Chapter 22: Decomposition and Nutrient Cycling Flashcards
Primary production depends on the up take of what by?
- essential mineral nutrients by plants
What is the original source of mineral nutrients for plants to up take?
- Atmosphere (carbon) or weathering of rocks and minerals (N, P, K, Ca, Mg, S etc)
What happens to the nutrients once in the food chain?
- a lot of them get tied up…you have lots of nutrients but they get locked up in biomass until they are released via decomposition
What is a large proportion of total nutrient pool in most ecosystems?
- nutrients in living tissues
Nutrients in dead organic matter are mineralized by?
microbial decomposers
Once nutrients in dead organic matter are mineralized by microbial decomposers what can happen?
- they can be taken up and incorporated by plants again via internal cycling
Give a generalized model of nutrient cycling in a terrestrial ecosystem!
- NPP
- retranslocation via litter fall of leaves
- dead organic matter accumulates on forest floor
- decomposition/mineralization of organic matter
- yields soil nutrients
- these are taken up by plant
- incorporated into plant tissues
- NPP again
What is up with decomposition?
- key process in recycling of nutrients within ecosystems
- results in release of energy and conversion of organic compounds into inorganic nutrients
- decomposers deed on dead organic matter or detritus
What are microbial decomposers?
- bacteria, particularly for dead animal matter
- fungi, particularly for cellulose plant matter
- they secrete enzymes that break down compounds. Some products absorbed as food (we eat mushrooms)
- succession of microflora (theres a change in communities over time, maybe other things move in after another had broken down the material a bit )
- decomposers are eating by microbivores
Detritivores?
- animals that feed on dead material (including dung)
- result in fragmentation of dead organic matter (detritus )
- characterized by body with
- fragmentation helps decomposition - better to break signs up not pieces and it break down easier
Rate of decomposition is related to?
- quality of plant litter as substrate for decomposers : types and quantities of carbon compounds present
- Physical environment: soil properties (texture and pH) and climate (temperature and precipitation)
* moisture and temp are two big ones!
ex: ripe tmato will break down faster than a stick…lol
- warm and wet vs cool and dry
Explain decomposition of spartina on exposure to air!
- hangs around a lot longer in anaerobic environment
- oxygen (aerobic) helps break down quicker
- of you want to enhance decomposition, bubble it
Mineralization?
- during decomposition, microbial decomposers transform elements contained in organic compounds into inorganic forms
Explain the mineralization example pertaining to the litter bag!
- litter bag C:N (50:1 - 100:1)
L> plant litter - consumption of plant litter as source of energy (carbon) and nutrients
- C:N (10:1 - 15:1)
fungi bacteria
L> CO2 loss from microbial respiration - mineralization: transform orgnaic compounds into mineral nutrients
- immobilization: uptake and assimilation of mineral nutrients by decomposers -> necessary to supplement the relatively low N content of plant litter!
- Net mineralization rate = mineralization rate = immobilization rate
What affects rate of nutrient cycling?
- climate affects rate of primary production and decomposition and therefore rates of nutrient cycling (greater in warm, wetter climate)
- nature of organisms (life span, growth rate) also affects nutrient cycling e.g. plankton vs trees
- trees take long time to break down. Plankton recycle quickly (small - high surface area to volume ration in the water column to break down faster)
____ determines rate of nutrient uptake.
- primary productivity
___ determines rate of nutrient release.
- decomposition
What occurs between nutrient uptake and release?
feedback between the two
**balance between PS and nutrient cycling when one stops the other does too
Explain feedback in nutrient cycling in a low nutrient availability area!
-low nutrient availability –> low nutrient uptake –> low leaf nutrient concentration –> low net primary productivity–> low nutrient return to soil n litter –> low net mineralization rate –> low nutrient availability
Explain feedback in nutrient cycling in a high nutrient availability area!
- high nutrient availability –> high nutrient up take –> high leaf nutrient concentration –> high net primary productivity –> high nutrient return it to soil in litter –> high net mineralization rate –> high nutrient availability
Terrestrial vs Aquatic Ecosystems ?
- primary production an grazing vary between land and aquatic
- standing crop biomass on land accumulates and is stored
- blooms in the aquatic occur but it doesn’t accumulate in the water column
- vertical separation between sones of production and decomposition
- in terrestrial systems, plants bridge these two zones
- in aquatic environments, not always the case
- Terrestrial: Zone of primary production = canopy…Zone of decomposition = forest floor
- Aquatic: Zone of primary production = photic zone/ surface waters. Zone of decomposition = benthic zone/ bottom sediments
Long term biological retention of nutrients in forests occurs where?
- stored in tree limbs, trunk, bark , roots and soil organic matter
In aquatic environments, availability of nutrients depends on? Long term storage?
- turnover in phytoplankton and zooplankton
- deep bottom sediments
- aquatic has much more turnover …on land nutrients don’t really move a lot from where they were produced
Open-water Ecosystems
- In deeper waters, primary production and decomposition locations? What is special about temperate and polar regions?
- In deeper water, separation between surface waters where primary production occurs and decomposition in bottom sediments
- in temperate and polar regions, this separation (thermocline) breaks down in fall and spring
- *nutrients sit on tourmaline (so dense - act as a barrier to primary production, nutrients can’t get to the bottom or back up until there is a turnover)