and feeding the poorer stock concentrates to eliminate loss from 

 starvation at critical periods. 



Jardine and Anderson, 1919. — In an account of range management on the 

 National Forests, Jardine and Anderson (1919: 17) have discussed briefly the 

 general indicators of overgrazing: 



