Decomposers: The end and the beginning

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Decomposers The end and the beginning

• James Danoff-Burg
• SEE-U
• Columbia University

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Food Sources of the Players in our Ecological
Drama

• Producers - get energy from sun
• Consumers - get energy from living tissue
• Decomposers - get energy from dead tissue

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Roles of Decomposers

• Break down tissue of dead organisms
• Convert it into novel tissue
• Called Secondary Production
• Make available nutrients for plants
• Thus, they begin the energy cycling process again
  by recycling energy back into the community

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Relative Values

• Most species rich - Consumers
• Most biomass - Producers
• Most taxonomically diverse - Decomposers
• Have fungi, bacteria, protista, and animalia

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Decomposers at a Carcass

• Vertebrates (macrofauna)
• Large invertebrates (mesofauna)
• Smaller invertebrates (microfauna)
• Fungi (microfauna)
• Protists (present throughout)
• Bacteria (present throughout)

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Forensic Entomology

• Applied succession theory
• Used to solve crimes
• Date the time of death or deposition of a body
• Great accuracy initially, less accurate with
  increasing time
• Primarily study beetle and flies

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Decomposers at a Log

• Bacteria, Protists, and Fungi
• Smaller invertebrates (ants and termites)
• Larger invertebrates (roaches, beetles, etc.)
• Small mammals

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Succession Involving Decomposers

• Degradative
• single large resource (log, carcass)
• resource is exhausted at the end
• regular progression of species through that
  resource
• unidirectional process of succession
• this is the case for all successional processes

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Population Control

• Producers
• Bottom-up control (sunlight and resource
  availability)
• Consumers
• Either bottom-up (resources) or top-down (from
  predation, etc.)
• Decomposers
• Bottom-up
• Explosive population growth with resource
  availability

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Todays Activity at the BRF

• How does road intensity affect the decomposer
  community?
• Roads detrimentally affect the populations of
  many species
• Impact of road changes with group of organisms
• Some plants and insects only respond a few meters
  in
• Larger vertebrates (birds) avoid to 200 m

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Question and Hypotheses

• How does road intensity affect the decomposer
  community?
• Ho it doesnt
• Ha1 Road intensity decreases diversity of the
  decomposer community
• Ha2 Road intensity improves diversity of the
  decomposer community

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Study Organisms

• Necrophagous beetles
• ecological category for anything feeding on
  carrion
• Carrion beetles (Silphidae)
• Rove beetles (Staphylinidae)
• Scarab beetles (Scarabaeidae)
• Leiodid beetles (Leiodidae)

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Experimental Layout

• Three road types (5 of each road)
• single lane dirt road
• closed canopy
• low to no traffic intensity
• two lane paved road
• relatively open canopy
• moderate traffic intensity
• four lane paved road
• open canopy
• high traffic intensity

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Sampling Method

• Hanging baited traps
• 2-liter bottles
• two flap openings
• baited with a single chicken thigh per trap
• left out for 5 days (set out on Sunday)
• Count richness and abundance of beetles in lab
• only beetles- no flies
• flies can fairly easily escape the trap

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Data Collection

• Go to field
• Collect traps
• Count, ID larger beetles, release
• Preserve smaller ones with alcohol
• Count under microscope
• Sort to morphospecies

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Analyses Presentation

• Count, chart, chi-square tests
• Write up a PowerPoint presentation of entire
  project
• Each person makes up two slides
• Finish everything by 430 pm