Production Flashcards
Trophic level
the position in food web; determined by number of energy transfers from primary producers to that level
Primary producers
occupy first trophic level
Herbivores
(primary consumers) occupy the second trophic level.
Carnivores
(secondary consumers) occupy the third trophic level
Carnivores that feed on carnivores
occupy 4+ trophic level
primary production
-amount of energy fixed by autotrophs over an interval of time (measured as a rate)
-Rate at which energy from the sun used to make
sugars by plants
Biggest source of primary production is
photosynthesis by plants, phytoplankton, and cyanobacteria.
aside from photosynthesis, what else produces primary production
Also can occur via chemosynthesis by some species of bacteria.
Secondary production
is the assimilation of organic matter by heterotrophs to produce biomass
Plants do not produce energy for
the benefit of herbivores.
Redfield Ratio
ratio at which elements are fixed by plants during photosynthesis
what are the Two measures of primary production
Gross Primary production
Net Primary production
Gross Primary production
Total amount of energy fixed by
all autotrophs in an ecosystem
- GPP =
Photosynthesis
Net Primary production
The total amount of energy fixed by all the autotrophs in the
ecosystem, minus the cost associated with its fixation.
NPP =
Photosynthesis - Respiration
how to know difference between GPP and NPP
only NPP refers to the amount of energy available to consumers in an ecosystem.
(AR+HR)
Respiration
how much fixed carbon is used for cellular respiration, and what does it support?
half of it.
Used to support biosynthesis and cellular maintenance
how do plants respond to environmental conditions
allocating carbon to growth of different tissues
-Allocation of NPP to storage organs provides insurance against loss of tissue to herbivores, disturbances/damage such as fire or frost
Substantial amounts of NPP (up to 20%) may be allocated to
defensive secondary compounds
how is Primary Production quantied
NPP is estimated by measuring increase in plant
biomass in experimental plots and scaling up to the
whole ecosystem
-harvest techniques, remote sensing
Harvest techniques
- Measure increase in biomass over the growing season
- Radial growth of wood must be considered
- DBH – “Diameter at breast height”
measuring NPP belowground is
more difficult
-Fine roots turn over more quickly than shoots – they die and are replaced quickly so harvests must be more frequent
-Roots may exude carbon into the soil or transfer it to mycorrhizal or bacterial symbionts
Remote sensing
Remote sensing quantifies wavelengths that are reflected off of the earth’s surface
NDVI:
Normalized difference vegetation index
-basically assessing Chlorophyll concentrations - a
spectral signature that may be a proxy for GPP/NPP
what is NDVI used to estimate
used to estimate CO2 uptake and NPP, deforestation, desertification, atmospheric pollution, and other phenomena
NDVI of zero
An area with nothing growing
NDVI values < 0
suggest a lack of dry land;
The ocean will yield an NDVI of
-1
NDVI of one
dense, healthy vegetation
Terrestrial primary production is
generally limited by
by temperature
and moisture
Highest rates of terrestrial primary productivity occur in
warm, moist conditions
Actual EvapoTranspiration (AET)
total amount of water that evaporates and
transpires during given time period (usually a year)
how is Primary production highly correlated with AET
Ecosystems with the highest AET are warm and receive
large amounts of precipitation.
* Ecosystems tend to have low levels of AET either
because they receive little precipitation, are very cold,
or both.
* Both hot deserts and cold tundra exhibit low levels
of AET.
AET is Highly correlated with
annual precipitation
NPP can be increased by adding
nutrients to the soil
Liebig’s law of the minimum
-plant growth is not limited by the total amount of all soil nutrients available but by the soil nutrient variable that is present in the lowest quantity
Marine NPP usually greatest near the shores of oceans, where…
- nutrients from terrestrial runoff arrive
- nutrients arise from disturbance of bottom sediments
- nutrient upwellings arrive from the greater water depths
phosphorus causes
eutrification, increases phytoplankton population
Marine Primary Production- where is highest primary production
Highest rates of primary production by marine phytoplankton are generally concentrated in areas with higher levels of nutrient availability – near shore areas.
Dead zones
hypoxic areas (< 2mg/L oxygen), typically a consequence of pollution, eutrophication, and high rates of decomposition, that are essentially devoid of marine life.
