UNITED STATES DEPARTMENT OF AGRICULTURE 
1 BULLETIN No. 1059 
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Contribution from the Forest Service 
WILLIAM B. GREELEY, Forester 
Washington, D. C. 
May 19, 1922 
RESEARCH METHODS IN THE STUDY OF 
FOREST ENVIRONMENT. 
By Carlos G. Bates, Silviculturist in Charge of Fremont Forest Experiment 
Station, and Raphael Zon, Forest Economist. 
CONTENTS. 
Page. 
Introduction *. 2 
Object 2 
Scope 4 
Sample plot method 6 
Need for a permanent organiza- 
tion in forest investigations 6 
Forest experiment stations 7 
Short-term studies 7 
The simple physico-physiological 
concept 8 
Measurement of environmental con- 
ditions affecting vegetation 11 
Climatic characteristics of local- 
ity | 11 
Natural climatic regions 11 
Data obtained by the Weather 
Bureau 11 
Knowledge of existing stations 
necessary 12 
Periods of growth and rest 12 
Special observations on climate 
and soil of locality 13 
Location of instruments for 
study of growth 13 
Location of instruments for 
study of reproduction 13 
Air temperatures 15 
Problems 15 
Exposure of thermometers 17 
Standardizing thermometers _ 18 
Maximum, minimum, and cur- 
rent temperatures 18 
Hourly temperatures 19 
Frosts 24 
Mean temperatures 24 
Annual summary 25 
Instruments 25 
Soil temperatures 26 
Purposes to be served 26 
Problems 27 
82769—22 1 
Page. 
Measurement of environmental con- 
ditions affecting vegetation — Con. 
Soil temperatures — Continued. 
Time of observations 28 
Daily mean soil temperatures. 28 
Readings 31 
Tabulation 31 
Hourly soil temperatures 31 
Summary of soil temperatures. 34 
Annual summaries of soil 
temperatures 34 
Apparatus 34 
Special suggestions on surface 
measurements 37 
Instruments 38 
Solar radiation — light 39 
Concept of the functions of 
radiant energy 39 
The nature of sunlight 41 
Horizontal and vertical ex- 
posures 44 
Total radiation on the site 45 
Isolation under canopies 45 
Light measurements in rela- 
tion to minimum require- 
ments 46 
Apparatus and methods for 
radiant energy measure- 
ments 49 
The radiometer 49 
The thermopyle 49 
The bolometer 49 
Pyrheliometers 50 
Thermometric sunshine re- 
corder , 50 
Solar thermograph 51 
Photo - chemical photome- 
ters 54 
Comparison photometers 55 
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