BIEB 174 FINAL

tropical wet forests

warm, rainy, near equator

tropical dry forests

warm, dry; wet summers, dry winters

tropical grasslands/savannahs

warm, seasonally rainy; limited tree cover due to lack of rain, fire, herbivory

warm deserts

very hot and dry, cool winters

temperate forest

seasonally cold, low light, high rain

boreal forest/taiga

very cold, low light, warm summers

subtropical gyres = equatorial upwelling zones

warm, ample light, low nutrients = low chlorophyll, primary productivity, smaller phytoplankton

subpolar gyres = coastal upwelling zones

large seasonality in temp, light limiting, seasonal nutrients = higher chlorophyll and primary productivity = blooms; larger phytoplankton

polar gyres

abundant nutrients, cold, low light in winter; bloom in summer, low biomass winter; dominated by large phytoplankton

higher sea surface height

subtropical so it has downwelling and less nutrients

lower sea surface height

subpolar, upwelling, more nutrients

pools and fluxes of the carbon cycle

rocks (land) > ocean > atmosphere

residence times (least to greatest)

marine biomass, atmosphere, deep ocean, rocks

carbonate chemistry

CO2 goes into ocean surface and dissolves

reacts with seawater to make bicarbonate ions

bicarbonate ions dissociates into carbonate ions

ocean becomes more acidic because H+ ion is released

what is K in relation to carbonate chemistry

[CO2*]/[pCO2] = higher CO2* then CO2 gas is more soluble

solubility better in colder water

solubility pump

CO2 being transported to deeper ocean based on how soluble the water is

colder waters can absorb more CO2

accounts for 90% of DIC in ocean

biological pump

phytoplankton absorb CO2 and use for photosynthesis

phytoplankton are eaten the carbon is distributed throughout the food chain

adds 10% of DIC in ocean

remineralization

organic matter broken up to release the nutrients back into the water

sinking particle flux

orgo matter at the surface sinks down and is chemically broken down

flux increases DIC

most of the matter is remineralized as it moves down

where is the biological pump the strongest

areas of upwelling and abundant nutrients because there are a lot of phytoplankton

oxygen minimum zones

pockets of no oxygen because sinking orgo matter consumes it

emitted carbon

½ in atmosphere

¼ land and ocean

pools and fluxes in the global nitrogen cycle

atmosphere > sedimentary rocks > ocean > land biota > marine biota

natural nitrogen fixation on land and ocean

equal

anthropogenic inputs

equal to total terrestrial natural n fixation

what is the main large scale balance of n on earth prior to anthropogenic addition

N2 fixation = denitrification

nitrogen fixation

N2 gas → ammonium

• strong triple bond, requires enzyme: nitrogenase

• fixers have high P requirement

what does nitrogenase require

iron and molybdenum

where is N2 fixers found

areas of low N, high P, ample light, aerobic conditions

diazotrophs

symbiotic cynobacteria in phytoplankton that do photosynthesis found in low N and are limited by low Fe and P

harber-bosch

N2 → NH3 under high temp and pressure

nitrogen assimilation

takes up nitrogen from environment (and other elements) to make organic matter

redfield ratio

C:N:P (106:16:1) = relative nutrient requirements

how do nutrients reach cells

molecular diffusion that transfers nutrients along concentration gradient (high → low)

only effective short distances

nutrient depleted boundary layer

cells nutrients absorb faster than they are supplied

nutrient/nitrogen assimilation

saturates at high concentrations because cells have limited number of membrane transporter proteins

diffusion for plants

how roots gets nutrients

mass flow driven by transpiration and gravity

must have some concentration of nutrients

how to maximize diffusion

plants increase root length

phytoplankton increase surface area

nitrogen remineralization

returns fixed nitrogen to water/soil from orgo matter

facilitated by heterotrophic bacteria and faster in warmer temps

nitrification

ammonium → nitrite → nitrate through oxidation

aerobic, inhibited by light, acidifies soils/water

rxn driven by bacteria

denitrification

nitrate → N2 gas

anaerobic process

heterotrophic bacteria

anthropogenic N input patterns

biological N2 fixation will increase a certain amount

agricultural N inputs increase

combustion input decrease

where would oxygen minimum zones occur

high surface productivity and strong flux of organic matter to depth

acid deposition

lowers pH of soils and changed water/soil chemistry

effect of adding N to plant communities

increases primary productivity, lowers species diversity

N favors faster growing, taller plants that compete with other plants

remineralization

orgo matter → ammonium

high denitrification rates in ocean

old water = low oxygen

pools of phosphorus

rocks > land > terrestrial biota > ocean > atmosphere

• tightly bound, released through weathering (long time)

• continually recycled from orgo matter

anthropogenic inputs of P

fertilizers

P limitations

plants in older soils respond more to p because as soil develops, weathering increases bioavaliable P

ocean is not p limited

pools and fluxes of sulfur cycle

rocks > ocean > soil > atmosphere

burning fossil fuels release SO2 → reacts with atmosphere to form sulfuric acid

structure of clay

thin plates with negative charge, absorbed cations

DMS hypothesis

sunny day → phytoplankton production increases → DMS increases, cloud formation → cloud blocks sunlight = cooler/limits sunlight → lowers production

when is DMS negative and positive feedback?

short time scale = negative feedback

long time scale = positive feedback

pools and fluxes for iron

abundant on earth, limited in ocean because bound to insoluble organic molecules (ligands)

iron on rocks and land will get into ocean (wind carries dust or glacier sediments)

what is iron needed for

photosynthesis, respiration, nitrogen fixation

why is iron low in the ocean

scavenging, binding to organic ligands, uptake by phytoplankton

liebig’s law of minimum

growth determined by the most limiting resource

• not limited by concentration of element but rather being relative to the demand of the cell

• Fe is in low quantity but not necessarily limiting but P could limit growth since cells require more P

examples of coupled nutrient cycles

symbiotic cyanobacteria in phytoplankton found in low N = low chlorophyll

n fixers found in warm, ST gyres with low N

what is sulfur required for

proteins and enzymes (nitrogenase)

results of iron fertilization experiments

addition of iron increased chlorophyll and spurs blooms until nitrogen and p are consumed

effects of acidic soil

addition of H+ ions → kicks cations off clay → cations and anions leech out → no more nutrients in soil so productivity decreases

photoautotrophs

form organic matter from photosynthesis

mixotrophs

consume both dead and live organisms and can photosynthesize

consumption efficiency

proportion of lower trophic level ingested by the next higher level

portion not ingested remains as standing biomass or detritus

consumption efficiency in the ocean

very high compared to land because everything is edible

assimilation efficiency

proportion of ingested energy that is assimilated into an organism; varies from 5-80% depending on type of food

herbivores generally have lower Eassim

portion that is not assimilated becomes detritus

production efficiency

proportion of assimilated energy that is converted into consumer production

portion not convert is respirated

homeotherm

maintains temperature homeostasis, higher respiration costs

poikilotherm, ecotherms

internal temperatures vary strongly, lower respiration costs

where does biomass accumulate

in terrestrial systems moreso than the ocean; concentrated in producers due to trees

biomass in aquatic systems concentrated in consumers since producers are completely eaten

physical weathering of parent material

no chemical changes

the breaking of rocks into smaller pieces to increase surface area for chemical weathering

chemical weathering

involves a chemical change (primary → secondary mineral)

promoted by water and heat

stimulated by acidity such as carbonic acid around roots

describe clay particles

small/fine, high surface area to volume ratio

give water holding capacity to soil

what is CEC

cation exchange capacity = how much negative charge

fulvic acid (SOM)

organic matter contributes to CEC and is important to highly weathered soils with low clay content

high bulk density

high clay content = compacted and lower som = very dense

has low infiltration and increases runoff

when is reduction of O2 favored

aerobic soils

when is denitrification favored

soils that are compacted, waterlogged, depleted O2, high nitrate

when is sulfate reduction/methanogenesis favored

low nitrogen

what elements are water soluble and easily dissolved

Ca, Na, Mg

what accumulates in highly weathered soils

Fe and Al oxides

impact of adding chelates

loosely binds to metal ions to make them soluble

what is humus

broken down SOM, very stable and contributes to CEC

vertical movement in soils

leaching = loss of nutrients through water moving downward

creates layers in soils

what nutrients are likely to be lost

inversely related to binding, monovalent charge lost more easily

• AL3+ > H+ > Ca2+ > Mg2+ > K+ = NH4+ > Na+ (cations)

• PO3- > SO3- > Cl- > NO3- (anions)

aridisols

no orgo layer, no plant growth

shallow leached later

hard pan (calcic layer)

gelisol or histosol

thick organic layer with slow decomposition due to waterlogging (histosols)

gelisols = permafrost

spodosol

conifer litter releases organic acids that cause very leached layer

mollisols

high productivity in grasslands and deciduous forests

top layer or mineral soil mixed with OM and humus

fertile, high water CEC

oxisol

shallow organic later with high recycling rates

highly leached, old soils

state factors

external to ecosystems and control bounds over type of ecosystem in given location

topography

influences soil loss through erosion

fine grains slip downhill and promote erosion (steep hills)

slopes

coarse, shallow soils with low orgo c

flat areas

deep, fine soils with high orgo C

availability of mineral nutrients in soil

dependent on weathering

young soils have more P and highly weathered soils are acidic with low CEC, plant growth is p limited

climate and how it affects soil formation

chemical weathering rates are faster in warmer/wet conditions

loss rates = wind and erosion

carbon uptake and decomposition higher with increasing temps

potential biota

can interact with other state factors such as climate

when does surface runoff occur

infiltration is slower than precipitation

hydraulic conductivity

affects rate of infiltration

smaller particle size = more surface area ratio