Midterm 2 Material Flashcards
What are the three things soil microbes are important for?
- Nutrient cycling
- Pathogenesis/disease
- Chemical breakdown and carbon transformation (decomposition)
What is a key morphological trait of fungi?
Filamentous growth
What are the advantages of being filamentous fungi?
They have a large surface area, are able to degrade wood and complex carbon (because filaments can go into wood fibers and pull them apart by growing into them), can move things from one place to another, and can wrap around/tie things
What are the disadvantages to being filamentous fungi?
-Are sensitive to disturbance (they break easy)
- Taking samples causes them to die
- Need more resources as bigger
What is a mycorrhizal association?
is a symbiotic structure formed by a fungus plus a plant
Can plants refuse a mycorrhizal association?
Yes plants can refuse association if it’s not energetically useful for the plant- when the plant isn’t under stress and has lots of P and N it doesn’t associate
What is the difference between acquisition of phosphate by mycorrhizal roots versus just regular roots?
Regular roots have depletion zone in which the root will take up phosphate, mycorrhizal roots extend past this depletion zone which then takes up phosphate outside of zone- makes it more efficient
Can phosphours move to plants? Can nitrogen?
no and yes
What are the benefits/disadvantages of being small as bacteria?
are resilient to physical disturbance
have better surface area to volume ratio
have small energy requirement
less predation
can form biofilms on things
Can hide
stuck where they are
smaller than things they try to eat sometimes (ie humic substances)
Can bacteria hide in soil?
yes, can be hidden by clay
How bacteria get nutrients?
Bacteria need water to be running through to bring them nutrients as they can’t actively go get them
Why are bacteria a lot more abundant in tillaged soils?
Because fungi get killed off due to the tillage which leaves more bacteria relatively
Why are fungi a lot more abundant in forested soils?
Because forest ecosystems are very acidic and fungi are acid tolerant, also because forests provide a lot of wood and stuff that fungi feed on.
Are bacteria diverse?
yes taxonomically and functionally, involve both bacteria and archae
What is bioremediation?
is the study of looking at how bacteria break up pollutants
What are antibiotics?
is when organisms (bacteria or fungi)put out chemical signals to kill eachother, bacteria make antifungal and fungi make antibacterial, they both also develop resistance so it’s constant evolution
What 3 functions can bacteria do?
nitrogen cycle
phosphorus cycle
carbon cycle
What three things prevent decomposition?
climate (environmental protection)
Soil texture/mineralogy (Physical Protection)
Composition and structure of the SOM (Chemical protection)
What is the definition of decomposition?
the physical an chemical breakdown of chemical compounds, moving them along a continuum from fresh to humidified
Why is decomposition important?
Because it takes nutrients that are unavailable and make them available again
Releases gases (CO2) back to atmosphere
lets us see regeneration after disturbance
removes dead biomass
Puts co2 back in atmosphere
What are the two pathways of decomposition?
physical and chemical
What consists of the physical pathway of degradation?
leaching and fragmentation
What consists of the chemical pathway of degredation?
mineralization
for ex ammonification
How do we measure degradation?
you collect litter, dry it, weigh it into bags, dry and weigh contents of bags and calc the loss of mass and plot results
What do degradation plots look like?
Look at mass loss over time, usually is an exponential decline
What does the eqn of degradation look like? What’s k?
ln Lt/L0 = -kt
k is a constant obtained from the exponential model of specific plants
What species is the fastest to decompose? What species is the slowest to decompose?
Acer Saccharum
Betula populifolia
What way do we quantify k from an exponential curve?
K= litterfall (how much litter there is)/ litter pool (amount of litter that falls down)
The larger the k the faster the what?
degradation
What is the effect of temperature and water on soil OM?
As ppt increases and temp increases the percent of organic matter in soil plateaus, ORGANIC MATTER DECREASES at higher temps and higher water amounts
Is there an optimal temp for soil decomposition to happen? Why?
yes, because too cold decomposition slows down and too hot decomposition slows down.
Feb 9 lec
Feb 12 lecture
As the C:N ratio increases what happens to the decomposition rate? Why?
It decreases, this is because microbes don’t have the energy to break down products as they become nitrogen limited which they need for their metabolic processes
What important element is usually limiting ecosystems?
nitrogen
Why is nitrogen important for life (plants)?
Because it’s a major substance in plants next to water, is a building block of life, is in chlorpphyll, cytochromes, alkaloids and many vitamins
and plays roles in metabolism, growth, reproduction, and heredity
Why is nitrogen important for life (cellular wise)?
because it’s a crucial apart of amino acids, fatty acids, sugar residues, and nucelobases
How does nitrogen limit ecosystems?
It needs to be fixed into systems and limits primary productivity in most terrestrial ecosystems
What are the three forms of nitrogen in the atmosphere?
Gaseous form
-Di-nitrogen
-Traces gases
Organic:
- Biomass components (amino acids, nucleic acids)
-SOM
Inorganic
-Ammonium
-Nitrate
-Nitrite
What are the differences between ammonium, nitrate, and nitrite?
Ammonium and nitrate- both have positive charges , ammonium more acidic and leaches readily
Nitrite- is smaller type, very reactive
Nitrate needs to get reduced to ammonia to be taken in biochemical pathways
What are the inputs of nitrogen (naturally)?
N2 fixation (biotic, abiotic)
Atmospheric deposition (wet and dry)
Fertilization
erosion
What are the outputs of nitrogen?
Biomass removal
Erosion
Volatilization
Leaching/infiltration
Why are terrestrial system usually limited by N?
Because N2 in it’s gaseous form is triple bonded, requires a lot of energy to break the bond so decomposers can fix it and use it for plants
In what ways can nitrogen be fixed?
abiotic and biotic
What are the abiotic ways nitrogen can get fixed?
Atmospheric- thunder and electric discharge cooks N2 into nitrate
Industrial
What are the biotic ways nitrogen can get fixed?
through free-living organisms- aerobic bacteria, anaerobic bacteria, and blue green algae
or symbiotic organisms- such as stem nodules and stem nodules
How does the symbiosis between legumes and rhizobia work?
legumes feed co2 to rhizobia to provide energy for the bacteria to fix nitrogen as it doesn’t have to use the energy to fix carbon
How do rhizobium nodules get created?
the bacteria makes nodules in plants roots, the nodules are anaerobic as nitrogen needs to be reduced to be fixed
Why are nodules pink?
has hemoglobin that scavenges oxygen and prevents it from interfering with N fixation
Why does atmospheric N deposition change over time?
Because of industrialization (get more nitrogen deposition in areas with higher industry)
the haber-Bosch process (an artificial way to make nitrogen)
Livestock production
How does the haber-bosch process work?
Nitrogen from the air and hydrogen from natural gas in a 1:3 ratio gets pressures and cooled to make ammonia. The unreacted gases get recycled.
What are the consequences of nitrogen deposition?
lake/stream acidification/eutrophication
decreased plant biodiversity
changes in soil nutrient cycling
How does nitrogen deposition affect the fungal community structures?
when nitrogen deposition is low there’s more decomposition genes expressed so fungal biomass and richness increases. When the deposition is high, fungal biomass and richness decreases and stress genes are more expressed. More symbiosis is found when N deposition low and primarily saprotrophic when N deposition high.
Why does nitrogen addition decrease fungal decomp activity?
Because fungi will just use free energy that rather using their own energy to break down lignin to get nitrogen
Feb 14 lec
What is the environmental response of added N in detritus and soil mass?
Lower decomposition, high soil carbon pool, lower N mineralization
What is the environmental response of added nitrogen in plant biomass N?
higher productivity
higher tissue nitrogen
Higher N cycling
Higher herbivory
species change- exmaple less symbiosis
What is the environmental response to adding nitrogen interms of leaching losses?
higher soil acidification
higher plant mortality
What are the four types of nitrogen transformations?
Organic to inorganic (Nucleotide to ammonia)
inorganic to organic (ammonia to amino acid)
oxidized to reduced (No3- to NH4)
reduced to oxidized (NH4+ to No3-_
What are the 6 types of nitrogen transformations?
Fixation/Immobilization
* Mineralization
* Volatilization
* Nitrification
* Denitrification
* Conversion
to trace gasses
Explain what fixation/immobilization is for nitrogen gasses?
fixation- getting nitrogen from atmosphere into plant material
Immobilized- taken into plants from soil solution
Explain what mineralization is?
Is the release of an ion from it’s biotic form
What is volatilization (in terms of N)?
gasses escape from soil
What is nitrification?
is a process of oxidizing ammonia, fungi and bacteria do this, make ammonia to nitrite to nitrate
Why is nitrification two steps long?
because diff organisms do each part, AOB and NOB