Week 3 Part 1 Flashcards
What are the two variables in all the hypotheses of biodiversity
Degree of overlap in ecological function of species
Variation in strength of ecological functions of species
What is the complementarity hypothesis
As species richness increases there will be a linear increase in community function. Each species added has an equal effect
What is the redundancy hypothesis
The functional contribution of additional species reaches a threshold. As more species are added there is an overlap in their function or redundancy among species.
What is the dirver and apssenger hypothesis
Strength of ecological function varies greatly “Driver” species have a larger effect; “passenger” species have a minimal effects
What is the variation on the driver and hypothesis
It assumes there could be overlap between dirver and passenger functions
What is primary production
The chemical energy generated by autotrophs during photosynthesis and chemosynthesis
What is primary productivity
Rate of primary production
What is the currency used to measure primary production
Carbon because energy assimilated by autotrophs is stored as carbon compounds in plat tissues
What is GPP
The total amount of carbon fixed by autotrophs
What does GPP depend on
Photosynthetic rate
What is photosynthetic rate influence by
Climate and leaf area index
What is LAI
Leaf area per uint of ground area. Can be greater than one because of overlapping leaves
What is leaf area index
The incremental gain in photosynthesis for each added leaf layer decreases because of shading
Does the leaf index increase by the same incriments each time
No eventually the respiratory costs associated with adding leafs outweight the photosynthetic benefits leafs also start to overlap so you are getting less and less sunlight
How much carbon fixed do they use in photosyntheis for cellular respiration
Half
Are all tissues photosyntehtic
NO
What does respiration rate increase with
Temperature so tropical forests have higher respiratory losses
What is NPP
Net reprsents biomass gained by the plant esseintaly is the energy left for plant growth and for consumption by detritivores and herbivores
NPP= GPP-Respiration
What is a good indicator of ecosystem health
NPP
In terrestrial ecosystems how do you measure NPP
The increase in plant biomass usually uses harvest techniques measure biomass before and after growing season
What corrections need to be made for measuring NPP
Herbivory and mortality
Why is measuring below-ground NPP more difficult
Fine root turn over more quickly than shoots- they die and are replaced quickly
Roots may excude carbon into the soil or bacterial symbionts
Harvests must be more frequent and additional correction factors are needed.
What else could measure NPP
Chlorophyll concentration can be a proxy GPP and NPP which can be estimated using remote sensing methods that measure reflection of solar radiation
What is NDVI
A commonly used estimate of productivity based on reflection
Can esitmate CO2. NPP, Deforestation, desertification and other phenomena
What has a high and low NDVI
Vegetation has a high level and water and soil has a low NDVI value
What is NEE
The net change in CO2 is GPP minus total respiration
What is more refined esitmate of ecosystem of carbon storage
NEE over NPP
Equation for NEE
GPP-(AR+HR)
What is the variation of NPP correlated with
Climate
NPP increases as percipitation increases up to a point but when there is too much percipation too much cloud cover so less light
NPP increases with increasing average annual temperature
Why is there variation in the temperature graph
Perceptation varries
ammount of sun they reccive
wind
soil factors (abiotic features that are not related to climate)
What tends to determine NPP in terrestrial ecosystems
Nitrogen
What was the theme with fertilization and plants in different levels resource communities
Plants from resource poor communities tend to have low growth rates and require less nutrients so they respond less to fertilization than plants from resource rich communities (rich get richer)
What happens in nutrient-poor communites are fertilized
Often a change in species composition
What is NPP limited by in aquatic ecosystems
Phosphorus and nitrogen
How is NPP measured in Aquatic systems
Change in chlorophyll concentration or number of phytoplankton cells
What happened in the study of the great lakes and adding more nutrients
Results showed that phosphorus was the nutrient in limited phosphorus it resulted in massive increases in cyanobacteria
Where did most of the nutrients come from in rivers and streams
NPP is usally low so it comes from terrestrial organic matter the water flow limits phytoplankton growth; most NPP is from macrophytes and attached algae
In the ocean what is NPP limited by
Nitrogen but near the equator it appears to be limited by iron
What do scientist think iron fertilization could do and would it work
Reduce global warming because CO2 uptake by phytoplankton would increase. However a large-scale fertizaltion of ocean is unlikely to be a solution the CO2 taken up by phytoplnakton is returned to the atmosphere via respiration of zooplankton and bacteria and iron sinks to the bottom
Where is average rates of NPP higher
Land surface is higher than the oceans and found in the tropics
Why is there variation of NPP in aquatic ecosystems
Variation of nutrient inputs NPP peaks at mid latitudes where ones of upwelling are found which than can bring nutrient rich deep water to the surface
