dividual as well as in a collective manner. Regular, cyclic 

 changes of the habitat, such as the usual diurnal daylight and 

 darkness and conditions accompanying the progression of the 

 seasons, are not considered here. 



The physical factors of a habitat are constantly fluctuating. 

 Some individual factors may fluctuate independently of the 

 other factors so that there is an infinite complexity of conditions 

 over either a short or a long period of time. These changes of the 

 individual factors and of combinations of factors are fluctuations 

 about the respective means. ^^^ The variations are characteristic 

 for the respective climatic provinces, localities, and sites; and the 

 climatic elements vary, from year to year, in a random and thus 

 unpredictable manner. 



The fluctuations occur over large, local, and small areas. Those 

 over a large area include such categories as climatic region, biotic 

 province, or physiographic province. Generalized information, 

 such as climatic information, is usually available concerning such 

 large areas; the existing meteorological net is applicable to them, 

 but it furnishes only limited climatic information for local areas. 

 The variation in the date of snow disappearance is indicative of 

 local variation." There are also fluctuations between stands and 

 within stands; the meteorological net furnishes no significant 

 climatic information for this scale of area, although there have 

 been limited meteorological studies of certain small areas. 



Fluctuations of environmental factors are usually not percep- 

 tible with mere observation, especially for a short period of 

 time. Detailed observation and measurement of some factors, 

 such as soil moisture, soil temperature, air temperature, and 

 precipitation are needed for a considerable period to reliably 

 determine the nature of fluctuation changes. 



If the fluctuations in the habitat changes are beyond the eco- 

 logical amplitudes of the existing species, then a fluctuation form 

 of change within the community can be expected. The types and 

 magnitudes of intracommunity fluctuation which result from a 

 complex fluctuation in the habitat are numerous and varied. 

 Fluctuation within the community results from interrelations in 

 both the habitat and the organisms. This becomes manifest in the 



Habitat Patterns, Changes, and Climax • 1.47 



