disturbances and pop growth - ecosystem change

non-equilibrium ecosystem model

communities change constantly in response to distrubance

disturbances…

• remove organisms and alter resource availability

• and affect organisms differently

disturbances foster diversity how?

by opening up habitats for less competitive species BUT

• too much/frequent

  • stress exceeds tolerance

  • slow growing species are excluded

• too little or infrequent

  • competitive species dominate

small-scale disturbances

create patches of habitat diversity (ex: tree falls over, then it opens up new niches and opportunities for growth)

large scale disturbances

can be integral parts of functioning ecosystems (ex: periodic fires)

Primary succession

occurs on barren land

ecosystem pioineers (primary producers typically) help develop a layer of soil and facilitate (or inhibit) colonization

birdSs help bring nitrogen and phosphorus

**LONG PROCESS

Secondary Succession

existing vegetation was DISTURBED or destroyed and soil remains but the vegetation gradually returns

***its not starting from scratch

Climax community

final stage of succession

• stable and self-sustaining ecological community

• organisms = well adapted

Exponential growth