Lecture 7: Nutrient supplying and cycling Flashcards
Nutrients
chemical elements an organisms uses for its metabolism and growth
enter ecosystems through chemical breakdown of minerals in rocks and through fixation of gases in atmosphere
Nutrients enter food chain with plants following chain of
production, consumption, decomposition, and recycling that keeps them cycling in system
Nutrients from taken up by plants
C: CO2
H: H20
O: CO2/H20
N: NO3- and NH4+
P: H2PO4-
S: SO4-
What is 90-98% of nutrients taken up from plants?
C, H, O
Function of C, H, O in plants
C: carbohydrates and derivatives
H and O : basic building blocks for organic molecules
N and P usually
limit productivity in terrestrial and aquatic ecosystems
How do nutrients enter ecosystems?
Bedrock
Fixation of atmospheric gases
Atmospheric deposition
How does bedrock help nutrients enter ecosystems?
Rocks contain minerals composed of nutrient elements
Weathering causes rock to breakdown and minerals to enter soil
Nutrients become available for biological processes
What is the ulitimate source of phosphorus (and most other nutrients) that supports plant growth?
Minerals in bedrock
How does fixation of atmospheric gasses help nutrients enter ecosystems?
Some bacteria can access N2 and turn it into biologically available form of nitrogen –> nitrogen fixation
Air is full of N2, but issue is
plants and animals can not use N2 (not usable form due to strong triple bond)
How to make N2 useful for plants?
nitrogen fixation: N2 –> NH4
Nitrogen fixation
Convert nitrogen in atmosphere into form that can be used by living things
Bacteria: use enzyme nitrogenase to convert N2 into chemically available from NH4
lighting stirkes
Industrial, Harber Bosch process: uses lots of energy, fossil fuelss
N fixation symbiosis
Plants: need nitrogen, have lots of carbon
Bacteria: can fix nitrogen, need carbon
What is the ultimate source of nitrogen that supports plant growth
N2 gas in the atmosphere
How does atmospheric deposition help nutrients enter ecosystems?
wind moves dust around the globe
rain can bring particles form atmosphere into the soil
____ of primary minerals in major source of new P to ecosystem
Weathering
____ is the major source of new N to ecosystems
Fixation
What is problem with weathering and fixation?
processes take a long time
How do plants recycle a lot of their own nutrients?
Leaves have high nutrient concentrations than wood
In fall, nutrients broken down in leaves and transported to stems and roots where they are stored (retraslocation)
Detritus fuels
decomposition
Microorganisms role
break down and mineralize nutrients (producing NH4) which is main form of soil N availability in many ecosystems
Earthworms, termites, nematodes role in decomposition
consume litter and break into finer particles (increase surface area)
Bulk of detritus is …
plant material: organic compounds difficult for plants and animals to take up directly
Mineralization
chemical conversion of organic matter into inorganic forms
Bacteria need carbon and nitrogen so they get from
detritus
Bacteria break down litter and take
C and N that they need
N is sometimes left over often
What is done with leftover N by bacteria?
Plants take up this leftover N in soil with their roots and use it to fuel primary production
___ can control rates of decomposition
Climate
Decomposition is faster in climate with
warm moist conditions
Soil moisture influences availability of
water and O2 to microorganisms
wet soil have low O2 concentration to inhibit detritivores
dry soil do not have enough water fr microorganisms
why is composition of plant litter important?
major control on decomposition and nutrient availability (N and P) in the soil
Plant litter C:N is between
10:1 and 40:1
Microbes need C:N to be about _____ to _____
25:1, build their bodies + maintenance and respiration
What C:N is good for enriching the soil in available nitrogen?
40:1, microbe would use what it needs and have carbon left over, slower decomposition
10:1, microbe would use what it needs and have nitrogen left over: faster decomposition
left over released into soil and available to plants
When N is left over from plant litter, it is used for
nitrogen mineralization (breakdown of organic nitrogen and production of plant available NH4 and NO3)
Properties of litter influence decomposition rates
Lignin strengthen plant cell walls for soil microorganisms difficult to degrade –> decomposes slowly
secondary compounds can inhibit or promote microbial growth
