Decomposition

Detritivores and Osmotrophs

Consumers of dead organic matter (Figure 9.2)

Bacteria (animal moslty) and Fungi (plant mostly)

Protozoa, micrometazoa that feed on bacteria and fungi (and themselves)

Larger invertebrates: millipedes, pill bugs, earthworms

Chemical and Mechanical breakdown of detritus

Leaching, Fragmentation

Immobilization vs.Mineralization of nutrients

Microbial Enrichment

Animal Decomposition faster, more labile material, even bones

Detritus vs. Grazer Food Webs: seagrasses, saltmarshes, streams

Factors Controling Decompositon Rates

Quality of the detritus: labile-refractory

Temperature: poikilotherm dominated.

Detritus Quality: Figure 9.5

Fast; redbud, aspen, mulberry

Slow: oaks, pines- high in lignins, secondary metabolites

Decomposition rates: litterbags

Negative exponential function: % mass loss = e^-kt

K extinction/decomposition coefficient, defines the slope

0.693/k= t_1/2; half life or turnover time

Temperature greatest determinant of detritus turnover time

Science 271:393

Quality also important

Habitat	Half Life (yrs)
Tropical Forest	0.36
Temp. Hardwoods	1.01
Temp. Conifer	4.86
Boreal Conifer	11.23

Science 268:1606

Amount of NPP proportional to flux into detrital pool

Detrital pool mass not related to NPP

At equal temp, generation time of plant community controls t_1/2

Mineralization vs Immobilization Fig 9.11, Fig. 9.14

Increase in N, P content due to microbial biomass:

microbial enrichment

Consumption of microbial biomass releases these nutrients

Aquatic Systems

Microbial Loop, DOM, sinking rates

Sediment Diagensis