VEGETATIONAL ANALYSIS 6S_ 



other agency. It becomes necessary, therefore, to know something 

 of the vigor and prosperity of the species before classifying it as 

 a true community member. 



Vitality need not always be listed for all species, but it must be 

 considered in evaluating their importance, whether it is done sys- 

 tematically or not. Vitality classes or degrees of vitality include : 

 ( 1 ) ephemeral adventives, which germinate occasionally but can- 

 not increase, (2) plants maintaining themselves by vegetative 

 means but not completing the life cycle, (3) well-developed plants, 

 which regularly complete the life cycle. 



Changes in the vitality of species are often indicators of com- 

 munity change or plant succession. Dominants decreasing in num- 

 bers and reproducing feebly indicate future radical changes. Rap- 

 idly increasing numbers of a species previously of little importance 

 may suggest the new dominants to come. 



Stratification— The necessity for recognizing the strata of a 

 community becomes obvious when sampling is attempted. The 

 several strata that may occur were described under sampling pro- 

 cedure. Diagrams of stratification combined with cover are often 

 used effectively to show the relative significance of the several lay- 

 ers in a stand. The physical and physiological requirements of spe- 

 cies in different strata can be appreciated fully only when the 

 stratification both above and below ground is clearly worked out. 

 Then the micro-environments of these strata may be considered in 

 terms of cause and effect. 



Periodicity .—The conspicuous rhythmic phenomena in plant 

 communities are those related to seasonal climatic change, and, of 

 these phenological changes, the obvious ones have been given most 

 attention. Flowering and fruiting^ periods have been noted for so 

 long that they are fairly well known; in fact, phenology is often 

 thought of as referring only to these phenomena. In community 

 studies the terms aspect dominance and seasonal dominance have 

 been used to describe situations in which a species or group of 

 species appears to be dominant for a portion of the year, usually 

 because of conspicuous floral characters. 



Of equal importance to the community is the seasonal develop- 

 ment of vegetative parts. The seasonal aspect of the individual may 

 proceed through several phases, including a leafy period, a leafless 



