COMBINATIONS OF ENVIRONMENTAL FACTORS 



211 



MACROCLIMATES AND MICROCLIMATES 



The abstraction called climate is a more 

 or less formalized integration of environ- 

 mental elements such as temperature, hu- 



20 30 



RAINFALL IN 



40 

 INCHES 



50 



Fig. 51. Temperature-rainfall relations of the 

 .vilt disease of cucubit plants; severity increases 

 'rem A to D. ( Redrawn from Tehon. ) 



50 100 150 50 100 150 



PRECIPITATION IN MM. 



Fig. 52. Rainfall-temperature graphs for 

 years of heavy damage to Illinois crops from 

 chinch bugs (A), contrasted with years in 

 which the damage was light ( B ) . ( Rearranged 

 from Shelford. ) 



midity, insolation, and time. Its structure 

 may be visualized by the relations outlined 

 in Table 15. 



Table 15. The Anatomy of Climate (After 

 Trewartha, 1937) 



A climate may be either regional or gen- 

 eral, and both have macroclimatic or micro- 

 climatic aspects. Knowledge about macro- 

 climates is based on records taken at net- 

 works of observing stations that are placed 

 at a height of 1.5 sometimes 2 or more, 

 meters above the ground surface. This is 

 the climate to which man is most exposed; 

 it may, in fact, be designated as human 

 cUmate. 



The lowest few feet of the atmosphere 

 are suflBciently different in cUmate as to be 

 properly called a microclimate or plant 

 climate. The vertical reach of the plant cli- 

 mate varies with the height of the vegeta- 

 tional cover; over bare, or practically bare, 

 ground it reaches to a height of about 1.5 

 meters. The considerable, though still rela- 

 tively scanty, body of early knowledge deal- 

 ing directly with plant climates was sum- 

 marized in 1927 by Geiger, 



Another and smaller climate can also be 

 recognized; it may be called an insect 

 climate and is, relatively speaking, a micro- 

 microclimate. Little is known with certainty 

 about the characteristics of the thin layer of 

 air, only a few millimeters thick, that im- 

 pinges on the surface of the ground and 

 penetrates the small superficial nooks and 

 crannies where many insects spend the 

 major portion of their lives. 



Among others, Uvarov (1931) empha- 

 sized the importance of the ecoclimate, 

 which is the name he proposed for the sum 



