WEATHER CONDITIONS AND PLANT DEVELOPMENT 



GEORGE P. BURNS 



Vermont Agricultural Expenment Station 



The effect of weather conditions on plant development has been 

 one of the chief problems studied during the past few years by the 

 ecologist, the agriculturalist, the forester and in some cases by the 

 plant physiologist. The weather, however, is a variable mixture 

 composed chiefly of different amounts of light — direct, diffuse, white, 

 yellow, red, etc., or darkness; moisture — precipitation, humidity, 

 soil-moisture, etc.; heat, temperature of the air and soil; wind, etc. 

 Each of these component parts varies within short intervals of time 

 and each has its effect direct or jndirect on the living plants. The 

 problems of the effect of weather conditions, then, is largely a physio- 

 logical problem and such problems should be attacked only by means 

 of accurate experiments under controlled conditions. 



The ecologists have been attempting to change from the old 

 descriptive methods in which the results of a more or less accurate 

 study of the vegetation of a given area were published. Sometimes 

 this study was accompanied by a few tables of meteorological data 

 gathered from a nearby U. S. Weather Bureau station. In only a 

 few cases were attempts made to relate these data to the descriptive 

 part of the study and one was often at a loss to know why they were 

 included in the publication. This type of work has served a good 

 purpose in a preliminary way but is now outgrown. More accurate 

 methods have been introduced by advanced workers and ecologists 

 have adopted the plan of gathering their own data with instruments 

 placed in the field, the attempt being made to place them under the 

 same weather conditions as those of the plants under consideration. 



The largest amount of data has been collected on evaporation rates 

 by workers with atmometers. This is probably due to the fact that 

 these instruments are inexpensive as compared with the cost of the 

 recording instruments necessary for collecting other data. But they 

 lack standardization, many kinds, shapes and sizes being in use. 

 Since no atmometer can be made to work exactly as a plant, ecologists 

 should adopt arbitrarily one type in order that data wherever col- 

 lected may be compared. Some ecologists have gone deeply into this 

 phase of the work and are well equipped with field instruments record- 



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