Biogeochemical Cycle Flashcards
What are 4 abiotic components of an ecosystem that contribute to chemical reactions?
atmosphere
water
soil
parent material (rocks)
Define the biogeochemical cycle
the flow of nutrients between the abiotic to the biotic and back to the abiotic components of an ecosystem
What are the 2 major biogeochemical cycles? what is the third?
gaseous
sedimentary
hybrid
where are the major pools of nutrients in the gaseous cycle?
atmosphere and ocean
What scale does the gaseous cycle occur at?
global
what major nutrients have gaseous cycles?
nitrogen
CO2
oxygen
Where is the biggest pool of nitrogen?
the atmosphere
Where are the main pools of nutrients in the sedimentary cycle?
soil
rocks
minerals
How are the nutrients involved in the sedimentary cycle released from abiotic to biotic components?
through the weathering and erosion of sedimentary materials (rocks, soil, minerals)
Which element has no gaseous phase to contribute to a gaseous cycle?
phosphorous
what are the 2 phases of the sedimentary cycle?
rocks: the Earth’s crust is weathered releasing mineral salts
solution: soluble salts enter water cycle
Describe hybrid cycles
a combination of gaseous and sedimentary cycles
Which element has a hybrid cycle?
sulfur
Where are the major pools of sulfur?
earth’s crust and atmosphere
What drives gaseous and sedimentary cycles?
the flow of energy through an ecosystem - usually light, but sometimes geothermal energy
What other cycle are the gaseous and sedimentary cycles connected to? explain
the water cycle
water carries soluble nutrients and other materials throughout an ecosystem
What is an example of how the water cycle is connected to biogeochemical cycles?
Hubbard Brook
describe the basic steps involved in the BGC cycle
atmospheric input > plant tissues > retranslocation (internal cycling) > litterfall > DOM > output or decomposition and mineralization > soil nutrients also influenced by rock/mineral weathering > output or plant uptake > assimilated into plant tissues
How is decomposition/mineralization quantified?
soil litter bag experiments
How is incorporation of nutrients into plant tisuse measured?
CO2 uptake over time
ex. immobilization of C14 in Mirror Lake and filtering algae
How does the type of cycle influence how nutrients enter an ecosystem?
nutrients with a gaseous cycle enter through the atmosphere via uptake of gases or precipitation
nutrients with sedimentary cycles enter through the weathering of rocks and minerals
nutrients (S) with hybrid cycles can enter both ways
What nutrients have sedimentary cycles?
P
Ca
Mg
K
Si
What brings supplementary soil nutrients into a terrestrial ecosystem?
wet fall: rain, snow (precipitation)
dry fall: airborne particles, aerosols
What happens as precipitations fall to the forests on earth?
rain from atmosphere land on tree canopies and down stems and pick up nutrients on leaves and stems
What is an example of how outputs represent a loss of nutrients from the ecosystem?
human harvesting (farming, logging)
Explain how human harvesting (farming, logging) affect nutrient flow in ecosystems?
human harvesting of plants/biomass is a permanent loss of nutrients from the ecosystem as the nutrients are being removed from the ecosystem and not contributing to cycling
How are nutrients lost through human harvesting replenished in the practice of farming? what is a consequence of this?
fertilizer application
a consequence of removing biomass and nutrients with it, and then applying fertilizers can cause leaching
Explain how fires affect nutrient flow in ecosystems?
fires convert standing biomass (ex. trees) and soil organic matter into ash
ash affects the chemical and biological properties of soil = many nutrients become readily available
What is a consequence of fires?
soil chemical and biological properties are changed by ash and this increases the amount of nutrients that are available
What process can phosphorous undergo because of a fire?
pyomineralization: rapid mineralization of phosphorous in the soil = rapid availability
Explain how the BGC cycle can be viewed from a global perspective?
usually, the output of one ecosystem is the input of another
ex. streamflows from the HB watershed flow into Mirror Lake (outputs from river ecosystem to inputs in lake system)
What other factors need to be considered when viewing the exchange of nutrients between ecosystems (global perspective)?
global circulation patterns
How is the concentration of CO2 measured in forests?
by measuring the [CO2] at different heights in the atmosphere with a meteotower with laser detectors for [CO2] over time
or through gas chromatography
Explain how height of [CO2] varies throughout a 24 hour period in forests
[CO2] is at highest concentrations closer to the soil in the mornings (12am-8am)
[CO2] is low and closest to tree heights during midday because of increased photosynthesis during peak light hours
[CO2] increases, height increases and decreases, in afternoon-midnight
??? graph super confusing
How does CO2 concentration vary throughout a 24 hour period? why?
it fluctuates because photosynthetic activity also fluctuates in response to daily sunlight and temperature changes
decreases after sunrise
begins to increase in afternoon
decreases sharply after sunset
Why is [CO2] always high on the forest floor?
respiration of soil microorganisms
Looking at a global and seasonal cycle, what happens to [CO2] in the winter in Alaska? in the summer?
[CO2] steadily increases from Nov to May as respiration > photosynthetic rates
[CO2] steadily declines from June-October as respiration < photosynthesis
How much carbon does the earth contain?
100 million gigatons (10^23 grams)
Where is most of the world’s carbon stored? does it contribute to the global carbon cycle?
sedimentary rock, doesn’t contribute globally
What is the amount of carbon from the global carbon pool that contributes to the global carbon cycle? how is it divided/what are its sources?
55000 Gt total
10,000 Gt from fossil fuels
38,000 Gt from oceans
- 1650 Gt from DOM
- 3 Gt from LOM
1500 Gt from DOM in soil
560 Gt from LOM in soil
750 Gt from atmosphere
How much carbon do fossil fuels contribute to the global carbon cycle?
10,000 Gt
How much carbon do oceans contribute to the global carbon cycle? describe what sources contribute
38000 Gt carbon in the form of bicarbonate (HCO3-) and carbonate ions (CO3-)
dead organic matter: 1650 Gt
LOM (phytoplankton): 3 Gt
How much carbon do terrestrial ecosystems contribute to the global carbon cycle?
DOM in soil: 1500 Gt
LOM in soil: 560 Gt
How much carbon does the atmosphere contribute to the global carbon cycle?
750 Gt
How does the contribution of oceanic carbon compare to that of terrestrial to the global carbon cycle?
oceans and terrestrial environments contribute roughly the same amount of carbon from DOM
oceans: 1650 Gt
soil: 1500 Gt
but living OM in soil contributes significantly more than in oceans
oceans: 3 Gt
soil: 560 Gt
What processes are involved in the carbon cycle?
photosynthesis for uptake and assimilation of CO2 from atmosphere
consumption and decomposition of carbon from living biomass into DOM
combustion produces CO2 in atmosphere
respiration of living organisms releases CO2 into atmosphere
Where is the main exchange site for CO2 between the atmosphere and ocean?
the surface of the ocean
What does the uptake of CO2 in the ocean from the atmosphere depend on?
reactions between CO2 from the atmosphere and carbonate (CO3^2-) ions in the ocean to form bicarbonate (HCO3-)
How is carbon physically circulated around the globe/oceans?
ocean currents and
through photosynthesis and the food chain (biological)
what is the net uptake of carbon in oceans/year?
1 Gt/year
What is the net loss of carbon from oceans? what process causes this loss?
0.5 Gt/year caused by sedimentation (geological)
Where does the net uptake of CO2 from the atmosphere/the carbon sink occur?
the terrestrial surface
How is CO2 taken up from the atmosphere by terrestrial ecosystems? how is it returned?
taken up by photosynthesis
returned by respiration (especially microbial decomposition)
T or F: more carbon is stored in living matter than in soils
false!! more carbon is stored in soils
1500 Gt in soil vs 560 Gt in living biomass
How does the average amount of carbon in soil vary around the earth (think of latitudes and biomes and decomposition)? why?
the average amount of C per unit volume of soil INCREASES from the tropical regions poleward to boreal forests and tundra
this is due to rates of decomposition
- latitudes closer to the poles are colder = slower decomposition = higher [C] in soil
- tropical/mid-latitudes are warmer = faster rate of decomposition = lower [C] in soil
Where is carbon mostly sequestered in cooler, polar regions like boreal forests/tundra? what about in tropic regions?
polar: more carbon stored in soil = slower decomposition
tropics: more carbon stored in biomass = faster decomposition
Where does the most accumulation of OM occur globally? what factors, then, contribute significantly to C decomposition?
in regions where decomposition is slow because of frozen or saturated soils
temperature and moisture content of soil are major influencers of decomposition
Rank the major carbon reservoirs on earth in order of highest carbon concentrations to lowest
rocks and sediments
oceans
methane hydrates
fossil fuels
terrestrial biosphere
aquatic biosphere
Briefly describe the oxic/aerobic carbon cycle
inorganic CO2 in the atmosphere is fixed into organic carbon by
a) oxygenic photosynthesis (via bacteria, cyanobacteria, or plants)
b) chemolithotrophy (using H2S as energy source to fix CO2)
oxygenic respiration converts organic C back into inorganic CO2 which is released into the atmosphere
Briefly describe the anoxic/anaerobic carbon cycle
inorganic CO2 from the atmosphere is
a) converted into acetate via acetogenesis to convert into OM
or
b) converted into OM via anoxygenic photosynthesis (uses H2S as energy source)
or
c) converted into methane (CH4) via methanogenesis which can then be converted back into inorganic CO2 via methanotrophy (oxidize CH4 > CO2)
then organic carbon fixed anoxically can
a) be converted into methane via methanogenesis (assisted by syntrophy) which is then converted back into inorganic CO2 by methanotrophy (oxidation of methane)
or
b) converted into inorganic CO2 via anaerobic respiration and fermentation
What is chemolithotrophy?
organisms that fix CO2 using energy from H2S
What are the 2 ways CO2 can be oxygenically fixed into OM?
chemolithotrophy or oxygenic photosynthesis
How is organic C oxygenically converted back into inorganic CO2?
aerobic respiration
What are 2 ways CO2 can be fixed into OM in anoxic conditions?
acetogenesis or anoxygenic photosynthesis (uses H2S as energy source)
What 2 ways can organic matter fixed in anoxic conditions be converted into inorganic CO2?
anaerobic respiration and fermentation
or
methanogenesis (assisted by syntrophy) to convert into CH4 then methanotrophy to oxidize CH4 into CO2
How does methanotrophy and methanogenesis contribute to cycling carbon?
in anoxic conditions:
a) CO2 can be converted directly into methane via methanogenesis and then oxidized by methanotrophs back into CO2
b) organic C can be converted into methane via methanogenesis + syntrophy and then CH4 can be oxidized into CO2 by methanotrophs
What function do methanotrophs have?
they convert CH4 (methane) into CO2 by oxidizing CH4
What process converts organic carbon into methane?
methanogenesis (and sometimes with help of syntrophy)
What is the major difference between anaerobic respiration and fermentation?
both occur in anaerobic conditions
in a. respiration: bacteria use nitrate, iron or sulphate as final e- acceptor
in fermentation, bacteria use an organic molecule as a final e- acceptor
Where do methanogens exist?
soil
sediment
insect and ruminants’ guts
explain how termites contribute to the carbon cycle
termites have bacteria and flagellate in their guts which contain enzymes to degrade cellulose
flagellates in termite guts have methanogens which contain the cofactor enzyme to convert CO2 into methane
ie., they produce and release a ton of methane
Where would you find a species like Isoptera zootermopsis (termites) in BC?
wet forests
How are the carbon and nitrogen cycles linked?
as primary producers convert CO2 into organic carbon,
if OC is high, N2 fixation is increased, which increases CO2 fixation = increases OC
if OC is low, N2 fixation is decreased,
the carbon cycle and nitrogen cycle both effect each other and can cause increases or decreases in the other cycle
CO2 fixation and N2 fixation
How does fixation of CO2 by primary producers into OC affect N2 fixation?
if production of OC is high, N2 fixation is increased, which increases CO2 fixation, which increases production of OC
if production of OC is low, N2 fixation is decreased, which decreases CO2 fixation, which decreases OC production
How does denitrification (nitate > nitrogen gas) link to the C cycle?
if denitrification (NO3- > N2) is increased, CO2 entering C cycle is decreased, decreasing amount of OC produced
How does [nitrate] in N cycle connect to the C cycle?
if NO3- is high, CO2 fixation into OX is high and denitrification into N2 is high
How does ammonium (NH4+) and nitrification (NH4+ > NO3-) connect to the C cycle?
if NH4+ is high, primary production is high and nitrification of ammonium (NH4+) into NO3- is high
if NH4+ is low, primary production is decreased
How is atmospheric N2 fixed?
Fixation causes N2 to split into two atoms of free nitrogen (2x N)
each combines with hydrogen = 2x ammonia (NH3)
What is the compound formula for:
nitrate
nitrite
nitrogen gas
ammonia
ammonium
nitrous oxide
nitrate = NO3-
nitrite = NO2-
nitrogen gas = N2
ammonia = NH3
ammonium = NH4+
nitrous oxide = N2O
What is the fixation of nitrogen?
atmospheric N2 into ammonia (NH3)
How much energy does N-fixation require (g of glucose needed to fix 1g of N)?
a LOT
to fix 1g of nitrogen, nitrogen-fixing bacteria need to use ~10g of glucose
Why do plant roots experience competition for NH4+?
2 groups of aerobic bacteria also use it for their metabolism
What is nitirifcation?
the process of OXIDIZING ammonium into nitrite (NH4+ > NO2-) and then nitrite into nitrate (NO2- > NO3-)
Is nitrification an oxidative or reductive process?
it’s oxidation of NH4+ to NO3-
What organisms convert ammonium (NH4+) into nitrite (NO2-) in the nitrification process?
Nitrosomonas, Nitrosolobus, Nitrosopumilus (Archaea)
Oxidation is the loss or gain of hydrogen? reduction?
oxidation is the LOSS of hydrogen ions
reduction is the GAIN of hydrogen ions
What organisms convert nitrite (NO2-) into nitrate (NO3-) in the nitrification process?
Nitrobacter oxidize nitrite (NO2-) further into nitrate (NO3-)
Why is NH4+ oxidized into nitrate after it’s been converted into nitrite?
because nitrate is more stable and plant available
What happens to the nitrate produced by nitrification?
it can be taken up by plant roots or released into the atmosphere via denitrification
Who discovered nitrification and isolated Nitrosomonas?
Winogradsky ~1890
What is denitrification? what type of conditions does it occur in?
the process of REDUCING nitrate (NO3-) into nitrous oxide (N2O) and N2
anaerobic conditions rare and seasonal to terrestrial ecosystems
What organisms denitrify nitrate into N2?
Pseudomonas sp, mainly, and other diverse bacteria that contain reductase enzymes (Bacillus and Paracoccus)
What happens to the nitrogen that has been denitrified?
N2O and N2 are released into the atmosphere
What type of ecosystem is denitrification most common in? why?
wetland ecosystems and bottom sediments in aquatic ecosystems because denitrification occurs only in anaerobic conditions
What processes / activities / ecosystem components contribute to global N cycling?
N fixation
nitrification
denitrification
human activities
internal cycling in terrestrial and aquatic systems
lightning fixes N2
Describe the N cycle in oxic conditions
N2 fixation into NH3 (ammonia)
then
a) nitrification of NH3 into nitrite (NO2-) and then into nitrate (NO3-). Nitrate is then either assimilated into proteins as NH2 and ammonified into NH3, or DRNA converts it back to NH3 . OR nitrate enters anoxic cycle
or
b) NH3 is assimilated into NH2 protein groups, ammonification then converts NH2 back into NH3
Describe the N cycle in anoxic conditions
N2 is fixed into NH3
a) NH3 is assimilated into proteins as NH2 and then ammonified back to NH3
NO3- from oxic cycle enters:
NO3- associates directly with DRNA and becomes NH3
NO3- is converted to nitrite (NO2-) which is then:
a) NO2- associates with DRNA and becomes NH3
b) NO3- is denitrified into NO2- which is further denitrified into N2
c) NO2- is converted into NO and N2O and then N2
d) NO2- is directly anammoxed into N2
N2 is fixed into NH3
Give some examples of organisms that fix N2 into NH3?
aerobic:
- cyanobacteria
- azotobacter
anaeorobic:
- Clostridium
- purple and green phototrophic bacteria
- methanobacterium (Archaea)
symbiotic (in legume roots or alder trees):
- rhizobium
- bradyrhizobium
- frankia
What organisms can do ammonification (organic N to NH4+)?
many organisms
What is anammox?
the anoxic ammonia oxidation into N2
NH3 + NO2- > N2
What organisms can do anammox?
Brocadia
Which prokaryotes can fix N2 in legume roots? alder trees?
legumes: rhizobium and bradyrhizobium
alders: frankia
all symbiotic
Which type of N2 fixing organisms are in Mirror Lake?
Cyanobacteria (aerobic)
What processes result in losses of nitrogen from the biosphere?
denitrification and anammox both involve converting nitrogen compounds in the biosphere into N2 gas
In what ways has human activity altered the global nitrogen cycle?
land conversion from forests and grasslands into agriculture fields and the application of fertilizers to these fields = imbalance of fixation and denitrification
vehicle exhaust and combustion contribute N2O, NO, and NO2 to the atmosphere - N2O + atomic oxygen = ozone
T or F: phosphorous has no gaseous cycle and therefore no atmospheric pool
true, Phosphorous has only sedimentary cycle
How is phosphorous cycled between ecosystems?
only cycled between land and ocean, not through the biogeochemical cycle (is not gaseous)
Where are the main global reservoirs of phosphorous?
in rock and natural phosphate deposits
How is phosphorous released from rocks and deposits?
weathering, leaching, erosion, mining
How much of the total global phosphorous is usually available in soils for plants?
very small portion
What regulates phosphorous availability to plants?
internal nutrient cycling
What are the 3 states in which the phosphorous cycle moves in freshwater and marine ecosystems?
particulate organic phosphorous (Pp)
dissolved organic phosphates (Po)
inorganic phosphates (Pi)
How does phosphorous enter lakes and oceans?
it’s exported from terrestrial ecosystems
What are common inputs of phosphorous in aquatic ecosystems from terrestrial? where do these contributors source their phosphorous?
industrial activities and food/fertilizers/agricultural activities input Pi into water systems
Pi comes from guano/manure, phosphate rock weathering and mining
sediment build up returns Pi to phosphate rocks
How is phosphorous circulated within aquatic systems?
Po released from dead organic matter and excretions, taken up by bacteria which produce Pi and release it into the water
How is phosphorous circulated within terrestrial ecosystems?
Po in dead organic matter is decomposed and mineralized into the soil into Pi which is taken up by plants and then consumed by animals
How much phosphorous is in the atmosphere globally?
very little, airborne transport = ~1*10^12 g P/yr via soil dust or sea spray
How much phosphorous is transported from rivers to oceans globally? how much of this is available for NPP? what happens to the rest of it?
21*10^12 g P/yr
of this, 10% is available for NPP the rest is deposited in sediments
What unit of measurement are both N and P measured in? What about C?
N and P in teragram/yr
C in gigaton/yr
Where is most of the global phosphorous stored?
in sediments (highest)
in oceans
soils (second highest)
minable rock
T or F: internal cycling of P in marine ecosystems is high
true
What type of BGC cycle does sulfur have?
hybrid - both sedimentary and gaseous
What form does sulfur have in atmosphere?
H2S
What are the atmospheric sources of S (H2S)?
fossil fuel combustion
volcanic eruptions
ocean surface exchange
decomposition
How is H2S converted into a form that can be an input in surface ecosystems?
it interacts with O2 to produce water soluble SO2 (sulfur dioxide) which is then released to the surface in precipitation as H2SO4 (sulfuric acid)
What form of sulfur is transported to surface ecosystems through precipitation? what does this input lead to?
H2SO4 - sulfuric acid (weak)
leads to acidification of surface systems which require buffers to prevent this change
What are the steps of atmospheric sulfur conversion into surface ecosystems (sulfide/sulfur oxidation)?
atmospheric H2S + O2 = atmospheric SO2 (soluble)
SO2 + H2O = H2SO4 in rain
What happens to sulfur when it enters terrestrial ecosystems?
plants take it up and assimilate it through metabolic processes (photosynthesis starts it) into sulfur-containing amino acids which are transferred to secondary consumers when PP are consumed
What returns sulfur to the soil and sediments after its been metabolized by plants and entered the food chain?
death and excretion release sulfur
What form of sulfur is released by bacteria?
hydrogen sulfite (HSO3) or hydrogen sulfate (H2SO4)
T or F: different types of bacteria have different interactions with sulfur
true, colourless, green, and purple bacteria have distinct interactions
what are sedimentary sources of sulfur?
pyritic rocks that contain FeS when weathered or mined release sulfur
ex. feltspar, mica
What are 2 examples of pyritic rock?
feltspar, mica
What happens when pyritic rocks release sulfur?
FeS reacts with O2
produces FeSO4 (ferrous sulfate) and sulfuric acid if water is also present
What compound released from pyritic rocks is commonly found in the Saanich Inlet? how can we tell it’s present?
FeSO4 preciptate, it’s a dark black compound
How are FeSO4 (ferrous sulfate) and sulfuric acid harmful to aquatic ecosystems?
they can acidify the water and kill aquatic life
Is the sulfur cycle more important in marine or terrestrial ecosystems?
marine
methane has larger impact in terrestrial cycles
What are the key processes in the sulfur cycle?
sulfide/suflur oxidation into sulfate (H2S > S > SO4^2-)
- aerobic and anaerobic
Sulfate reduction (SO4^2- > H2S)
- anaerobic
sulfur reduction (S > H2S)
- anaerobic
sulfur disproportionation
organic S oxidation or reduction
desulfurylation (organic S > H2S)
What are some examples of prokaryotes that contribute to sulfide or sulfur oxidation in aerobic conditions? H2S > S > SO4^2-
sulfur chemolithotrophy by Thiobacillus, Beggiatoa (colourless), etc
What are some examples of prokaryotes that contribute to sulfide or sulfur oxidation in anaerobic conditions? H2S > S > SO4^2-
purple and green phototrophic bacteria, some chemolithotrophs
Give a local example of where you’d fine aerobic sulfide/sulfur oxidizing prokaryotes?
Beggiatoa can be found in Saanich Inlet
Give a local example of where you’d find anaerobic sulfide/sulfur oxidizing prokaryotes?
purple and green phototrophic bacteria can be found at Mt Doug
What are some examples of prokaryotes that contribute to sulfate reduction? (SO4^2- > H2S) is this process aerobic or anaerobic?
anaerobic
soil and sediment
Desulfovibrio, Desulfobacter, Archaeoglobus (Archaea)
What are some examples of prokaryotes that contribute to sulfur reduction? (S > H2S) is this process aerobic or anaerobic?
anaerobic
many hyperthermophilic Archaea
Desulfuromonas
What is the major source of oxygen globally?
the atmosphere
What 2 processes generate the production of oxygen in our atmosphere?
degradation of water vapour: 2 H2O > O2 + 4H+
photosynthesis: H2O + light + CO2 > O2 + CnH2nOn
What is expected for the net atmospheric amount based on the processes of respiration and photosynthesis? is this the case?
it’s expected that oxygen lost from aerobic respiration would balance the oxygen gained from photosynthesis
not true. the amount of oxygen in our atmosphere has surpassed the amount used in respiration
What are all the sources of O2?
breakup of water vapour
photosynthesis
water and carbon dioxide linked by photosynthesis
How is oxygen biologically transferrable?
it can be exchanged biologically through different molecules transformed by living organisms
ex. hydrogen sulfide oxidation to sulfates releases O2
ex. ammonia oxidation to nitrates releases O2
What did a female Stanford scientist discover about oxygen? explain
H2O is a source of O for organic carbon oxidation
she found that input of H2O causes the carbon benzene ring with S-CoA to open and initiate the central acetyl-CoA pathway that leads to the Kreb’s cycle of ATP generation
What attribute of O2 makes the O cycle so complex?
oxygen is highly reactive so it’s involved in many different reactions
ex. photosynthesis, respiration, and carbonate, nitrate, and ferric oxides production
What are 3 reactions that remove oxygen from cycling?
CO2 + Ca = carbonates
O2 + nitrogen compounds = nitrates
O2 + Fe compounds = ferric oxides
What is ozone (O3)? How has it been affected by human actvities?
it’s an atmospheric gas in the stratosphere that protects the planet from harmful UV radiation
unregulated use of CFCs depleted ozone layer
What are two examples of compounds that link biogeochemical cycles?
nitrate contains nitrogen and oxygen
apatite contains phosphate and calcium
Do heterotrophs and autotrophs require nutrients in the same proportions for every process?
no, they require different proportions for different processes
which process has fixed proportions of nutrients?
photosynthesis of hydrogen, carbon, and oxygen
What considers the quantitative relationships of elements working in combination ?
stoichiometry
How is Liebig’s law of the minimum involved in BGC cycling?
one limiting nutrient can effect other nutrient cycles because of plant requirements
What is a major example of how Liebig’s Law of the Minimum applied to Nitrogen influences another cycle?
nitrogen availability effects a plant’s ribusco concentration
a plant’s rubisco concentration determines the photosynthetic rate and carbon assimilation
therefore, the C cycle is directly affected by the N cycle
What is rubisco?
arguably the most important enzyme in the biosphere as it allows CO2 to be incorporated into plant cellulose and drives the Calvin/Kreb’s cycle
Ribulose-1,5-bisphosphate carboxylase/oxygenase
How has the human application of nitrogen-based fertilizers and fossil fuel use disrupted the N-cycle?
significantly increased nitrogen oxides in atmosphere
increased N deposition in soil (in areas where it’s occurring the amount may not be significant, but if it’s transported to forest ecosystems = highly significant)
What are 6 soil types mentioned?
brown chernozem
black chernozem
gray brown luvisol
humo-ferric podzol
humic gleysol
melanic brunisol
What regions would you expect to find brown and black chernozem?
Grasslands, prairies, Russia, Kelowna
What regions would you expect to find grey brown luvisol?
Northern BC
What regions would you expect to find humo-ferric podzol?
east coastline
What regions would you expect to find ferrel-humic podzol?
west coastline + VI
What regions would you expect to find humic gleysol?
Fraser Valley, super saturated
What regions would you expect to find melanic brunisol?
Garry Oak, interior
Which soils require highest Nitrogen inputs to grow wheat crops? least?
highest: humic gleysol because very water saturated soils
least: brown chernozem (ideal for farming)
How are layers arranged in the soil?
in horizons
surface
organic layer (litter)
mineral (A) - clay, silt, sand
mineral (E)
bedrock
What is Ae soil layer?
eluviation in soil where water brings Fe lower in the horizon (white layer)
What is Bf soil layeR?
iron rich layer
red in colour
What influences the rate of N uptake by plants and N concentration in plant tissue?
soil nitrogen concentration
What type of relationship exists between photosynthetic capacity and leaf nitrogen? what is the trend?
strong relationship because N-based enzymes and pigments are used in photosynthesis
trend: as [N] increases, NPP increases (to a point)
What is nitrogen saturation? what occurs if this happens?
when other nutrients become more limiting than nitrogen, ecosystems are nitrogen saturated and become less productive
What happens when N-mineralization is too high?
NPP decreases
NO3- is leached at higher rates and nitrification increases
when NPP decreases, Ca:Al and Mg:N ratio decrease = more are released into the soil
What is a consequence of nitrate leaching?
soil acidification because SO3- loss = base cations lost
increases soil toxicity as Aluminum ions increase due to loss of buffering
What happened to N leaching in european forests when N deposition increased?
As N deposition increased, N leaching also increased
what did the study on spruce populations in northeastern US find?
as nitrogen levels increased, leaf Ca:Al ratios decreased which reduced tree growth due to reduced uptake of Ca
How does uptake of Ca affect trees growth?
Ca is required for sapwood
less Ca = less sapwood = less water transport = decreased leaf amount = decreased CO2 uptake = decreased growth
other than Ca, what other micro-nutrient affects tree growth?
Mg because it’s important in chlorophyll
