BULLETIN 1059, U. S. DEPARTMENT OF AGRICULTURE. 



Page. 

 Measurement of environmental conditions af- 

 fecting vegetation— Cunt inued. 



Special observations on climate and soil of 

 locality— Continued . 



Precipitation 6u 



Exposure of gauges 60 



Snow depths 61 



Sn<>w-scalc readings 61 



Tabulat ion 63 



Instruments 63 



Soil moist ure and soil qualities 66 



Osmosisasa factor in water absorption. 66 



Problems and some definitions ..... . . . 71 



Total moisture determinations 73 



Soil wells for representative points. .. 73 



Technique of periodic sampling 76 



Determination of nonavailable moist- 

 ure 79 



Direct determination of wilting coeffi- 

 cient SO 



Indirect methods for wilting coeffi- 

 cient S4 



Capillary moisture 85 



Moisture equivalent 93 



Hygroscopic coefficient 97 



Calculation of the available moisture. . 100 



Availability of the moisture 101 



Coefficient of availability 102 



Osmotic pressure in plant tissues. . 103 

 Method of determining freezing 



points 107 



Osmotic pressure in soils 109 



Vapor transfer in soils 109 



Vapor transfer method 112 



Computing the coefficient 120 



Other soil properties to be studied 121 



Acidity and alkalinity 121 



Hydrogen-ion concentration 122 



Mechanical analysis of soils 123 



Determination of humus 123 



Loss on ignition 127 



Ammonia-soluble humus 127 



Capillary conductivity 128 



Chemical analysis for nutrients 129 



Summary of soils discussion 136 



Special equipment 142 



Page. 

 Measurement of environmental conditions af- 

 fecting vegetation— Continued. 



Special observations on climate and soil of 

 locality — Continued . 



Atmospheric humidit y 



Instruments 



Wind movement - 



Instruments 



Evaporation 151 



Objects and nature of evaporation meas- 

 urements 151 



Instrumental methods 154 



Free-water surface. 154 



Measurement - 154 



Nonfree-water surface 155 



Piche evaporimeter 155 



Porous cup atmometer 156 



shive's nonabsorbent porous-cup 



atmometer 157 



st andardization 159 



Computation of field results 159 



Exposure 160 



Forest Service evapori meters 161 



Observations 162 



Tabulation 163 



Direct transpiration method 164 



Cobalt-chloride method 164 



Method of excised twigs 165 



Method of potted plants 166 



Instruments ■ 168 



Phenology 168 



External field observations 170 



Internal or physiological observations 171 



Field observations, photographs, and maps. . 172 



Appendices 175 



A. Vapor pressure tables for barometric 



pressure 21.42 inches • 175 



B. Osmotic pressures and freezing-point 



depressions 198 



C. Titration methods for alkalinity and 



acidity 199 



Alkalinity test 199 



Acidity test 200 



List of references 201 



INTRODUCTION. 



OBJECT. 



Forestry, like engineering or medicine, is largely an applied science. 

 Its development is based on fundamental knowledge of the natural 

 sciences. Knowledge of the tree itself, is purely botanical and 

 physiological science. The first contact with its enemies and biotic 

 aids leads into mycology and zoology. Investigation of the effect 

 of environment upon the tree necessarily involves consideration of 

 geology and soils, physics and chemistry, climatology and sola 

 radiation, as well as the biology of the tree's living companions. 

 In measuring the volume and growth of tree and stands, as well 



