Yellowstone National Park 1988 Succession is the gradual

Yellowstone National Park, 1988

Succession is the gradual change in a community involving species in one stage being replaced by different species in the next stage. • The time involved in succession is on a scale of tens, hundreds and even thousands of years. • Causes: • Abiotic factors • Biotic factors

Abiotic factors such as windstorms, droughts and fire can cause change in a community of plants and animals.

Biotic Factors also change communities over time. Insect epidemics can kill trees. Overgrazing can selectively remove species of plants from a forest.

0 5 yrs The first species to colonize or grow in an area are called pioneer species Only pioneer species are able to grow after a major disturbance in a community due to the lack of soil or nutrients. Examples: lichens and mosses Animals begin to inhabit the area. Usually, insects appear first, then rodents and larger mammals are the last to appear.

0 yrs 5 yrs 15 yrs Opportunistic species take advantage of the work done by the pioneer species. Pioneers modify the environment in such a way that it becomes less suitable for their growth but more suitable for other species. Opportunists eventually replace pioneer species. Examples: grasses & weeds

0 yrs 5 yrs 15 yrs 25 yrs Over time, the decay of pioneer species, grasses and shrubs adds nutrients to the forest floor allowing more complex species to grow.

0 yrs 5 yrs 15 yrs 25 yrs 50 -80 yrs The biodiversity of a community continues to increase as it ages. A variety of plants and animals will inhabit the area.

0 yrs 5 yrs 15 yrs 25 yrs 50 -80 yrs 150+ Succession takes hundreds of years before completion. Species replacement continues until the community is dominated by competitively superior species. Once the community reaches a stable state of maturity it is called a climax community.

Timeline 0 yrs 5 yrs Pioneer species (lichens & mosses) 15 yrs Grasses and Small shrubs Larger shrubs and dwarf trees Biodiversity 25 yrs 50 -80 yrs Larger Trees Climax community (Mature/stab le ecosystem) 150+

Two Types of Succession Primary succession- a change in an environment where soil never existed before. Examples: recently formed lava flows or rocks exposed when glaciers melt. Lichens and mosses (Pioneer species) first grow on the rock then soil forms from decayed mosses.

Two Types of Succession Secondary succession also occurs on smaller scales. When Secondary successiona changethe in an environment where one tree falls, sunlight reaches forest floor. This soil already includeofareas destroyed by brings many exists. changes Examples to this section the rainforest fire, clear-cutting, or insect epidemics.