1. Environmental Systems
Ecological Succession: Be able to describe the process of primary and secondary succession in a named habitat.
Environmental Systems

2. Primary succession: The gradual establishment, through stages, of a climax ecosystem, that has not been occupied before.

4. Primary succession will occur after a volcanic eruption

5. Primary succession occurs after a glacier retreats

6. Glacier Bay, Alaska

7. Secondary succession: The reestablishment, through stages, of a climax ecosystem, that has been cleared by natural or human means.

8. Secondary Succession: A bare patch of ground covered in grasses two years later

9. Secondary Succession
When natural vegetation has been disturbed, removed or destroyed.
Abandoned farms
Burned forests
Heavy pollution
Deforestation
A huge storm

10. Some Definitions:
Sere: Another name for succession. A set of stages of evolution of an ecosystem.
Pioneer stage: First stage in a sere which is dominated by opportunist species. (r-strategists)
Climax community: Populations of organisms living together in the climax stage. (K-strategists)
Climax stage: Final stage in a sere where all species are in balance. For example: A mature forest

11. Pioneer Species

12. Pioneer species tend to be r-strategists

13. Climax Species tend to be K-strategists

14. K - strategists

15. Sequoia (redwood) trees are K-strategists

16. Lithosere: Succession on land
The evolution of bare ground to forest.
Pioneer species……………………………………Climax forest

17. Hydrosere: Succession of ponds and lakes to forests.
Describe the changes that you see.

18. Hydrosere:
The gradual conversion of ponds and lakes to forest ecosystems.
With time ponds and lakes are gradually filled with eroded sediments.
The sediments moves in the shorelines and eventually fills in the lake.
The plant sequence is as follows: lake plants, reeds, grasses, shrubs, & trees.

21. Succession along a beach:
The gradual conversion of sandy beaches and desert margins to forest.
Wind moves sand into dunes
Organic material, seeds, and moisture are blown in behind the dune.
Hardy salt tolerant grasses and vines establish themselves trapping more soil.
Plant succession follows the lithosere.

22. Succession along a beach:

23. Be able to describe and explain the changes during succession.

26. Changes during succession
Pioneer species: lichens and mosses that extract nutrients from dust and bare rock.
Then: Bacteria, fungi, insects, small worms add organics to the soil
Early succession plants: grasses, herbs
Midsuccessional plants: grass and low scrubs
Late successional plants: trees
Climax community: depends largely on climate and edaphic factors

27. Climatic factors Precipitation Temperature
Insolation (Incoming Solar Radiation)

28. Edaphic Factors
Factors having limiting affects on plant growth that are not climatic. Soil Factors
Examples:
Alkalinity of soil
Extreme acidity
Iron toxicity
Zinc deficiency
Low nutrients in soil

29. Rate of Primary Succession
Primary succession is fastest in humid tropics.
It is slowest in the dry polar areas.
Why?

30. Succession after a forest fire

31. Secondary Succession after a fire
Nutrient release to soil
Regrowth by remnant roots and seeds
Invasions from neighboring ecosystems
Rapid restoration of energy flow and nutrient cycling

34. Secondary succession after farming

36. Changes during succession
Biomass increases
Resource allocation; nutrients initially stored in soils become stored in vegetation.
Mineral cycling slows

37. Changes in Energy Flow
Trophic levels increase from 2 levels to 4 -5 levels.
More trophic levels transfer more energy.
Food webs become more complex.
The total productivity of an ecosystem increases.
Biomass and biodiversity is maximized in a climax ecosystem.

38. Changes in Productivity

39. Abiotic Changes pH: 8  5.5 N: increases C: increases
Exchangeable ions decrease

40. Know the factors affecting the nature of climax communities.

41. The Nature of climax communities.
The system is in a stable equilibrium
Remember the system is open
Matter and energy may cross system boundary.
Inputs are in proportion to outputs.
The system changes less thus keeping habitats intact over time.

42. The Climax Community:
Specialization is encouraged as all niches are occupied.
Each species must enhance competitive abilities and take care of young.
High nutrients available (but used) due to large amounts of biomass.
High moisture available as forests capture their own transpiration and encourage rain.

43. Climax Community: Mineralized nutrients (Nitrogen) increases.
Organic matter in the soil increases
Mineral cycling decreases as plants are adapted to maintaining themselves and not growing or establishing themselves.
These nutrients become less available to plants as they adhere to soil particles or are stored as dead matter in ground.

44. Compare early to late succession
Biomass
Productivity
Food chains
Species diversity
Niche specialization
Feeding relationships
Size of individuals
Life cycles
Population control mechanisms
Fluctuation
Mineral cycles
Stability

45. Food chains Short Long, complex Species diversity Low High
Early succession Late succession
Biomass small High
Productivity high Low
Food chains Short Long, complex
Species diversity Low High
Niche specialization Broad Narrow
Feeding relationships General Specialized
Size of individuals Smaller Larger?
Life cycles Short Long
Population control density density
independent dependent
Fluctuation More Less pronounced
Mineral cycles Open Tend to be closed
Stability Low High

46. Source of this PowerPoint: www.nido.cl/~doehlke/succession.ppt