Nov. i6, 1914 Revegetation of Range Lands loi 



production, (3) development and maturity of seed, (4) viability of the 

 seed crop, and (5) establishment of reproduction. 



Owing to the relatively unfavorable conditions for plant growth and 

 the demands made upon them for summer range, the high mountain 

 lands are the ones most in need of revegetation. For this reason the 

 life history of the forage plants and the factors affecting their activities 

 were studied more intensively in the Hudsonian zone than elsewhere. 



INCEPTION OF GROWTH 



The time at whicn growth begins in the spring varies widely in the 

 different zones. Thus, in the heart of the Hudsonian zone growth begins 

 ordinarily about five weeks later than in the Canadian zone immediately 

 below and seven weeks later than in the Transition zone. Even in the 

 same zone the beginning of the growth period may vary by as much as 

 ID days from year to year, depending chiefly upon the climatic condi- 

 tions during the spring, especially in May and June, but also to a certain 

 extent upon the amount of snow accumulated during the winter. One 

 year the early season may be charactenzed by warm, sunny days, and 

 as a consequence the snow cover, especially on the more exposed situa- 

 tions, may disappear as early as June 20, though this is rather exceptional. 

 In another year the snowfall in May and June may be as heavy as at 

 any time during the winter. North and east exposures are always later 

 in responding to growth than south and west aspects of the same eleva- 

 tion. Considerable difference exists also in the time when growth begins 

 on different portions of the same slope. 



The influence of local conditions on the inception of growth was well 

 shown in the case of a north slope in the Hudsonian zone with an altitude 

 at the crest of 7,850 feet and an incline of from 15° to 18°. With a suc- 

 cession of warm, sunny days the snow began to disappear first from the 

 crest, then from the slope, and finally from the base. As the snow 

 melted, growth began almost immediately. Before it had fairly begun 

 on the slope, however, the crest showed a sparse covering of green, while 

 a similar relation later existed between the slope and the base. In the 

 early part of the season there was a marked difference between the 

 amount of soil moisture at crest, slope, and base, the average percentages 

 being 23.2, 27.6, and 39.9, respectively. As the season advanced, how- 

 ever, moisture conditions gradually became equalized, and in the latter 

 part of the growing season the moisture content of the entire slope was 

 practically uniform. For this reason, though growth began on the crest 

 from three to six days earlier than upon the slope and from seven to nine 

 days in advance of that on the base, toward the end of the growing period 

 the vegetation as a whole presented a strikingly uniform appearance. 



The period of growth resumption in each zone lasts ordinarily about 

 20 days. In the Hudsonian zone this period usually begins about June 



