Dehiscent 



Refers to a structure that breaks open at maturity, e. g., 

 a pea pod. cf. Indehiscent. 



Deme 



One or more populations of a Taxon, an interbreeding 

 population. 



Demography 



The study concerned with the analysis of populations in- 

 cluding births, deaths, age, etc. 



Dendrochronology 



The dating of events or historical periods by the study 

 of growth rings of trees. 



Dendrology 



The study of trees. 



Denitrification 



The change of nitrogenous compounds by certain bac- 

 teria in which free nitrogen is formed. 



Density (Population, Species) 



The number of individuals in relation to the space in 

 which they occur, refers to the closeness of individuals to 

 one another, cf. Population density, Abundance, Cover. 



Density-dependent Factor 



An influence that is dependent upon a certain density 

 of individuals in order to be fully effective, e. g., a limited 

 number of prey animals for the number of predators present 

 in an area. 



Density-independent Factor 



An influence that is effective without regard to the den- 

 sity of individuals in a population, e. g., very unfavorable 

 weather such as a blizzard. According to Andrewartha (1954) 

 and Birch this factor is non-existent. See Non-reactive factor. 



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