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509 Final


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Role of rivers in global water cycle
transportation system for water and sediment
What is a dystrophic lake
high inputs of allocthonous carbon -carbon builds up and eventually dry up -acidic -high CO2
What four types of material loads do rivers transport?
-dissolved load -suspended load -bed load -water
What is retention storage in watershed hydrology?
Evaporation, moisture stays in soil
What is detention storage in watershed hydrology?
Water is detained but ultimately ends up in the river
What does a shredder eat?
-Large allocthonous carbon fragments (e.g., leaves) that are colonized by bacterial & fungal communities -some have commensal guy flora, others have specialized enzymes
What is an estuary?
Semi-enclosed transition zone between terrestrial drainage systems (rivers) and large receiving body of water (oceans)
What is a dystrophic lake?
-high inputs of allocthonous carbon -small, tea-colored, lots of littoral vegetation -eventually become peat bogs and dry up due to carbon build up
Why is global atmospheric N increasing?
Release of NOx from human activities such as the burning of fossil fuels and forests.
What is blackbody radiation?
Short-wave radiation from the sun is re-radiated from the earth as blackbody radiation (long-wave)
Three most important GHGs driving climate change
CO2, methane, nitrous oxides
% of N delivered to oceans from rivers is anthropogenic?
27 to 39%
% of P delivered to oceans from rivers is anthropogenic?
about 50%
2 factors that determine whether an estuary is stratified, poorly mixed or well mixed
1) river flow 2) tidal mixing
How does topography contribute to creation of arid regions?
-mountains create rain shadow effect -rain clouds hit mountain and temperature drops to dew point -rains on windward side -when clouds move to other side they have no rain -example: Rocky Mountains and desert on other side.
What are oases?
Spot in desert where elevation is at or just above water table?
How are oases formed?
Through strong winds blowing sand away down to bedrock (water table) and there is a place for water to collect
What is C4 photosynthesis?
Plants use a different enzyme during photosynthesis with a higer affinity for CO2 so photosynthesis can occur while stomata are partially closed (to minimize water loss)
What is "convergent evolution"? (an example)
When plants and animals of different species evolve with very similar characteristics. -milkweeds and cacti look very similar
What is C3 photosynthesis?
Most common form of photosynthesis, almost all plants do it.
What is CAM photosynthesis?
plants open stomata at night and close during the day
What factors lead to "dust bowl" and why?
-repeated plowing of arid grasslands -drought -> loss of vegetation that had been holding soil in place
What is desertification?
Process of land becoming a desert
What human behaviors contribute to desertification? Why?
-overgrazing -> native plants are used to sparse, infrequent grazing by large mammals so overgrazing wipes out plant species which hold down soil and keep nutrients -collection of wood for fuel -> removal of vegetation decreases ecosystem stability -incorrect irrigation -> salinization
Benefits of irrigating crop land in arid regions?
-farm in otherwise un-farmable areas -increase food security -increase crop intensity
Costs of irrigating crop land in arid regions?
-depletion of water table/aquifers -increase salinization of soil/water -desertification -loss of biodiversity
2 abiotic forces that dominate ecology of desert systems? Explain
1) wind - difficult for vegetation to take hold 2) precipitation - limited availability restricts species that can survive
Two critical attributes of disturbance?
1) frequency = how often disturbance happens 2) magnitude = size of disturbance
3 agricultural practices that contribute to soil erosion? How?
1) slash and burn -> increases runoff (and thus removal of soil nutrients) 2) moldboard plow -> lifts nutrients and organic matter to surface where they leach away or erode 3) high disturbance shifting cultivation -> overfarming/overclearing which leads to erosion
What is the "genetic revolution" in agriculture?
Insertion of specific genes (from other species) into plants and animals to increase resistance to disease, drought.
What is slash and burn agriculture
practice of slashing forests, burning them, and then planting crops on the ashes -> erosion increases, soil nutrients are lost, forests do not recover quickly
Definition of monoculture and its risks
-plant one species of crops ->increases risk of 1 pathogen being able to eliminate food crops -lose genetic diversity of other species of that crop
Define "a" and "c" in the Nicholson-Bailey predator-prey model
a = Type I numerical response c = Type I functional response
What assumptions are used for "a" and "c" in the Nicholson-Bailey model?
-no limits on satiation -no egg limitation -no limits on handling time -> fundamentally unstable which leads to increasing oscillations which drive predators and prey to extinction
3 effects predators can have on prey other than consumption
1) death by competition (e.g., caribou crowd in wolf-safe areas and compete for food) 2) decline in birth rate (e.g., caribou crowd in wolf-safe area, population density increases so birth rate goes down) 3) decline in growth rate (e.g., largemouth bass force bluegill sunfish to edges with less food meaning they don't get enough nutrients to grow)
What is an example of a trophic cascade?
Piscivorous fish -> eat more zooplantivorous fish so their population declines -> allows population of large zooplankton to increase which surpress population of phytoplankton biomass
Define connectance and interaction strength
Connectance = ratio of observed links in web to all possible links Interaction = average of interaction coefficients for every pair of interactions in web
Major climatic differences between temperate deciduous forest and coniferous forest?
Average mean temp -temperate deciduous forest (13-25C) -coniferous forest (5-20C)
What can cause temperate decidous forest to change to grassland?
If average precipitation declines
2 factors that instigate primary succession
1) volcanic activity 2) glaciation
2 factors that instigate secondary succession
1) fire 2) clearcutting
What might prevent succession preceeding to expected biome in a given geographic region?
-variations in temperature and rainfall? -frequency and severity of disturbance -biotic interactions
Views of Clments and Odum
ecological succession was deterministic – in that disturbed sites would evolve towards a community that maximized ecological utility. However, Clements felt that the system would evolve into what he vaguely defined as the “best possible ecosystem”, while Odum envisioned succession areas evolving into a biome that maximizes energy flow through the system.
Views of Gleason and Egler
succession was not deterministic but the result of individual species characteristics. However, while Gleason held that succession was the result of the responses of each species to the particular set of physiological constraints of the environment, Egler held that succession resulted from the differential growth rates of the specie propagules left following a disturbance.
Define tolerance (related to successional processes)
the relationship where the presence of one species has no impact on the colonization of another
Define facilitation (related to successional processes)
presence of one species increases the suitability of the environment for a second species to colonize the area Most important after primary succession
Define inhibition (related to successional processes)
presence of one colonizer competes with and thus inhibits the growth of another colonizer
Contributions of forests to NPP of earth
surface - 9.5% % of NPP - 47.4%
Contributions of marine systems to NPP of earth
surface - 70.7% % of NPP - 32.1%

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