ceedingly complex and that perhaps we 

 have been unable to discover a depend- 

 ence of plants on grazing animals which is 

 real and important. This is certainly to be 

 reckoned one of the notable paradoxes of 

 nature. Thus, in spite of all our study and 

 thought, from the observations of herds- 

 men before Abraham's time to the results 

 of scientifically designed experiments in 

 the present day, we have very little real 

 comprehension of what is perhaps one of 

 nature 's simpler mysteries. 



■ Climatic 

 Studies 



Climatic studies were started early in the life 

 of the Utah Experiment Station, and through- 

 out the Station's history three major types of 

 such studies have been continued. In his report 

 of the Station's first year of work, Sampson 

 wrote : "In order to propose experimental work 

 intelligently one of the essential and initial 

 steps is to study the conditions which control 

 vegetation, stream flow and the like." As a pre- 

 liminary to the studies of erosion on the 

 Wasatch Plateau, measurements and records of 

 the temperatures of air and soil and of precipi- 

 tation and soil moisture were made at 10,000 

 feet. Thus began the years of recording of 

 temperatures and precipitation on Watersheds 

 A and B and later on other areas. Records of 

 temperature and precipitation on Watersheds A 

 and B constitute the first major studies of cli- 

 mate in this particular area; of course they had 

 immediate direct bearing on the erosion 

 studies; additionally, over the long term they 

 provided important information used in the 

 plant studies that were part of the revegetation 

 phase of the grazing and range program. 



The several plant communities have their in- 

 dividual requirements for moisture, sunlight, 

 warmth, etc.; so a second set of studies was 

 undertaken at the Station to (1) obtain a com- 

 parison of the climatic requirements of the 

 main plant communities and (2) determine 

 quantitatively the relation between local en- 

 vironmental factors and plant growth. 



In 1913, Sampson set up meteorological sta- 

 tions at elevations of 7,100, 8,700, and 10,000 

 feet in the heart of the oakbrush, aspen-fir, and 

 spruce-fir associations, respectively (Sampson 

 1918a). At these stations the major climatic 

 factors (air temperature, precipitation, evapo- 

 ration, barometric pressure, wind velocity, and 

 sunshine) were recorded so that many environ- 

 mental characteristics of each type-zone were 

 well known. Study of the influence of weather 

 on the development of plants began in 1915 

 and continued through 1916. The plants used 

 for study at each weather station were a pedi- 

 greed strain of Canadian field pea, cultivated 

 wheat, and native mountain brome. They were 

 grown in potometers protected by screens. In 

 the potometers two types of soil were used: 

 infertile clay loam typical of areas where ero- 

 sion and washing had diminished the humus 

 and soluble salts, and fertile clay loam that had 

 not been subject to erosion and washing. 



This study produced voluminous and varied 

 information about the three types of plants and 

 about the climate of central Utah. Sampson's 

 report also includes a wealth of information 

 about techniques of the study and about capa- 

 bilities and limitations of the equipment used 

 in it. His correlations between environmental 

 factors and plant growth and other physical ac- 

 tivities were profitable reading for ecologists 

 and botanists in his own time and are still in- 

 formative a half-century later. 



Sampson's study showed that growing sea- 

 sons averaged 120 days in the oakbrush type, 

 105 in the aspen-fir, and only 70 days in the 

 spruce-fir type. Average annual precipitation 

 was greatest in the aspen-fir type but only 

 slightly greater than in the spruce-fir associa- 

 tion. Later studies by Lull and Ellison (1950), 

 based on longer periods of time, indicated that 

 precipitation increases with elevation; thus, the 

 spruce-fir zone had the highest precipitation. 

 Precipitation in the oakbrush type was barely 

 half that in the higher elevation aspen-fir type 

 (Sampson 1918a). Evaporation during the 

 growing season was, as would be expected be- 

 cause of high temperatures and low humidity, 

 greatest in the oakbrush type; but high wind 

 velocity in the spruce-fir type (about 100 per- 

 cent greater than in the types immediately 

 below) resulted in evaporation comparable 

 with that in the oakbrush. Both duration and 



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