FOREST TYPES IN CENTRAL ROCKY MOUNTAINS. 23 



Maximum and minimum thermometers in shelter, 8 feet above ground. 



Air thermograph, 8 feet above ground. 



Hygrograph, 8 feet above ground. 



Psychrometer, read daily at 9 a. m. 



Anemometer, on post in opening, 4^ feet above ground. 



8-inch rain gage, on post in opening. 



Marvin shielded gage in opening, since 1913. 



1-foot soil thermometer is bulb of telethermoscope having no direct connection 

 with the air above. This has been compared at various times with thermometers 

 in iron, wood, and porcelain tubes. The porcelain tube is retained for frequent 

 checking. 



4-foot soil thermometer, in iron pipe, beginning August, 1913. 



Soil well, with moisture determinations weekly, at depths of 1, 2, and 3 feet, 

 during open seasons since 1913. 



W-A2: Wagon Wheel Gap south slope Douglas fir. — This station is 

 directly opposite Al on the same watershed, the elevation and slope 

 being almost identical, but the aspect almost south. The stand is 

 here also predominantly one of Douglas fir, but is more open than 

 on the north slope. The trees have attained much larger size. 

 (See PL X, fig. 1.) Aspen is restricted to the base of the slope 

 below the station, or to gullies, and only bristlecone pine among 

 conifers competes with the fir. Specimens of the pine are here 

 rare, and become numerous only on the more rocky ground at the 

 top of the slope. Limber pine is relatively rare in the Rio Grande 

 region, and bristlecone pine appears largely to replace it on rocky 

 ground and wind-exposed points. 



Although air temperatures were recorded at this station during 

 its earlier years, the longer record covers only soil temperature and 

 soil moisture. The soil temperature at 1 foot has been determined 

 by a thermometer in a wooden tube since January, 1913, and at 4 

 feet by the one in an iron pipe since October, 1913. 



W-C: Wagon Wheel Gap pine-fir. — Elevation, 9,360 feet; aspect, 

 east; slope, 30 per cent. At the initiation of the stream-flow experi- 

 ment, the point here mentioned was established as a control 

 station with whose conditions those on the two watersheds might 

 be compared. It lies on an east slope between them, and is not 

 affected by forest cover of any kind except as a few aspens form a 

 windscreen for the rain gages. It is, then, spoken of as a pine-fir 

 type only because it lies about on the line between the Douglas fir 

 forest on the higher slopes and the occasional yellow pines which 

 occur on warm, exposed breaks below. (See PI. IX, fig. 2.) In 

 fact, the soil conditions here, and more markedly on the flatter 

 ground just below, seem to be prohibitive of coniferous growth by 

 reason of the presence of a considerable amount of alkali (carbonate 

 of soda) . 



The plan at this station has been to measure particularly those 

 conditions which are more or less general for the locality, and which 

 could not be conveniently recorded at points farther from head- 

 quarters. The equipment has consisted ol : 



Maximum and minimum thermometers, in shelter, at 10 feet above ground. 



Air thermograph, in shelter, at 10 feet above ground. 



Psychrometer. 



Anemometer, on tower, about 15 feet above ground, with register. 



Wind-vane, on tower, about 18 feet above, ground, with register. 



Sunshine recorder, electric thermometric, with register. 



Tipping-bucket rain gage, 3 feet above ground, with register. 



