Lecture 18

Monday, March 9, 2009

1. Several processes combine to one net behavior

Lecture 3 - MM uptake and flux

PS3 - CO2 in the atmosphere

• how much is the long term trend
• what is the variability
  • 0.5% per year of 355 = 1.8
  • sin with amplitude of 3 means plus/minus 3, range of 6, over any annual cycle

PS3 - population harvest had three levels of processes

• "Logistic Equation" controlled the overall trend
• sin function on the carrying capacity that varied over 6 time units
• random factor on the growth rate that went between 1.0 and 0.8
  • multiplied growth rate times this factor
  • variation was highest when rate was highest
  • might see the opposite in many situation

2. "multiple representations" means getting all the information in each

using that information

PS3 - headers of the graphing give key clues

• population
• area and radius
• time and height
• MM

PS3 - CO2 question, put the answer into words

1990 levels were 355 ppm and increase at 0.5% compounded with a seasonal variation of +- 3 ppm

3. comments on PS#3 and MR#2

PS#3

MR#2

• open system for energy, closed system for nutrients
  • control by light availability or nutrients
• threshold model should include positive feedback
• what is lost when constraining description to a system model ?
  • everything is a measured quantity, all fish in the reservoir are equal
  • information can only go to flows, no other behavior of stocks
• graph of birth_rate vs. population as an example of a threshold
  • low populations can have very inefficient reproduction
  • lecture ??

4. interactions between two factors in control

examples:

• light and nutrients (as above)
• water and light (common for plant studies)
  • water, light, CO2, nutrients
• water, energy (fossil fuel), money

create a model structure that controls growth rate of a plant as a function of water availability and light

• two separate flows
• controls one phenomenon - gross increase in plant biomass