VEGETATIONAL ANALYSIS 



67 



period, a flowering period, a fruiting period, an embryo period, 

 and perhaps others. Rarely will all the species of a community 

 have these periods strictly coinciding. Consequently, in temperate 

 climates, the community as a whole usually has seasonal aspects, 

 which are termed vernal, estival, autumnal, and hibernal. The 

 structure and species of a community are strongly influenced by 



FlG. 28. Aspect dominance as illustrated by chandelier cactus (Opimtia 

 arbor -esc ens) in a mixed prairie community (Bouteloua-Hilaria). El Paso 

 County, Colo. The cactus makes up only 8.9 percent of the total cover.— 

 Photo by R.B. Livingston. 



the extent to which periodic phenomena in the individuals are 

 adjusted to each other. 



Light and moisture conditions on the floor of a deciduous forest 

 during the vernal period permit the growth and maturation of nu- 

 merous herbs before the estival period. When the trees and shrubs 

 are in full leaf, these herbs are already declining to a fruiting or 

 resting condition and are unaffected by the reduced light and 

 moisture available to them. These vernal herbs are a part of the 

 community and must be so considered. 



Another illustration of a periodic phenomenon that may be im- 

 portant in sociological relations is the time of growth. Height 

 growth has been systematically studied for numerous woody spe- 



