Nutrient Cycling Flashcards
Ecosystem Ecology -
- focuses on understanding how
organisms and chemical & physical
processes interact.
What is an ecosystem?
A region that contains interaction biotic and
abiotic factors
Biogeochemistry:
the study of the physical, chemical, and biological
factors that influence the movements and transformations of elements
nutrients(essential nutrients)
Elements that are required for the development, maintenance, and reproduction of organisms
how do nutrients enter ecosystem
(1) chemical breakdown of minerals in rocks or
(2) fixation of atmospheric gases
Macronutrients –
essential elements required in large
concentrations
Micronutrients –
essential elements required, but only in
small concentrations
functions of:
Carbon
Nitrogen
Phosphorus
main component of structural compounds
enzymes
ATP, DNA, cell membranes
Physical weathering
Chemical weathering
Biological weathering
-physical breakdown of rocks
-Chemical reactions that release soluble forms of the mineral elements
-Plant roots, lichens
how do soil horizons form?
weathering, accumulation of
organic matter and leaching
leaching
movement of dissolved
particles from upper to lower layers
acidic soils and how they form
As soils develop, they tend to get more acidic (due to biological
activity/organic acids/CO2 and leaching of cations)
* Acidic soils have low nitrogen availability, can be toxic
phosphorus characteristics
-P is essential to energetics, genetics and structure of living systems.
-It is not abundant in the biosphere
–> instead is in mineral deposits, no atmospheric resevoir
-Can be a limiting factor for [freshwater] aquatic primary production, not usually for terrestrial primary production
Phosphorus cycle
Weathering: P is usually (naturally) released to
ecosystems via weathering of rocks
2. Absorption: plants uptake P from soil/water and
incorporate them directly into tissue
* Animals gain Phosphate (PO43-) via plant tissue (or
herbivore tissue)
3. Return to environment – decomposition
1) Animal eliminate excess P via urine
2) P returns to the environment via decomposition of
plants and animals
4. Some P gets buried in settlements, which over time,
becomes rock (and the cycle continues)
Nitrogen (N) cycle
- Nitrogen-fixing bacteria capture N2, converting
it to ammonia or ammonium in the soil - nitrogen fixation - This is than taken up by plants and used to
make organic biomolecules. - The nitrogen-containing molecules are passed
to animals when the plants are eaten. - They may be incorporated into the animal’s
body or broken down and excreted as waste,
such as the urea found in urine. - When the animal dies, the N is returned to the
soil via decomposition
Mineralization/Ammonification
-release of N as ammonium (NH4+)
following decomposition by bacteria and fungus
-Excretion of ammonium by all organisms
-Ammonium can be directly taken up (immobilized) by bacteria and primary producers
Nitrification:
conversion of ammonium to nitrite (NO2-), and then quickly
nitrate (NO3-).
Denitrification:
conversion of nitrate to nitrous oxide (N2O), then dinitrogen
(N2) gas
the five transformations of N
1.Nitrogen fixation
2.Immobilization
3.Mineralization/ammonification
4.Nitrification
5.Denitrification
Carbon
-Its what makes organic molecules, organic.
-Carbon gasses (CO2 and CH4) play a critical role in controlling global climate.
-Carbon is removed from the atmosphere via photosynthesis (coupled with uptake of essential nutrients)
Carbon (C) cycle in terrestrial ecosystems
-CO2 is removed from the atmosphere via photosynthesis (in plants/algae/ cyanobacteria)
-Animals consume the primary producers, acquire C that is stored within them.
-CO2 is returned to the atmosphere
CO2 is returned to the atmosphere via
respiration in all living organisms.
* Decomposers can also break down dead / decaying organic matter and release CO2.
* Some CO2 is returned to the atmosphere via the burning of organic matter (forest fires).
* CO2 trapped in rock or fossil fuels can be returned to the atmosphere via erosion, volcanic eruptions, or burning of fossil fuels.
Carbon (C) cycle – in aquatic ecosystems
CO2 has to be first dissolved in water before it is available to
primary producers
* When dissolved CO2 turns into two compounds (in equilibrium):
* Bicarbonate HCO3-
* Carbonate CO32-
-CO32- may combine with dissolved calcium to precipitate
out as calcium carbonate CaCO3
where is carbon stored in earths interior?
how is it released
Carbon in the Lithosphere includes coal, oil, natural gas
* Volcanic eruptions may release some of the carbon
Decomposition
The process by which organic matter is broken down
into simpler organic or inorganic matter
what does decomposition facilitate
Accompanied by a release of CO2 as well as nutrients (PO43-, NH4+) are released for uptake by primary producers.
Decomposition rates are influenced by:
- Temperature - warmer temps mean faster rates of reactions
- Moisture
- Chemical composition of decaying matter
- Chemical composition of the environment
Decomposition rates: Actual evapotranspiration
-A measure of the total amount of water that evaporates and transpires off of a landscape
-Decomposition rates (here, again of leaf litter) are much more rapid in warm, wet regions than in cooler, drier regions
Decomposition rates: leaf chemistry
-Softer leaves with higher N content higher rate of decomposition
The higher the ratio of lignin to N, the longer it
took to decompose
-more N in soil make higher rate
Decomposition rates: Aquatic environments
Increase with increasing temperature,
* Decrease with increasing structural tissue content
* Increase with nutrient availability
-Moisture, of course becomes unimportant as a factor
in some aquatic systems, primary productivity controlled by
top-down processes
-energy the same in each trophic level
in terrestrial systems, primary productivity controlled by
bottom-up processes
What plays the biggest factor in bottom up control
Limited resources
Aquatic ecosystem nutrient cycling
Higher herbivory rates
less autotroph biomass
less detritus
less detritivore biomass
–> Overall quicker cycling of nutrients
Terrestrial ecosystem nutrient cycling
Lower herbivory rates
more autotroph biomass
more detritus
more detritivore biomass
–>Overall slower cycling of nutrients
what happens when nutrient cycling does not occur in single stationary location
nutrient spiraling
Spiraling length (S)
The length of stream required for an atom of a nutrient to complete a cycle from release into the water column to re-entry into the benthic environment
V=
average velocity at which a nutrient atom moves downstream
T=
average time for a nutrient atom to complete its nutrient cycle
Where spiraling lengths are short,
a particular nutrient atom may be used many
times before it is washed out of a stream system
If V is low and the T to complete a nutrient cycle is short,
nutrient spiralling length is short
what are the two properties that characterize Nutrient spirals
Spiraling length
Nutrient Retentiveness
Nutrient Retentiveness
the tendency of a stream to retain nutrients. Inversely related to spiraling length.
Long spiraling length
= low nutrient retentiveness
– Nutrient availability low because nutrients transported
downstream more quickly.
– Nutrient atom used few times before being washed
downstream.
Shorter spiraling length
= high nutrient retentiveness
— Nutrient availability high because nutrients transported
downstream more slowly.
— Nutrient atom used many times before being washed
downstream.
Macroinvertebrates
consume large proportion of algae (available nitrogen)
Higher abundance of macroinverts leads to:
- Speed up the nutrient cycling in streams
* Faster nutrient cycling = Greater primary production - Higher nutrient retention and decrease of
downstream nutrient transport
–> act as a first buffer against eutrophication!
Effect of large grazers
Large grazers, like deer, may increase primary productivity of
ecosystem through increased rates of nutrient cycling.
* On top of this nutrient cycling shift, heavy grazing shifts composition of plants (eat more palatable species, leaving behind seedlings of less palatable species!)
Without large grazers,
nutrient cycling occurs more slowly
(dominance of decomposition and
feeding of small grazers
Long turnover times:
* Short turnover times:
nutrients remain locked up in plant biomass
nutrients do not remain locked up for long
Haber Process:
-artificial nitrogen fixation
-Combines N2 gas and H2 gas using a metal
catalyst under high heat and pressure to
form NH3 (ammonia).
- without could only make food for 4 bil
Through combustion of fossil fuels,
the Haber process, and N-fixing
crops,
we have doubled the
amount of fixed nitrogen per year.
how is acid rain produced
Nitrogen oxides, produced by combustion (industry, households, vehicles), when combined with water vapor form acid
Problems caused by acid rain
- forest dieback
- decrease of pH in aquatic & terrestrial ecosystems
- corrosion of human infrastructure
- negative impacts on human health
- acid rain can impact areas distant from the origin
why do cars have catalytical converters-
reduce acid rain
Methemoglobinemaa (“blue baby syndrome”):
nitrates in drinking water (usually from agricultural runoff) can cause hemoglobin in blood to oxidize, reducing its capacity to carry O2
where are resevoires for phosphorus
Marine sediments–>Sedimentary rocks–>Incorporation into soils, via weathering–>Available for active cycling
