Hubbard Brook Flashcards
How can evapotranspiration be calculated from HB field data of forested watersheds?
P = S + ET
ET = P - S
where ET = evapotranspiration
P = precipitation (input)
S = streamflow (output)
What is considered nutrient input in a forested ecosystem like HB, according to Likens and Boorman?
precipitation (P) carrying chemicals
What is considered nutrient output in a forested ecosystem like HB, according to Likens and Boorman?
streamflow chemicals (S)
What is the mathematical relationship between precipitation and streamflow at HB?
P = ET + S
as P increases, S also increases (linear)
ET will not change over time because the buffer is maintained, the amount retained remains stable
What is the main source of silica at HB?
weathering of rocks
What is the fate of nitrate (NO3-) from precipitation during summer at HB?
Are nutrients lost evenly throughout the year in the streamflow at HB? explain
no
there’s a peak in the spring with the snowmelt (S > P) and a decline in the summer when there’s more water taken up by plants (S decreases)
What is the impact of clear cutting on mineral nitrogen?
huge loss of NO3- from leaching
How does Douglas-fir vary in nutrient budgets for Ca, Mg, K? explain
define mixotrophy
when organisms are both photosynthesizers and hetertrophs
Is mixotrophy important in Mirror Lake? where, why?
yes!! because they can photosynthesize and consume other organisms
common at surface in summer when lots of light
common throughout water column when less light
What kind(s) of cyanobacteria are found in Mirror Lake?
anabaena
chroococcus
merismopedia
Why are the cyanobacteria(s) found at Mirror Lake important?
because they are mixotrophs
Anabaena and Chroococcus can also fix N2
Who were the major authors from the HB models?
Likens and Bormann
What years did the HB study run?
1963-2013
What were the major papers published from the HB study?
Likens, G.E. (2013). Biogeochemistry of a Forested Ecosystem
Bormann, F.H., Likens, G.E. (1979). Pattern and process in a forested ecosystem
Likens, G.E. (1985). An ecosystem approach to aquatic ecology: Mirror Lake and its environment
What was the main lake involved in the HB model ecosystem study?
Mirror Lake
According to Likens and Bormann, what moves the inputs and outputs of ecosystems?
meteorlogic (atmospheric), geologic, and biologic drivers
in the conceptual model for HB, what are the inputs to an ecosystem?
meteorlogic (atmospheric) inputs
particulates in the air and gaseous particles
in the conceptual model for HB, what components are part of the intrasystem cycle of an ecosystem?
nutrients that have no prominent gaseous phase and cannot leave the boundaries of the ecosystem
organic compartment:
- living plant mass
- animal biomass (herbivore, carnivore, detritivore, omnivore)
- dead biomass (litter, dead animals)
available nutrients:
- on exchange sites
- in soil
primary and secondary minerals:
- mineral (rocks)
- precipitation
How are atmospheric inputs connected with the organic component of an ecosystem in the conceptual model?
atmospheric inputs are taken up by living organisms
and organisms release gases into the atmosphere
How are atmospheric inputs connected with the available nutrients of an ecosystem in the conceptual model?
atmospheric inputs are either wet or dry
wet: precipitation (snow, rain)
dry: ash, dust
are deposited onto plants or soil surfaces
organisms and soil release gases into the atmosphere
How are minerals connected with the available nutrients of an ecosystem in the conceptual model?
minerals can be released and become available through weathering of rocks
available nutrients can form secondary minerals and add to the mineral component
How are the organic components connected with the available nutrients of an ecosystem in the conceptual model?
living organisms can immobilize (uptake) forms of nutrients
living organisms can mineralize nutrients in the soil, leaching of nutrients, throughfall, streamflow, exudation of nutrients to enter soil
In the conceptual model, what represents P in a watershed ecosystem?
P = precipitation (inputs)
the atmospheric (wet and dry deposition/precipitation), geologic, and biologic inputs
majorly precipitation
In the conceptual model, what represents S in a watershed ecosystem?
S = streamflow (outputs)
the atmospheric, geologic, and biologic outputs
In the conceptual model, what represents ET in a watershed ecosystem?
ET = evapotranspiration
the biological release of gases
Where is the HB watershed?
New Hampshire, USA
How many watersheds are in the HB?
6
Describe the geographic region surrounding the HB watershed experiment
In New Hampshire, USA
the watershed is proximal to Mt Cushman (977m) and Mt Kineo (1015m) all with rivers/streams running down to Mirror Lake (213m)
Which watershed at HB was clearcut? when?
in 1966-67, watershed 2 was clearcut
Which watershed at HB was the control?
watershed 6
What was the unit of study for the HB?
watersheds
What was the scientific approach to studying the hydrology of HB?
small watershed approach
devices (buckets, funnels) in multiple locations used to measure the inputs (precipitation in mm/yr) and concentrations of chemicals sampled
and weirs at independent streams were used to measure the outputs (streamflow in mm/yr) and concentrations of chemicals sampled
ET = P - S
Generally, how will the volume of water delivered through streamflow vary?
daily, seasonally, annually
describe the average hydrologic budget (water volume for P, S, ET) for watershed 6 measured from 1963-2009
P was highest at 1400 mm/yr
S was mid btw 800-1000 mm/yr
ET was lowest ~500 mm/yr
P was measured at 1400 mm/yr in watershed 6, how does this compare to volume of input in Victoria? Kamloops? Tofino?
pretty high
Victoria ~
Kamloops very low
Tofino very high ~3000 mm/yr
What part of Vancouver Island does watershed 6’s P compare to?
Campbell River
~1400 mm/yr
Which two components of measuring hydrology in HB are correlated when looking annually?
P and S
with increased P, S increased
but P always higher than S
When looking annually, how does ET compare to P and S in watershed 6? is it correlated/related?
ET is not correlated with P and S and does not follow the same trend
ET remains fairly constant because P - S = ET
when looking monthly, how do P and S trend in watershed 6?
P remains fairly constant with little seasonal variation
S increases in winter months because uptake of water by plants slows down during these months
S significantly increases and surpasses P in the spring because snowmelt
Why is precipitation higher than streamflow in watershed 6 in most months?
most of the year, plants are taking up water and photosynthesis is
Which variables, when annual ppt is plotted against annual streamflow or ET has significant correlation? what does this mean for the ecosystem?
precipitation and streamflow are significantly positively correlated
this means that the ecosystem is limited by precipitation
Based on the standard errors of the mean for the 4 watersheds’ P, S, and ET values, is the small watershed method accurate?
yes, the standard errors were between 0.45-1.30
high confidence in the values
Why is streamflow higher than P in the Spring?
snowmelt increases with warming weather = huge output of water flow in the streams
Why is there a peak in streamflow in the Fall months?
In the Fall, the uptake of water by plants is decreasing, so the amount of water leaving the watershed will be higher
In watershed 6, are the concentrations of Si, Ca, sulfate (SO4^2-) higher in P or S? why?
higher in S because Si, Ca, and Sulfate all have mineral inputs (sedimentary BGC cycles)
they do not enter the system from the precipitation, but from the rocks/minerals
In watershed 6, is nitrate (NO3-) higher in P or S? why?
higher in P
because Nitrogen has a gaseous BGC cycle and the major input of N is from the atmosphere
How do the minerals measured in watershed 6 (Ca, Sulfate, Nitrate, silica) compare to each other in their concentrations in P and S?
Ca, SO4^2-, and Si are in higher concentrations in the streamflow because their inputs are from sedimentary cycles - mineral/rock weathering
whereas,
nitrate (NO3-) is higher in P because its input is from the gaseous cycle - atmospheric input
What did the HB study of H+ ions in precipitation show? how is this related to acid rain?
because acid rain was a huge problem in the 1970s, and was addressed by decreasing/regulating use of sulfur in human activities,
[H+] ions in precipitation decreased over periods of years as precipitation became less acidic
How was the issue of acid rain addressed?
regulating the use of sulfur and NOx for human activities
H+ ions in P decreased over years and the HB study showed this
What was causing the problematic acid rain?
emissions of sulfur (SO2) and nitrogen based chemicals (NOx) from the US
How did HB show ecosystem recovery as sulfur and nitrogen-based chemicals were becoming more regulated in the US?
Watershed 6 showed recovery as the concentration of basic cations increased in the streamwater (S)
base cations have buffering capacities to neutralize acidic ions
How does acid rain harm watershed ecosystems? how can we chemically measure that this is happening?
as H+ ions increase in the P inputs, the watershed system loses it’s capacity to buffer acidic ions = less base ions in S
What did the HB study find about the affect of acid rain on cation concentrations in P and S in watershed 6?
Ca, Mg, K, Na were higher in the stream water than in precipitation, but were all decreasing in [] in the streamflow over years
this means that less cations are present in the streamflow, lowering the capacity of the system to buffer the acidity being inputted
Why are the units to measure concentration of Ca, K, Mg, Na different than for measuring P and S?
the units to measure the nutrients need to account for some nutrients have single charges or double charges
ex. Na+ vs. Ca2+
In watershed 6, why does the H+ ion decrease in P but not in S over time? why does H+ decrease over time in P? (over years)
As NOx and SO2 emissions are regulated and decreased, the amount of H+ ions in the P will decrease
H+ is constant in the streamflow, this means that more is being retained in the system than lost = H+ is buffered within the system
What is the difference between ammonium and nitrate in watershed 6 P and S? why is there a difference? (over years)
Ammonium in P is higher and is stable in S = ammonium is positively charged so it adheres tightly to clay particles within the system is harder to lose in the S
nitrate’s P and S overlap and follow the same decreasing trendline:
nitrate is negatively charged and is repelled by clay particles, so it’s easier to be lost in the S
How does sulfate compare to nitrate and ammonium in terms of P and S for watershed 6 (over years)?
Sulfate is much higher in the stream flow than in the precipitation
this is because S has both a sedimentary and gaseous cycle, whereas N (nitrate and ammonium) are both gaseous only
How can we tell that the system is acting as a buffer for acid rain in watershed 6?
looking monthly
the concentration of H+ is higher in precipitation than in the streamflow which has stable concentration
stable concentration of H+ in the stream flow means that more of the H+ coming in from P is being retained by the system (not lost in S) = the system is buffering the H+ ions
What is throughfall?
precipitation that falls through plant leaves
What is stemflow?
precipitation that falls along plant stems
how is the net change of solutes in precipitation calculated for watershed 6?
precipitation under canopy - precipitation over canopy = net change
What does the net change of solutes in precipitation mean for the biology of watershed 6? Use calcium as an example
the net change for the method that included stemflow in the under canopy measurements was significantly larger than that for the method that only considered throughfall
so, stemflow is enriched with nutrients and acts as an important input of nutrients in the soil
ex. Calcium
Calcium was much higher under the canopy when both throughfall and stemflow were considered (0.67 v. 0.41) = higher net change in Calcium overall (0.45 v. 0.09)
so calcium increases from the stemflow P
What are some examples of organisms on tree stems that can contribute to the nutrient input in stemflow?
moss and lichen have Ca, N, and some N2 fixing bacteria (lichen)
What was n for watershed 6?
46 years
study ran from 2009-1963 = 46 years
Which key nutrients had mean net losses from watershed 6 over 46 years?
sulfate
Dissolved organic carbon
dissolved silica
Which key nutrients had mean net gains from watershed 6 over 46 years?
ammonium
nitrate
phosphate
Are nutrients lost or gained from the system when P > S?
gained (less in streamflow)
Are nutrients lost or gained from the system when P < S?
lost (more in streamflow)
why are there peaks of losses of key nutrients from watershed 6 in the spring and fall?
this is driven by the hydrologic cycle
during spring there’s the snowmelt and during fall there’s more precipitation than plants are taking up
Overall, there’s a monthly average loss or gain of cations in watershed 6 over the 46 years?
losses of Ca, Mg, Na, Al, and Si
= higher in S than P
Overall, there’s a monthly average loss or gain of H+, ammonium, and phosphate in watershed 6 over the 46 years?
gain
higher in P than S
Why are the average fluxes of ammonium, phosphate, and H+ higher in P than S?
these nutrients are being retained in the system
some of the differences are significant, but not all
why did K, sulfate, chloride and dissolved organic carbon have seasonal variation in S but not P in watershed 6 when looking at monthly averages for 46 years?
they follow the hydrologic cycle as well, so the increase of water flowing out of a system in spring and fall due to snowmelt and lack of water intake by plants increases the loss of these nutrients
what does the average flux of nitrate in watershed 6 (over 46 years, looking at monthly averages) tell us?
nitrate has seasonal variations in loss in streamflow with
peak in april with high water flow
dramatic dip in summer months to the fall = nitrate is tightly regulated because it is needed for photosynthesis
How did the concentration of calcium change in the HB ecosystem from 1963-69 to 1987-92?
aboveground biomass increased
below ground biomass increased
throughfall and stemflow decreased
leaf litter remained the same
why is stored calcium (in living biomass) higher in 1987-92 than in 1964-69?
stored calcium in living biomass increased because the system improved at retaining Ca from the stemflow and throughfall
stemflow and throughfall decreased over time - this calcium is being stored in biomass instead of lost in streamflow
How did the concentration of sulfur change in the HB ecosystem from 1964-69 to 1993-98? what does this mean?
higher concentration in above and below ground biomass
decrease in stemflow/through fall and decreased P input
this means concentrations of S in the atmosphere decreased (emissions reduced) and more sulfur is being retained by the system than lost in streamflow outputs
How can NPP be an indicator of ecosystem recovery from acid rain?
if nitrogen is being retained by a system, NPP will increase, and the ability to retain and uptake NO3- instead of it being leached in the streamflow means that there’s more plants photosynthesizing
What did the second HB study look at?
how BGC cycles are effected by clear cuts (long term disturbances)
Which watershed was used as the experiment in the second model?
watershed 2 was clearcut
What is the overall trend of nitrogen retention in HB?
in every season, there’s a decrease in the years between 1960-1985ish or so
there was overall, less nitrogen being retained annually in those years, but has since increased (due to increased buffering capacity of system and decreased S and NO emissions in P) to more seasonal variation than annual
varied in fall, spring and winter, stable in summer
What is ecosystem succession? How was the second model based on this?
it’s the gradual succession of plant growth after a major disturbance over many years
a disturbance was induced on watershed 2, it was clear cut, then the scientists studied how it rebounded
What are the 4 stages of forest succession?
disturbance - watershed 2 clearcut
- reorganization phase - new plant species begin to grow
- aggradation phase -
- transition phase - dominant species begin to replace pioneer species
- steady state phase - decomposition = production (production has slowed down to the rate of decomposition) -mature forest
How does decomposition compare to production during the reorganization phase?
D»_space; P
How does decomposition compare to production during the aggradation phase?
D «_space;P
How does decomposition compare to production during the transition phase?
D < P
How does decomposition compare to production during the steady state phase?
D = P
How were the succession phase boundaries measured?
by determining tree community composition
defining the forest structure by determining importance values of trees
What are importance values? how are they calculated?
the weight of contribution of trees to the forest community structure
calculated by measuring
Diameter at Breast Height (DBH)
frequency (# of a single species/total trees)
density (# single species species/ rn^2)
What method was used or could be used to measure importance values of trees?
Transects of different trees at different elevations
What were the types of trees in this HB study?
Large DBH:
Sugar maple (Acer saccharum)
Yellow birch (Betula alleghamensis)
Beech (Fagus grandifolia)
Paper birch
balsam fir
red spruce
mountain maple
striped maple
mountain ash
Which trees had highest importance values overall and therefore dominate the forest?
Sugar maple and beech mostly but
also yellow birch
their values decrease at high elevations
Which species were more dominant at higher elevations (still with low IV)?
Paper birch
balsam fir
red spruce
mountain maple
striped maple
mountain ash
what is unique about American Beech’s leaves?
they do not lose their browning leaves until the following season - they have incomplete abscission
What does looking at the flow of energy (carbon) in the control (watershed 6) show us for what we would expect in a healthy, uncut ecosystem?
High carbon input (high NPP) and very low carbon output
carbon is highly retained in the system
How did the clearcut effect P, S, and ET in watershed 2 compared to watershed 6? explain
Precipitation didn’t change (they’re in the same geographic region)
Streamflow rapidly increased in W2 (way above W6)
ET rapidly decreased in W2 compared to W6
S increase in W2 would be caused by less plants present to uptake water entering as P
ET decreases for the same reason, there’s nothing there to retain the water
How did the clearcut effect Ca, K, and nitrate in S in watershed 2 compared to watershed 6? explain. Which of the 3 was the most significant loss?
Ca, K, and nitrate all increased significantly in S in W2 and remained relatively constant in W6
with no plants present to assimilate these nutrients, they would easily leach out of the system through streamflow
nitrate was lost most significantly, NO3- is very water soluble and easily lost
which nutrient was most significantly lost from W2 after the clearcut?
Nitrate
What explains this massive loss of nitrate from W2 after the clearcut? which succession phase does this occur in?
Microorganisms are continuing to decompose OM and mineralize ammonium and convert it into nitrate, but now there’s no plants present to uptake the nitrate and because it’s water soluble, it’s easily lost
occurs in the reorganization phase
Approximately how long was the reorganization phase?
~6 years to resemble something like the prior forest
How did they determine the forest was recovering from the clearcut?
after ~6 years of increased losses of Ca, K, nitrate and OM in streamwater
the streamwater started showing decreasing concentrations of these = more were being retained
what did they find in terms of forest community structure after 20 years?
groundcover (herbs, shrubs) and saplings decreased significantly and trees increased significantly
a slow transition of components as trees replace one another
ex. Prunus replaced by Betula replaced eventually by Acer saccharum (sugar maple) and Fagus grandifolia (beech)
How does GPP compare in an old-growth Douglas-fir forest to an eastern deciduous forest (like HB)?
DF > eastern
How does NPP compare in an old-growth Douglas-fir forest to an eastern deciduous forest (like HB)?
similar NPP but eastern slightly higher
How does net ecosystem production compare in an old-growth Douglas-fir forest to an eastern deciduous forest (like HB)?
NEP = GPP - ecosystem respiration
equivalent NEP even though different contributors and very different GPP
high GPP - high ecosystem respiration = low NEP (DF)
low GPP - low ER = low NEP (eastern)
How does overall ecosystem productivity (NEP/GPP) compare in an old-growth Douglas-fir forest to an eastern deciduous forest (like HB)?
eastern deciduous forests are more productive overall than DF
Why would eastern deciduous forests have lower maintenance efficiency and autotrophic respiration than an old-growth DF forest?
DF forests are mostly coniferous trees that do not lose leaves seasonally, whereas deciduous trees drop leaves seasonally = less respiration
How do P, S, and ET compare in an old-growth Douglas-fir forest to an eastern deciduous forest (like HB)?
P is much higher in DF, so S and ET are both going to be higher (there’s just more water moving through the system)
but
ET % is higher in deciduous than in DF (48% in deciduous v. 34% in DF)
How does net loss of Ca, Mg, and K compare in an old-growth Douglas-fir forest to an eastern deciduous forest (like HB)?
DF has much higher net losses of these nutrients than ED
How does the total loss of nitrogen in a DF forest that has been burned by a wildfire compare to an undisturbed one?
undisturbed has no loss, actually accumulates
wildfire DF forest has significant loss (736 kg per ha per yr) via volatilization and leaching
which lake did Likens and Bormann study for the HB experiments?
Mirror Lake, downstream from the watersheds
why did they study a lake ecosystem?
because lakes receive inputs from terrestrial systems
In lakes, how are O2 and CO2 affected with depth?
dissolved O2 decreases and CO2 increases
which nutrients were very high in the lake during Spring months? why?
dissolved silica and nitrate
because snowmelt, increased streamflow input carrying these nutrients from the terrestrial systems
What method is used to study bacterial populations in lake water columns?
there’s a few: microscopy, hemacytometer, or petroffauser method
Which method to study bacterial populations did they use for mirror lake?
Petroffhauser method - a smaller volume of liquid
and DAPI (fluoro dye) to count live cells
What did they find for bacterial populations in mirror lake?
the decrease of O2 with depth is correlated to increase of bacterial uptake of O2
bacteria concentrations increase with depth in summer but remain constant in winter
How did phytoplankton biomass vary seasonally in mirror lake?
decreased in fall/winter with decreasing T
increased in spring/summer with increasing temperature
What are the 3 important bacteria in Mirror lake? Which is most common?
all 3 are cyanobacteria
Anabena
Chroococcus (most common)
Merismopedia (least common)
What depths are Anabena most common in Mirror Lake in summer and winter?
Summer most common at 3m (shallow)
None in winter
What depths are Chroococcus most common in Mirror Lake in summer and winter?
Summer most common at 3m, but found at fairly high [] at all depths
None in winter
What depths are Merismopedia most common in Mirror Lake in summer and winter?
Summer most common at 6m (deeper)
none in winter
What is unique abut Anabena and Chroococcus and lacking in Merismopedia?
Anabena and Chroococcus (especially C) are N2 fixers
Merismopedia doesn’t fix N2
Describe Chroococcus
it’s a unicellular cyanobacteria that contains nitrogenase for fixing N2 at night and does oxygenic photosynthesis with O2 and light
it is the most abundant N2 fixer in Mirror Lake
describe Anabaena
it’s a filamentous colonial cyanobacteria that contains a heterocyst for fixing N2
less abundant in Mirror Lake
very efficient N2 fixing and photosynthesis because they can occur at the same time unlike Chroococcus
Describe Merismopedia
polysaccharides surround cell walls to keep a bunch of cells together in a checkerboard like fashion
does not fix N2
What makes Anabaena more efficient at N2 fixing and photosynthesis than Chroococcus?
Anabaena has a heterocyst that uses energy produced by photosynthesis to conduct N2 fixation - they occur simultaneously
whereas
Chroococcus does not have a separate domain for the two processes so N2 fixation must occur at night so photosynthesis can occur during the day
Describe the succession of phytoplankton populations in Mirror Lake over a year (seasonal)
early summer: diatoms and Chrysophyceae (Dinobryon)
late summer: Cyanophyceae (cyanobacteria) and Peridineae (dinoflagellates)
Winter: Cryptophyta and Chrysophyceae (Dinobryon)
Which of the dominant phytoplankton found in each season are mixotrophs?
Chrysophyceae (Dinobryon)
Peridineae (Dinoflagellates)
Cryptophyta
Why do mixotrophs exist at both the water surface during the summer and throughout the water column in the winter?
Because they can photosynthesize and consume other organisms for energy
What is the cell wall of cyanobacteria made of?
peptidoglycan
Explain the C14 fixation by bacteria study
in a microcosm, 14CO2 is added to a sample of lake water and incubated
then filtered at 0.45 um
cells stick to filter and liquid scintillation can be used to measure 14C
What month was daytime 14C fixation by phytoplankton the highest?
June-July - photosynthesis is at its peak so CO2 fixation is highest
what is the seston in an aquatic system?
what is suspended in the water column
What contributes the most to the mean annual standing stock in the seston of Mirror Lake?
detritus
Do zooplankton or phytoplankton contribute the more to the mean annual standing stock in the seston of Mirror Lake? How does this compare to terrestrial ecosystems?
phytoplankton in aquatic
in terrestrial, zooplankton would contribute more
Describe the microbial loop in the seston of Mirror Lake
What contributes the most to mean annual standing stock in the benthic zone of Mirror lake? where in the benthic zone are they most active?
bacteria
in the sediment
What is the input for the benthos of Mirror lake?
the detritus from the seston zone
What contributes the most to the outputs of organic carbon from Mirror lake?
phytoplankton then zooplankton
Why does a short term small-scale disturbance (such as clear cutting W2 at HB) result in such dramatic changes to nutrient dynamics?
because of the role of soil bacteria
What is a consequence of mass nitrate leaching from stream systems into lakes?
eutrophication
T or F: over time, after a disturbance like clear cutting, forests can recover
true
What is the main reason there was high loss of Ca2+ in the forested ecosystem at HB?
the SO2 and NOx emissions
What results from loss of Ca2+ in forested ecosystems?
acidification (increased H+ ions)
What was the UN convention that addressed the SO2 and NOx emissions/acid rain?
Convention on long-range transboundary air pollution in 1979
- SO2 in 1985
- NOx in 1988
HB helped contribute to this understanding
What was the UN convention that addressed CFCs and the ozone depletion?
Vienna convention on protection of the ozone layer (1985)
Montreal Protocol on Substances (CFCs) that deplete the ozone layer (1987)
What did long term studies on ozone depletion 23 years after the Montreal Protocol (1987) show?
that over time, with decreased CFC emissions, the ozone layer could replenish
What makes getting control over the emissions/responses of CO2, CH4, and N2O challenging?
they are all driven by microbial processes that we don’t fully understand
What microbial organisms contribute mostly to CO2 in the atmosphere?
cyanobacteria in aquatic and bacteria in soil
What microbial organisms contribute mostly to CH4 in the atmosphere?
methanogens (Archaea)
methanotrophs (bacteria)
Are methanogens Archaea or Bacteria?
Archaea
What microbial organisms contribute mostly to N2O in the atmosphere?
nitrifiers (proteobacteria, thaumarchaea, Brocadia)
denitrifiers (proteobacteria(
