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Ecological Succession: Change over Time Two Types of Succession Primary succession - An ecosystem starts from bare rock Secondary succession – Ecosystem is built from a previous ecosystem Starts with soil

Important Terms  Sere: A set of stages of changes in an ecosystem.  A snapshot of ecosystem  Pioneer organisms: First species that begin to populate a sere, typically r-strategists.  Ex. Weeds, lichens  Climax community: Populations of organisms living together in a sere where all species are in balance.  Ex. A mature forest, many K- strategists

Pioneer Species

Primary Succession No soil in a terrestrial system No bottom sediment in an aquatic system Takes hundreds to thousands of years Need to build up soils/sediments to provide necessary nutrients

Primary succession will occur after a volcanic eruption

Primary succession occurs after a glacier retreats Image source:

Primary succession occurs after a glacier retreats

Time Balsam fir, paper birch, and white spruce forest community Jack pine, black spruce, and aspen Heath mat Small herbs and shrubs Lichens and mosses Exposed rocks Primary Ecological Succession

Secondary Succession Begins with soil from previous ecosystem Ecosystem has been Disturbed, Removed, or Destroyed Abandoned farms Burned forests Deforestation A huge storm

Annual weeds Mature oak and hickory forest Young pine forest with developing understory of oak and hickory trees Time Shrubs and small pine seedlings Perennial weeds and grasses Secondary Succession

Yellowstone 1998 Forest Fire

Secondary Succession in Yellowstone Following the 1998 Fire

Conditions during succession Early Stages (Pioneer Communities) Gross Productivity = Low Few producers Net productivity = High No consumers doing respiration No taxes to take away!! Nutrients in soil Later Stages (Climax Community ) Nutrients in soil decrease Gross Productivity is High Many producers Net productivity = low Many consumers all doing respiration = a very large amount of taxes