Decomposers: The end and the beginning

James Danoff-Burg

SEE-U

Columbia University

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

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

Relative Values

Most species rich - Consumers

Most biomass - Producers

Most taxonomically diverse - Decomposers– Have fungi, bacteria, protista, and animalia

Decomposers at a Carcass

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

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

Decomposers at a Log

Bacteria, Protists, and Fungi Smaller invertebrates (ants and

termites) Larger invertebrates (roaches, beetles,

etc.) Small mammals

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

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

Today’s 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

Question and Hypotheses

How does road intensity affect the decomposer community?

Ho: it doesn’t Ha1: Road intensity decreases diversity

of the decomposer community Ha2: Road intensity improves diversity of

the decomposer community

Study Organisms

Necrophagous beetles– ecological category for anything feeding on

carrion Carrion beetles (Silphidae) Rove beetles (Staphylinidae) Scarab beetles (Scarabaeidae) Leiodid beetles (Leiodidae)

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

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

Data Collection

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

Analyses & Presentation

Count, chart, chi-square tests Write up a PowerPoint presentation of

entire project Each person makes up two slides Finish everything by 4:30 pm