THE RESEEDING OF DEPLETED GRAZING LANDS. 31 



major portion of the native grazing lands are antagonistic to the 

 establishment of introduced plants. This is due primarily to one or 

 all of three conditions : Excessive elevation, poor soil, coupled with 

 insufficient moisture, or too much and too aggressive native vegeta- 

 tion. 



ALTITUDINAL LIMITATIONS. 



There are three chief causes of failure at high altitudes: First, 

 only the strongest and best seeds can produce vigorous plants, and 

 even this scanty original stand is often materially thinned out during 

 the first season ; second, the plants can ramify or stool out and spread 

 only at a very slow rate; third, the plants produce such a small 

 quantity of viable seed (note Table 5 )that the possibility of increas- 

 ing the stand from seed production is practically eliminated. 



The altitude above which seeding to cultivated species should not 

 be undertaken varies with latitude, and is approximately 3,500 feet 

 higher in southern Arizona than in eastern Oregon. Because of this 

 variation the character of the native vegetation is the best criterion 

 for determining the maximum altitude at which reseeding is justi- 

 fiable. As a concrete example, in the Wallowa Mountains, as pre- 

 viously shown, it has been found that the growing season is so short 

 and the temperature is relatively so low at an altitude slightly 

 exceeding 7,500 feet above the sea that no species thus far tried has 

 made a satisfactory growth. 1 Here is the true timber-line tree — 

 whitebark pine (Pinus albicaulis) — mountain bunch grass, heaths, 

 huckleberry, and the lower zonal forms of arctic- alpine species. 

 vVhere the whitebark pine becomes scrubby — timber line locally usu- 

 ally occurs slightly above 8,500 feet on north slopes — it invariably 

 follows that the altitude exceeds that at which reseeding will pay. 

 (See PL VIII, fig. 2.) The same principle applies to high mountain 

 seeding in any locality, and it is safe to say that seeding to cultivated 

 forage plants will not prove economically successful above the alti- 

 tude at which the true timber-line species attain a good size and grow 

 vigorously. Allowing for the influence of the different slopes and 

 exposures on growth, timber-line trees do not usually make their 

 maximum development when grown within 1.000 to 1,500 feet of 

 timber line, and it may therefore be more specifically stated that 

 seeding should not be attempted within 1.000 or 1,500 feet of timber 

 line. 



SOIL AND VEGETATION COVER. 



Below 1,000 to 1,500 feet of timber line, then, the only areas suited 

 to artificial seeding are those which have sufficient moisture and a 

 deep soil with considerable organic matter, such as are found in 



1 At more southerly points, as in California, good stands of timothy have been secured 

 at an altitude of 10,000 feet. 



