Lecture VI. Biogeochemical cycles Flashcards
chemicals are NOT lost they are ___
cycled within ecosystems
What do biogeochemical cycles describe?
they describe the flux of atoms and molecules between biotic and abiotic reservoirs
Inaccessible reservoir > Accessible reservoir > Organisms
Look at the biogeochemical cycle chart showing the above cycle for carbon nitrogen and phosphorus
N2 is converted for uptake by plants via ____ by ____
nitrogen fixation, rhizobia
What is mycorrhizal fungi
increases plant phosphorus uptake, fungi that live within the plant root, help get plant the nutrients it needs to grow. [positive biomass impact]
decomposers (detrivores) are important because
they play a key role in the general pattern of chemical cycling
as mean annual temperature is rising what happens to the decomposition rate?
as temperature rises we see that decomposition increases as well.
What is a trophic cascade
In top down control predators can initiate what is called a trophic cascade by suppressing their prey, which releases the next lower trophic level from predation/herbivory
Ex. Wolves impact on elk populations near streams/rivers (elk eating tons of plants but once wolves were introduced, there was less erosion because elk population decreased in size hiding from wolves and a rebound in plants and shift in ecosystem)
Reservoir
Place where type of atoms ormolecules accumulate or are held for a relatively long period of time.
Flux
Rate of movement between reservoirs
What are the four main chemicals we will be working on for the biogeomemical cycles
Water, nitrogen, carbon, phosphor
What are the four types of biogeochemical reservoirs
a) lithosphere b) hydrosphere c) atmosphere d) organisms
Explain the nitrogen cycle
N2 found in atmosphere > bacteria in plants convert nitrogen gas to ammonia (NH3) > plants take in roots, assimilated, plants and cows die, decay, bacteria convert that nitrogen to ammonium
Nitrifying bacteria convert ammonium into nitrites then nitrates, compounds usable by plants
Is earth a closed or open system for elements and nutrients
Earth is a closed system for elements and nutrients
What is the primary physical phase in which water is used
Liquid water is the primary physical phase in which water is used, (97% water is oceans)
Explain the process of the water cycle
Biotic parts, cow drinks water, for abiotic parts, evaporation from lakes and oceans, it is also undergoing evapotranspiration where it evaporates through the plant condensation, then it precipitates, runoff and the whole thing happens again
Explain the process of the carbon cycle
Plants get carbon through photosynthesis and phytoplankton in the ocean, if biotic, cows simply eat plant or we eat the cow, goes back through cellular respiration as carbon dioxide. Can be buried as fossil fuels and can be extracted through wells
Explain the process of the nitrogen cycle.
N2 > Nitrogen Fixation > NH3 Ammonia > Fertilizer > Plants take in through roots > we get nitrogen through the plant by eating it > plant/cow dies, > decay and bacteria/fungi make ammonium (can be used by plants) > nitrifying bacteria convert ammonium to nitrite to nitrate > (nitrate can also be used by plants) > leaching and eutrophication runoff of algae in streams > denitrifying bacteria sends back into the atmosphere.
What is rhyzobia
Root nodules of nitrogen fixing bacteria that live on plant roots, the plant gives rhizobia sugars, rhizobia helps the plant get better nitrogen nutrients (mutualism - heavily reliant)
What are some limiting nutrients in many marine and terrestrial ecosystems?
Nitrogen and Phosphorus are both limited nutrients in terrestrial ecosystems. Since both are limiting, it can lead to eutrophication
In low nitrogen environments, why do insectivorous plants exist?
Through predation, plants can get the nitrogen they need to survive through other organisms by trapping insect prey.
Explain the process of the phosphorus cycle?
Rock is uplifted, causing phosphorus to ruse, weathering and erosion leads to phosphorus moving into soil to the water supply, fertilizers add phosphorus and since its limiting, it can lead to eutrophication, assimilation, eat plants, eventually we die, through excretion and decomposition we return that phosphorus to the water supply, it becomes sediment, and will become phosphorus rock and eventually rise again.
What are detritivores, what role do they play?
Decomposers, play a key role in general patterns of chemical cycling
What is the rate of decomposition controlled by
Temperature, moisture, oxygen, and nutrient availability
Hubbard Brook Experimental Forest, what is it?
They built dams and clear-cut watershed and measured how much nitrate was in the water that was clear cut vs was not clear cut. Deforested areas had higher nitrate than non-cut areas. FORESTS ARE SUPER IMPORTANT FOR KEEPING NITRATES SAFE IN WATER
