EFFECT OF GRAZING ON WESTERN YELLOW PINE. 3 



These areas, which are near the western edge of the deeply dis- 

 sected central Idaho plateau, are characterized by a very broken 

 surface, steep slopes, and numerous streams with deeply cut canyons. 

 The soft granite, which underlies most of this part of the Forest, in- 

 terspersed with numerous veins of quartzite, outcrops frequently on 

 the steeper slopes and along the ridges, and the soil which is derived 

 from it is very porous and dries out quickly. Narrow flats along the 

 streams and occasional broader basins — probably once the beds of 

 small lakes — are covered with alluvial soil of considerable depth. 



Annual precipitation in the areas occupied by western yellow pine 

 averages between 20 and 25 inches, of which a large part falls as snow. 

 Snow usually goes off between mid-April at the lower altitudes and 

 early June at the upper limits of yellow pine, and growth starts im- 

 mediately thereafter. Considerable rain falls in June; but after the 

 first week of July there is generally very little rain, except occa- 

 sional thunder showers, until the first part of September. In early 

 September a fall rainy period, with snow at the higher altitudes, is 

 usual. During the summer, days are usually hot and nights cool. 

 Altitudes above 5,000 feet are apt to be visited by killing frosts at 

 any time, while the lower altitudes are, as a rule, free from frost 

 from June 10 to September 1. 



The grazing season for sheep commences some time in May in the 

 lower western yellow pine country and about the middle or end of 

 June in the higher and more remote areas, such as the Deadwood 

 allotment, and lasts until the feed dries and becomes comparatively 

 unpalatable, about the middle of August. The sheep are then held 

 on the higher ranges until driven down by snow or cold weather, 

 after which they sometimes spend a short time on the western yellow 

 pine range on their way out to the open country. 



Western yellow pine and Douglas fir seeds germinate for the most 

 part during May and the first half of June at the lower, and during 

 June and early July at the higher elevations, and occasional seed- 

 lings appear all through the summer. Lodgepole pine germination 

 continues in considerable quantity during most of the season. West- 

 ern yellow pine seedlings to a very large extent, and lodgepole pine 

 to a less extent, occur in small compact bunches, the result of the 

 seeds being buried by chipmunks. 



THE DEADWOOD ALLOTMENT. 



On the Deadwood allotment, which represents the upper exten- 

 sion of the range of the western yellow pine type, and all of which is 

 above 5,000 feet altitude, the timber is largely a mixture of varying 

 proportions of western yellow pine (Pinus ponderosa), Douglas fir 

 (Pseudotsuga taxifolia), and lodgepole pine (Pinus contorta), with 

 some alpine fir (Abies lasiocarpa), Engelmann spruce (Picea engel- 

 manni), whitebark pine (Pinus albicaulis), and a very few specimens 



