Ecology Ch.22

What is decomposition?

Breakdown of dead organic matter

fragmentation> mineralization —> soluble nutrients

What is the rate of decomposition?

The rate at which nutrients become available to primary producers —> determined by mineralization

influenced by temperature, moisture, pH, and chemical composition, and soil type

soil types - classified by size of particles

sand = largest particles - does not hold water for a long time —> air can get in

silt= medium sized

clay = very small/fine particles- retain water for a long time—> air cannot get in

How does pH affect plant species richness?

more acidic = less species richness

Acidic soil has poorer nutrient levels and cycling

How does climate/ water affect the activity of decomposers?

Increases with water and temperature to a certain point

How does type of detritious

How does nitrogen affect decomposers?

Adding more nitrogen allows decomposers to decompose things they normally don’t have the energy to do

How do you measure decomposition?

1. litter bags

How are litter bags used to measure decomposition?

Put things in a bag and after a time, measure to see which one weighs less. Less weight = more decomposition.

Leaves with a higher carbon: nitrogen ratio lose less mass

Increased N availability increases decomposition rates

Higher temperature may also play a role

Describe a generalized biogeochemical cycle

What is the phosphorous cycle?

Sink: marine sediements(lost into rivers/ocean) —> unavailable to terrestrial producers

Pool: sedimentary rock—> breakdown of rock makes phosphorus available to soil

Can cause algae blooms

1. Geological uplifting that makes rocks available on surface

2. rocks is weather by rain and gets in soil

3. Some is lost to the sink and go to the ocean. This forms sediment and eventually leads to new rocks

4. Some is released to the soil —> helps plants grow —> animals eat plants —> animals and organic matter eventually decomposed by decomposers to recycle phosphate

Describe the Nitrogen Cycle

Sink AND Pool: the atmosphere

Prokaryotes important: N2 fixing bacteria convert N2 to NH3 —> not all organisms can use NH3

Nitrifying bacteria convert NH3 to NO2(nitrate) or NO3(nitrite) —> NO3 (nitrite) is the form that is usable by most species

Three fates of NO3

1.NO3 is assimilated into plants and passed to animals when animals eat them

2. NO3 is denitrified and passed back to the atmosphere.

3. Denitrifying fungi and bacteria convert NO3 back to NH3 and it is recycled in the food web

Describe the Carbon Cycle

When is retention of nutrients highest?

At intermediate stages of forest succession

How does disturbance effect nutrient availability?

It can cause nutrient loss

For example, deforestation,