RESEARCH METHODS IN STUDY OF FOREST ENVIRONMENT. 11 



reached, as it is then limited in its extensions for light and soon can 

 not make the needed annual additions to its transporting system. 



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

 prevails in the discussion of the individual environmental conditions. 



MEASUREMENT OF ENVIRONMENTAL CONDITIONS 

 AFFECTING 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 genera] climatic studies of the forest regions, and to some 

 extent in studying (lie conditions for growth in established stands, 

 the data collected by the [Jnited States Weather Bureau at its numer- 

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



number of these -tat ions 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 appeal-, therefore, that the regular observations of the 



Weather Bureau will furnish US principally with precipitation and 



temperature data bv which the broader forest regions may be da 



