Ecological Succesion

Succession n Do ecosystems ever change? n Were there ALWAYS forests? n SUCCESSION is the name given to a predictable series of changes in an ecosystem over time –Organisms themselves can change the environment (ex. Nutria burrows) –The new environment becomes no longer suitable for the original group of organisms –One set of organisms gradually replaces another…

Forces of Change n What n What factors can cause ecosystems to change? –Volcanoes –Floods –Hurricanes –Human –Human activity –Disease –Drought –Fire n Stages n Stages of succession –PIONEER –PIONEER stage (ex. Moss, Water Plants) –CLIMAX –CLIMAX community (ex. Mature rainforest)

Primary & Secondary Succession n PRIMARY n PRIMARY Succession –When –When the starting point is an abiotic abiotic environment n Volcano n Flood n SECONDARY Succession –When –When an existing ecosystem is disturbed n Fire/lightning n Disease n Hurricanes n Human n Human activities

Ecosystem recovers after a major volcanic eruption in Mount St. Helens 1973: The Mountain Peak 10 years before eruption 1983: 3 years after eruption 2000: Vegetation re- growth around the volcano

Gradual Changes n Wetland n Wetland Succession –p36-37 –As –As water plants colonize, sediments are trapped by the roots, and the ecosystem becomes drier the environment dries out, water plants can no longer compete for resources, and larger “land” plants colonize, which shade-out the other plants n Forest n Forest Succession –Fires –Fires & tree-falls create opportunities for different species to colonize (ex. Yellowstone National Park) –Tree –Tree falls create canopy gaps gaps (sunlight comes in, allowing other plants to colonize)

Wetland Succession

Sedges and floating plants close over the open water, trapping sediments in their roots, and gradually drying out the pond

Forest Succession

Transects Because of the change in availability of sunlight and water, there is a predictable pattern of change in the vegetation as you walk from a field into a forest. This transitional zone between ecosystems is called an ecotone.