7Secondary succession: The reestablishment, through stages, of a climax ecosystem, that has been cleared by natural or human means.
8Secondary Succession: A bare patch of ground covered in grasses two years later
9Secondary SuccessionWhen natural vegetation has been disturbed, removed or destroyed.Abandoned farmsBurned forestsHeavy pollutionDeforestationA huge storm
10Some 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
16Lithosere: Succession on land The evolution of bare ground to forest.Pioneer species……………………………………Climax forest
17Hydrosere: Succession of ponds and lakes to forests. Describe the changes that you see.
18Hydrosere: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.
21Succession along a beach: The gradual conversion of sandy beaches and desert margins to forest.Wind moves sand into dunesOrganic 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.
26Changes 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 soilEarly succession plants: grasses, herbsMidsuccessional plants: grass and low scrubsLate successional plants: treesClimax community: depends largely on climate and edaphic factors
27Climatic factors Precipitation Temperature Insolation (Incoming Solar Radiation)
28Edaphic FactorsFactors having limiting affects on plant growth that are not climatic. Soil FactorsExamples:Alkalinity of soilExtreme acidityIron toxicityZinc deficiencyLow nutrients in soil
29Rate of Primary Succession Primary succession is fastest in humid tropics.It is slowest in the dry polar areas.Why?
36Changes during succession Biomass increasesResource allocation; nutrients initially stored in soils become stored in vegetation.Mineral cycling slows
37Changes in Energy FlowTrophic 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.
40Know the factors affecting the nature of climax communities.
41The Nature of climax communities. The system is in a stable equilibriumRemember the system is openMatter and energy may cross system boundary.Inputs are in proportion to outputs.The system changes less thus keeping habitats intact over time.
42The 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.
43Climax Community: Mineralized nutrients (Nitrogen) increases. Organic matter in the soil increasesMineral 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.
44Compare early to late succession BiomassProductivityFood chainsSpecies diversityNiche specializationFeeding relationshipsSize of individualsLife cyclesPopulation control mechanismsFluctuationMineral cyclesStability
45Food chains Short Long, complex Species diversity Low High Early succession Late successionBiomass small HighProductivity high LowFood chains Short Long, complexSpecies diversity Low HighNiche specialization Broad NarrowFeeding relationships General SpecializedSize of individuals Smaller Larger?Life cycles Short LongPopulation control density densityindependent dependentFluctuation More Less pronouncedMineral cycles Open Tend to be closedStability Low High
46Source of this PowerPoint: www.nido.cl/~doehlke/succession.ppt