UNITED STATES DEPARTMENT OF AGRICULTURE 



DEPARTMENT BULLETIN No. 1233 



Washington, D. C. 



October 6, 1924 



FOREST TYPES IN THE CENTRAL ROCKY MOUNTAINS AS AFFECTED BY 



CLIMATE AND SOIL. 



By Carlos G. Bates, 

 Silviculturist, Fremont Forest Experiment Station, Forest Service. 



CONTENTS. 



Page, 

 l 



Introduction 



The method of study 4 



J ►escription of the localities studied 7 



The growing season 25 



Absolute and comparative conditions in the 



various forest types '. 27 



Air temperatures 27 



Wind, humidity, and evaporation 52 



Soil temperatures 84 



Sunsliinc 112 



Precipitation 116 



Soil moistures 121 



Page. 



Recapitulation 132 



( icneral character of the climate 132 



Temperatures and temperature gradients 134 



AVind , humidity , and e vaporation ] 30 



Winter soil temperatures 137 



Precipitation and soil moisture 139 



Conclusions 141 



Applications 150 



Literature cited 152 



INTRODUCTION. 



In "Physiological Requirements of Rocky Mountain Trees/' (6) l 



by the writer, published in the Journal of Agricultural Research 

 (Apr. 14, 1923), the relative physiological requirements of the 

 species composing the various forest types of the central Rocky 

 Mountains have been discussed. The present work on climatic and 

 soil conditions affecting the same forest types supplements that dis- 

 cussion. The two papers are, indeed, so closely related that the one 

 is indispensable to the understanding of the other. 



In the earlier paper the results of a number of laboratory studies 

 were presented, in the hope that such comparisons, made under 

 controlled conditions equally affecting all of the species involved, 

 might permit judgment of the relative physiological requirements, 

 and thereby make it possible more definitely to decide what condi- 

 tions of the environment are really important in controlling distribu- 

 tion and what are merely variable concomitants of these controlling 

 conditions. If the ensuing discussion presented from the stand- 

 point of field observations does no more than reconcile the two 



'Parenthetical figures (italic) placed in the text refer to corresponding numbers under ''Literature 

 cited" on page 152 of this bulletin. 



73045°— 24 1 1 



