RESEARCH METHODS IX STUDY OF FOREST ENVIRON M E XT. 11 



It is hoped that this discussion will clarify the point of view which 

 prevails in the disccussion of the individual environmental conditions. 



MEASUREMENTS OF ENVIRONMENTAL CONDITIONS AFFECT- 

 ING FOREST VEGETATION. 



The character of the forest and its very existence are determined 

 by the climate, soil, and subsoil of the locality. The general charac- 

 ter of the region, including the character of the vegetation and of 

 the soil, is determined in the highest degree by the climate. The 

 climate affects the region and vegetation in two ways: (1) It is at 

 present the most important factor in the environment of the vegeta- 

 tion; (2) it has affected the present environment in its historical de- 

 velopment; for instance, in the formation of the soils, their present 

 physical and chemical composition being largely the result of the 

 past climate in combination with other natural factors. The deter- 

 mination of the important features of a climate is not a simple mat- 

 ter. It must rest upon a sufficiently long series of observations at 

 well-equipped meteorological stations. 



CLIMATIC CHARACTERISTICS OF LOCALITY. 



NATURAL CLIMATIC REGIONS. 



The characteristics of a climate must be studied first of all by 

 natural regions and the study based on the observations of several 

 stations located in different parts of the same region. The climate of 

 individual localities may best be analyzed by comparison with the 

 climate of the entire natural region in which the locality is found or 

 of a control station centrally located. 



DATA OBTAINED BY WEATHER BUREAU. 



For general climatic studies of the forest regions, and to some 

 extent in studying the conditions for growth in established stand-. 

 the data collected by the United States Weather Bureau at its numer- 

 ous regular stations may be used to good advantage. At the greater 

 number of these stations only data on air temperatures and precipita- 

 tion are obtained. At the larger stations data on humidity, sun- 

 shine, barometric pressure, etc., are obtained, but because of the al- 

 most universal location of such stations in towns and cities the 

 applicability of the data to forest conditions is often very question- 

 able. It appears, therefore, that the regular observations ^ the 

 Weather Bureau will furnish us principally with precipitation and 

 temperature data by which the broader forest regions may he 

 defined. The use of these same data in strictly local studies will 

 depend entirely on the minute examination of the conditions sur- 

 rounding the station. 



