Ecological Succession

2. Ecological Succession • Ecological succession: the process of ecological change in an ecosystem where one community is replaced by another community over time • Two types of succession: • Primary succession: formation of a brand new ecosystem. • Secondary succession: recovery of an old ecosystem.

3. Primary Succession • Primary succession occurs when a community forms in an area that has not been previously occupied Ex. Exposed rock, lava, melted ice, eroded sand

4. Primary Succession • Occurs over a LONG period of time • Pioneer Species= the first organisms to grow in a new environment • Ex. Lichens and mosses in primary succession • These organisms can grow in areas where others cannot • Over time these organisms decompose and release nutrients to form a layer of soil that larger, more complex plants can grow in

5. Primary Succession Once enough soil has been generated to retain nutrients, small plants, flowers, ferns, and shrubs can begin to grow.

6. Primary Succession • These plants can further break down the rock, allowing more soil to be formed and retained. The seeds from other plants, even trees become able to grow, and over time large plants become able to inhabit the area.

7. Primary Succession As new species of plant move in, new animal species become able to inhabit the area. Organisms growing in each stage may even hinder their own survival, but pave the way for future organisms.

8. Primary Succession • Eventually, a mature community results, in which there is little change in the composition of species. Climax Community = a mature and stable community of plants and animals This is reached towards the END of succession!!

9. Secondary Succession • Secondary succession occurs in an area that was previously occupied by living organisms, but the community was destroyed by a disturbance. Ex. Fire, farming, hurricane, etc.

10. Secondary Succession • Established community is destroyed but soil is still intact therefore it takes less time than primary succession • Pioneer Species for secondary = weeds and grasses • Process typically begins with weeds and grasses that are able to grow quickly, and proceeds until a Climax Community is reached

11. Think About It • Where in succession you would expect to find organisms and stages that last for short periods of time? Long? • Short periods at the beginning, long at the end • Why might secondary succession tend to occur more quickly than primary? • Because you don’t have to make soil from scratch in secondary succession like you do in primary • What kinds of organisms would you expect to find in an area where disturbances are frequent, or intense? • Pioneer species like lichens, mosses, short grass

12. Succession Summary Baking cookies from scratch with flour, butter, sugar, etc. Building a brand new ecosystem from scratch; no soil Volcano erupts, glacier melts Mosses and lichens (because they can make soil!!) Mature and stable climax community Recovering a previously existing ecosystem after a disturbance; soil intact Weeds and grasses (maybe some moss and lichens, but soil is there) Baking cookies with pre-made dough Forest fire, hurricane, farming Mature and stable climax community