Soil ground stuff lets gooooo Flashcards
How much soil is moderetly degraded world wide?
33%
Describe the microbial mass of soil ecosystems
- Primary consumers - Microbial biomass
- Most abundant group in soil
- Most cant be cultivated using normal techniques so use DNA to estimate
Roles
* Breakdown og material
* Nutrient transformation/availability, gas exchange
* Structural stability, binding the soil together with polysaccharides
symbiosis
Describe mycorrhizal fungi
- Mycorrhizal fungi
- Colonise corticle tissue of roots
- Fungal nutrients to plant, plant carbon to fungus
*
describe the protozoa/protists
Protists
* single celled eukaryotes
* Soil movement via soil solution
* Photoautrophs, algae
* Heterotrophs protozoa, feed on bacteria and fungi
Produce cysts to survive unfavourable conditions
Decribe mesofauna
Mesofauna 0.1 - 2mm
* Microarthropods
Enchytraeid worms - keystone in boreal forest and tundra
What is mull and mor?
Mull
• Deciduous forests
• High litter nitrogen, low lignin and phenolics
• Fertile neutral pH soils, abundant bacteria and earthworms
Mor
• Coniferous forest, low litter nitrogen, high lignin and phenolics
• Infertile, acidic soils, absence or earworms
• High abundance of fungi and microarthropods
What s mull and more
Mull - mixture of organic matter and mineral soil of crumbly or compact structure with the transition to lower layers not sharp.
Mor - organic matter practically unmixed with mineral soil, usually more or less matted or compacted.
What are the 4 theories of how diversity loss influences ecosystem functions
Redundancy: As long as biomass main trophic groups are maintained, the less important ones can go extinct and high functionality will be retained
Rivot: all species have a role, wont retain high level functionality
Idiosyncratic: all species have a role, but some more important than others, so depends on the species
Insurance hypothesis: The more stable a system is, the great er its capacity to buffer environmental extreems
More diverse species can survive a changing environment
What is a simple method for determining soils biodiversity gradient on fertility?
Using various size seives as a proxy for the soils biodiversity
Then use that as inoculum
But does give anything for importance of particular bacteria over others fo e.g.
What was found in the experiment when diversity in soils calculated via 16s DNA and then measured multifunctionality of the soil (services, processes etc)
Microbial diversity drives multifunctionality in terrestrial ecosystems
Direct and indirect soil feedback from soil biota?
Plant-soil feedback mechanisms act as major drivers of plant community dynamics and ecosystem processes. Plants change their environment via direct and indirect mechanisms.
Direct: root herbivores, pathogens and symbionts. i.e. AM diversity increases plant diversity and productivity. Edits the community by increasing growth of seedlings of slower growing plants, allowing them to compete.
Indirect: Altered nutrient cycling, like tanin in pine needles. Effect on the soil decomposer system and therefore the nutrients supply.
Why do the types od grasses on the e sand dunes differ as u go further back
- Grass specific root pathogens
- Festuca favoured when ammophila is exposed to soil borne pathogens
Why do invasive species often do well
Invasive species
* Invasive species dont accumulate pathogens as quick (less host specific pathogens) so grow well in soil other than their own
Rare plants dont grow so well in their own soil due to host specific pathogens that accumulate in their own soil, negative feedback, modifying the soil in a beneficial way to the plant.
Why do pine dominate in boreal regions
Most plants utilise inorganic nitrogen. Pine trees have symbiosis that allows them to utilise organic nitrogen. They modify the soils to reduce nitrogen minerilasation, reducing organic nitrogen content.
- Tannic acid in the pine needles
- Controls nitrogen release as organic as it reduces microbial mineralisation of organic nitrogen
- meaning most nitrogen is inorganic
Pine trees unlike other species are able to take up inorganic N via their MA
so these pine trees are chemically shifting the nitrogen content to one which benefits them.
How can the slow-growing, phenolic rich
herb (Acomastylis) and fast—growing grass
(Deschampsia) coexist in alpine meadows?
- These slow growing plants have phenolic rich litter
- Increases soil microbial activity (not AM)
- Increases microbial N uptake
- Reduces that available to the fast grass, keep it in check, as it needs more N than the slow growing.
What are HErbivors effects on soil ecosystems
Effects:
* Selective grazing, limiting certain species but not other
* Modifies litter
* more nutrient return as Faecal matter, better for plants
Whats decleration and acceleration
Deceleration, low grazing pressures
• Defended plants have Low N and high polyphenal (talin) content
• Selective grazing for non defended plants
• Dominance of Defended plants
• Negative effect on nutrient cycling by the talin
• Few grazers mean little feacal return
• Low nutrient availability, slows plant growth
Acceleration, high grazing pressures
• Dominance of fast growing grazing tolerant plants with high nitrogen
• High feacal return of nutrients
• High nutrient availability
What caused the moose population collapse?
- Palitable species getting fed on by the moose became less dominant
- Confers became more dominant
- Reduced leaf litter quality
- Reduced soil microbial activity
- Slowed down processes like nitrogen mineralisation
- Not compensated by the faeces
- Reduction in productivity
Moose population collapsed due to this negative
How do Serengetti grazers influence the grasses? (they preferentially graze some grasses that have better nutrients for pregnancy)
- Suggest the grazers influencing the plants to produce more N when entering pregnancy
- Grazed plants suck up more sodium, providing a rich sauce of minerals for the animals in pregancy
Grazers can modify the system to increase the carrying capacity
- Grazed plants suck up more sodium, providing a rich sauce of minerals for the animals in pregancy
What are tinbergens whys?
Tinbergens whys (for behaviour
* 4 questions to ask * Whats the survival value or funciton of it * What causes it * How they develop it Whats the evolutionary history of it
What is game theory
Game theory theories the conditions for reciprical altruism to occur.
Game Theory
- Suggests best strategy depends on what the other does
- Worked out that tit-for-tat is the best option, do what the other did
Group living has:
* Significant costs
* High competition for the same resources etc
* So what are the benefits
- Easier to defend, so better access to resource
- Defence strategies
- Can cooperate for resource gathering
Shared parenting
What is communal courting
Communal courting, gene shopping where female chooses the best
Intersexual and intrasexual selection
Intersexual selection: one sex chooses mates based on an attractive features
Intrasexual selection: members of one sex usually males, compete over partnerswith the winner performing the most matins
What studies demonstrate the impact of turning tropical forest into agriculture?
Termites and nematodes
What did studies on functional redundency reveal?
They supported it, they found there was high levels of functional redundancy down to a level, at which further reduction of species resulted in negative effects.
Alternativley, increasing diversity only brought positive effects up to a point, at which increasing past that point didn’t lead to increased positive effects.
Do differences in species of mycorrhizal fungi affect their impact? How did the mesocosm experiment show this?
Mesocosm experiment
- Gradient of AM diversity
- But also varying types
- Allowing to see if its just AM diversity/richness or if its specific types/combinations
- Increased diversity of AM, increased productivity
increases hyphal length, took up more phosphorus and transferred more to the plant - Some redundancy here though at high diversity
How do pine trees maintain dominance in boreal forests?
- Boreal forest
- Low nitrogen, infertile soils but high productivity
- Microbial minerlisation of organic nitrogen to plant
- Evidence plants also use organic forms
- Tannic acid in the pine needles
- Controls N release as organic N
- Reduces microbial minerilisation of organic nitrogen
- Preferentially used by these dominnant pine trees
Pine trees unlike other species are able to take up Organic N via their MA - so these pine trees are chemically shifting the nitrogen content to one which benefits them
How does the slow-growing grass coexist with the fast-growing grass in alpine communities? Surely occupying the same niche, competitive exclusion?
- These slow growing plants have phenolic rich litter
- Increases soil microbial activity
- Increases microbial N uptake
Reduces that availble to the fast grass, keep it in check
Give an example of Acceleration from grazing.
Grazing of sheep in the scottish highlands
Serengetti grazers moving to grasses that had nutrients beneficial to late stage pregnancy during that time.
Nutrients found to be much higher in areas where the grazers were. Grazers found to modify ecosystems to elevate nutrient stress.
Define Semelparity and iteroparous with reference to seasonality.
Semelparity: Breeds once
Iteroparoud: breeds many times as season events or continuous events.
What was the resource seperation ratio defined by southgate?
He defined it using d/w.
* if d, the measurable resource is big enough for w, the variation then resource partitioning can occur
But its only assuming one resource at a time.
