biogeochemistry exam 2

lets get this shit

life- what do we need?

* materials (C,H,N,O,P,S)
* energy to build ATP

photosynthesis

* autotrophs, a.k.a self feeders

chlorophyll (light reaction)

calvin benson cycle

* evolved over 2 billions years ago (cyanobacteria
* no super efficient but hasn’t really changed since its evolution
* drastically change O2 atmosphere concentration

oxic respiration

* autotrophs & heterotrophs
* oxidation process → releases CO2
* 1 glucose = 38 ATP 4 metabolic processes

(gycolosis-cytosol)

(krebs-mitochondria)

primary production

* amount of plant produced over time

(mass/area/time : gm-2d-1)

biomass

* total amount of plant material at a point in time (gm^2)

gross primary production (GPP)

* all CO2 fixed into organic matter of plant (over a period of time)

net primary production (NPP)

* rate of organic matter available for other uses beyond supporting energy cost (respiration) of primary producers

NPP=GPP-Ra

* Ra - autotrophic respiration

Re=Ra+Rh

* Re - ecosystem respiration
* Rh - heterotrophic respiration (microbes)

net ecosystem production (NEP)

NEP=GPP-Re

* can be positive or negative
* only CO2

(just know) NECB

* overall ecosystem C balance from all sources and sinks (physical biological)
* anthropogenic
* other forms of C

net ecosystem exchange (NEE)

* exchange of CO2 b/w ecosystem and atmosphere

net ecosystem production (NEP)

* ≈ NEE
* NEP=GPP-Ra-Rh or NEP=NPP-Rh

NEP=NPP-Rh

* NPP : C that is stored in plants and what they “provide” to the ecosystem
* litter inputs
* herbivory
* very little NPP escapes decomposition and is stored in ecosystem
* Rh is closely correlated w/ NPP because NPP is the input(quantity quality)


* Rh : what is transpired by heterotrophs in the ecosystem
* heterotrophic respiration
* largest avenues of C loss from an ecosystem
* decomposer microbes and their predator account for most Rh

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decomposition definition

* physical and chemical breakdown of detritus
* detritus : dead plant, animal, and microbial material

organic material (OM)

* dead plant material leaf root system litter
* animal bodies & residues

The three phases of decomposition ???

phase 1: leaching

phase 2: fragmentation

phase 3: chemical alteration

1\.) leaching

* physical process by which mineral ions and small water soluble compound dissolve in water (forms dissolved organic matter (DOM))
* absorbed by organisms
* react w minerals in soil
* exported from system
* RAPID (if h2o present..CLEOOOOO NOORRR ;( )
* (mostly) labile : compounds easily broken down
* le suga
* la animo acids

2\.) fragmentation

* larger pieces of organic matter broken into smaller pieces by soil/animals they eat and create surfaces for microbe colonization
* INCREASE SURFACE AND MASS
* mix into soil and return OM to soil as fecal pellets and respire CO2 (Rh)
* INCREASE portion of litter that is accessible to microbial attack
* pierce protective barriers (cuticle, bark, skin, exoskeleton o_O)
* INCREASE FRAG/ INCREASE DECOMP
* feeding activity of animals

3\.) chemical alteration

* chemical changes that occur to OM
* primarily by heterotrophic microbes
* OM → (mineralization) → CO2
* (inorganic) mineral
* nutrients
* water
* OM → (transformation) → complex organic compounds OM soil mineral complexes
* recalcitrant : resist further microbe breakdown

evolutionary forces that shape decomposition

* those that maximize growth, survival, and reproduction of soil organisms

decomposition

* feeding activity of soil animals
* heterotrophic microbes
* OCCURS TO MEET THE ENERGETIC AND NUTRITIONAL DEMANDS OF DECOMPOSER ORGANISMS

OM → (mineralization) → CO2

* (inorganic) mineral
* nutrients
* water

* important in c-cycle bc of carbon balance
* heterotrophic respiration → Re = Rh + Ra
* the release of nutrients that are tied up in OM is essential for maintaining productivity and nutrient cycle
* rate of decay is a control over productivity

organic carbon storage

* climate mitigation
* plant nutrition

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* can persist for a long time
* controls biological activity
* physical and chemical ____???

controls over decomp. change w time

* senescence : deteriorate w time
* bacteria and fungi already colonized while on plant

decomposition rate

rate that mass is lost over time

d/dt = e^-Kt

* d/dt : change in quantity over time
* K : decomposition rate constant
* units: time ^-1
* (negative exponential model)

what influences K?

* # of intrinsic (litter quality) factors
* # of extrinsic (environmental and biological) factors

mean residence time (MRT)

* time required to decompose under steady state conditions
* 2 ways to measure
* measure mass loss over time and fit curve to estimate K, then MRT = 1/K
* MRT = litter pool/ litter fall so K = litter fall/ litter pool

litter pool/mass of litter in the area →

g litter m^-2 / g C m^-2

litter fall

litter traps to catch leaves stems and root ingrowth cores

microorganisms

microbes

fungi

* relatively larger standing stalk


* turnover time: weeks
* filamentous hyphae
* reproduce sexually/asexually by sporulation
* breakdown of all classes of plant molecules

bacteria/archea

* small standing stock
* 1-10 days
* single cell
* large surface : volume (rapidly absorb substrate)
* reproduce by cell division
* can grow and divide quickly

Fungi + bacteria? (the perfect 2???)

* both can secrete extracellular enzymes to break down OM
* partially degraded OM + enzymes + microbial biomass on and within the OM makes it more palatable for other decomposers

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slay

rate of decay and amount of OM remaining is controlled by

* substrate quality
* microbial community
* players, biomass, activity, nutrients
* environment
* moisture, temp

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substrate quality

* litter quality
* size of molecules
* large molecules cannot pass through membranes
* types of chemical bonds
* ester bonds vs aromatic rings
* regularity of structures
* lignin has highly irregular structure
* no specific enzyme.. so broken down slowly by nonspecific enzymes
* toxicity
* phenolics kill or reduce activity of microbe
* nutrient concentrations
* nutrients (N,P) are required by microbes to produce new microbial biomass

NPP = GPP-Ra

* support biomass and activity of decomposers
* some OM persists storage
* plant biomass dies
* litter then goes through
* mineralization
* transformation
* leaching

litter inputs → decomposition products

* nutrients enter
* climate/environment (aid w decomp??)
* temp
* moisture
* oxygen

temperature in decomp

* INCREASE TEMP = INCREASE RATE OF REACTION
* decomposer organisms have a thermal tolerance range and optimum
* acclimate and adapt overtime
* in general
* INCREASE TEMP = INCREASE DECOMP
* highest in warm moist condition if oxygen is available

moisture in decomp

* water facilitates the diffusion of substrate nutrients to microbe and waste products away from microbes
* INCREASE MOISTURE = INCREASE DECOMP
* until soil becomes so waterlogged that aerobic conditions inhibit decomposition

oxygen in decomp

* terminal electron acceptors in oxic respiration
* anerobic metabolism e- acceptors (NO3^- & SO4^2-)
* less energetically favorable than oxic respiration

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* LOW O2 → results in lower microbial biomass; DECREASES DECOMP
* LOW O2 → limits macroinvertebrate; DECREASES FRAGMENTATION AVAILABLITY in the ecosystem will part determine the quality of litter and microbial biomass/activity

nutrients in decomp

* the effects of nutrients on decomp are largely indirect and mediated by C quality of the substrate

biological stoichiometry

* living things need a certain ratio of carbon to build their bodys and offspring
* nutrients (C:N ; C:P)
* high C:N (low N) - decay slower (general pattern)
* low C:N (high N) - generally decay quickly

microbial population growth

look at the powerpoint stuff. check lecture 13

* the one with green boxes

microbial pop growth STARVED FOR N

* substrate N limited
* not enough N to meet/sustain microbe population and activity growth


* ABSORBS (NH4+) from ecosystem
* N IMMOBILIZATION

microbial pop growth STARVED FOR C

GAGA OOOO EEH

* microbial growth is often C limited
* need to decompose the OM to meet energy demands of decomposer if substrate has SURPLUS N for microbial needs
* RELEASE N to the ecosystem
* N MINERALIZATION

take a step back, g. consider what dictates substrate quality and C:N

* C → structural
* N,P → physiology
* photosynthesis

plant economics spectrum (PES)

* ecological traits are functionally coordinated and adapt along environmental gradients
* a way to conceptually organize trade-offs between resource acquisition and conservation

PES plant

* LES : leaf economic spectrum
* WES : wood economic spectrum
* RES : root economic spectrum

investing strategy→ RESOURCE RICH ENVIRONMENT

* resource acquisition
* traits that promote fast C acquisition
* photosynthesis
* large leaves
* high nutrient content
* N&P
* fast growing (not structurally complex)
* low tissue longevity (low density)

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decomposition (tissue quality)

* low C:N (high N)
* not structurally complex
* faster rate of decay

investing strategy→ RESOURCE POOR ENVIRONMENT

* resource conservation
* traits that promote conservation of tissues
* lower productivity
* smaller, denser
* structurally complex (cellulose lignin gurl)
* well protected tissues
* lower nutrient concentration
* long tissue longevity

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decomposition (tissue quality)

* high C:N (low N)
* complex and defended (jealous tbh..)
* slower rate of decay

fresh litter inputs → flux rate → decomposition products

* inputs → nutrients
* climate/environment
* temp, moisture, O2
* decomposer → community activity and pop size and composition determines decomp rate and extent
* INTERCONNECTED
* each component must be thought of within the entire context

2 questions idek she if answered… lmk ;-;

1. what kind of litter is being produced
2. does the environment support high or low microbial biomass and activity

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part of lecture 13 notes :)

major reservoir (nitrogen-cycle)

* atmosphere N(triple bond)N
* N2 nonreactive

reactive N (n-cycle)

* inorganic reduced
* NH3 : ammonia
* NH4+ : ammonium
* inorganic oxidized
* NO3- : nitrate
* N2O : nitrous oxide
* organic
* DON
* urea
* amines
* amino acids

new inputs to ecosystem (n-cycle)

* N fixation
* N deposition (not focused in class)

losses from ecosystem (n-cycle)

* denitrification
* leaching
* fire → volatilization N
* biomass removal

internal cycling (n-cycle)

* mineralization
* immobilization
* nitrification
* plant uptake

pools and fluxes W/IN ecosystem

* inputs (N-fixation) and losses (denit, leaching) are relatively small in comparison to the internal cycling
* mineralization
* immobilization
* nitrification
* plant uptake
* vast majority of nutrients that support GPP are recycled in the ecosystem
* recycled N supports approx. 90% annual plant demand

N mineralization & immobilization

* balance is a critical regulator of N availability for GPP
* (1) N absorbed by plants used by plant to build plant body and for its physiology eventually plant tissues die → litter
* DOM contains C, N, P
* (2) microbes break down organic matter during this process dissolved organic matter is released through action of exoenzymes
* also called dissolved organic nitrogen DON
* microbes absorb it and use the C to meet their energy needs and also use the C and N to build new microbial biomass

microbes require a certain ratio of C:N (10:1) STARVED FOR N

* if DON is N poor (high C:N) the microbe must take NH4+ from the environment to meet its needs
* N IMMOBILIZATION
* N is taken into the microbes body and others cannot use it until the microbe secretes it → enzyme or dies and decomposes
* ex. N poor → sawdust

microbes require a certain ratio of C:N (10:1) STARVED FOR C

* is DON is N rich (low C:N) and the microbe has a surplus of N after its needs are met then it releases NH4+ to the environment
* N MINERALIZATION
* keeps eating (yum) to get C and releases N
* ex. N rich → manure

mineralization vs immobilization, which one occurs?

general rules

* C:N 25:1 or lower : mineralization
* C:N > 25:1 : immobilization

within the soil profile usually both are happening simultaneously and the balance between them regulates the size of the soluble N pool

* must also consider if the environment supports high microbial activity and pop growth bc the carbon status of the microbes is what is driving the decomposition
* → magnifies the effects if substrate quality (C:N) on the rates of immobilization vs mineralization
* C:N → determines mineralization vs immobilization
* climate → effect rate

nitrification

* NO3^-
* nitrate can be taken up by the plants and microbes but must then be reduced to NH4+ so more energetically expensive
* negative charge so less likely to stick to soil particles (generally have a neg. charge) than NH4+ cation
* nitrification rate is key for controlling magnitude leaching loss
* find nitrification in places that support HIGH N MINERALIZATION (tropic) or places w added NH4+ fertilizer
* agriculture

NH4+ amount and availability determine rate and amount of nitrification

* bc nitrification substrates (NH4+, NO2-) are not rich in energy
* nitrifiers grow slow and compete poorly for NH4+ against plants and microbes immobilizing N competition regulates nitrification rates

external source of soluble reactive N

* nitrogen fixation : N2 → NH3
* N-FIX LIMITED TO WARM, HIGH LIGHT ENVIRONMENTS W/ ENOUGH P
* enzyme : nitrogenase
* denatured by oxygen so nitrogen fixation requires a low or no oxygen environment (anaerobic)
* N-fixing microbes : bacteria
* free-living or form symbiotic relationship w/ plants
* very energetically demanding to fix N can use up to 25% of GPP
* only competitively advantageous in low N systems bc if reactive N is available it is energetically cheap to take it up and other microbes would outcompete the comparatively slow growing N-fixers or plants would not feed N-fixers to get N they would simply take it up from the environment
* enzymatic reaction so INCREASE in WARMER TEMPERATURE

why does N limitation exist is organisms can fix it? what constrains N fixation?

* energy availability
* need HIGH productivity to fuel it
* HIGH light
* WARM temps (tropics)
* not shade but sunny
* overstory or disturbed open canopy
* other nutrients available = P
* require a lot of ATP
* N-FIX LIMITED TO WARM, HIGH LIGHT ENVIRONMENTS W/ ENOUGH P

pathways of N loss

* denitrification : NO3- → NO2- → NO → N2O →N2
* form of anerobic respiration - heterotrophic bacteria
* bacteria facultative anaerobes

other pathways of N loss

* leaching of dissolved organic nitrogen (DON) or NO3- nitrate
* often large fluxes after disturbance when there is reduced uptake NO3, NH4 → NO3
* occurs when fertilizer application exceeds plants and microbial demands
* fire volatilizes N
* the amount lost and forms (NO-, N2, NH3) depends on the temperature of the fire

phosphorus (P)

* essential for all organism
* DNA, RNA, ATP & phospholipids that form cell membranes
* limits or colimits primary production in many ecosystem both terrestrial and aquatic (lakes, streams, oceans)
* especially tropical forest and freshwater ecosystems
* P - rarely found in elemental form
* orthophosphates (basic→acidic)
* PO4^-3 (pH 14)
* HPO4^-2 (pH 10)
* H2PO4- (pH 5)
* pH 5, 10 → primary forms taken up by the plants
* H3PO4 (pH 0)
* PH3 - phosphines
* gas form extremelly rare
* negligible atmospheric component
* Porg - organic P

weathering

* break down of primary (rocks) minerals over time
* jESUS CHrIST mARIE! THeyRE miNERalS! (bb moment lol)

P cycle

* one of the slowest biogeochemical cycles on earth
* boooo
* atmosphere does not PLAY.. a significant role since P-compounds are solid (not gas)
* they can dissolve in water or be in particulate form
* main P source to the oceans is runoff from river
* 15 (looks like 1.5 on her notes tho.. idk hard to see lmk) Mt dissolved P
* 20 Mt suspended particulate P
* Prock weathering non-reversable
* background levels in an ecosystem depends on the parent material
* parent material: what rocks are made of
* controls the amount of P in the rock to begin with

weathering controlled by BOTH biological and physical aspects

* weathering rates INCREASE WITH
* INCREASE TEMPERATURE
* INCREASE PRECIPITATION
* INCREASE SLOPE
* INCREASE VEGETATION

shorter cycle w in the geologic P cycle

* P can cycle 100,000 + years before reaching the bottom of the ocean
* only a small component enters the “fast” cycle
* most remain bound up in rocks
* aww :c

mineralization and immobilization (p-cycle)

* inputs: OM
* output: H2PO4-
* soil microbes
* rate and amount immobilized or released depends on
* environment (moisture, temp)
* C:P of substrate (litter)
* >300:1 immobilization
*

adsorption and desorption (p-cycle)

* fast and reversible
* P from soil solution is attached/bound to the surface of soil particles adsorption
* the reverse desorption
* clay surfaces or Fe and Al oxide (+ charges) depends on soil type
* INCREASE CLAY or INCREASE Fe & Al oxides then
* INCREASE P will be unavailable bc bounded/absorbed
* oxisols → soil order → highly weathered tropics dominant colloid are Fe, Al oxides

precipitation and dissolution (p-cycle)

* precipitation: process by which metal ions (Al3+, Fe3+) (Ca 2+ - calcarous soil) react w phosphate ions in the soil solution to form minerals such as Al-, Fe-, Ca-, phosphate
* slow involves a permanent change into metal phosphate but metal phosphate can release phosphate back upon dissolution
* dissolution : release rate slow - form of weathering of a secondary mineral

P uptake by plant

* assimilation
* available P moves through soil by diffusion
* take up mostly HPO4^2- and H2PO4-

form symbiotic relationship w/ mycorrhizal fungi

(but we already knew that bc we’re girl bosses su)

* long filamentous hyphae
* INCREASE ROOT SURFACE which INCREASES the PROBABLILITY of encountering P
* appox. 80% terrestrial plants form mycorrhizal symbiosis
* critical step in the evolution of land plants

fixed P pool ⇔ active P pool ⇔ solution P

* 3 pools exist in equilibrium w each other
* fixed P pool → primary mineral
* active P pool → absorbed, secondary mineral, organic matter-P

factors that influence P availability

* clay content (absorption)
* soil minerology \[Fe, Al\] (absorption)
* soil pH
* high pH Ca+
* low pH Al- , Fe-
* organic matter
* mineralized → release P
* competes for absorption sites

phosphates in cleaning products

* prevent Ca and Mg ions from binding w soap
* banned in 17 states
* NOT TEXAS (who wouldve though tho)
* EPA sets voluntary limits

aquatic ecosystem

* P often limits primary production
* if you add P → stimulate rapid growth of phytoplankton and algae
* FW & estates coast w carbonate sediments or co-limited N and P

algal blooms (shallow aquatic environment)

* shades out benthic primary producers leading to sediment resuspension switching system to an alternate stable state
* phytoplankton dominated
* can be toxic depending on community composition of algae
* harmful algae blooms
* red tide
* can create dead zones
* INCREASE ALGAL GROWTH which sink and decompose but aerobic respiration of decomposers takes O2 out of water column
* hypoxic zones
* cannot sustain many organisms

human alternation of global P cycle

* humans → mine P approx. 23 Tg (10^12g)/ year
* spread it all around
* fertilizers, livestock feed, trade livestock move food crops
* INCREASE CONSUMPTION of P → approx. 3% annually
* INCREASE POPULATION
* meat

humans effing up (p-cycle)

* we release lot of P from rocks (concentrated) @ a rate that exceeds new P rock formation

5 countries hold approx. 85% of P in minable deposits

* morocco (#1)
* china (#2)
* south africa
* algeria
* syria

will we run out of P?

* no known substitues
* estimated peak of production
* 2030
* BUT recent discovery “new” reserves pushes this date back a few decades

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>_> i needa see the source for that bc w ohio i be trippin

push for sustainable management to →

protect aquatic environments, promote food security