UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 700 



Contribution from the Forest Service 

 HENRY S. GRAVES, Forester 



&J9*^mrU 



Washington, D. C. 



PROFESSIONAL PAPER 



October 14, 1918 



CLIMATE AND PLANT GROWTH IN CERTAIN 

 VEGETATIVE ASSOCIATIONS. 



By Abthuk W. Sampson, Plant Ecologist, Forest Service. 1 



CONTENTS. 



The problem 



The experiments 



Preparation of plants. . 

 Planting 



Measurement of plants . 

 Experimental error 



Measurement of physical factors . 



Comparison of the climatic characteristics of 



the three plant types 27 



Correlation between growth and environ- 

 mental factors 41 



Summary of the data obtained 69 



Conclusions , 71 



THE PROBLEM. 



The relation of climate to the growth and development of vegeta- 

 tion is of profound importance in both practical and experimental 

 agriculture. It is extremely useful to know the cause of successful 

 growth and establishment, or of partial success or failure, of various 

 species in different plant associations and under widely contrasted 

 climatic conditions. The climatic requirements of various plant types 

 are largely responsible for the results obtained in the case of experi- 

 mental seedings and plantings of most species. Once the adverse 

 climatic factors are definitely known, failures with plants may be 

 largely avoided by the judicious selection of sites or of species espe- 

 cially adapted to withstand the limiting factors. Therefore, a series 

 of experiments was undertaken, (a) to obtain a comparison of the 

 climatic requirements of the main plant types, and (b) to determine, 

 quantitatively, the relation between various environmental factors on 

 the one hand and plant growth and certain other physiological func- 

 tions on the other. The results obtained appear to be conclusive 

 in most instances and should prove of value both in experimental and 

 in practical agriculture and forestry. 



1 The author is indebted to F. Merrill Hildebrandt for material assistance in procuring 

 and assembling the data presented in this paper. 



56866°— 18— Bull. 700 1 



