FOREST TYPES IN CENTRAL ROCKY MOUNTAINS, 19 



Evaporiineters, inner-cell, Type 4, January 1, 1917, to September, 1918. 



1 and 4 foot soil thermometers, in iron pipes, October 1, 1916, to September, 

 1918. 



Soil thermograph, October 1, 1916, to October 16, 1917. 



8-inch rain gage, under shelter of trees, October 1, 1916, to February 2S, 1918. 

 12-inch tipping-bucket rain gage, with register, August 1, 1917, to September 

 21, 1918. 



F-17: Frances Douglas fir. — Elevation, 9,300 feet; aspect, easterly. 

 This station is situated near Frances, Colo., on a steep mountain 

 side, in the bottom of a gulch opening to the east. The ground in 

 the immediate vicinity of the station is not far from level, but it 

 rises precipitously a few rods to the west. The situation is appar- 

 ently such as to give marked air-drainage effect at night, ana to 

 cause stagnation of the air during the day. The temperature records 

 of this station are thought to have considerable comparative value, 

 because the station is at almost the same elevation as Fremont, and 

 similarly situated on the east slope in the Douglas fir zone. 



The forest surrounding the station was at one time a fairly even 

 stand of comparatively small Douglas firs. It has been almost com- 

 pletely destroyed by cutting and fires over a large area, and in this 

 locality there is almost no reproduction. A little higher the granitic 

 and glacial soils are being occupied by lodgepole pine. 



F-18: Fraser Basin lodgepole pine. — Elevation, 8,5G0 feet; aspect, 

 northerly; slope, 1 to 2 per cent. This station, in north-central Colo- 

 rado, is situated in the broad valley of the Fraser River, which at 

 this point runs slightly west of north. The drainage area to the 

 south of Fraser comprises about 100 square miles, and the valley at 

 this point has widened out into a meadowlike basin of very little 

 slope, having a width of fully a mile between the forest-covered 

 slopes on either side. Although it is thus considerably removed from 

 the forest, there appears no reason for any great difference between 

 the atmospheric conditions over the station and those over the forest. 

 The locality is characterized by precipitation so well distributed over 

 the entire year that, although the month of June is usually about 

 the driest, the melting snow furnishes abundant moisture for the 

 early part of the growing season. The winter temperatures are 

 extremely low, but always accompanied by a good snow blanket. 

 Under these conditions lodgepole pine attains the best development 

 noted anywhere in Colorado, both as to stature of trees and density 

 of stands. (See PI. VI, fig. 2.) 



The character of the soil, considered in connection with the well- 

 distributed precipitation, probably is an important factor in this 

 development. The soil in the forest is of granitic origin but is so 

 thoroughly broken down as to contain a high percentage of clay, and 

 consequently to have a high water-retaining capacity. 



The lodgepole forest about Fraser comes down on all slopes prac- 

 tically to the edge of the valley and to an elevation within 100 feet of 

 that of the station; to the south, where the valley is narrower, the 

 forest extends entirely across it. This fact might lead to the con- 

 clusion that the forest does not reach the station on account of the 

 forbidding conditions of an alluvial soil. It is also interesting to 

 note that there is no transition zone between the mesophvtic condi- 

 tions of the slopes and the ''desert" conditions of the valley. To 

 be sure, a very few specimens of western yellow pine may be found 

 on the lower hills, while somewhat more frequently a clump of 



