decomposition

What is decomposition?

It is the breakdown of organic matter into inorganic energy and nutrients

Why is decomposition important?

It recycles nutrients back into living ecosystems for producers

What are detritivores?

They are organisms that physically break down dead material

• Ex: earthworms, millipedes, isopods, nematodes, slugs

What would happen without decomposers?

Nutrients would be locked in dead matter and eventually lead to ecosystems collapsing

What is the most abundant decomposer in soil?

Bacteria, next to fungi and nematodes

What are leaf litter sifters?

Wired meshes that separate small organisms from leaf litter and soil samples

What is a Bernese funnel?

A device that uses light/heat to dry out litter from above and cause organisms to move downward to avoid desiccation, resulting in them falling into a collection container

What are pitfall traps?

A pit with a container buried in the ground that captures ground dwelling and mobile organisms that fall into it from the surface

What are soil cores?

cylindrical, vertical samples of soil extracted from the ground that are used to sample organisms within the soil itself

What is a litter bag?

a bag with a mesh surface large enough to let decomposers into the bag (bacteria) and small enough to hold leaf litter

Why does mesh size matter?

It must allow decomposers into the bag and keep leaf litter contained

• the smaller the mesh size, the lower the decomposition

• the larger the mesh size, the higher the decomposition

What does the first-order decay model describe?

It describes how mass decreases over time

What does the first-order decay model tell us about the decomposition rate?

It is proportional to the amount of material remaining

What does the decomposition rate depend on?

It depends on how much material is left

• More mass = faster decomposition

• Less mass = slower decomposition

What happens to decomposition overtime?

Slows down as less labile compounds are present and more lignin compounds are present

What are the 3 main drivers that control the litter decomposition rate (K)?

• Climate (Physical: temperature + moisture)

• Litter quality (chemical: C:N, lignin)

• Decomposition (biological: microbial activity, oxygen)

How does climate affect decomposition?

As the temperature and moisture of an environment increases, decomposition increases in speed

• But too high or too low of a moisture can cause it to slow down

How does litter quality affect decomposition?

Litter with high nutrients and low lignin decomposes the fastest

How do decomposers affect decomposition?

The more larger and active decomposers are, the faster decomposition occurs

What is wilting point?

The point at which the water in the soil is not enough for plants to grow, causing them to wilt

What is field capacity?

The amount of water remaining in soil after excess water has drained away by gravity

What is the climate decomposition index (CDI)?

A metric that combines temperature and precipitation to predict the decomposition rate

Why is decomposition faster in a stream than in a forest?

Because it allows for easier breakdown of organic matter, has more moisture and higher oxygen, leading to more decomposers being present and resulting in faster decomposition

What is aerobic decomposition?

The breakdown of organic matter with oxygen, which results in fast decomposition

• NO2, SO2, H2O is exclusively gained

What is anaerobic decomposition?

The breakdown of organic matter without oxygen, which results in slow decomposition

• H2S, CH4, NH3 is exclusively gained

How does a C:N ratio affect decomposition?

Because a high C:N results in slower decomposition, while a low C:N results in faster decomposition

Why does a high C:N ratio slow decomposition?

because there is low N available, leading to microbes becoming N-limited and resulting in slow growth and decomposition

Why does a low C:N ratio speeds up decomposition?

because there is lots of N available, leading to fast growth and decomposition

What is the order of decomposition between cellulose, lignin, and hemicellulose?

Hemicelllulose > Cellulose > lignin

when does a litter decompose quickly?

• Low C:N ratio

• Low lignin content

• High nutrient content

• Easily digestible compounds

When does a litter decompose slowly?

• High C:N ratio

• High lignin content

• Low nutrients

• Tough/complex structures

What are the four components of plant litter in order of decomposition?

Labile compounds > Non lignified cellulose > Lignified cellulose > Lignin

Why do ligin compounds decompose the slowest?

because they are the most resistant to breakdown and have complex chemical structures

Why do labile compounds decompose the quickest?

because they breakdown the easiest and have simple chemical structures