Unit 4 Notes
Wetlands Notes
• Okefenokee Swamp Ecosystem
o Input
§ 95% of water from precipitation
§ 5% from inflowing streams
o Output
§ 80% evapotranspiration
§ 20% river outflow
o Ramsar wetlands = incredibly important
o Sediment Profile
§ Water
• Peat between water and sand
• Peat is compressed organic matter
o Decomposing very slowly
o Underwater most of the time
• Pure peat because no input of sediment
o No rivers feed into Okefenokee
• Buildup of peat forms an island where trees can root
§ Sand underneath the water
§ Clay underneath sand
§ Limestone underneath that
§ More clay underneath that
o Landscape Mosaic
§ Different stages of succession
§ Lakes, prairies, shrub-scrub, swamp island, forest stands (especially
cypress)
§ Succession occurs as peat builds up
• Lakes to develop forests
§ Mosaic maintained by fire
• Major fires occur periodically, mostly from lightning during
extreme drought
• Can burn down peat to create open water habitats
o Release minerals (ash) from organic matter
o Releases N (especially N2 but also NH3, N2O, NOX)
• Depressions from the burning fill in with water
o Abundance of carnivorous plants
§ Well adapted to life in a limited system
• Especially N-limited
• Schlesinger
o Wetlands ideal conditions for removal of reactive nitrogen
§ By denitrification
, § And for sequestration of N and P in organic matter
§ Important sources of dissolved organic matter to downstream and
coastal ecosystems
o No good estimates of wetland contribution to global N2O emission
§ Assumed production is lower than in upland soils
o Heightened capacity for denitrification, CH4 production, soil carbon storage
§ From lack of O2 in wetland sediments
o Aerobic oxidation dominates organic matter decomposition in most terrestrial
ecosystems
§ Microbes in flooded soil must use anaerobic pathways to obtain energy
from organic matter
o Microbial consumption of O2 in wet soils exceeds O2 supply through diffusion
§ Without O2, microbes cannot use oxidative phosphorylation to
decompose organic polymers to CO2
§ Rely on alternate electron acceptors
• NO3-, Fe3+, Mn4+, SO42-
o Wetland Hydrology
§ Water enters wetland by
• Precipitation
• Tributary inflows
• Near-surface seepage
• Exchange with deeper groundwater
§ Water leaves wetland by
• Groundwater recharge
• Surface outflows
• Evapotranspiration
§ 𝑉 = (𝑃! + 𝑆" + 𝐺" ) − (𝐸𝑇 − 𝐺# − 𝑆# )
• Wetland volume = inputs – outputs
§ Residence time of water limits capacity of biota to change composition of
waters passing through
§ Wetlands connected to oceans/salt lakes have higher concentrations of
salts
• Salt marshes may change salinity from fresh to full-strength sea
water with one tide cycle
• More inland may experience saltwater intrusion only on rare
occasions
• Few species of herbaceous vegetation adapt to full-strength
seawater
o Salt = difficult to maintain osmotic balance
o Wetland Soils
§ Soils permanently inundated with water above soil surface
§ Saturated soils with water table at or below surface
§ Soils where water table depth always below surface
, o NPP highest in wetlands with nutrient enrichment or high nutrient turnover
o Free Energy
§ ∆𝐺 $ = −𝑛𝐹∆𝐸
• Gibbs free energy
• n = number of electrons
• F = Faraday’s constant (23.061 kcal/V)
• E = difference in electrical potential between oxidation and
reduction reactions
• -DG = exergonic (energy yielding)
o +DG = endergonic (require energy)
$
§ ∆𝐺 = ∆𝐺 + 𝑅𝑇𝑙𝑛𝑄
• Actual free energy yield
• R = universal gas constant (1.987*10-3 kcal/K*mol)
• T = temperature (K)
• Q = reaction quotient
o Concentration of reaction products relative to
concentration of reactants
o Highly poised soils resist change in redox potential
§ Poise: redox is buffering capacity: pH
§ If exposed to atmosphere, soils are poised
• Because O2 maintains high redox potential under most conditions
§ Soils with lots of Mn4+ and Fe3+ less likely to produce substantial amounts
of H2S or CH4 during short-term flooding events
• Because it is unlikely that microbes can sufficiently deplete these
electron acceptors
• Turn to less efficient oxidizing constituents
o SO4, CO2
§ Nitrate can oxidize reduced sulfur, iron, or manganese compounds in
anoxic sediments
• Energetically favorable
• Manganese rarely found at high concentrations
• Inland Waters
o Freshwater ecosystems rest upon terrestrial ones
o Wetlands vary in hydroperiod
§ Depth, duration, frequency of inundation
• Hydroperiod: duration and depth of period of flooding
§ Anoxic conditions from seasonal/permanent saturation of soils of
sediments with water
• For carbon storage
• Biogeochemical transformations
• Plant adaptations
§ Saturated/flooded is when the relative depth goes above wetland ground
surface
Wetlands Notes
• Okefenokee Swamp Ecosystem
o Input
§ 95% of water from precipitation
§ 5% from inflowing streams
o Output
§ 80% evapotranspiration
§ 20% river outflow
o Ramsar wetlands = incredibly important
o Sediment Profile
§ Water
• Peat between water and sand
• Peat is compressed organic matter
o Decomposing very slowly
o Underwater most of the time
• Pure peat because no input of sediment
o No rivers feed into Okefenokee
• Buildup of peat forms an island where trees can root
§ Sand underneath the water
§ Clay underneath sand
§ Limestone underneath that
§ More clay underneath that
o Landscape Mosaic
§ Different stages of succession
§ Lakes, prairies, shrub-scrub, swamp island, forest stands (especially
cypress)
§ Succession occurs as peat builds up
• Lakes to develop forests
§ Mosaic maintained by fire
• Major fires occur periodically, mostly from lightning during
extreme drought
• Can burn down peat to create open water habitats
o Release minerals (ash) from organic matter
o Releases N (especially N2 but also NH3, N2O, NOX)
• Depressions from the burning fill in with water
o Abundance of carnivorous plants
§ Well adapted to life in a limited system
• Especially N-limited
• Schlesinger
o Wetlands ideal conditions for removal of reactive nitrogen
§ By denitrification
, § And for sequestration of N and P in organic matter
§ Important sources of dissolved organic matter to downstream and
coastal ecosystems
o No good estimates of wetland contribution to global N2O emission
§ Assumed production is lower than in upland soils
o Heightened capacity for denitrification, CH4 production, soil carbon storage
§ From lack of O2 in wetland sediments
o Aerobic oxidation dominates organic matter decomposition in most terrestrial
ecosystems
§ Microbes in flooded soil must use anaerobic pathways to obtain energy
from organic matter
o Microbial consumption of O2 in wet soils exceeds O2 supply through diffusion
§ Without O2, microbes cannot use oxidative phosphorylation to
decompose organic polymers to CO2
§ Rely on alternate electron acceptors
• NO3-, Fe3+, Mn4+, SO42-
o Wetland Hydrology
§ Water enters wetland by
• Precipitation
• Tributary inflows
• Near-surface seepage
• Exchange with deeper groundwater
§ Water leaves wetland by
• Groundwater recharge
• Surface outflows
• Evapotranspiration
§ 𝑉 = (𝑃! + 𝑆" + 𝐺" ) − (𝐸𝑇 − 𝐺# − 𝑆# )
• Wetland volume = inputs – outputs
§ Residence time of water limits capacity of biota to change composition of
waters passing through
§ Wetlands connected to oceans/salt lakes have higher concentrations of
salts
• Salt marshes may change salinity from fresh to full-strength sea
water with one tide cycle
• More inland may experience saltwater intrusion only on rare
occasions
• Few species of herbaceous vegetation adapt to full-strength
seawater
o Salt = difficult to maintain osmotic balance
o Wetland Soils
§ Soils permanently inundated with water above soil surface
§ Saturated soils with water table at or below surface
§ Soils where water table depth always below surface
, o NPP highest in wetlands with nutrient enrichment or high nutrient turnover
o Free Energy
§ ∆𝐺 $ = −𝑛𝐹∆𝐸
• Gibbs free energy
• n = number of electrons
• F = Faraday’s constant (23.061 kcal/V)
• E = difference in electrical potential between oxidation and
reduction reactions
• -DG = exergonic (energy yielding)
o +DG = endergonic (require energy)
$
§ ∆𝐺 = ∆𝐺 + 𝑅𝑇𝑙𝑛𝑄
• Actual free energy yield
• R = universal gas constant (1.987*10-3 kcal/K*mol)
• T = temperature (K)
• Q = reaction quotient
o Concentration of reaction products relative to
concentration of reactants
o Highly poised soils resist change in redox potential
§ Poise: redox is buffering capacity: pH
§ If exposed to atmosphere, soils are poised
• Because O2 maintains high redox potential under most conditions
§ Soils with lots of Mn4+ and Fe3+ less likely to produce substantial amounts
of H2S or CH4 during short-term flooding events
• Because it is unlikely that microbes can sufficiently deplete these
electron acceptors
• Turn to less efficient oxidizing constituents
o SO4, CO2
§ Nitrate can oxidize reduced sulfur, iron, or manganese compounds in
anoxic sediments
• Energetically favorable
• Manganese rarely found at high concentrations
• Inland Waters
o Freshwater ecosystems rest upon terrestrial ones
o Wetlands vary in hydroperiod
§ Depth, duration, frequency of inundation
• Hydroperiod: duration and depth of period of flooding
§ Anoxic conditions from seasonal/permanent saturation of soils of
sediments with water
• For carbon storage
• Biogeochemical transformations
• Plant adaptations
§ Saturated/flooded is when the relative depth goes above wetland ground
surface
