chapter 7 decomposers and decomposition. decomposition?

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Chapter 7 Decomposers and Decomposition

Author: barrie-eaton

Post on 29-Jan-2016




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  • Chapter 7Decomposers and Decomposition

  • Decomposition?

  • DecompositionDecompositionbreakdown of chemical bonds formed during the construction of plant and animal tissue.Organisms that feed on dead organic matter or detritus Microbial decomposersbacteria and fungiDetritivoresanimals that feed on dead material

  • Carbon Carbon sequestrationCO2 vs. organic matterForests vs. barren landAtmosphere vs. biomass

  • Stages of decompositionLeachingloss of soluble sugars/dissolved compoundsFragmentationreduction into smaller particles physical/chemical fragmentation

  • Energy processingEnergy and nutrients from organic compoundsoxidation of carbohydratesrespiration

    Mineralizationorganic inorganic

    Immobilizationinorganic organic

  • DecomposersGroups based on sizeMicrofloramost common decomposersbacteriaanimal materialfungiplant materialAerobicrespirationAnaerobicfacultative/obligate anaerobesFermentationsugars organic acids/alcohol

  • DecomposersMicrofauna/microflora
  • Food QualityEnergy and nutrient sourceLitterdead plant materialQuality related to chemical bonds/structuresimple sugars vs. complex carbohydratesLignincomplex class of carbohydrateslittle net gain of energy for decomposers

  • Rate of decompositionInverse relationship between rate and lignin contentQuality influences feeding of large detritivores

  • Aquatic environmentsPhytoplanktonlow lignin contentVascular plantshigh lignin content

    O2 dependentLow O2 absence of fungi

  • Animal matterChemical breakdown easier than plantsFlesh consumed by scavengers70% decomposed by bacteria and arthropods (maggots)Temperature dependent

  • Fecal matterMostly decomposedHerbivorespartially digested organic matterSpecialized detririvores larvae incubate and feedTumblebugsincubate larvae

  • Physical influenceTemperature and moistureInfluence rate of decompositionDecomposition highest in warm/wet climatesTemperature parallels CO2 release

  • NutrientsNitrogen nutrient valueOrganisms require N for growth during mineralizationMineralization and immobilization taking place simultaneouslyNet mineralization rate

  • Stages of nutrient concentrationWater soluble compounds leachedDependent upon soil moistureN increasesimmobilization from other sourcesAs C quality declines net release of NDependent upon original nutrient content

  • Aquatic decompositionSimilar to terrestrial ecosystemsInfluenced by abundance of waterMore stable environment favors decompositionMore accessibility to detritivores

  • Aquatic systemsParticulate organic matter (POM)Coarse particulate organic matter (CPOM)Fine particulate organic matter (FPOM)Water depth determines organic makeupBenthic organic matter bacteriaAerobic vs. anaerobicDissolved organic matter (DOM)

  • Aquatic sourcesDOM readily available Sourcesalgae, zooplanktonDeath of phyto/zooplanktonBacteria concentrate DOMMineralization and immobilization of nutrientsExcretion of exudates and feces

  • Organic matter processingPhysical mechanismWater soaked leaves sink5 30% organic matter leached

    Biological mechanismCovered with bacteria & fungiCPOM & FPOMDegrade cellulose and metabolize lignin

  • Shredders attack CPOMFeed also on attached microbesBecomes FPOMFilterers / collectors gather FPOMFeed also on attached microbesGrazers feed on algal coatingsleftovers enter stream as FPOMGougers feed on woody debrisPredators feed on all the above Flowing water

  • Nutrient passes from water column plants consumer another consumer poop = nutrient cyclingDownstream flow = new dimension Physical retentionStorage in wood detritusLeaf sedimentsBeds of macrophytesBiological retentionUptake and storage in plant/animal tissue

  • Recycling, retention & downstream displacementDownstream transport + nutrient cycling = nutrient spiralingOne cycle = Uptake of an atom from DOMPassage through food chainReturn to water for reuseSpiraling = distance of one cycleshorter cycle = tighter spirallonger cycle = more open spiral

  • River Continuum ConceptFrom headwaters to mouth continuum of changes in conditions

    Headwater streams (1-3) Swift, cold, forestedStrongly heterotrophicDominant organismsShredders CPOMCollectors FPOM

  • Midorder streams (4-6) Riparian vegetation importantCanopy opens primary productionTemperature increases / current slowsPrimary production > community respirationDominant organismsCollectors FPOMGrazers algae & macrophytes

  • Higher order streams (6 10) Channel wider & deeperVolume of flow increasesAutotrophic production decreasesShift back to heterotrophyEnergy from FPOMUtilized by bottom dwellersPhytoplankton & zooplankton population minimal