Species diversity of vascular plants was determined in 51 seral communities ranging form 0.2—200? yr old. Species richness (S = number of species), information content (H'pop = oSsi = 1 pi loge pi), redundancy R = (H'pop o H'max)/(H'max o H'min), and evenness (J'pop = H'pop /logeS) were calculated for numbers of individuals in four strata (ground layer, shrub, understory, and canopy. Richness (S) in the strata and major growth forms (herbs, woody vines, shrubs, and trees) increased rapidly following their establishment, then at a decreasing rate throughout the remainder of succession. Equitability, (1 o R, J'pop), on the other hand, increased to near maximum levels immediately after establishment but changed little thereafter. Contrasts in seral richness and equitability trends suggest differing regulatory mechanisms–equitability being regulated primarily by short term factors (resource levels) and richness by long term factors (community stability and evolutionary time).