Succession: the replacement of one community by another over time -- can see gradual change in vegetation, dominant species --most often seen following a disturbance Two major categories of succession Primary: establishment of life where none existed before Secondary: after an existing community is disturbed

Studying succession in one area could take decades -- old fields provide one solution -- good records show when agricultural fields were used and abandoned -- succession at various stages can be seen at one point in time

Standard sequence of succession: Pioneer or early successional species (ESS) -- r-selected weedy species -- produce lots of seeds, favor disturbed areas -- high vagility, disperse to disturbed areas rapidly -- at first, no competition for light, nutrients in soil http://alfalfa.okstate.edu/ http://biology.clc.uc.edu/ crabgrass broomsedge

Middle successional species (MSS) -- longer-lived, slower growth than ESS -- begin to shade out ESS species -- includes perennials (live 3+ yrs) and shrubs http://external.oneonta.edu/

Late successional species (LSS) -- long-lived, slowest growth -- more K-selected species -- trees, larger shrubs and other persistent species

Old field succussion of ESS species in NC Field winter summer winter summer winter summer winter abandoned II III Crabgrass ------- Horseweed ---------------- Ragweed --------- Aster --------------------------- Broomsedge ------------------------ ----------------- flowering

Climax Community: the community that will ultimately dominate and persist in a given environment -- suggests final sere is ultimate result of succession -- outdated concept as communities constantly change, just rate of change slows -- no true climax, just a steady state chaparral grassland redwood forest

Succession at a forest in Washington D.C. Relative density of saplings large trees 40 20 0 20 40 White oak Black oak Red oak Blackjack oak Tulip tree White ash Red maple Beech Sugar maple Undisturbed for 67 years

Study of succession important for: Community dynamics, competition Forces that regulate community structure Most communities today in some form of succession, need to know future changes Old growth limited and rare, but some in NC