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

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

Primary succession will occur after a volcanic eruption

Primary succession occurs after a glacier retreats

Glacier Bay, Alaska

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

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

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

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

Pioneer Species

Pioneer species tend to be r-strategists

Climax Species tend to be K-strategists

K - strategists

Sequoia (redwood) trees are K-strategists

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

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

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.

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.

Succession along a beach:

Be able to describe and explain the changes during succession.

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

Climatic factors Precipitation Temperature Insolation (Incoming Solar Radiation)

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

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

Succession after a forest fire

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

Secondary succession after farming

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

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.

Changes in Productivity

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

Know the factors affecting the nature of climax communities.

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.

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.

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.

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

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

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