Succession 11/3

Succession Succession- the increase in complexity of the structure and species composition of a community over time. When you have a blank ecosystem what species come colonize first, second, third and finally balance out the system.

Succession Succession happens in steps called seral stages.

Primary Succession Primary Succession- colonization of newly created land. Examples: volcanic eruptions sand dunes uncovered glacial deposits

Primary Succession 1 st things to colonize an area are called pioneer species. 1. Colonization No soil at the beginning of primary succession. Colonizers: Lichen, mosses (r-selected) - Drought resistant and help break down rock to create soil. - When they die they create organic material.

2. Establishment As the soil builds water can be held better and shallow roots can establish. As these plants die, organic material is added Establishing species: grasses, small plants, small invertebrates that break down plant matter. Primary Succession

3. Competition Weathering and rock breakdown create enough soil for K-selected species. K- selected species start to push out r-selected colonizers. Competition species: shrubs, shade-intolerant plants, pine trees. Primary Succession

4. Stabilization Soil in now fully established and nutrient rich. This allows for deep roots and water retention. Fewer new species are coming in. Slower growing, less productive, longer life cycles Stabilization species: (K-selected) shade tolerant trees, oak, spruce, Douglas fir, maple Primary Succession

Climax Community –Maximum possible development a community can reach. Stable, self perpetuating. Equilibrium, organisms die at the same rate they grow. Biomass is stable. Biodiversity is high, K- selected species with specific niches are present. Primary Succession

Secondary Succession Secondary succession- colonization of already established land. Occurs on already established soil. Seeds can lay dormant Shortened/ Faster seral stages Examples: Fire Flood Human activity (clear cutting) (agriculture) Natural disaster

Disturbance Disturbance can send the community back to a previous stage

Changes that occur during succession Size of organisms increases Food webs become more complex Soil depth increases Biodiversity increases NPP and GPP rise and then fall Production/Respiration ratio falls Why do these changes occur???